Need crankcase rear cover

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Need crankcase rear cover

Postby johnmcguire » Tue Nov 12, 2013 11:04 am

My 948 went to the machine shop for a boring experience but returned with a few parts missing. I'm sure this has never happened before.
I need a crankcase rear cover for a 948 Sprite. This is the half circle oil retainer at the rear of the case above the crankshaft and attached to the case. Does anyone have one that I might purchase as this is not readily available as a new part?
The car is ready and the engine sits while I try to find this missing link!
Thanks, John McGuire. 828-230-9562. johnmcgu@charter.net
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Re: Need crankcase rear cover

Postby trevor » Tue Nov 12, 2013 11:36 am

Might be a good time to check with Gerard and see if he has a rear oil seal hit for a 948. I know the 1275 version he sells incorporates the bit you are missing.
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Re: Need crankcase rear cover

Postby trevor » Tue Nov 12, 2013 11:38 am

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Re: Need crankcase rear cover

Postby Charlie Tolman » Wed Nov 13, 2013 1:12 am

If you obtain an original oil retainer cover, it might not prevent an oil leak.
The shallow helical groove cut into the crankshaft will work well if the clearance between the crank surface, the rear main cap, and the oil retainer cover are correct.

If the block has been "line bored" for the main bearings, there is the possibility that the above mentioned clearance might not be correct.

Maybe some of the forum readers can advise you on this clearance number.

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Re: Need crankcase rear cover

Postby johnmcguire » Wed Nov 13, 2013 10:01 am

As always, thanks for the expertice and advice.
At least the missing part turned up. It was in the bottom of the machine shop cleaning bath.
I would be interested to know what the clearance should be.

I painted both the front and back plates a beautiful Austin green. Do I need to clean off the paint where they fit to the block? It is flat and smooth but the paint thickness will change the clearances at least a little.

Am I correct that the bolts for the cam retaining plate were safety wired rather than using lock washers?

It's okay so a novice to ask such dumb questions, isn't it?

John
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Re: Need crankcase rear cover

Postby perdido » Wed Nov 13, 2013 10:46 am

John,
Clean the paint off of any surface that will have another part attached to it. Some of these require a good seal to function correctly and the paint could be a weak point. As far as the rear seal is concerned, you really want to get this right or you will have a rather large oil leak. This is not a very easy thing to do and has baffled many a machine shop! From all reports, Gerard's rear seal kit functions well and solves this problem, plus you have Gerard to help walk you thru the process.
Good luck, Rut
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Re: Need crankcase rear cover

Postby Charlie Tolman » Thu Nov 14, 2013 12:50 am

I have assembled engines where the front and back plates were fully painted, and also where they were painted only outside the regions defined by their associated gaskets.
Neither technique generated any problems.
You might want to remove the paint in the areas where there will be oil flow; the timing chain cover region is an example.

The factory used "shake-proof" washers on the cam plate bolts. I have used medium strength Loctite (blue) to secure the three bolts.

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Re: Need crankcase rear cover

Postby Joe Schlosser » Wed Nov 20, 2013 12:28 pm

The clearance between the half circle part that bolts to the block and the crankshaft is as close as you can get it. Generally about the thickness of a piece of paper.
This may not be factory spec but it does work along with good venting in keeping the oil in the pan
There is a post by Ron Bartel (Former HP Natl champ) on the Production Car forum regarding doing this. Technically this should be filtted before the align bore.
However to get the clearance you may may need to elongate the bolt holes and file off part of the piece to be flush with the block. He recomends adding a dowl pin to keep the location. Howevr if you are not racing and going to being doing bearings every season the pinning is probably not needed.
Once you have tightened the cover you need to remove the crank and take out your pieces of paper you used for the clearance and make sure that everything spins smoothly.
Joe
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