<VV> Was> PISTON SLAP - story about rings
Chsadek at comcast.net
Sat Nov 2 10:33:10 EDT 2019
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.
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
This message was sent by the VirtualVairs mailing list, all copyrights are the property
of the writer, please attribute properly. For help, mailto:vv-help at corvair.org
This list sponsored by the Corvair Society of America, http://www.corvair.org/
Post messages to: VirtualVairs at corvair.org
Change your options: http://www.vv.corvair.org/mailman/options/virtualvairs
This email has been checked for viruses by Avast antivirus software.
More information about the VirtualVairs