Rebuilding Lotus 907 Engine

I've recently acquired a Jensen-Healey with a very smokey Lotus 907 engine in it. Seems to run fine but for that problem (and a bad miss when cold, due to oil fouled plugs). The exhaust pipe is full of soot and hard acceleration leaves a cloud worthy of James Bond making a getaway....

I also got a later engine from an Elite. I plan on stripping it down, rebuilding it over the next couple months and then give the J-H a big Christmas present. I'd planned on not doing the engine til next Fall, but it smokes so, so badly that I don't think it will pass inspection due next April and be allowed on the roads.

The Jensen-Healey Preservation Society has what I think is a pretty good overview of rebuilding these engines and some of the go-faster improvements, but...

What books or printed sources are there for rebuilding these engines?

What are the best or useful public or free sites with useful information?

TIA

There are no independently published workshop manuals for Jensen-Healey or Lotus... like Haynes' or Chilton's. There are unauthorized copies and scans floating around on eBay and such, but they're just copies and nothing new.

The Jensen-Healey's 907 evolved over the years and there were significant changes. Like rope seals Vs lip seals and a completely different way of mounting the oil pick-up in the block.

The Jensen-Healey manual covers those early Jensen-only versions, but the Lotus manuals don't mention them. On the other hand, all the 907 manuals seemed to be works in progress with additional information all the time. So a later Lotus manual would be a good thing to have just because they're more complete. However, Lotus manuals are pretty pricey and only the Engine and Technical Data sections would apply, so not very economical. Maybe it's time to get friendly with a Lotus owner near you.

The 1983-87 Esprit Turbo & S3 Service Notes (aka, workshop manual) had a Technical Data Section TDA that back filled a lot of data about the natrually aspirated 907 & 912 engines that never appeared in earlier manuals. As such, it's a helpful supplement for any 907 owner. Contact me offline and I can help you put your hands on one.

The JHPS is a great resource for J-H owners and you should get to know them. They do have some sources for parts that are interesting and a good pool of knowledge. However, I don't agree with everything that they preach. Listen there, but keep an open mind and get an alternate view point before drawing your own conclusions. Especially when it comes to non-standard performance tuning.

Try subscribing to some of the Lotus mailing lists on YahooGroups. Especially the early naturally aspirated Esprit Group. Just go there and do a search for S1S2S3Owners. Then browse the "Files" section and hangout for a while. You will find a lot of technical knowledge there that will apply directly to your 907 (you may have to ask).

Are you thinking of a straight OEM rebuild, or do you intend to hotrod it a bit? If the latter, then the best thing you can do to a 2.0 liter 907 is stroke it to 2.2 liters. That doesn't sound like much, but it makes a huge difference in torque. And the 907 is such a torqueless wonder that any help is appreciated.

Regards,
Tim

The "Shop Manual" I have here is likely an early one, has VERY little on body/chassis, not much more with regard to the engine. Compared with what we're used to (ie: Bentley, factory Lotus manuals, etc.) as "shop Manuals" it is a disappointment.

Tim's right: Suss out the Lotus guys' sites/forums and hope there's a good knowledge base and some well heeled owners.

What block does the 907 use?

It was an "in-house" designed Lotus block. Alloy 'n liner'd. For the Esprit, and used in the J-H... Before the Esprit was released.

Didn't they also use them in the wedge shaped front engine cars (eclat, elite) also?

Yup. It was a "leaner". Bit lower profile for stuffin' it into an engine bay with a lower height.

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Yup. It was a "leaner". Bit lower profile for stuffin' it into an engine bay with a lower height.

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Still stripping the spare engine down...

What it looks like.

From the front, with the pan flat:


From the top, showing the wet liners:



and the head:



More "goodies" to follow in due course... I hope.

Still trying to figure out the distributor.... /ubbthreads/images/graemlins/confused.gif

Front two holes look a lot cleaner than the back two, James.

Head's a three piece affair. I've a 907 here as a planter. /ubbthreads/images/graemlins/devilgrin.gif

I did save the cam troughs and bump-sticks.

I didn't realize they leaned "that much", but under a turbo, I know they are legendary. I also know that if you overtorque the head bolts, it will skew the head, and help the headgasket to blow (and cause other problems).

Alloy blocks with wet liners are "tetchy" about that kinda thing... and you HAVE one of those. When you start it on a COLD morning, don't even THINK about throttle app until the temp gauge comes off'n th' peg. You'll be buyin' head gaskets by the six-pack.

...just a word in yer ear.

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Front two holes look a lot cleaner than the back two, James.
/ubbthreads/images/graemlins/devilgrin.gif

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Is this a common problem? This is my spare that I'm stripping down. The one in it badly fouls the rear plug. That's 2 out of 2.... /ubbthreads/images/graemlins/frown.gif

Accumulating bits, will post photos in due course.

Excel (Toyota type 58) 5 speed tranny and bell housing, should help a lot with motorways and driving at speed (.78 top vs 1:1) and I should be getting the lighter steel Esprit flywheel to go with it....

I've acquired a 2.2 crank & bearings (the bearings cost as much as the crank!) and will be getting high compression pistons and a later model head....

Am I having fun! I think....

Only problem I see is the DPO had the carbs set wrong.

The reason I have a 4-pot planter is I bought it for the five speed gearbox attached to it. For the +2... "project pending".

Some eye-candy for ya:


An Esprit conversion, but it'd work on yours too! /ubbthreads/images/graemlins/wink.gif

Now thats a clean engine. Im about to put a 907 with eclat gearbox into an AH Sprite project. Anyone out there ever done this? It looks like it should fit OK. Next few weeks will tell

HOLY COW Neil!!! What are ya plannin' to use as a diff? And for tyres?!?!

A friend shoe-horned a Buick (Rover) V-8 into a Frogeye back in the mid-70's: shortened the axle tubes from a GM car (details are hazy... it was a LOOONG time ago). It would literally SPIN itself around like a top if you weren't careful. Really a handful to drive. A 907 would be a ~bit~ more tractable but still a BEAST. Keep us up on this li'l project, will ya?!

Jensen Healey rear axle is planned (same stud pattern and not much wider) A friend here until recently had a rover V8 with a narrowed jag back end in his frogeye. Hes just gone back to 1275 power funny enough

More valuable as a 1275 than a BUICK, I suspect.

Certainly easier to drive. /ubbthreads/images/graemlins/grin.gif