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davevr6car

Help! Obsolete main bearing shells

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Hi,

I'm rebuilding my S4s engine after a spun big end bearing. I had to get the crank reground to +0.010". So i need a full set of main bearings, 0.015"OD 0.010" ID. I have tried the usual dealers but they have none in stock and Lotus have none either and say they are obsolete.

Does anybody know where I can get a set from.

Cheers

Dave

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QED list standard, +10 thou, +20 thou and +30 thou main bearings on their website. OE and non OE are shown in all sizes except the +10 which is non OE only. It may be worth giving them a call.

Edited by sailorbob

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Looking at QED's site I'd say they're +10 is actually -10 , as in 10 thou' ground off the crank.

Derek, they do not seem to list bearings that are externally larger which is what David needs (actually needing externally larger and internally smaller).

Just a thought, what about Mr Kemp. I'm sure he'd know of somebody he could source them from [email protected] Tel: 01964536423

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Cheers lads for the help.

Andy I tried Gary Kemp, but he doesn't stock them and the same with QED.

1 in 100 engines of this guise that lotus manufactured had to have the main bearing carrier honed out to correct themanufactoring errors.

The mains are therefore oversized or made larger by 0.015" outside dia. I got my crank main bearings ground and polished so they are now smaller by 0.010" so I need "thicker" bearings by 0.010" or -0.010" internal dia.

So my problem is, and which maybe a problem for a lot of people on here, is that if you want to rebuild the bottom end of your engine there are no main bearings in these sizes available.

Dave

cheers

Dave

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I'm sure those were in the parts sale a long while back. Really cheap. I didn't purchase any as I don't have an over-size bored block but I'd guess a few people bought them not realising their application.

Dave, you may end up having to purchase a replacement bottom end.

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I didn't twig the mains had oversized OD's. If they are unavailable then probably the only option left is to have the main caps mating faces machined and align bore / hone the main bearing.

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I would have to replace the block and bottom end.

If I got the main bearing housing casing skimmed and then the block and casing align bored to accept the standard outside dia bearings, would this not alter the stroke of the crank, ie would it not bring the piston closer to the head?

Dave

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Dave.

No and yes.

No, it wouldn't alter the stroke. Yes it would bring the pistons closer to the head (too close).

You'd then have to look at a shim for the head to correct the compression ratio.

By bottom end I did mean block, ladder and sump (they're all supposed to be matched).

I guess you'd really want to keep the engine number the same as was in the car originally. That means a replacement block is out of the question unless you go for a brand new block never been finished and assigned to an engine.

If you are prepared to change the engine number then try Mike Taylor for a bottom end, for an early HC Turbo he was charging around £200 but a later one (the block was refined with some small changes) it would probably be more money if he even has one.

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Have you tried PNM? Pete usually has some creative ideas.... e.g.certain Vauxhall bearings could be made to fit by altering the tangs,

Edited by 910Esprit

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Derek,

Even by getting the caps and block machined, how is this going to make the bore smaller. It will reduce the vertical height of the bore, but not the width.

I might have had some luck. I have located some bearing from different sites on the internet. Why would lotus sell individual shells/bearings. You would think that they would come in matched pairs / sets, up and lower.

When I was getting the crank reground, the engineer smiled when I told him it was a lotus crank, he said you mean a crank out of a Bedford! According the 2.2 crank is identical to the ones in the old bedford!!

Dave

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The width will be reduced. When you machine the main bearing registers the bore shape changes from being a circle (assuming it's round to start with) to being two segments aligned with each other along their chords. The chords will be shorter than the diameter of the original bore.

You can easily prove this to yourself by drawing a circle on a piece of paper and drawing a line through its center. Next draw a series of lines parallel to the diameter. The farther away from the center the shorter the lines get :)

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Just done some rough calcs; you would need to take ~7 mm off to reduce the bore by 15 thou.

I think another solution is required, maybe white metal the bores or have inserts fitted.

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Derek,

Even by getting the caps and block machined, how is this going to make the bore smaller. It will reduce the vertical height of the bore, but not the width.

I might have had some luck. I have located some bearing from different sites on the internet. Why would lotus sell individual shells/bearings. You would think that they would come in matched pairs / sets, up and lower.

When I was getting the crank reground, the engineer smiled when I told him it was a lotus crank, he said you mean a crank out of a Bedford! According the 2.2 crank is identical to the ones in the old bedford!!

Dave

Yep. Check back on the history of the 9xx engine and you'll see it used the bottom end of the Vauxhall engine to assists in developing the head and then later on (still in development) the Lotus specific bottom end was prepared.

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Yep. Check back on the history of the 9xx engine and you'll see it used the bottom end of the Vauxhall engine to assists in developing the head and then later on (still in development) the Lotus specific bottom end was prepared.

Yeap, the old guy said he recognised the crank, and said it was exactly the same as the old magnum cranks

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Dave

My understanding that the Chrysler 318 V8 (1967-2002) bearing can be adapted to fit the Lotus engine. The Chrysler Block Housing Bore is 2.6925/2.693. The standard Lotus Block Housing Bore is 2.6655/2.666 plus the .015 oversize that you have and is still under the 2.6925 dimension. This is on the JHPS Message board that also uses the Lotus 907 engine.

Anyway hope this helps

1jh2go

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