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Jensen Healey into Lotus Esprit?


Monkeybooze

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Hello!,

General technical question about modifications needed to a 2.0L Jensen engine (907) '72 vintage I aquired quite cheap into an '84 S3 2.2 (is this a 910?). I've disassembled everything in the 907 and things look excellent. It looks as though the engine was rebuilt with a new crank pistons/liners/cams e.t.c then ran without oil changes. It looks like it had terminal head gasket failure and slightly worn big end bearings (the remaining oil in the sump was like treacle). There are no signs of scoring at all on any of the bore surfaces.

I'm probably barking up the wrong tree but I understand it is possible to convert to a 2.2 with the lotus crank. The days are numbered on my own S3 (oil in the water) so I'm preparing for the worst.

The only thing I can find is that piston 4 has a bit of a "dink" in it's skirt that either I did upon dissassembly or some wally did when then put it back together. Can I iron this out somehow?

The Jensen brigade offer a 2.2 conversion kit, and the pistons over there in the US are excellent value for money ($5-600 for a full forged set). Think it is an Australian sourced kit for Holdens and the like that needs mods to the main end bearings.

I'm a bit of a noob to the Lotus fraternity, but the engine is just too good to bin it. What should I do?

Thanks,

Paul

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Paul

A 910 is a Turbo motor (unsuitable for NA conversion as compression too low)

I believe a 912 is a 2.2 N/A motor.

Wouldn't recommend the expense & uncertainty of converting the Jenson motor - e.g. what spec cams does it have, is the sump compatible etc?

I'd sell it to a Jenson enthusiast and find yourself a genuine 2.2 (they come up regularly on ebay) - but where is your original motor?

cheers Steve

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You could do it, but as mentioned, the sump would be wrong, the crank and cams would need swapping for the 912 ones, The water pump has its outlet the wrong way, as does the cylinder head (latter can be converted). The origianl 907 and the later 912 are generally the same but the 912 was an upgraded block and sump arrangement to facilitate component sharing with the turbo engine (910) which went wet sump as soon as the later block was available as the earlier ones twisted due to the increased power.

In effect you'd have to swap most of the components from the 912 to the 907 block to make it work, so I'd say you may as well just re-build the 912. At least then it's still the original engine / at least a 912.

Andy

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Attached a few piccies.

The current 912 is in the Esprit at the moment, the car runs fair and is strong under load as ever albeit my worry about the appearence of oil in the water bottle. The engine has alot of piston slap when first started. The usual 4 accelerator pumps and turn-key sometimes results in the engine running for 4-5 seconds (it starts immediately) and then stalling when started from cold. The choke is useless and usually causes more trouble. I think it could be electrical as I have hooked up a time light and there is a missfire on all cylinders that seems to be intermittent at idle. - Distributor rotor arm is pretty wobbly when toggled - so is this normal or is it the bearings in the distributor causing this? My 907 comes with a good condition distributor, a different model, but could it be used? The cap is egg-shaped, a lucas 23 D4.

I'm not sure about the Jensen's engines history and need to identify if it is stock or not. The crank looks plenty big enough in the block and you would be hard pushed to see any more throw without the con-rods hitting the sides? Could it be a 2.2 already? Is there a quick way to identify it?

The sump is a very heavy item - see picture. Might be of interest for others on the site.

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if you have oil in water and the engine still runs ok, you have a headgastget issue... much less work to change that than try and put a worse engine in... at best the jensen engines are 150bhp... and notorisly fragile if it is from an s1 healey...

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The engine was from a '72, which means it's from a mk1 Jensen Healey. I believe it is possible to put a 2.2 crank in it, but those engines where really prototypes (or a 0-series). The engines used in the later mk2s is essentially the same engine as in the S1 Esprit, though with a different sump, and 8.4 compression and Strombergs if it was sold in the States.

I'd go for a rebuild of the S3 engine.

Edit: For checking what crank is in it, use a stick through the plug hole to check the stroke. 69mm is a 2.0, 77mm is a 2.2.

--

Joachim

Edited by SubWoofer
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