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19064 - autocross project car for SCCA's FSP class  Rating:  Rating
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 Posted: 11-06-2015 11:48 pm
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stevegarnjobst
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I recently purchased Jensen Healey #19064, a yellow 1974 JH5, with the intent to campaign the car in the SCCA's F Street Prepared autocross class. The SCCA is re-classing the J-H for the 2016 season, moving it from a class where it's been totally uncompetitive for many years, into a class where it should be a good match for the top vehicles.

SCCA's Street Prepared (SP) allows extensive suspension and wheel/tire options, but permits only limited bolt-on engine upgrades, and most interior and bodywork parts must stay intact. SP rules do include a provision for update/backdate across model years, so parts from the entire production run of the J-H may be utilized. This allowance will be particularly useful in removing excess weight from the car, as I already have a set of lighter Series 1 bumpers sitting in the garage, waiting to replace the ridiculously heavy Series 2 bumpers now on my car.

Based on the unique aspects of the SP rules, I'm planning an upgrade path that should be a bit outside the norm for J-H's. I plan to document the build, and share any unique parts developed with the J-H owner community.

-Steve

Attachment: 00B0B_2lY1Ky9t1nh_600x450.jpg (Downloaded 169 times)

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 Posted: 11-06-2015 11:58 pm
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stevegarnjobst
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So a bit more about the car I'm starting with.

It's a very mechanically sound vehicle that received what appears to be a relatively competent amateur body-off restoration about 8 years ago. It isn't a show car, but appears rust-free and relatively free of issues at this point.

The car appears almost totally stock, with the exception of some Spax shocks and a replacement fuel pump. Note: the engine was replaced with an identical unit from another low-mileage J-H that was parted out, due to bodywork issues.

Although SP permits some modifications that permanently change the vehicle (fender cutouts/flares in particular), my goal for this build is to only make modifications that are easily reversible.

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 Posted: 11-07-2015 12:21 am
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stevegarnjobst
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Preliminary list of planned modifications:

Basic retrofit/removal
retrofit Series 1 bumpers
remove vapor control system
remove spare tire & bracket
remove stereo system
replace stock battery w/lightweight AGM battery (8 lbs)

Cockpit upgrades
replace stock steering wheel with Mountney leather wheel
replace stock seats with Kirkey Pro Street Drag race seats
replace stock belts with 3" lap belts

engine/drivetrain upgrades
Replace Strombergs w/EFI system (currently planning to use the LotusBits kit, featuring Jenvey throttle bodies)
Electronic ignition
Replace stock exhaust system with lightweight single pipe system, probably custom-fabricated
Header - could use input on this. Is the available 4-1 header measurably superior to the stock 4-2-1 unit? I have a perfectly serviceable 4-2-1 unit on the car now. Is it worth replacing?
Replace engine-driven fan with electric fan
limited slip differential (more to come on this after my visit to the UK later this month)
Note: no cam or other internal engine upgrades allowed in SP

Suspension upgrades
Upgraded springs (currently thinking 550 front, 250 rear)
Custom Speedway Engineering blade-adjustable swaybars
QA1 double-adjustable aluminum shocks
rear suspension conversion to 3-link with Watts link. Lots of thought going into this one. The end result could be a set of bolt-in upgrades that dramatically improves the J-H rear suspension. Still working through the details, though.

brake upgrades
lightweight disc brakes front and rear (HiSpec Motorsport)

wheel/tire upgrades
255/40-13 Hoosier A7's on 13" x 10" wheels

That's the basic plan. I look forward to sharing my progress throughout the Winter, and am sure I'll be asking for guidance as I deal with the challenges of upgrading a 40 year old British car.

Last edited on 11-07-2015 12:26 am by stevegarnjobst

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 Posted: 11-07-2015 06:29 am
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Tim Murphy
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Duplicate post.

Last edited on 11-07-2015 06:33 am by Tim Murphy

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 Posted: 11-07-2015 06:32 am
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Tim Murphy
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Can you remove the convertible top and the frame? The frame is steel and very heavy. I think the gas tank needs to be addressed. Changing to EFI seems like a long, involved project. Maybe do that later. I would run it close to stock and schedule your mods and upgrades based on those runs. Try to keep your car street and track ready as you do your upgrades. A common mistake made by inexperienced amateurs like me is taking everything apart then never getting it all together again.

Last edited on 11-07-2015 06:37 am by Tim Murphy

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 Posted: 11-07-2015 08:36 am
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stevegarnjobst
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Tim Murphy wrote:
Can you remove the convertible top and the frame? The frame is steel and very heavy. I think the gas tank needs to be addressed. Changing to EFI seems like a long, involved project. Maybe do that later. I would run it close to stock and schedule your mods and upgrades based on those runs. Try to keep your car street and track ready as you do your upgrades. A common mistake made by inexperienced amateurs like me is taking everything apart then never getting it all together again.

Tim,

Building a car to limited prep race rules like those in SCCA Street Prepared can sometimes be an odd process. Often the allowances seem to offer very wide latitude in some areas, but very little flexibility in others. For instance, while the rules offer a great deal of flexibility to re-engineer a fixed axle rear suspension, I must retain the stock soft top and stock fuel tank.

In the case of the soft top, the only way I could remove it would be if Jensen at some point provided written documentation indicating the soft top could be removed from the car as an option for normal use. If anyone has a copy of any such directive from Jensen, PLEASE send it my way!

For the fuel tank, the only way I could replace it is by meeting more restrictive safety rules, which would mean adding a roll bar for an open vehicle. That would add more weight than I can remove with a fuel cell, so the stock tank stays.

The EFI may not happen for the car's first season - it all depends on how smoothly the suspension upgrades go. The Watts link, in particular, may be a little tricky, as I have limited space for the mounting brackets, and will have to re-route the exhaust and a few other minor items.

As for keeping the car drivable, this isn't my first build of this type, so I'm pretty used to a phased upgrade process. This particular build is also relatively mild, compared to some of my past vehicles, as it will remain street legal and fully capable of being driven to local events. For reference, I have attached a photo of my old Miata race car. Definitely NOT street legal, it weighed 1,760 lbs and made over 300whp. Fun car, but expensive to keep running.

-Steve

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 Posted: 11-07-2015 08:47 am
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stevegarnjobst
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Note - I typically keep pretty close tabs on weight reduction efforts. I have a set of corner-weight scales sitting in my garage, so I can easily verify the impact of any change.

The baseline starting weight for the car is 2,432 lbs, which includes a full tank of fuel and the spare tire. I have a long way to go, in order to reach my target weight of 2,100 lbs.

First reductions:
remove spare tire & bracket -35.2 lbs
lightweight battery -26.7 lbs

Last edited on 11-07-2015 08:48 am by stevegarnjobst

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 Posted: 11-08-2015 03:38 am
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Tim Murphy
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Steve, thanks for the reply. You obviously have a lot of experience building race cars and I none. I was just sharing thoughts that came to mind when I read your post. I am glad to see a JH being modified and improved by someone with experience. Thanks for your plan on documenting and sharing your build.

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 Posted: 11-08-2015 11:15 am
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stevegarnjobst
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Tim Murphy wrote:
Steve, thanks for the reply. You obviously have a lot of experience building race cars and I none. I was just sharing thoughts that came to mind when I read your post. I am glad to see a JH being modified and improved by someone with experience. Thanks for your plan on documenting and sharing your build.
I welcome all suggestions & comments. While I've been wrenching on cars for a while, the J-H is a new experience for me. While the cars generally seem pretty simple & straightforward, I'm already discovering a few of those wonderful idiosyncrasies British car designers seem particularly adept at. For example, I spent over an hour yesterday replacing a fuel tank vent line - a task that should have take a few minutes, save for the idiotic location of the fitting on the fuel tank.

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 Posted: 11-09-2015 12:41 am
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Tim Murphy
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I don't know the rules, but those large, molded, rubber front floor mats are heavy. Replacing those with some carpet mats purchased at an auto parts store will save around 10, 15 pounds by my guess.

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 Posted: 11-09-2015 02:46 am
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stevegarnjobst
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Tim Murphy wrote:
I don't know the rules, but those large, molded, rubber front floor mats are heavy. Replacing those with some carpet mats purchased at an auto parts store will save around 10, 15 pounds by my guess.

Interesting you should mention those mats. I was staring at them today, thinking about how heavy they probably are.
It's allowable to remove the mats - in fact, they are typically supposed to come out if not securely fastened. I probably need to put something down on the floor to provide a bit of traction, but that will be a lot lighter than the mats. In my Miata, I coated the floors with truck bed liner paint, which provides a very durable, high traction surface. Not 100% sure I want to use that stuff on the J-H, as it's pretty difficult to remove later, but you have me thinking...

Last edited on 11-09-2015 02:47 am by stevegarnjobst

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 Posted: 11-09-2015 06:44 am
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Tim Murphy
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The mats are heavy. If you went with truck bed liner paint I don't think you would have to remove it later, JH floors are notorious for rusting, water leaks in thur the air vent in front of the windshield when the car is washed or caught in the rain. So most floors have had some anti rust treatment and look bad. Just cover with carpet or mats for everyday use if necessary.

In the interest of safety I want to point out Ron Earl's post about a failure of his drive shaft or U joints while racing: http://www.jensenhealey.com/forums/view_topic.php?id=786&forum_id=10&page=1

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 Posted: 11-09-2015 10:22 am
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subwoofer
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Would you be allowed to replace the bumpers with the early type? Should save a quite few tens of pounds right there, the rubber bumpers are heavy. I can't remember where I heard it, but the pair weighs in at around 110 pounds?

Changing over to EFI shouldn't be too much work, especially with Mike's pieces. But expect a trip to a (steady state) dyno to make the most of it.

Are you allowed to increase the compression ratio? The JH desperately needs at least one more point of compression, preferably two or more.

--
Joachim

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 Posted: 11-09-2015 11:11 am
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stevegarnjobst
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subwoofer wrote:
Would you be allowed to replace the bumpers with the early type? Should save a quite few tens of pounds right there, the rubber bumpers are heavy. I can't remember where I heard it, but the pair weighs in at around 110 pounds?

Changing over to EFI shouldn't be too much work, especially with Mike's pieces. But expect a trip to a (steady state) dyno to make the most of it.

Are you allowed to increase the compression ratio? The JH desperately needs at least one more point of compression, preferably two or more.

--
Joachim


I already have a set of Mark 1 bumpers sitting in the garage, waiting for a trip to the powdercoat shop. The set only weighs 29.4 lbs, including the brackets. I haven't pulled the rubber bumpers off yet, but don't doubt the 110lb figure, as those things are HUGE.

Unfortunately, high compression pistons and/or cam upgrades aren't allowed. So power upgrades will be limited. Going with EFI should at least help keep the power more consistent and predictable. I have a very meticulous tuner I've worked with for years who can optimize the tune for me. I assume this will take a bit of work, as Mike's base maps likely assume some of the upgrades I'm not allowed.

Last edited on 11-09-2015 11:20 am by stevegarnjobst

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 Posted: 11-09-2015 11:20 am
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stevegarnjobst
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Tim Murphy wrote:
In the interest of safety I want to point out Ron Earl's post about a failure of his drive shaft or U joints while racing: http://www.jensenhealey.com/forums/view_topic.php?id=786&forum_id=10&page=1
That's scary. Drivetrain safety measures, such as SFI bellhousings, tranny blankets & driveshaft hoops aren't required for my prep level, but installing a hoop may be a good minimum safety measure.

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 Posted: 11-09-2015 12:29 pm
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subwoofer
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stevegarnjobst wrote:
Unfortunately, high compression pistons and/or cam upgrades aren't allowed. So power upgrades will be limited. Going with EFI should at least help keep the power more consistent and predictable. I have a very meticulous tuner I've worked with for years who can optimize the tune for me. I assume this will take a bit of work, as Mike's base maps likely assume some of the upgrades I'm not allowed.

Are you allowed to touch the head? Just cleaning up the bowls of the ports and radius grinding the seats should make the head flow better, and pulling the cams together a bit will add overlap and move the torque a bit upwards in RPM, if you balance it so it will take the extra RPM.

But: personally I would never go racing in a car without even a roll bar, a 6-point cage is really the minimum. Are you serious that you can race with the stock windscreen and nothing else?

--
Joachim

Last edited on 11-09-2015 12:30 pm by subwoofer

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 Posted: 11-09-2015 12:48 pm
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stevegarnjobst
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subwoofer wrote:
Are you allowed to touch the head? Just cleaning up the bowls of the ports and radius grinding the seats should make the head flow better, and pulling the cams together a bit will add overlap and move the torque a bit upwards in RPM, if you balance it so it will take the extra RPM.

But: personally I would never go racing in a car without even a roll bar, a 6-point cage is really the minimum. Are you serious that you can race with the stock windscreen and nothing else?

--
Joachim

No head porting allowed. I can do intake & exhaust port matching up to 1" deep, which is apparently of some help on these engines. I'm hoping to make it through the first season without tearing the engine down, as I have plenty of suspension sorting to accomplish before more power will become a priority. Since I'm not allowed to change the stock valve springs or connecting rods, I was assuming a higher rev limit wouldn't be advisable. However, if I can safely get a few hundred extra revs with a balanced, but otherwise internally stock 907, that could be useful. Even if the power is falling off, avoiding extra shifts can be valuable in autocross.

No roll bar required for the low speed autocross events the car will primarily be used for. It's also a street-legal vehicle, so I would be concerned about street safety with a roll bar, as they're typically not safe to use without a helmet - especially in a smaller vehicle, where your head is so close to the bars. If I ever choose to use the car for higher speed track events, it will receive appropriate safety upgrades (roll bar, full safety harness, extinguiser, etc).

-Steve

Last edited on 11-09-2015 12:50 pm by stevegarnjobst

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 Posted: 11-18-2015 03:10 pm
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Esprit2
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Steve,

The very early 907 Mk I intake ports were 24.5 mm tall. Later, they were increased to 25.5 mm as a running change. At the time of the change, the production of the small port head ended and the large port head became the official standard service replacement. Sorry, but no, I don't know the date or engine number of the port change, but I do believe it was within the life span of the Jensen-Healey's 907 Mk II engine.

If the Update-Backdate rule would apply to that, and if your engine's ports are the small ones (minority of all 907s built), then you could have a small but real increase in port size available. The 907 responds very well to intake improvements, and the 1mm larger ports along with just port matching could pay noticeable dividends.

The J-H 907's stock C-cams were designed to run at 110 MOP, both intake and exhaust. The first test engines met then-current emissions standards, but Lotus was looking down the road at the already announced 1974 standards. The engine met those coming requirements as well, but by such a narrow margin that Lotus wasn't comfortable in terms of warranty costs relative to the engine staying in compliance with age and wear.

The cam timing was changed to 115 MOP for both intake & exhaust so the first production engines could pass the coming 1974 standards by a wider margin. However, that lowered the power by 10 Hp, and the engine became lethargic by comparison to the original 110 timing.

Later J-H engines did go to 110/110 from engine #4030, and North American engines went to 100 IN/110 EX from engine 10480. That last config, along with really lame ignition timing and lean mixture, was the weakest of the lot and lead to the "torqueless wonder" nick name.

Both 110 & 115 MOP are on the same pulleys, whether both values are marked or not. No new parts are required, it's just a matter of how the pulleys are installed. Flip the pulleys over and rotate them a few teeth, and there's the other MOP. Would that violate the rules for your class?

Set both stock cams to 110 MOP, set the static ignition timing to 12 BTDC, BALANCE the carbs, set the idle mixture for peak manifold vacuum at slow idle, and use the 25.5 mm intake ports with a port-matched manifold. That won't unleash a monster, but the engine will at least run like it's interested.

The original tappets were chilled cast iron, and 'old' ones are prone to cracking. I often find cracks the full height of the skirt, and I've had two crack in half in my hands during inspection. A tappet failure is as effective as a broken timing belt at wiping out valves. If you're going to use the engine in competition, bouncing off the rev-limiter, then I strongly recommend that you install a set of the later steel tappets.

When the steel tappets were introduced, Lotus discontinued manufacture of the cast tappets, and the steel ones became the standard service replacement. So, going steel shouldn't be a breach of the rules since you're using factory spec parts.

Cast tappets were the #1 limiter in setting the 907's rev limit. Rods were #2, but at a higher rpm.

Lotus steel tappets are expensive. Both JAE in California and Garry Kemp in the UK sell aftermarket steel tappets that are less expensive while arguably being better. Their tappets also come with optional crown thicknesses that can be used to compensate for re-ground cams, or to move the range of 'required' valve shims further up into the 'available' range. Valve recession and/or grinding the valves forces the use of thinner and thinner shims. When you get to the bottom of the range of available shims, thinner tappet crowns can move the required shim thickness back up higher into the available range.

Factory balance specs were:
Rods to within 2 grams
Crank to within 15 grams
Pistons to within 3.5 grams.

Doing better than that is pretty easy, and still meets the 'within' wording. Shot-peen the stock rods, balance, balance, balance everything from piston crowns to clutch, and you could be running at 8000 rpm with otherwise stock parts.

Regards,
Tim Engel

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 Posted: 11-18-2015 03:19 pm
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Esprit2
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The current composite cylinder head gasket's crushed thickness is 0.020" thicker than the old steel-asbestos-steel gasket's. That lifts the head 0.020" higher off the block deck, lowering the compression ratio by about half a point. 8.4:1 becomes 7.9:1. The maximum cut on the bottom of the cylinder head for truing the surface is 0.020". I'm just sayin'.

From the introduction of the new gasket onward, Lotus decked the block 0.020" lower and seated the liners another 0.020" deeper into the block to maintain the correct 'nip' (the liner's exposure above the block deck). For most owners of an older engine, that's not a very practical option. If you ever rebuild the engine, including replacing the original pistons, specify a half-point higher compression than you're really targeting.

All 907s were built with the original low-spec head studs, and they're known to stretch with sustained full throttle running (track days, motorsports, etc). Stretch leads to blown head gaskets.

The 'new' composite gasket requires the use of Lotus' later upgrade head studs (identifiable by a depressed dimple in the upper end), along with a revised, higher torque spec. The gasket's higher torque spec 'will' over-stretch the original 907 studs.

"IF" you don't replace the low-spec head studs, then stay with the original 'Lotus' torque spec out of consideration for the studs. You won't be getting the full advantage of the composite gasket, but you won't be over-stretching the studs either.

Note that the J-H head torque spec was too high, crushed the old gasket, and caused problems with blown gaskets. Lotus reduced the torque spec to a level that didn't crush the gasket, or over-stretch the studs. If you're going to stay old-school, it would be better to follow the Lotus torque spec instead of the one in the J-H Workshop Manual.

Lotus Cylinder Head Torque Spec:
(Tighten Cold, Oiled Threads & Washers)
70 Lbs-ft - Front & Rear Pairs
75 Lbs-ft - Three Middle Pairs
Work up to it in several smaller steps, working from the center outward in a criss-cross pattern.

Regards,
Tim Engel

Last edited on 11-18-2015 05:25 pm by Esprit2

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 Posted: 11-18-2015 03:28 pm
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stevegarnjobst
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Tim,

This is VERY helpful information! My J-H is a later '74 JH5, so I'm assuming it came with the larger port head. However, the engine was replaced, so I'm not 100% sure the current engine is identical to the original. I'll definitely need to verify everything.

Were all the stock tappets cast iron? If so, I'll likely need to replace them, as the engine is reportedly an un-rebuilt unit with 30K miles.

The timing changes are allowed. In fact, I can even add adjustable cam pulleys. I noticed Lotusbits has some vernier units on the shelf - might they be worth having?

By the way, do you have any recommendations for head/balance work? I've had good luck with Headwerks in the past, but I have no idea if they have experience with these engines. Is there anyone semi-local you recommend for 907 work?

-Steve

Esprit2 wrote:
Steve,

The very early 907 Mk I intake ports were 24.5 mm tall. Later, they were increased to 25.5 mm as a running change. At the time of the change, the production of the small port head ended and the large port head became the official standard service replacement. Sorry, but no, I don't know the date or engine number of the port change, but I do believe it was within the life span of the Jensen-Healey's 907 Mk II engine.

If the Update-Backdate rule would apply to that, and if your engine's ports are the small ones (minority of all 907s built), then you could have a small but real increase in port size available. The 907 responds very well to intake improvements, and the 1mm larger ports along with just port matching could pay noticeable dividends.

The J-H 907's stock C-cams were designed to run at 110 MOP, both intake and exhaust. The first test engines met then-current emissions standards, but Lotus was looking down the road at the already announced 1974 standards. The engine met those coming requirements as well, but by such a narrow margin that Lotus wasn't comfortable in terms of warranty costs relative to the engine staying in compliance with age and wear.

The cam timing was changed to 115 MOP for both intake & exhaust so the first production engines could pass the coming 1974 standards by a wider margin. However, that lowered the power by 10 Hp, and the engine became lethargic by comparison to the original 110 timing.

Later J-H engines did go to 110/110 from engine #4030, and North American engines went to 100 IN/110 EX from engine 10480. That last config, along with really lame ignition timing and lean mixture, was the weakest of the lot and lead to the "torqueless wonder" nick name.

Both 110 & 115 MOP are on the same pulleys, whether both values are marked or not. No new parts are required, it's just a matter of how the pulleys are installed. Flip the pulleys over and rotate them a few teeth, and there's the other MOP. Would that violate the rules for your class?

Set both stock cams to 110 MOP, set the static ignition timing to 12 BTDC, BALANCE the carbs, set the idle mixture for peak manifold vacuum at slow idle, and use the 25.5 mm intake ports with a port-matched manifold. That won't unleash a monster, but the engine will at least run like it's interested.

The original tappets were chilled cast iron, and 'old' ones are prone to cracking. I often find cracks the full height of the skirt, and I've had two crack in half in my hands during inspection. A tappet failure is as effective as a broken timing belt at wiping out valves. If you're going to use the engine in competition, bouncing off the rev-limiter, then I strongly recommend that you install a set of the later steel tappets.

When the steel tappets were introduced, Lotus discontinued manufacture of the cast tappets, and the steel ones became the standard service replacement. So, going steel shouldn't be a breach of the rules since you're using factory spec parts.

Cast tappets were the #1 limiter in setting the 907's rev limit. Rods were #2, but at a higher rpm.

Lotus steel tappets are expensive. Both JAE in California and Garry Kemp in the UK sell aftermarket steel tappets that are less expensive while arguably being better. Their tappets also come with optional crown thicknesses that can be used to compensate for re-ground cams, or to move the range of 'required' valve shims further up into the 'available' range. Valve recession and/or grinding the valves forces the use of thinner and thinner shims. When you get to the bottom of the range of available shims, thinner tappet crowns can move the required shim thickness back up higher into the available range.

Factory balance specs were:
Rods to within 2 grams
Crank to within 15 grams
Pistons to within 3.5 grams.

Doing better than that is pretty easy, and still meets the 'within' wording. Shot-peen the stock rods, balance, balance, balance everything from piston crowns to clutch, and you could be running at 8000 rpm with otherwise stock parts.

Regards,
Tim Engel

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