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Rebuilding/Upgrading the Engine - Advice Sought  Rating:  Rating
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 Posted: 12-13-2006 02:28 am
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James Wilson
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I've reviewed in the forum what people have done and suggested in rebuilding their engines and I'd be interested in knowing what people's views are on the bits and pieces I've accumulated to rebuild mine as a fast road car. I've acquired:

1) a cross-drilled 2.2 crank and bearings.

2) a set of 10.9:1 Mahle pistons.

3) a later, high compression head.

4) a steel flywheel (~13 lbs)

5) I'll use a later Elite 907 block instead of my early one.

6) 107 cams for both Intake and Exhaust.

to be acquired/done:

7) twin Dellorto 45s- spec 9?- have manifold already.

8) SS intake and exhaust valves

9) HTD cam belt system

10) Balancing during the rebuild.

11) Ignition- either Petronix or Electronic, haven't really made my mind up.

12) Water pump- replace/rebuild for higher output.

13) The piston rings, gaskets, oil seals, etc.

I'm basically rebuilding the engine to a Lotus 912S spec except for using 2x107 cams instead of the 104/107 combo.

Advice Please:

Will it be advisable to use a steel girdle/strengthening plate to reinforce the lower block? I've seen comments suggesting it go between the block and bearing carrier, or between the carrier and the sump. Is there a supplier for these? Materials? Thickness? Any advice/comments about the design or fabrication of one?

I'm still unsure about the 104/107 or 107/107 cam choice. Its not going to be raced, but.... I'll very probably install a full set of competition valve springs so a cam-swap wouldn't mean having to pull the head to change springs then. 

Head porting. Where to start? Where to stop? Port matching?

I've seen a number of comments about controlling the oil flow to the head, but it'd be useful for someone to basically draw me a picture showing where to constrict the oil flow.

Hardware: Head Studs/Bearing Caps/Con Rods- I think I should get these new in any case, but are better ones needed for a non-race application?

My pistons seem an odd set, three are marked "A" and one "B"- can they be mixed? I understand these designations were used to denote slightly different sizes- is this likely to cause problems (balance) or with fit?

Other: I've acquired a Lotus/Toyota W58 transmission with bellhousing and will be installing it too when the engine is done. I've a spare sub-frame for the front that will be rebuilt and the whole front suspension/engine/transmission done at the same time.

I'm still acquiring parts, and intend on seriously starting the rebuild in January.

Thanks.

James.

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 Posted: 12-13-2006 11:10 pm
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Paul Koehler
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WOW! It really looks like you have got your guano together. I as well look foward to your replies.

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 Posted: 12-13-2006 11:45 pm
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Greg Fletcher
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Yes, this will be a cool car when done. If it's a fast road car, I don't think adding a support plate to the block is the best use of resources. Some extra doweling could be desirable, but even at that I'm not sure if I'd do it to my car.

If you're on-board with an improved head and the cost of porting, I'd consider a pair of 104 cams as those will really take advantage of increased air flow. A number of owners run 104s on road cars. Uprated valve springs are a good choice on either. I'd recommend you find a good machine shop that knows Lotus heads for the porting and assembly. Remember, it's always cheaper to pay more up front to have it done once than have it redone multiple times (I can't tell you how often I've heard that happen).

A light wieght connecting rod, like Carrillos are great, go-fast bits, but figure $900 for a set. The stock ones are quite durable and just need a precision balance. On the pistons, I'd say it's important that they are a matched set and all weight exactly the same when you're ready to install.

The Pertronix Ignitor is a simple, durable and superior unit. For the money it's a big improvement. I wouldn't use anything else.

I'd add a proper, high quality 3 row radiator to go with all this. The original 2 row is a bit of a joke.

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 Posted: 12-14-2006 03:56 am
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Dan Eiland
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I can't agree more with Greg's advice. I've asked many of these questions before and I'm in the middle of doing the 2.2L update as I write this. I just came from the machine shop today and photographed my engine block and bearing carrier being modified to accept the addition of dowels to all ten bolts surrounding the main bearings. They should be finished by tomorrow. I modified the oil feed galley to the head myself and can send you photos and the information on doing this yourself. Make sure you get the crank and all the parts that mount to the crank precision balanced as Greg suggested. Well worth the expense. There are a lot of great suggestions that have been made on this forum, but in the end I decided to follow the ones by Garry Kemp and Greg. Also make sure you have the block align bored (honed). Do this after having the dowels added. You can get the dowels from Dave Bean, probably others as well. If you need information I have been storing information sent me on this update for a while and can send it to you. You can reach me at deiland1@elp.rr.com .

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 Posted: 12-14-2006 10:45 am
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Harkes
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my 2.2L engine is built by Garry Kemp and was built with torque being more important than top end HP as i'll be using the car for the road. Who wants to drive over 200 KM per hour in a 30 year old convertible?

To get a torquey and fast road car Garry chose his custom version of the 104 cam in combination with the 107 cam (104 inlet, 107 exhaust)

So it comes down to your driving style, basically. I would advise the 104/107 combo.

For the rest: the pistons do worry me a bit. If not sure, follow the safe route and get a matching set of pistons like Greg advised. Garry Kemp might have a set for you lying around (used or new) as well as cams if you need them (i have BTW 2x true 107 cams lying around)

Garry 10 dowelled my block. A strengthening bearing carrier is not really necessary, especially not for road use, Garry advised me. When you mean to drive your car on track (which i don't think you will do, since you mentioned 2 x 107 cams) and need lots of top-end HP (and therefore 2 x 104 cams)  then a bearing carrier could be wise.

I am running with the toyota supra W58 5speed gbox and Lotus Exel bellhousing (which i converted back to mechanical clutch operation..) so if you need info..

you need to source some parts from Conversion Components or JHPS for the gbox conversion. Conversion Components has made strengthening bearing plates for the 907 before. I'm not sure if he still makes them or needs a batch of 10. But in case you are going down this route, then this is a potential source.

good luck and do post lots of pictures on the JHPPG.com

Last edited on 12-14-2006 10:56 am by Harkes

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 Posted: 12-14-2006 06:34 pm
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Scott Robinson
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I believe the A or B stamps on the Mahle pistons relate to weight, not size. If you get the whole shebang balanced I don't think there is a need for abandoning what you have.

The Mahle's aren't considered quite as robust as the J&Es though. Still, may be tough to sell 3As and a B if the common perception is that they're different sizes.

Scott

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 Posted: 12-15-2006 11:57 am
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James Wilson
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I've a copy of the Workshop Manual and page 4 Has piston diameters- Grade "A" as 3.7467-3.7472 and Grade "B" as 3.7472-3.7477 and I believe that they were originally installed all from the same grade.

The differences could be as much as .001 between the "A" minimum and the "B" maximum, though the mid-points of the ranges would be 1/2 that. I suspect that it might matter, but I've never run across this before and do not know. I may have to phone a local machine shop and ask them. I intend to have the pistons thoroughly checked and balanced in any case so the weights should be virtually identical- but what about the fit to the bores....

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 Posted: 12-15-2006 01:27 pm
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Scott Robinson
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I stand corrected and apologize for the misdirection. Teach me for listening to an "expert" instead of researching myself. Glad you did.

S-

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 Posted: 12-15-2006 01:45 pm
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James Wilson
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Don't apologize- I'm new at all this and have tried to look up as much as I can.

But this has me a little puzzled.

While it may not generally be a good idea to mix "A" and "B" the tolerances themselves might allow "A"s at the upper end of their range to be close enough to "B"s at the lower end of theirs to maybe be used together. But if my set of "A"s are at the lower end, and the "B" at its upper, then they probably shouldn't. How much variation in the diameters of the pistons might be acceptable?

I just don't know... And even if I did, I haven't the tools to measure them....

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 Posted: 12-15-2006 03:15 pm
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Jensen Healey
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The pistons need to match the liners. If you have three "A" and one "B" liner, you are good to go.

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 Posted: 12-15-2006 05:40 pm
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Greg Fletcher
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Acceptable is certainly a word subject to interpetation. The mid to early '70's were heady times at Lotus and Jensen Motors. Both companies did a lot of questionable redo and repair as needed to keep production moving and the different piston sizes are one of them. At the time that was considered an AOK proceedure to occasionally correct some existing problem. The original owner would never had known. If I was rebuilding this engine for 2.2 liter, I'd want to put in a set of oversized JE or CP pistons and bore out the liners to suit. There's a very big difference between what a typical dead-stock 907 engine is off the production line compared to what you can do with it now by rebuilding it with high quality pistons, rings, valves cams, a precision balance and a careful assembly.

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 Posted: 12-16-2006 12:13 am
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Dan Eiland
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I just had the 10 dowels added to my block. Cost was $480USD. All labor and equipment charges. They charge $100 per hour on the CNC machine. If you ask me it cost a bloody fortune. That comes out to $48 per hole. I expected around $250 to $300 total. Seems everything is costing double what I thought it would. Next is to have the block align honed and then as soon as the aluminum clutch is built I will have all the parts balanced. Taking both engine blocks to my regular engine builder and machine shop tomorrow. This is the shop that will align hone the block and balance all the parts. Should I have them true up the surfaces that come together between the MBC and the Block? I need them also to move all my engine bolts from my old engine to my new engine. Anything I am forgetting?

Just a reminder this is a 2.2L upgrade.

 

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 Posted: 12-21-2006 12:43 am
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James Wilson
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I've finished stripping down the spare block and find that it had 2 "A" and 2 "B" pistons fitted. So much for believing they were installed in full sets. I've had a chat with the machine shop and they'll fit the pistons to the bores individually so that the clearances are maintained. 

I may be able to use these without any grief after all.

I found one of the original, stock pistons in this spare engine was broken.

But only a little piece, between the first and second rings. The bore looks OK and I can't feel any scratching or gouges...

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 Posted: 12-28-2006 09:41 pm
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James Wilson
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Greg Fletcher wrote: Yes, this will be a cool car when done. If it's a fast road car, I don't think adding a support plate to the block is the best use of resources. Some extra doweling could be desirable, but even at that I'm not sure if I'd do it to my car.
....
I'd add a proper, high quality 3 row radiator to go with all this. The original 2 row is a bit of a joke.

Greg:

Your comments are well appreciated, but I was wondering if you could elaborate a little on why you're not sure that the dowelling would be helpful. I've looked at the block and bearing carrier and must confess I don't see much room for the dowels and would wonder whether the drilling for the dowel might not weaken as much as it helps.

The engine seems to run without overheating or even getting particularly hot. Boosting the compression will create more heat, but I'd hope an upgradedwater pump would help, and the climate here in Scotland is not known for heat- a day in the mid-70s is considered a "scorcher"!

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 Posted: 12-28-2006 10:03 pm
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Greg Fletcher
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I have no doubt that the doweling is helpful, I just think it's more than most of us need. I have my 2.2 project waiting in the wings for after I get my restoration car back on the road (the car has a stock engine in at the moment). For the kind of driving I do, I don't think I need to spend the time and money on doweling the block. I just need a fun, go-fast sports car that can get up to 95mph with little effort and be able to cruise local highways at 80mph, or be able to sit in traffic for hours at a time in blistering summer temps. I'm not going to be thrashing it at any track events. The old 907 in my last JH did a great job all those of years of everyday driving without any problems so I don't see any need to fix what isn't broken.

The original water pump is more than adequate as long as the impeller is not damaged and is set correctly. We do need the 3 row radiators in California, a 907 that set up right with a 3 row radiator will never overheat. My old JH did the Death Valley British Car Endurance Run one July some years back (118 degrees F) and ran as cool as a cucumber.

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 Posted: 12-28-2006 10:54 pm
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Dan Eiland
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I was talking with Garry Kemp who recommended I open up the water entry to the block a little. The way he puts it, as it came from the factory you can just get part of your finger through there where as on the newer Lotus blocks you can get your thumb through the same opening. Garry says it helps considerably in cooling the engine, especially when done in addition with the three row radiator . I don't know how much help the hose fitting was at the back of the head on the Lotus heads, but I have one head with this fitting and one without. Is it worth having this fitting added to my new head? Where I live we deal with 110^+ temps the entire month of July, and June hangs around the 100^ mark most of the month. We get a cold spell in August and it cools down to 99^ most of the month. I'm adding a new aftermarket airconditioning system with heat, cool and defrost that will replace the original heating and cooling systems. Using all new parts accept I'm using an original JH compressor mount. I have a Lotus three belt pulley for the crank but it looks like it might not be far enough forward to match up to where the compressor pulley is located. May have to have a custom billet pulley made. I think I'll be running cool enough with the three row radiator, opening up the water entrance into the block from the water pump and adding a high efficiency electric fan to the system. What have others done to cool their vehicles when operating with air conditioning? I read somewhere that someone added an electric water pump to their JH but they had to block off the water return through the water pump. The person who wrote about doing this said it worked quite well.

 

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 Posted: 12-29-2006 01:01 pm
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Harkes
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Hi Dan,

the later lotus models came standard with this cooling fitting near Cyl. 4. Lotus 907 engines had a flaw in the cooling design as cyl 4 has the tendency to overheat .

the later cooling fitting at cyl 4 solves this issue. Like Greg said a 3 core radiator is highly recommended and the cooling opening to the block.

Garry Kemp built the rear cooling fitting in my 2.2L engine.

Garry also advised me to take an electric fan with thermostat and get rid of the yellow mechanical fan.... one gaines at least 5 HP because of it

cheers

erik

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 Posted: 12-29-2006 05:09 pm
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Greg Fletcher
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To clarify just a bit, the 907 will NOT overheat if the engine is within spec and has a radiator capacity appropriate to the area it is being driven in. The minor problem on the 907 engines, as I understand, is that they tend to get "hot spots" toward the rear of the cylinder head instead of keeping a more even temp throughout. Does that mean every owner should run out and try to fix this problem? I think not. For most people it's a non-issue. Most owners will never know this condition exists in normal service. Small improvements will certainly help a performance engine, but if you want to bypass all the early head issues completely and have a goodly sized budget, going with the vastly improved Lotus Zeus cylinder head would be the way to go. Garry Kemp often has one available.

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 Posted: 12-29-2006 06:59 pm
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Dan Eiland
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Greg, a very good suggestion, but like you say it is for those with deep pockets. I'm a public employee, so it is back to the machine shop to have them add a water port to the back of the head. Anyone know what size it should be? And what about the routing of the water lines? Anyone have a schematic of how the water lines should be run with the addition of the water jacket to the back of the head?

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 Posted: 12-30-2006 05:44 am
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James Sohl
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Just as a point of clarification, with what year did Lotus begin using Zeus to manufacture the cylinder head?  I have a 1984 910 which obviously has very different cam carriers and towers.  The remainder of the head looks essentially the same as the older, 907 heads.  Any help out there?  Thanks
Jim.

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