<VV> Was> PISTON SLAP - story about rings

[Charles Sadek]

My machinist, hot rod buddy takes on an engine rebuild project. I did the carbs, provided him a block, helped him check and prepared the block, fan height, linkages, distributor, etc. He has built a number of engines over the years. In this instance, doesn't make any difference. New pistons & cyl wall clearance, bearings, rings, did a valve job on good 110 heads. All together, put it on our new run-in engine stand.. smokes.. OK, vary rpm, etc. Oil pressure is good.  Still smokes, as in REALLY SMOKES. What the hell?
Eventually tore it down.. The Corvair ring sets from a major Corvair vendor had wrong oil rings. The center wave expander had no little tits/bumps on it to limit the scraper rings from going in and wedging themselves inward toward piston center. Away from cylinder walls. Now we checked ring gap, eye-balled groove to ring side clearance, compressed and installed. When we compressed the rings, the oil scraper rings stayed compressed... Who'da thunk it?
Check everything.. and count everything.. Smile.
Chuck Sadek

-----Original Message-----
From: VirtualVairs [mailto:virtualvairs-bounces at corvair.org] On Behalf Of N2VZD TIM via VirtualVairs
Sent: Saturday, November 2, 2019 8:38 AM
To: virtualvairs at corvair.org
Subject: Re: <VV> PISTON SLAP long story new problem motor

I now only buy the full fin cylinder kits with pistons.I have a motor on my table now that is another mystery. A few years ago I severely overheated my Rampy with .060 full fin cylinder setup ,270 cam ,reworked heads  going up the Mohawk trail into Mass from Troy NY after buying supposed high test from a small gas station. It started pinging very hard , no place to pull over at all , with traffic behind me . So by the time I got it pulled over at the top of the mountain at a closed up tourist trap , the oil was boiling , temp light on (belt still on!) and down a quart. This motor had @2000 miles on it , My expensive  dream motor which was running great. Well it still ran OK , but uses lots of oil. I tore it down twice  last winter , checked Cylinder clearances , etc , put a new finish on the walls , new cast iron rings in , and ran it on the stand. Smoked bad from #3 cylinder only (manifolds off) So I ordered a new cylinder and piston . That seemed to fix it. So I put it back in again (I was running a spare motor). It still used a lot of oil , not that bad on smoke , but sometimes a quart to a tank!.I changed the heads to 95HP , (I had a set ready ) thinking maybe a guide situation , still bad. So now  I have it on the bench again , another similar motor in running great. I guess my only option now is new Cylinder / piston sets. I checked the PCV setup. It will get torn down again  when I am feeling better.Not sure what I will do now , but it makes a good Carb tester so far...(rebuilding a bunch of my carbs)Regards, Tim Colson



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