36hp Piston Ring Question

[Homeresque]

Short version...can I use a 77mm oil ring or set to replace a broken oil ring/set on a 77.5mm piston? I haven't called WW yet to simply ask if they have some, but it sounds like finding 77.5 rings isn't easy.

Long version...building a WW Okrasa TSV motor for my '57 kombi. Its the original motor and the car only has 41k miles but sat for about 45 years after being driven in very dusty/dirty places in Michigan. The motor was absolutely black with grime from the dust, but when I split it open the inside looks very nice...no water damage, no sludge or carbon build up, nice clean oily sheen everywhere. Looks mostly bone stock unmolested except sometime #3 must have stuck a valve so one head dosen't match the other but all 8 valves are VW, #1-2-4 P/Cs are VW/Mahle 77mm and #3 is VW/KS 77.5mm, and #3 rod doesn't date match the other 3. It must have sat for a long time without the motor turned and a little condensation rusted on the bottom of #3, rusting around the oil ring on that piston, thus that oil ring was trash anyway but it wouldn't move and had to be broken off. The rest of the rings are fine.

I have the WW top end kit heads and manifolds ported and a cool old pair of 'Parabolic' brand velocity stacks, a Bosch/VW number 010 dist, the original TE6B1 coil, a Speedwell crank pulley and valve covers (but I think I'll go with the OGs), a Bugpack old school 40hp single muffler header set that I'll cut/bend/reweld to fit the motor and clear the bus, and WW 69.5 crank.

I'm planning to take the mess to Rimco to have the case tanked and soda blasted, plugs removed and galleys cleaned, and plan to get a clean bill of health for the crank and cam bores. Then have them recond/rebush the rods, and resurface flywheel, 8-dowell, and open up for 200mm. Originally was going to buy new P/Cs, but thinking used German VW is better than new Chinese Questionable I'd rather go with reusing my originals...after chiseling off the carmelized goo on the cylinders they look pretty good. I'm hoping Rimco can do a clean-up hone to the cylinders and call it good, but if not I'll just run the way they are, rings and all.

Then I'll buy a cam (WW, Okrasa Joe, Mr. Motorhead?), bearings, 21mm oil pump (use original 6mm cover), clutch, and take the mess to a builder (still deciding) to have him trim the piston skirts, clear the rods, get the rotating balanced and then shim the deck height and bolt the case together, giving me back the short block with the pistons hung.

Is there anything anyone would like to toss on? Being a bus I figure lightened flywheel no way, bigger clutch yes way. For the bus would the original 019 be better than the 010? If there's no solution for the one missing oil ring I'll just say f-it and run a new P/C set.

[Slow 1200]

myself I would definetely not build an engine with different piston sizes, I'd look for a matched set of pistons and barrels, they are not that expensive

[Homeresque]

Thanks. I hadn't really given that much thought, figured the repair was most likely done by a dealer and that was acceptable to do.
Guess I'll look for 77mm replacement.

[Peter_N]

[snowbug]

Hello, I had the opposite problem. I was building a 1300 super36 with WW69 crank. I thought I had a set of NOS 77.5 pistons and jugs. After machining the skirts I noticed one piston is 77mm. So I have this NOS p/c with clearanced skirt that I will not use. I will be using 3 NOS 77.5 and one used 77.5. Jim

[Homeresque]

Awesome!...Send me the 77mm!