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| Joined: | 05-01-2005 |
| Location: | Minneapolis, Minnesota USA |
| Posts: | 575 |
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When Lotus first stroked the 907 to 2.2 Litres, it picked up a roughness that hadn't been present with the short-stroke 2.0. That's not unusual... large displacement 4-cylinders to tend to shake a bit. Lotus tried a number of things to minimize the roughness/ vibration. Then, for what remaind after all they could do in the engine, they took two more steps.
1) The 4-seat models used a flex-plate instead of a flywheel. The same basic thing that's commonly used with automatic transmissions. The thin plate has enough flex in it to absorb much of the vibration that made it to the back end of the crank. The Esprits continued with conventional flywheels.
2) Lotus found that bolting the bottom of the clutch housing to the back/ bottom of the sump 'rigidized' the combined lump, significantly reducing vibration.
If you do go forward with installing a 910-based engine, it's stock sump will have two horizontal drilled-n-tapped holes in the rear face, but no J-H clutch housing will have matching bolt holes.
However, if you also upgrade to the Toyota W58 5-spd, and use the Lotus Excel's mating clutch housing, it will have the mating bolt holes required to make it all work.
Do you need this. No. There are a bunch of Jensen-Healeys with 2.2 Litre converted 907s, and you don't generally hear the owners complaining. But, "IF" you would appreciate a smoother running engine, then one small step in that direction is to use an Excel clutch housing with your W58 5-Spd.
Then, to shim the gap to zero, Lotus has two shim washers. One is a solid 0.020" thick washer (A911E1430F), and the other is a laminated brass (A082F6358F) with which you can peal off plies as required to achieve the correct shim thickness.
If you're going to 2.2 for low end torque and civilized traffic manners, then go all the way and use the Excel's crank (it's not cross-drilled) and flex-plate.
If you're going for maximum performance, then use the Esprit's, or Excel SE's cross-drilled crank, and regular flywheel.
Then balance everything that moves on an obcessive-compulsive scale.
Regards,
Tim Engel
Attachment: 00000008e - Bell Hsg & Sump Bolted Together - 97kb.jpg (Downloaded 142 times)
Last edited on 09-23-2019 09:12 pm by Esprit2