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Frank Schwartz
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I just removed the idler pulley and eccentric from a GT that is so rusty all that is worth saving is the engine and transmission etc. The idler pulley is different from earlier Lotus engines in that it seems to be the entire unit as one piece..the bearing and the running face (I guess you call it) seems to be a one piece unit. I have seen idler pulleys from other cars that were all one piece. Does anyone know if this unit is an over the counter item...or only available from Delta??
They show a different unit (this one) for 75 and GTs vs earlier JHs.

Thanks,
Frank

Brett Gibson JH5 20497
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Frank, it's a one piece unit and purchased whole, I have one on my JH5, I did cross reference it some time ago and the cost was about the same as Delta, basically not worth the trouble, runs about $75 if I remember correctly.
Brett

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Frank,

Jensen-Healy 'assembled' eccentric tensioner
Industry Standard ball bearings, such as ...

INA 6005-2RS
ID .............. 0.9843" (25mm)
OD ............. 1.8504" (47 mm)
Thickness: ... 0.4724" (12 mm)

Two of the 6005 ball bearings are assembled inside a proprietary outer steel ring/ roller, and with an eccentric hub pressed through the bores. The hex head for adjusting the eccentric is between the tensioner and the block, so access isn't as easy as it should be.

All "Lotus" tensioners (eccentric and spring-loaded) used a dual row/ double width, integral bearing/ roller. The bearing IS the tensioner roller.
ID ........... 1.214" (30.8356 mm) ... did the math and
OD .......... 2.478" (62.9412 mm) .... kept the decimals
Thickness: 1.179" (29.9466 mm)

SKF .......... 414871A ... Excellent quality, my favorite
SKF .......... VKM 14300 (??) In general, SKF is a quality brand.
Flennor ..... FS03299 ... Now sold by JAE
Ford ......... 1500004 ... 1977-1986 Ford Transit Van
INA .......... 531 0098 20 (??) In general, INA is a quality brand.
Timken ..... TKR 9841 (??) Timken production is in China.

Early Lotus Eccentric Hub ... P/N A907E0684FB
Later Lotus Eccentric Hub ... P/N A912E2176F
Either Lotus hub will work with the above bearings. I believe the significant difference was the size of the adjuster hex. The Lotus eccentric has the adjuster hex head on the front side. No special, thin, bent wrench required.

*~*~*
NOTE: There are minor dimensional differences between the JH and Lotus versions of the front seal housing. Due to those differences, the Lotus eccentric is not a direct plug-n-play upgrade for the JH 907. However, if you also swap in the Lotus front seal cover, then the Lotus tensioner will fit your JH engine. "OR"... Joe Van Ruth, 'qwerty' on this forum, has made up a Lotus-style eccentric that accepts the integral bearing/ roller, and fits the JH front seal housing. He sells them as a group buy on JHPS and the Jensen Healey Facebook page.
http://www.jensenhealey.com/forums/view_topic.php?id=2356&forum_id=2
*~*~*

DO NOT buy bearings by price. There's some cheap crap out there. If the bearing fails, it will take out the timing belt, and then the pistons wipe out the valves. "Cheap" can be really, really expensive.

Some new bearings feel rough out of the box. Hand try it before you buy it. Buttery smooth is what you want. Some of the Chinese bearings, in particular, have no business being anywhere close to a J-H/ Lotus timing belt.

Last edited on 07-10-2017 09:51 pm by Esprit2

Frank Schwartz
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You have me confused. I am familiar with the two bearing tensioner for the JH. I refer, however, to the single bearing unit which is a complete unit (less the eccentric) and is in the 75 JH and the 76 GT... Hopefully, I can find one of these as an over the counter unit...

Perhaps one of you has a part number for that one..
Frank

Brett Gibson JH5 20497
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Frank, Tim did supply the bearing numbers if you want to try over the counter.
SKF .......... 414871A ... Excellent quality, my favorite
SKF .......... VKM 14300 (??) In general, SKF is a quality brand.
Flennor ..... FS03299 ... Now sold by JAE
Ford ......... 1500004 ... 1977-1986 Ford Transit Van
INA .......... 531 0098 20 (??) In general, INA is a quality brand.
Timken ..... TKR 9841 (??) Timken production is in China.

Brett

qwerty
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Just approched this bearing today, looks like i have the integrated (once piece) roller AND it's installed up side down.

I'll see what i can get hold of tomorrow, Frank did you sort yours out? If not i will order two and send you one.

Attachment: Capture - Copy.JPG (Downloaded 153 times)

Last edited on 11-06-2016 09:11 am by qwerty

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Does that look pretty bloody loose too? I haven't touched it.

Attachment: Capture.JPG (Downloaded 151 times)

redracer
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Frank: I usually retrofitted the older style tensioners(concave outer surface as opposed to the flat integrated later style) since changing the 2 bearings was easier, faster, and cheaper than replacing the later one piece design; but if they are readily available and not too expensive, then look at the ones Brett & Esprit mentioned

Frank Schwartz
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From the picture, it looks correct...and it appears to be the two bearing type....I do not understand how it could be "upside down"... Remember, to remove it, you will have to slide off the crankshaft pulley....
I still have the single bearing unit on my bench and have not replaced the single bearing in it yet.

I have been working on Mike Linn's daughter's JH and just when I thought I was finished inside, I found the fan frozen and had to take the entire inside out to replace it. Also found many electrical problems that I had to fix...wiring on early JHs is not the exact same as later models, I found out....

Screenplay
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Is the "upside down" a reference to the position of the eccentric? The pic looks like it's installed according to the WSM - that is, tension is increased by turning the eccentric nut clockwise. However, as I recall Tim Engel has posted a tuotial recommneding turning the eccentric 180º so tensioning is increased by turning counterclockwise - I believe a failsafe in case the nut loosens.

Or perhaps it just looks upsidedown because qwerty is on the opposite side of the eqautor from many of the commentors here.

Clinton

Last edited on 11-06-2016 05:05 pm by Screenplay

qwerty
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Yes the upside down is a reference to the eccentric, nice one Clint, that may be why my lower A arms are back the front with the sway bar mounts pointing forward. :)

Upside down refers more accurately to being 180 degrees out or the bearing running closer to the aux pulley. Apparently we can install with the bearing center in either position (closer to the Aux pulley or closer to the Crank Pulley).

There are reasons for installing it closer to the crank pulley. In my picture above with the bearing closer to the aux sprocket imagine if the bearing spinning in it's normal anti-clockwise rotation and seizes/semi seizes or the lock nut starts to fail, the belt will loosen the stud (i'm assuming it's a stud) going into the block or the tensioner nut. The tensioner will swing away and the belt looses all it's tension and we don't want to talk about that. Additionally timing belts are not always uniform tension as it runs around the belt train, when the tension incrases it will apply force to the swinging action that is away from the belt and that swinging action would be anti clockwise this variation could slowly loosen off the threads over time.

Installing with the bearing center (blue dot) below the stud (big orange blob) in the image below (ie the bearing is closer to the crank pulley) and any of the above happens it will mitigate the risk of loosening the belt due to the pulley swinging (orange blob being the pivot point) into the belt and maintaining some tension until you pull over after hearing some god awful bearing noise from under the bonnet. Looking at the WSM it also looks to be dead center between the two sprocket diameters  when installed closer to the crank pulley.

Still looks like a one piece jobby to me, i'll check it out tomorrow. If it isn't i'll be equally as happy as i have ABEC3&5 6005's on hand.

Anyhoo i hope this helps. Besides i think i've hit a new PB on the number of times i've edited a post.

Attachment: Belt Tensioner.JPG (Downloaded 144 times)

Last edited on 11-06-2016 07:11 pm by qwerty

Esprit2
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When tensioning the timing belt, rotate the eccentric counter clockwise (as viewed looking at the front of the engine). If the eccentric is turned clockwise, it will tend to back-off in normal use, while counter clockwise stays put.

Do it wrong and you'll have belt tension problems long before the bearing seizes to the point of being able to screw the stud out of the head.

Regards,
Tim Engel

qwerty
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Thanks Tim, good rule to start with.

Here is mine in the WRONG position, has been like this for some time!!

Attachment: Wrong Position.JPG (Downloaded 132 times)

Last edited on 11-07-2016 08:04 am by qwerty

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And now in the CORRECT POSITION

Attachment: Correct Position .JPG (Downloaded 131 times)

Screenplay
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Qwerty,

I, too, ran one for many miles in the wrong position as I was following the instructions in the WSM. Thanks to Tim's tip It now looks like yours in the correct position.
I wonder if Lotus made this reccommondation in a later manual on the Esprit or if it's one of those things owners figured out over the years?

I also have a question: My current project, #18341, has a timing belt that rides near the rear edge of all of the toothed gears - cams and oil pump/distributor drive. Yet on other cars the belt rides in the center of the gears. Does anybody know why? Any thoughts on this?

Clinton

Last edited on 11-07-2016 05:41 pm by Screenplay

qwerty
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G'day Clint,

I thought the same abou the WSM, maybe this is why there were a few belts jumpimg teeth in the past. I posted up in detail for newbies like me for future reference as there's no one spot on the internet that explains it all, Just what's the right way and what's wrong way but not the why.

Tim's rule of rotating the eccentric counter clockwise nailed the what to do part.

Thoughts on your belt running at the back and relying on the principle of aligning a belt on a linisher/belt sander.

Only thing i can think of is that one or more of the sprockets in the belt train is out of alignment? The running surfaces need to be parallel and i'd imagine a hard problem to diagnose. You'd have to lean one of the cog's top forwards to have the belt run to the back side of the pulley.

I'd rule out the cams and the crank as they are mounted pretty solid. Is the tensioner stud bent at all? The Aux pulley could be out due to permatex etc build up on the oil pump/dizzy assembly gasket at the back.

Place a steel rule vertcally over all the sprockets and compare looking side on and see if the Aux sprocket is leaning forwards. The difference would be hardly noticeable so the longer the ruler the better.

Hope this helps.

Last edited on 11-08-2016 01:47 am by qwerty

Esprit2
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Screenplay wrote:
I, too, ran one for many miles in the wrong position as I was following the instructions in the WSM. Thanks to Tim's tip It now looks like yours in the correct position.
I wonder if Lotus made this recommendation in a later manual on the Esprit or if it's one of those things owners figured out over the years?
Lotus did add the instruction to later manuals. As I recall, the word was pretty well distributed via TSB's and the dealer network prior to making it into the manuals, but it did end up in print.

The 9XX engines continued in production for another 20 years or so after the J-H & GT went away. A lot more was learned about the engines than appears in the J-H WSM. Experience later showed that some early specs, like the recommended timing belt tension, were inadequate. It would be wise for J-H owners to have the "Engine" section as well as "Technical Data Section A" from later Lotus manuals. Not that every word applies directly, but there's good general info that can be useful.

Regards,
Tim Engel

Esprit2
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Screenplay wrote:
I also have a question: My current project, #18341, has a timing belt that rides near the rear edge of all of the toothed gears - cams and oil pump/distributor drive. Yet on other cars the belt rides in the center of the gears. Does anybody know why? Any thoughts on this?Belt tracking wasn't perfect in the beginning, but it wasn't far off. In the late 1970's ('79 ?), while 'metricating' the engine, Lotus modified the hub's width to better center the pulley's position under the belt's track.

But that's a small thing. If the belt is tracking way off center, then that does indicate that some shaft is off-axis somewhere... but there isn't just one scenario. It can be the tensioner bearing stud, as mentioned, but the cams are the more common source. Everything was pretty straight & true from the factory, but if the head has ever been milled to 'fix' a warp, then it's not uncommon for the new surface to not be parallel to the cams.

Also, when a head warps, the whole thing goes banana shaped, not just the bottom face. Truing the bottom doesn't straighten the top, and the cams may go cross-eyed.

Similarly, if the block has ever been decked or align-bored, it's possible that axis alignment was lost somewhere.

If the belt is running off the edge of the pulley, then that's a problem. But if it's just running a little off-center, but still on the pulley, don't sweat it. It's okay.

Regards,
Tim Engel

Brett Gibson JH5 20497
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I am in the process of bolting things back onto my rebuilt engine, and in doing so when I looked into the belt tension-er whole to put the stud back in, I noticed that the new front cover gasket was protruding slightly into the whole on just one side. Thinking this might put the tension-er bearing slightly off kilter I cleaned the bit out of the whole. Could this be an issue on just were the belt run's, I don't know, but the thought crossed my mind.

Brett

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Here is the page from the Lotus Esprit Turbo manual that talks about turning the eccentric tensioner counter-clockwise to tighten the timing belt.

To get the eccentric hub above the pivot bolt, as shown in the left illustration, it would have to be turned clockwise... which is not correct.

To get the eccentric below the bolt, as in the right illustration, turn it counter-clockwise.

Regards,
Tim Engel

Attachment: 9XX Timing Belt Tensioning - Esprit SE, S4, S4s, Section EF, pg 19 - 100kb.jpg (Downloaded 100 times)

Last edited on 11-09-2016 07:54 am by Esprit2

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Or, shown another way...

Attachment: 9XX Timing Belt - Routing & Tensioner Direction - 98kb.jpg (Downloaded 92 times)

Last edited on 11-09-2016 07:57 am by Esprit2

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Brett Gibson JH5 20497 wrote:
I am in the process of bolting things back onto my rebuilt engine, and in doing so when I looked into the belt tension-er whole to put the stud back in, I noticed that the new front cover gasket was protruding slightly into the whole on just one side. Thinking this might put the tension-er bearing slightly off kilter I cleaned the bit out of the whole. Could this be an issue on just were the belt run's, I don't know, but the thought crossed my mind.That shouldn't be a problem.

Regards,
Tim Engel

qwerty
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Tim would placing a bit of threadlocker (Loctite Medium Strength 243) on the stud into the block be a good idea? I noticed while tensioning mine the stud backed off while going counter clockwise.

EDIT: As per Tim's advice below and after removing the tensioner and understanding how it is held in place, Loctite is definitely not required.

Stud hole depth is approximately 30mm and thread on the stud is 25mm long. The stud threads in and seats on the shoulder of the stud thread, not bottoming out in the hole of the block so it will gradually tighten and not be a solid bottom out.

I threaded mine in until i felt a slight increase in torque and stopped there.


Last edited on 11-13-2016 05:22 am by qwerty

Esprit2
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It shouldn't be necessary. If you don't have a specific issue that needs a bandaid, then avoid using Loctite on studs (or bolts) into the block or head (any aluminum casting) unless it's called for in the manual. If you ever damage the external threads on a stud that's Loctited, then you'll have a heck of a time getting it out. It's hard to heat that much mass hot enough to kill the Loctite, and if you succeed, then the required temperature puts the aluminum at risk of being annealed.

I've never had the tensioner stud back out, but the Nyloc nut can loosen if the tensioner is turned in the wrong (clockwise) direction to tighten the belt. It's a simple thing to turn the tensioner counter-clockwise. Just do that and forget the Loctite.

One exception to no Loctite in the block is the three engine mount bolts in a triangle pattern on either side of the block. Those bolts do tend to loosen, so apply some blue, medium strength Threadlocker.

BTW, never add Loctite to a Nyloc nut. It attacks the Nylon patch inside the nut, causing it to degrade and lose it's grip. It's a chemical compatibility thing, not a lock/ don't lock thing.

Regards,
Tim Engel

Last edited on 11-10-2016 08:05 am by Esprit2

qwerty
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Thanks Tim,

No specific issue other that observing that the stud was rotating as well as the hex adjuster while removing. Remember i adjusted it the day before from an incorrect position to correct (anticlockwise) position this may have loosened the stud hence my question. I've never had a problem with 243 removal and never required heat to get it off. As noted never put Loctite or any compound on a Nylock. Being Nylon it will absorb moisture over time and expand to do a better job of locking.

I picked up some bearings today that may be worth a look at, High Temperature bearings ABEC 3, rated -30 to 150 Celsius. ( Standard bearings are rated to 80celcius) That means the seals and lubrication inside wont degrade under those temp ranges and the ABEC 3 tolerance will be a little tighter meaning less play in the roller. RPM rated at 7000.

BECO (Italian) Good stuff from experience. SKF also has equivalents.
Material Steel AISI 52100 (chrome steel) with special heat treatment stabilising
Radial Clearance C4
Quality Abec 3
Rubber seals rated for 150°c
Greased rated for 170°c

Special Application for Automotive Belt Tensioner BECO BHT 2RS 150° BTE COMP (Size 6005).

Last edited on 11-13-2016 05:13 am by qwerty

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Thanks for posting about the BECO bearing. I've not heard of that one before, and I'll add it to my list.

Regards,
Tim Engel

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Gaaahhh.. Replaced the belt and pulley today and although the old belt was tracking almost spot on center of the sprockets before the install it now runs flush with the rear of the sprocket.

Spent a few hours trying this and that,
Bent tensioner stud:No
Rotate Stud 90Deg to see if it made a difference: No
Rotate Stud 180Deg to see if it made a difference: No
Bearings pressed in too far or too short: tried both, no difference
Rotated Idler pulley back up to the top incorrect position - a little better but not much.
Rotated back down to the correct position - running to the rear again.
Flipped belt and reinstalled with front facing back: - Still runs to the rear.
Flipped belt back to correct arrow facing forward - Running to the back
Swapped belt to the HTN Version, Runs to the rear but not flush maybe 1-2 mm off
Swapped to the Second Blue belt i have, runs maybe 1mm off the rear.

I've got nothing, the belt i took off ran in the center. Is it possible that due to the slight convex shape to the idler pulley that it will stretch in and move to center over time? I will change back to the old belt soon and see it it runs center, if it does the issue lies with the belt and not the changes. I'll report back.

Ps changing the timinng belt is acutally quite easy now that i have done it 20 odd times in 2 hours :)


Attachment: Belt Tracking.JPG (Downloaded 70 times)

Last edited on 11-11-2016 09:56 am by qwerty

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BECO 6005 BHT 150

Attachment: BECO 6005 BHT 150.JPG (Downloaded 71 times)

qwerty
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Is this arc to the outer hub normal or wear?

Attachment: Arc to outer hub surface.JPG (Downloaded 68 times)

Last edited on 11-11-2016 09:52 am by qwerty

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Esprit2 wrote: Thanks for posting about the BECO bearing. I've not heard of that one before, and I'll add it to my list.

Regards,
Tim Engel

Thanks Tim, You're most welcome.

As noted SKF also has this type of bearing.

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That's an interesting blue belt. Where did it come from?

All I've ever used or seen were just your everyday basic black.

Frank

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Frank,

The blue belt is from Gates Racing, a specialty division of Gates Rubber. Their part number T104RB. It's available from any Gates Rubber distributor, including NAPA, O'Reilly, and RockAuto.com.

The blue belts are the latest materials technology, including HNBR rubber (Hydrogenated acryloNitrile Butadiene Rubber). The black trapezoidal tooth belts are HCR rubber, which is ancient mid-1960's technology.

Simply due to superior materials, the blue belts should be the best available (short of converting to the round-tooth belt), and run longer between replacements. However, Lotus is not doing development/ testing work on a 45+ year old engine, and Gates won't make recommendations for other company's engines. As a result, there's no formal recommendation for miles/ months between changes, but you can think of 'using the best'as an insurance policy against failure. It costs more at about US$65-75.

Blue round-tooth belts have been around for years, but the Gates factory that had the tooling for the trapezoidal tooth belts was not configured to run the new HNBR rubber. Apparently that has changed recently, and the blue trapezoidal belt is now available.

Blue is just the trademark of Gates Racing, and it has nothing to do with the belt's materials or construction.

Regards,
Tim Engel

Last edited on 11-11-2016 11:48 pm by Esprit2

Frank Schwartz
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Somewhat confusing...I'll check with my local store and see if they have the blue belt. My interest was merely for a little "dress up" under the hood.

So I understand, a blue round toothed belt as Lotus uses is also available, too???

I seem to be block headed..I only know the belts as square toothed and half moon (late lotus) ...what is the trapezoid???

Thanks Tim.
Frank

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qwerty wrote:
As noted SKF also has this type of bearing.SKF is a quality brand, and normally my first choice for bearings. But I'm always looking for quality alternatives... as well as bad alternatives to avoid.

Regards,
Tim Engel

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qwerty wrote:
Is this arc to the outer hub normal or wear?It might be normal wear, but it was not apart of the original design or manufacture. It is 'wear'. That could be contributing to your timing belt tracking off center. The blue belt is more stiff, and would not simply conform.

Regards,
Tim Engel

Last edited on 11-11-2016 11:56 pm by Esprit2

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Frank Schwartz wrote:
I'll check with my local store and see if they have the blue belt.Call ahead. Even if corporate NAPA/ O'Reilly's lists the belt, the local neighborhood store may not stock it. But they can order it and have it in a day or two. Or just mail order it from RockAuto.com, and save yourself some running around.
Frank Schwartz wrote:
So I understand, a blue round toothed belt as Lotus uses is also available, too???The round tooth belt is called a HTD (High Torque Drive). The Blue HTD belt that is available for the later Lotus engines is also made by Gates Racing (again, the blue is a Gates Racing trademark).

Not to put too fine of a spin on it, but "Lotus" never sold the blue HTD belt. It was an independent Lotus parts vendor, JAE, that worked with Gates Racing to develop the blue HTD belt for Lotus engines. As a result, JAE has exclusive rights to the blue HTD belt, but they distribute it to all other Lotus parts suppliers who want to buy it.
Frank Schwartz wrote:
I only know the belts as square toothed and half moon (late lotus) ...what is the trapezoid???The 'square' tooth isn't really square. The sides are tapered, and a tapered square is a trapezoid. We're talking about the same thing, just using different names.

Another advantage of the blue belt is that it's very stable. Continue to check the belt's tension on a regular basis, but it's highly unlikely that you'll ever have to re-set the tension after the initial installation.

Regards,
Tim Engel

Last edited on 11-12-2016 12:13 am by Esprit2

Frank Schwartz
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I understand. Thanks...oh take a look at what I just posted on intake manifold installation, since you are sitting there at our computer.
Thanks
Frank

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qwerty wrote:
Gaaahhh.. Replaced the belt and pulley today and although the old belt was tracking almost spot on center of the sprockets before the install it now runs flush with the rear of the sprocket.
(Snip)...
Ps changing the timinng belt is acutally quite easy now that i have done it 20 odd times in 2 hours :)

IMHO, there's nothing wrong with the belt running off-center, as long as it doesn't over-hang the edge, and is stable where it is (ie, doesn't wander). If you have a little OCD kicking in, then knock yourself out. But if you're trying to fix a real problem, I don't believe one exists. Your call.

You're right... the belt is quite easy to install once you get the hang of it. But that doesn't seem to be experience most owners 'want' to get. My record for replacing the 907's belt in a front engine car is 45 minutes. The mid-engine Esprit takes considerably longer.

Regards,
Tim Engel

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Esprit2 wrote: qwerty wrote:
Is this arc to the outer hub normal or wear?It might be normal wear, but it was not apart of the original design or manufacture. It is 'wear'. That could be contributing to your timing belt tracking off center. The blue belt is more stiff, and would not simply conform.

Regards,
Tim Engel

Would one of the kits pictured (Kemp High Performance engines) be a direct replacement? They advertise this as an upgrade from the S3 auto tensioner to manual and needs an M10 thread into the block, well we already have that so this may be a good upgrade for the part above plus as a bonus the tensioner nut is integrated into the hub so no more slop when adjusting and you get a new tensioner roller with every change.

I heed your advise on the belt tracking yet as i will be doing tension testing for the Gates Blue Belt. (i now have Kriket and Burroughs gauge) i need to get the tensioner correct.

Kit is from an Esprit S3 It's Mostly the diameter and length of the spigot going into the block that needs to fit. I assume the tracking of the pulley will still be positioned to sit center of the crank and Aux Pulley. If the tensioner hole in the block on the esprit is the same as the J-H then it should fit with no issue.

Attachment: Eccentric Tension Kit (Custom).JPG (Downloaded 59 times)

Last edited on 11-12-2016 04:00 pm by qwerty

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qwerty wrote:
Would one of the kits pictured (Kemp High Performance engines) be a direct replacement? They advertise this as an upgrade from the S3 auto tensioner to manual and needs an M10 thread into the block, well we already have that so this may be a good upgrade for the part above plus as a bonus the tensioner nut is integrated into the hub so no more slop when adjusting and you get a new tensioner roller with every change.
(Snip)...
Kit is from an Esprit S3. It's Mostly the diameter and length of the spigot going into the block that needs to fit. I assume the tracking of the pulley will still be positioned to sit center of the crank and Aux Pulley. If the tensioner hole in the block on the esprit is the same as the J-H then it should fit with no issue
That's the Lotus version of the eccentric tensioner. All the Lotus tensioners used the double-row bearing/roller, instead of the J-H assembly that uses two 6005 single-row ball bearings in a roller sleeve. The two major differences are 1) the purpose-made tensioner bearing/ roller, and 2) moving the adjuster hex to the front side, where it's easily accessible. The eccentric hub is a press-fit into the bearing's bore.

Garry Kemp has simply pulled all the Lotus parts together into a kit to replace the spring loaded tensioner... plus a couple you shouldn't need. Your engine already has the stud. I don't recognize the spacer sleeve in the upper left of Kemp's picture, above the eccentric hub. I'm GUESSING, but it looks to me that he's using that as a spacer to replace the boss that is not present on the earlier front seal housing (right in the attached JPEG).

But your J-H 907's front seal housing also has a boss for a tensioner eccentric, very similar to the Lotus seal housing. The question is, are the bosses & bores the same diameters for both the J-H and Lotus designs. I don't have a J-H part here to check, but I have a Lotus eccentric hub in my hands. Just measuring with a dial caliper (what the heck did I do with my micrometer?), the male boss is 0.810 OD x 0.720" tall. Check yours.

My guess is that the Lotus eccentric is a direct replacement for the earlier J-H eccentric, and Kemp's kit gives you more parts than you need for the conversion. Before you buy, see if you can get the hub alone for less money (check SJ, JAE, etc). Then buy a bearing, washer & Nyloc nut near you. The bearing is SKF 414871A (excellent), Flennor FS03299 (now sold by JAE), Ford 1500004 (1977-86 Transit Van), 31mm ID x 63mm OD x 30mm wide. Just beware. There are some inexpensive Chinese copies out there that are bad right out of the box. One in partricular has blue seals... pure crap. I make a point of asking for SKF.

qwerty wrote:
I heed your advise on the belt tracking yet as i will be doing tension testing for the Gates Blue Belt. (I now have Kriket and Burroughs gauge) i need to get the tensioner correct.Yup, it is nice to get the tensioner correct. The belt is tightly located fore-n-aft at the crank sprocket.

The curved back side of the V-belt pulley, and the backward curved washer behind the sprocket form a 'funnel' that guides the belt onto the narrow crank sprocket. There's not much room for the belt to wander off. That set's the belt's position on the engine, and is a constant on all the 9XX 4-cyl engines. Any tracking issues at the upper pulleys is a matter of the entire belt loop 'leaning'. Early cam/ auxiliary sprockets were not centered very well above the crank sprocket, so it's not unusual for the belt to be less than centered, even when everything is 'straight'. What looks like incorrect tracking may not be the belt getting off-track. In the mid-late 70's, Lotus adjusted the width of the hub to improve the pulley's position under an otherwise straight-tracking belt.

Good luck,
Tim Engel

Attachment: Sec ED - Engine - Front Main Seal Housing - 1974-80 907 74kb.jpg (Downloaded 50 times)

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And another view...

Attachment: Timing Belt - Pulleys and Tensioner - Parts Dwg EF - 97kb.jpg (Downloaded 133 times)

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On a related subject. The auxiliary pulley abutts against a little wire circlip that is not very strong. The pulley can get loose even when the bolt is properly torqued. Apply a little blue/ medium strength Loctite in the pulley bore prior to installation, but try to keep it out of the keyway.

If the pulleys were properly installed last time, heat and a puller will be required to remove the aux pulley. Just be careful not to direct the heat toward the lip seal directly behind the pulley. I wrap a wet rag around the shank of the shaft to protect the seal, then direct the torch flame back to front.

In contrast, apply Anti-Seize to the cam pulleys. They butt-up against a large shoulder and get clamped tightly. They're not going anywhere.

Regards,
Tim Engel

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Thanks Tim, That's most of the info i needed. I will measure the stock J-H spigot/male boss that pushes into the block and compare with your measurements. If the spigot/male boss matches then Geoff Kemp's Kit (or a Lotus Hub and one piece bearing/roller) may be a direct replacement for the J-H and in my opinion a much better design. The only extra piece we'll be buying in the kit is the stud (stainless apparently), this may still be needed if there are any offset differences though i doubt it. If you would reply with my measurement question below i'll be the guinea pig and try Geoff's kit to check the offsets and confirm it is a direct replacement. If all is well then the intial outlay will be a new Lotus hub and bearing but after that only the bearing will be needed for matainence when changing the belt.
*Snip "The two major differences are 1) the purpose-made tensioner bearing/ roller, and 2) moving the adjuster hex to the front side, where it's easily accessible. The eccentric hub is a press-fit into the bearing's bore."
The third major difference 3) The bearing's bore: the ID on the 6005 bearings is 25mm whereas the ID on the SKF 414871A is 31mm. This is why i'm after Geoff's Lotus replacement. Our current J-H 2 piece hub (in your pic above part 14 and 15 are two separate pieces and part 14, the adjuster nut, is sloppy as hell in the bore of the 6005's) will need to be swapped out for the Lotus hub to make use of the purpose-made tensioner bearing/ roller (SKF 414871A). The press fit surface of the hub will be larger on the Lotus version than the J-H Version to accept the SKF 414871A - It should measure somewhere just under 31mm. Would you please confirm with your lotus hub you had in your hands?

I hunted high and low for a replacement hub only yesterday to no avail, I messaged Geoff through ebay as currently shipping is not available to Aus so hopefully he will respond soon so i can get this shipped before the belt learns the tracking.

Good info on the Aux pulley, i'll check on it.

Last edited on 11-13-2016 05:46 am by qwerty

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qwerty wrote:
The third major difference 3) The bearing's bore: the ID on the 6005 bearings is 25mm whereas the ID on the SKF 414871A is 31mm. This is why i'm after Geoff's Lotus replacement.If the J-H and Lotus tensioners are functionally interchangeable (and I think they will be), then it would only be as complete assemblies. Don't expect any of the bits to interchange individually, other than the stud, washer & nut.
qwerty wrote:
The press fit surface of the hub will be larger on the Lotus version than the J-H Version to accept the SKF 414871A - It should measure somewhere just under 31mm. Would you please confirm with your lotus hub you had in your hands?

I hunted high and low for a replacement hub only yesterday to no avail, I messaged Geoff through ebay as currently shipping is not available to Aus so hopefully he will respond soon so i can get this shipped before the belt learns the tracking.
Have you tried SJ Sportscars, PNM Engineering, or Southwest Lotus Centre in the UK? Also, JAE or Dave Bean Engineering in California, USA?

Actually, your best bet might be a used eccentric from Lotusbits in the UK. If need be, Mike Taylor could also provide an inexpensive used front seal housing to match the tensioner. http://lotusbits.com/

I have the 'complete' tensioner here... ie, the eccentric pressed into the bearing. Unfortunately, that means I can't access the diameter you want measured. I do intend to take it apart to install a new bearing soon, but I don't have a hydraulic press of my own to do it now. Every Tuesday night is 'Toybox Night' (my buddy's shop), and he has a press. My plan was to do it then... this coming Tuesday. Is that good enough?

In the meantime, I can confirm that the hub is a press fit into the bearing's bore. The replacement bearing is a Flennor S03299 (I've also seen FS03299 referenced), and it measures...
1.214" (30.8356 mm) ID Bore <<<<<<<< ie, a slight negative fit with that.
2.478" (62.9412 mm) OD
1.179" (29.9466 mm) Wide

BTW, the bearing that is on this hub now is one of those inexpensive Chinese bearings I cautioned against using. No brand markings, but this one had black seals, not the blue ones I mentioned. A friend bought it for his Esprit Turbo, and it only lasted a few weeks. I popped the seals out, and it appears the manufacturer was very stingy with the grease. Like, almost none.

Regards,
Tim Engel

Last edited on 11-13-2016 07:01 am by Esprit2

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My thoughts also Tim only you combined it all in to one sentence... Well put! -  "If the J-H and Lotus tensioners are functionally interchangeable (and I think they will be), then it would only be as complete assemblies. Don't expect any of the bits to interchange individually, other than the stud, washer & nut."

Happy to wait till Tuesday, for the dimension, It doesn't have to be exact as it'll either be closer to 25 or 31mm and we'll have our answer. I've already ordered a SKF 414871A...

Also Blue Seals usssuallllly refer to a stainless bearing. Not always though.

I agree, bearings ain't bearings, most shops will tell you it doesn't matter where it's made as the big name brands have plants all over the world (which is true) but where they source their steel from, how they treat the steel and the quality of the plant and training most likely makes a difference.

Bearing choice is a bigger factor and choosing the wrong bearing for it's application can give it a bad name. Choose for the application, Let the bearing guy know where it's going to be used and he'll hopefully make a few educated suggestions considering for example, abutment, number of balls, type of cage and seals, load including vectors, tolerance "ABEC" rating and clearance "C" Rating, RPM Rating, ambient conditions heat/corrosion as well as extremes. They have BIG bearing encyclopaedias that they can address. Heat is a big killer to the lubrication and seals, and that bearing you pried the seal from may have just had it's grease boil off or may have been made to suit high rev 20,000rpm in which case it would have been filled with oil rather than grease or as you said just plain old inexpensive non branded poor quality.

If you simply ask for a 6005 bearing the shop guy will most likely just give you what he has on the shelf yet there will be a mountain of choices based on the variables above and probably more. I am no bearing guy, i just put the application forward and asked the questions to a good bearing shop, they had 11 dollar NSK 6005's on the shelf and was about to walk away with them when a knowledgeable sales person overheard the conversation and that's how i came across those Beco's. The SKF 414871A being specifically designed for the tensioner purpose will have had all these considerations implemented into it's design so we don't need to do the research and that's why i think exploring this whole interchangeability experiment will be well worth it. Sorry for the novel, Tim may just stroll in and boil this down to one sentence haha

I have tried some of those shops and will keep the hunt on for the Lotus hub tonight with your suggestions.

Cheers, Pete

Last edited on 11-13-2016 10:27 am by qwerty

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Update

This is a no go, the spigot diameter is fine but it is too is too long for the J-H front housing. Additionally once we faced the spigot down to size on a lathe so it would fit, the bearing sits too far inward so the belt will be running off the front edge, not by much ~3mm yet enough to cause a bit of worry.

I will be exploring this in the future to make another part suitable for a replacement for the J-H.

Last edited on 11-22-2016 10:33 am by qwerty

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If I understand you correctly, what you need is a version of the Lotus eccentric hub with more shoulder and less spigot... correct?

How about making a spacer ring to fit between the boss on the JH seal housing and the shoulder on the eccentric hub? Well... you've already shortened the hub's spigot? Then two spacers. One to put the spigot length back, and one to fill the gap between the seal housing and the hub's shoulder. I know, I know... that's starting to sound like a kluged up stack of parts; but it would work as a mock-up to evaluate the configuration.

You probably didn't intend to start a J-H upgrade parts business, but making a JH-specific version of the Lotus eccentric would be a good thing. IMHO, the purpose-built 'tensioner roller/ double-row bearing' is a better solution than the JH assembly of loose parts; and putting the adjuster hex on the front side is a great convenience.

Sorry if I led you down the primrose path on that one. The cylinder block and the eccentric hub are compatible in terms of the plane of the timing belt. It's the boss on the J-H front seal housing with which I have no dimensions or experience.

Keep us posted on where you go with this.

Regards,
Tim Engel

PS... for those of you in the USA, Happy Thanksgiving.

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If I understand you correctly, what you need is a version of the Lotus eccentric hub with more shoulder and less spigot... correct?
Correct. I thought about a spacer but given the thing has to stay in place i opted out of the spacer just more parts to come loose besides as you noted it would turn into a cheeseburger of parts...

I'll keep you posted, my mind has been keeping me awake tonight going over dimensions in my head. I'm also thinking of lessening the eccentric offset of the 10mm hole by a few mm to allow for more control when tensioning, as you mentioned and as i've found out it's bloody sensitive! Not too much or it will make installing the belt a little hard for some but just a little. Enlarging the diameter of the shoulder would be nice so it butts up against the full spot face on front seal housing.

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qwerty wrote:
I'm also thinking of lessening the eccentric offset of the 10mm hole by a few mm to allow for more control when tensioning, as you mentioned and as i've found out it's bloody sensitive! Not too much or it will make installing the belt a little hard for some but just a little.I agree the eccentric tensioner would be much better if it wasn't so hyper-sensitive to adjustments. A wrenching buddy and I have talked about doing the same thing, but we've gotten no further than talk. The issue is that you're splitting hairs between 1) not having sufficient travel to achieve enough tension on a range of belts, and 2) being way too hyper-sensitive.
qwerty wrote:
Enlarging the diameter of the shoulder would be nice so it butts up against the full spot face on front seal housing.
The shoulder that touches the boss on the seal cover can't be enlarged. It presses through the bearing bore from front to rear, so bore-size is as big as it can get.

Regareds,
Tim Engel

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The shoulder that touches the boss on the seal cover can't be enlarged. It presses through the bearing bore from front to rear, so bore-size is as big as it can get.
Heyyy? Not sure we're on the same page here. See pic below.

1) not having sufficient travel to achieve enough tension on a range of belts, and 2) being way too hyper-sensitive.
3) I trust Lotus did their homework on the offset as well so i'm mindfull of that too.


Attachment: 1.jpg (Downloaded 99 times)

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qwerty wrote:
Heyyy? Not sure we're on the same page here. See pic below.Brain fart, or brain not engaged. You're right.

Later,
Tim

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Jensen Healey specific hub coming along nicely. Directly squared over the crank pulley. Next we mill the hex, given the design it will be a 24mm Hex instead of a 22mm Hex. Pictured here in Ali but the final will be 4140 Steel possibly coated/treated for corrosion.

Attachment: J-H Eccentric Hub 1.JPG (Downloaded 83 times)

Last edited on 11-25-2016 02:02 pm by qwerty

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Jensen Healey Specific Manual Eccentric Hub

Ditch the 2x 6005's and replace with the superior 1 piece Timing Belt Bearing SKF 414871A or the Flennor FS03299 (as pictured) Either will fit.
  • Full concentric abutment with spot face on the block increasing rigidity.
  • Full concentric abutment with spot face on the block reducing carving of block spot face upon multiple readjustments.
  • Centralized Adjustment nut allowing normal spanners.
  • Protruding hex to allow for easier spanner fit.
  • Hard shoulder while pressing in to avoid misalignment with crank sprocket.
  • Reduced radial offset yet increased OD of roller to allow for more forgiving adjustment.
  • Wider Roller over the Stock J-H Shell.
  • Increased Diameter over stock J-H Shell.

Attachment: J-H Eccentric Hub 2.jpg (Downloaded 84 times)

Last edited on 11-25-2016 01:56 pm by qwerty

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Jensen Healey Specific Maual Eccentric Hub

Attachment: Jensen Healey Eccentric Tensiioner.JPG (Downloaded 81 times)

Last edited on 11-25-2016 03:57 pm by qwerty

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Front View: Untensioned

Attachment: Jensen Healey Eccentric Hub.JPG (Downloaded 82 times)

Last edited on 11-25-2016 02:06 pm by qwerty

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Nice Work! I'm impressed.

Tim

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Thanks Tim,

I've started a new thread on this as we have the final version done.

I did a check on a worn belt: Static tensioned at 140-160LBS on an old belt still had 60deg of rotation to go to max tension and 3mm of growth on the od of the roller.

Regards
Pete

Last edited on 11-29-2016 09:30 am by qwerty



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