Need guidance: 1098 "10CC" with 948 clutch

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Need guidance: 1098 "10CC" with 948 clutch

Postby Mowog-Jeremy » Sat Jul 21, 2012 5:05 pm

I'm new here.
My Bugeye is a 1959 (24,xxx) that was in a garage for 20 years.
I have had a couple of Minis for 20+ years and have rebuilt a few engines, etc. so this is not entirely new territory.
The Sprite is thankfully rust-free and so far I've done the brakes and several other jobs.

Here's the question:
How can a 948 flywheel be adapted for use on a 1098 "10CC" (i.e., 2" main journals) crankshaft?

Background:
The Sprite is all original except a 1098 'short block' (and the Chevy Malibu paint). Whenever this was done (and I bet it was about 40 years ago), the 948 head, carbs, distributor, flywheel, clutch, smooth case, etc. were all re-used.
It ran OK, but 'pinked' (high compression) and oil pressure was a little weak. I took it apart and the engine is good enough to rebuild and I have a 12G295 head. I'll use the distributor and HS2 carbs from an MG 1100 parts engine.
The clutch (with all the original 948 parts) worked fine before disassembly.
The 948 flywheel had 4 'extra' holes drilled and these are 'oval'-ed. No wonder it had a bad vibration (that I initially thought might be exhaust touching the body and then thought might be dead transmission mounts . . .)
(If this has been covered in the past, please give me a hint on how to search for the prior thread.)

Picture of modified flywheel that came out of my car and the spare 'stock' 948 flywheel.
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My Sprite as it sits in my workshop.
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Mowog-Jeremy
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Re: Need guidance: 1098 "10CC" with 948 clutch

Postby Charlie Tolman » Sun Jul 22, 2012 9:20 am

In addition to the four extra holes in the modified 948 flywheel, the central large hole has been enlarged.
The diameter of this hole should fit closely on the flanged portion of the crankshaft end. The diameter of the hole, and the concentricity (centering) of the hole is fairly critical for flywheel fitment on the crankshaft. Unless you have access to an expert machinist, I would advise against this type of modification.

If it was my car, I would obtain a new or used (in good condition) 1098 flywheel for the large main bearing version, 10CC. A flywheel from an early 1098 engine, 10CG, might not fit on the 10CC crank. ??

Also, if it was my car, I would have the 1098 flywheel drilled for attachment of a 1275 clutch. This clutch is superior to the 948 and 1098 clutches. I had this modification done on a 1098 engine, and the clutch worked very well. For a 948 engine, I obtained an aluminum flywheel that was drilled for a 1275 clutch. The clutch and flywheel combination should be dynamically balanced.

Charlie T.
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Re: Need guidance: 1098 "10CC" with 948 clutch

Postby Mowog-Jeremy » Sun Jul 22, 2012 8:18 pm

Thank you, Charlie.
I called around to some friends today and found a 10CC flywheel. I'll get my hands on it and go from there, noting your advice about the 1275 pressure plate and clutch disc.
My next issue is whether to use my (good) smooth case box with a broken top flange (top of bellhousing) or find a rib case . . . I'm working to locate a rib case.

Jeremy
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Re: Need guidance: 1098 "10CC" with 948 clutch

Postby Ragnars-Frogeye » Sun Sep 16, 2012 4:07 pm

Hallo Jeremy,
my frogeye is running with an 1098 (10CG) 1275 clutch and a smooth case gearbox. There aren't any problems. You have to change the release bearing to a 1275 because you must have a greater crank (?)

If your going to buy a ribcase you also need an other clutch withdrawal lever. What sort of release bearing you need then I don't know.
Greetings from Germany

Ragnar
http://www.ragnars-frosch.de
AN5L-1443
10CG engine
9CG gearbox
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