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renovated engine burning oil  Rating:  Rating
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 Posted: 03-22-2015 11:15 pm
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Esprit2
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Barthol wrote:
(Snip)... I have a semi automatic tightener but I cannot find out how to mount it. It looks like I am missing threaded hole in the engine. Is there anyone who have some photos / schematics showing how it is mounted. ?See the attachment. It doesn't show the block mounting hole details, but it does illustrate the general arrangement.

Yes, you do need two threaded bolt holes in the block. And since all J-H 907s are 'early' 907s, and none used the spring-loaded, semi-automatic tensioner, it's possible your engine won't have the second bolt hole.

In Lotus applications, there's usually something between the semi-automatic tensioner and the cylinder block. It may be an A/C compressor mounting bracket, or a belt snubber with short spacers on later engines, but something. On an engine with no accessory brackets, there will at least need to be a pair of longer sleeve-spacers to move the tensioner out to the plane of the timing belt. Examples of those parts are illustrated on the attachment, along with Lotus part numbers (probably no longer available from the factory).

I suggest you contact Lotusbits and ask for whatever parts you need to complete the installation of your tensioner to a J-H 907 with no accessory brackets or snubbers.
http://www.lotusbits.com/

*~*~*
There were several versions of the semi-automatic tensioner as it evolved over time. The early one had a spring loaded metal piston moving in the aluminum housing's bore. It would gall over time, and seize.

Later tensioners have a Nylatron plastic piston that solves the galling problem, and it will fit the early tensioner. However, if the bore is already galled, the damage is done and the plastic piston isn't any help. It needs a smooth, close-fitting bore.

In early versions, the body's central hinge was just a steel pin in bored aluminum holes. If the holes wore, the moving part of the tensioner could cock at an angle, and the belt would tend to run off center on the pulleys. The official fix was to replace the tensioner.

The later tensioner added Nylon bushings (shown in the attachment) to over-size hinge bores. If the bushings wear, just replace them and put the tensioner back in service.

Make certain there is no slop in the hinge that will allow the roller arm to cock off to either side.

Regards,
Tim Engel

Item .. Description .............................. Part Number
040 ... Snubber .................................. B907E1140F
041 ... Spacer, With Snubber ............... A907E1139F
042 ... Spacer, to block without Snubber A907E1138F
043 ... Stud. M10 ................................ B907E0504K
046 ... Bolt, M10 x 70 .......................... A075W2058Z

Attachment: Timing Belt, Pulleys & Automatic Tensioner & Snubber - 1980-87 Esprit.jpg (Downloaded 153 times)

Last edited on 04-25-2015 04:54 pm by Esprit2

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 Posted: 03-23-2015 06:22 am
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Barthol
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Hi All

You are right , I do not think I can repair the Stud with the Engine in the car.
As I have both Treads for the Semi automatic tensioner I think all I have to do is to make up a 1"" plate to get the correct distance.

I thought about changing the head But the head in the cat has the larger inlet Channels, and I doubt it will be possible to exchange the head , shimming it etc with the engine in the car.

I will fix the tensioner and change the oil to 20/50 mineral. If it continues to burn excessive oil I will pull it and do all the work in the bench.
The old 2 ltr will then have to go back for this season :-)

Thanks a lot for all of your inputs .

BR
Kim

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 Posted: 03-23-2015 06:21 pm
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Esprit2
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Here's an illustration showing the A/C compressor mounting brackets. Note the two welded-in bosses surrounding the bolt holes in the upper right of the bracket. The timing belt's semi-automatic tensioner mounts through those holes, and the bosses space it out to the plane of the timing belt. Without that bracket in place, some other form of spacer is required for the tensioner.

Regards,
Tim Engel

Attachment: AC Compressor Brackets - 1978-80 Esprit.jpg (Downloaded 154 times)

Last edited on 03-23-2015 09:16 pm by Esprit2

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 Posted: 03-23-2015 08:21 pm
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Esprit2
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Notice the front main seal housing on the left is for use with the early eccentric tensioner, and is similar to the J-H unit.

The later one on the right is for use with the semi-automatic tensioner, and with the eccentric tensioner as used on later engines.

Note that the early/ left one has a eccentric tensioner boss cast into it's top edge. I've not attempted to use an auto tensioner with that seal housing, and don't know if it will work as is; but it would be a simple cut to remove it. You have both the early seal housing and the auto tensioner, so check out the fit and let us know what you figure out.

Regards,
Tim Engel

Attachment: Front Main Seal Housing - 1974-80 907.jpg (Downloaded 153 times)

Last edited on 03-23-2015 08:45 pm by Esprit2

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 Posted: 03-23-2015 10:12 pm
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Jensenman
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I have a drill guide which I bought when a cylinder head bolt broke while disassembling an Isuzu Trooper V6. It was definitely accurate enough to center the bit in the broken off piece of head bolt. You'd have to remove the radiator etc for clearance but I bet it would work.

I think this one is plastic; you'd want to get a metal one.

Last edited on 03-23-2015 10:13 pm by Jensenman

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 Posted: 03-23-2015 10:27 pm
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Esprit2
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Review message #21. I've substituted a different JPEG attachment which illustrates a typical T-belt snubber (Aux Pulley location), the short spacers used with it, and the long spacers used to install the auto tensioner directly to the block. I think that's more relevant to what you're trying to do. Unfortunately, parts that old are probably no longer available from Lotus, but you might score some from Lotusbits.

Regards,
Tim Engel

Last edited on 03-23-2015 10:29 pm by Esprit2

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 Posted: 03-23-2015 10:49 pm
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Esprit2
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Illustrations end up pretty lo-res by the time they're uploaded to JHPS. You can download clearer versions from my Dropbox account, here:
https://www.dropbox.com/sh/kwl3ckub3in3wrm/AAA3CRJImDKvpslh-ySyQ_sza?dl=0

They're not large, hi-res files, but they're more legible than what shows up in a post.

Browse the Dropbox, there's some other stuff in there that you may find interesting.

Regards,
Tim Engel

Last edited on 03-23-2015 11:29 pm by Esprit2

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 Posted: 03-28-2015 06:42 am
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Barthol
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hi all

Thanks for all the help .
Esprit, that was a lot of valuable information:-)

I Decided to change the tightener, which turned out to be a real good choice. The bolt on the old one was louse , and I could rock it around in the block until i could just pull it out. Guess this was a late save .
There was some kind of thread insert but it had no threads left :-(

BR
'Kim

Attachment: JH bolt.jpg (Downloaded 132 times)

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 Posted: 03-28-2015 05:04 pm
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Barthol
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Hi,

I have taken off the head ( engine out )and looking into the cylinders there is a big clearence between the cylinder and the piston.
With the pistons in the middle of the bore i can actually move it from side to side ( inlet to exh) Using a dealer gauge shows me a clearance of 0,75 mm between the liner and the piston again with the piston in the middle of the stroke.
I insert the gauge from the top and guess that i can reach down to the top piston ring.
Is this the right way to measure the clearence between piston and liner?
Looking in the manual it looks like the clearance is supposed to be between 0.0965 to 0,1219 mm.

as previous I still measured compression of 190 psi whichh puzzles me , if the clearence is this big.

Any Ideas ( It all started with a lot of blue smoke under acceleration, - however the engine performed very well)

Br
Kim

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 Posted: 03-29-2015 11:11 pm
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Esprit2
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Barthol wrote:
(Snip)... Using a dealer gauge shows me a clearance of 0,75 mm between the liner and the piston again with the piston in the middle of the stroke.
I insert the gauge from the top and guess that i can reach down to the top piston ring.
Is this the right way to measure the clearence between piston and liner?
Looking in the manual it looks like the clearance is supposed to be between 0.0965 to 0,1219 mm.

as previous I still measured compression of 190 psi which puzzles me , if the clearence is this big.

Any Ideas ( It all started with a lot of blue smoke under acceleration, - however the engine performed very well
Kim,

The rings provide the compression seal, not the piston clearances with the liner. Excessive clearance will result in piston 'slap', which will result in excessive wear, and which can be heard.

The piston is not a straight-sided cylinder, rather it has a slight taper (smaller at the top, larger at the bottom). As a result, the diameter must be measured at a specified position:

Iron Liner ID -
Grade A = 95.275 - 95.288 mm (3.7510 - 3.7515") J-H
Grade B = 95.288 - 95.308 mm (3.7515 - 3.7520")
Bore diameter is measured using a bore gauge, or T-pins and a micrometer, across the thrust axis, at
50mm down from top edge.

Piston OD -
Grade A = 95.1662 - 95.1789 mm (3.7467 - 3.7472")
Grade B = 95.1789 - 95.1916 mm (3.7472 / 3.7477")
Piston Diameter is measured with a micrometer, 90° to wrist pin,
15.0876 mm (0.594") up from skirt's bottom edge.

Take both measurements above, then subtract to determine the clearance.

Piston/ Liner Clearance = 0.0965 - 0.1219 mm (0.0038 - 0.0048") J-H.
..................................... 0.1016 - 0.1270 mm (0.004 - 0.005") Lotus.
Same pistons, different corporate specs (Lotus rounded up the inch dimension).

The 'observed' clearance at the top of the piston will be larger, as you have noted.

Last edited on 03-30-2015 08:13 pm by Esprit2

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 Posted: 04-05-2015 09:15 am
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Barthol
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Hi again,

Just measured my valve stems and the "side to side " movement of the valve at 10 mm open ( using a dial gauge ) I then recalculated the Measurement to STEM / GUIDE clearences

I got the below tolerances measured in 1/100 mm and they all looks to be more than double of the max allowed 4,5 1/100 mm

Will this be the reason of my engine burning oil and covering my surroundings in blue smoke during acceleration?

When I send it out for reconditioning should I then go for the smallest possible tolerance between the guide and stem ?


inlet EXH
valve stem tolerence kalk tolerence stem tolerence kalk tolerence
1 7,130 11,000 4,890 7,100 25,000 11,113
2 7,130 40,000 17,780 7,105 22,000 9,779
3 7,135 20,000 8,890 7,130 25,000 11,113
4 7,125 20,000 8,890 7,100 22,000 9,779
5 7,135 10,000 4,445 7,110 30,000 13,335
6 7,135 25,000 11,113 7,130 20,000 8,890
7 7,135 20,000 8,890 7,125 27,000 12,002
8 7,130 28,000 12,446 7,110 26,000 11,557




stem dia 7,137 stem in mm
play min 0,800 clearense in 1/100 mm
play max 4,000

tolerence measured by checking wobble at 10 mm open then recalculted to stem



BR
Kim

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 Posted: 04-06-2015 04:02 am
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Esprit2
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Barthol wrote:
(Snip)... I got the below tolerances measured in 1/100 mm and they all looks to be more than double of the max allowed 4,5 1/100 mm

Will this be the reason of my engine burning oil and covering my surroundings in blue smoke during acceleration?

When I send it out for reconditioning should I then go for the smallest possible tolerance between the guide and stem ?
Kim,

Sorry, but I didn't follow everything you wrote; however "more than double of the max allowed 4,5 1/100mm" is a pretty clear statement.

If your current valve stem to guide clearances are twice the max allowed, then yes that could explain why the engine is burning oil.

And yes, when you have the valve guides re-done, shoot for the minimum side of the tolearance range. The clearances will tend to open up with wear, so new guide clearances should be closer to the minimum in order to optimise the service life before the clearances exceed the maximum limit again.

Here are the valve stem clearance specs:

Valve Stem Outsid Diameter - Intake & Exhaust
7.125-7.137mm (0.2805-0.2810")

Valve Stem Clearance in Guide - Intake & Exhaust
0.008-0.046mm (0.0003-0.0018")

Valve Guide Inside Diameter - Intake & Exhaust
(ream to size 'after' fitting into the head)
7.145-7.170mm (0.2813-0.2823")

Valve Guide Length - Intake & Exhaust
53.34mm (2.100")

Regards,
Tim Engel

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 Posted: 04-25-2015 01:58 pm
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Jensenman
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Valve stem excessive clearance will cause serious smoke this way: on deceleration in gear the throttles are closed which increases manifold vacuum. If there's any excess clearance at the valve stem, oil will get sucked between the stem and the guide. When the throttle is opened again, blue smoke.

On cast iron valve guides, the clearances need to be as close to minimum as possible. Bronze guides will need a bit more because they are prone to seizing. Since the 907 has cast iron guides and doesn't use valve stem seals in the first place, as Tim Engel says the stem to guide clearance should be minimal.

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 Posted: 04-25-2015 02:45 pm
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Barthol
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Hi

If I run the car at a constant speed of 50 MPH there is no smoke.
Then If I floor it the car accelerates but sth blue smoke is a lot ( really a lot)
and it continues as long as I run with full throttle.
On the overrun with closed throttle there is no smoke.
I have come to the conclussion that it must be related to at least the oil rings, maybe even the liner/piston clearence which is at max on 3 cylinders .

As new pistons is quite expensive I will tru changing the piston rings and the oil scraper ring ( being very carefull to achieve the minimum ring end gap.
If that does not help I will unfortunately be looking on a 7-800 GBP repair. new pistons/liners and rings:-(

BR
Kim

Last edited on 04-25-2015 02:45 pm by Barthol

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 Posted: 04-25-2015 04:52 pm
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Esprit2
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Kim,
'What you describe' indicates the rings are the cause of your smoke problem.

If you disassemble the engine again, then take advantage of the opportunity to check everything, including the valve stem to guide clearances. Removing and rebuilding the engine is too much work to do it over and over, always going in with your blinders on and looking for just one thing. If you open the engine, then check everything.

Last edited on 04-25-2015 04:59 pm by Esprit2

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 Posted: 04-25-2015 05:12 pm
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Esprit2
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The rings should not be gapped to a 'minimum', and there's such a thing as too tight. Each type of ring will have a specified gap 'range', so follow the manufacturer's instructions and make certain the gaps are within that range.

The engine is 40+ years old, so it's likely the rings you get from a J-H or Lotus specialist will be aftermarket alternatives, and not factory OEM rings. 'IF'the rings are anything other than factory OEM, then ignore the J-H manual and follow the installation instructions that come with the rings with regards to gap, side clearances, and ring orientation.

Check the piston to liner clearance.

The bore should have a pronounced 45 degree cross-hatch. The rings depend upon a good cross-hatch to wear-in and seal against the liner. If the cross-hatch is original and worn smooth, then the rings may take 'forever' to bed-in.

Don't use synthetic oil in a freshly rebuilt engine. It's too slippery, and it will inhibit the rings' ability to bed-in. Use a mineral oil during the break-in period, then (if you wish) switch to a synthetic at a later date.

Last edited on 04-25-2015 07:02 pm by Esprit2

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 Posted: 04-26-2015 05:50 am
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Barthol
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I have opened the engine, and unfortunately the piston to liner clearence is app 0,2 mm which according to the manual is to much.
The liners still have the Honing marks( guess that the guy I bought it from did that)
I defenitely meassures to big a ring gap at the moment , but new rings will as you say be gapped according to the spec received with the rings.
I am reluctant to replace the piston / liners as this is very expensive :-(
How important for the sealing is the Piston to liner wear? Is it not the rings which are doing the sealing ( scraping down the oil.?
Any idea on where to get the pistons if I have to buy new ones, and what types.?


BR
kim

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 Posted: 04-26-2015 05:24 pm
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Esprit2
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Barthol,

The liner bore is to be measured at 50mm down from top, across the thrust axis
Grade A = 3.7510 - 3.7515" (95.275 - 95.288 mm)
Grade B = 3.7515 - 3.7520" (95.288 - 95.308 mm)

The piston diameter is measured 15.0876 mm (.594") up from skirt's bottom edge, and 90° to the wrist pin bore:
Grade A = 3.7467 / 3.7472" (95.1662 - 95.1789 mm)
Grade B = 3.7472 / 3.7477" (95.1789 - 95.1916 mm)

Piston/ liner clearance is obtained by subtracting the piston OD from the liner ID:
Clearance = 0.004 / 0.005" (0.10 / 0.13 mm)

You report your clearance is 0.00787" (0.2 mm), which is too much.

*~*~*
The rings' proper fit is primarily responsible for the compression and oil seal; and the piston/ liner clearances has little to do with that. However, the piston can't be allowed too much room to flop around, or it will result in piston slap and excessive wear to the piston & liner.

Both proper ring fit and piston/ liner clearance are important, each for different reasons. It's not okay to discount the piston's loose fit because your first concern is ring sealing and stopping the excessive smoking due to oil getting past the rings.

I suspect (just guessing) the liners were worn and the previous owner honed them enough to clean up the surface and produce a good cross-hatch pattern; but in the process the liner ID ended up oversize.

What are the dimensions you measured for the piston ODs and liner IDs ?

*~*~*
OEM pistons & liners are no longer available from the factory, either Jensen or Lotus. Your only hopes for 'original' is to find a dealer/ specialist who is sitting on a set of NOS parts, or to buy good used liners.

However, if the liners are worn oversize, they don't have to be replaced. Instead, purchase oversized pistons, and have the liners bored as required to produce the specified clearance fit.

JE Pistons makes nice forged pistons for the 907 that are superior to the original cast pistons. They come with new rings and wrist pins, and can be ordered in several oversize diameters and several compression ratios.

Pistons and liners should be match machined. Don't just order pistons 0.0315" (0.8 mm) oversize from one source, and have the liners bored oversize the same amount by a local shop, and expect the clearance to turn out correctly. At a minimum, order the pistons first. Then take both the pistons and the liners to a machine shop hand have them bore the liners as required to produce the correct clearance fit. Each piston and liner pair becomes a matched set with their clearance near the minimum end of the specified range (above).

If you order JE Pistons from JAE in California, USA, then they work with a machine shop near them. Order oversize pistons, and ship you're old liners to them. They will bore the liners to fit the new pistons. For an additional fee, they will also gap the rings to fit. You receive matched piston, rings and liner sets that are ready to install. On your side of the pond, I 'presume' Garry Kemp in the UK provides a similar service.

Targeting piston/ liner clearance at the minimum end of the specified range give the greatest allowance for future liner wear. If the clearance ends up at the top of the range, then very little liner wear will be required to result in the clearance going out of spec too large.

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 Posted: 04-26-2015 05:56 pm
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Barthol
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Hi Esprit,

I measured the liners to be between 95,28- 95,32
pistons are measured to be between 95,10 - 95,13

as you can see the best clearance i have is 0,18 mm and the worst is 0,22mm

I guess that there is no way around new pistons?
the price of having the cylinders bored is easily 50GBP a pcs, so I guess that new liners is not much more expensive..

I think I will give Gerry Kemp a ring :-)

BR
Kim

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 Posted: 04-26-2015 06:20 pm
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Esprit2
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New liners need to be fitted to the block as required to produce the correct 'nip'... the liner's exposure above the block deck. At the factory, they had a large number of liners available, and selectively fitted liners to each block to get the nip right. If you order new liners, you might get lucky, or you might not. If the new liner's nip isn't right then you'll have to lap it into the block, or replace it.

If you're current liners fit the block correctly, it's my humble opinion that boring them to fit the new, oversize pistons is easier. But that's just me.

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