<VV> Corvairs

[jvhroberts at aol.com]

 In my EVER so humble opinion (and you ALL know how humble I truly am!), here's what I see as the list of issues with Corvair valve seats. Obviously, people like Warren have their own ideas, and their solutions do work, so, here goes...

1. Insufficient cooling. Obviously, since aluminum has a much higher CTE than steel, the hotter things get, the looser the fit. 
2. Seats aren't deep/wide enough. The more deeply seated, and the thicker the cross section, not only do you get a tighter fit, but the temperature mismatch between the seat and the head will be smaller. 
3. Seats not made of the best stuff. There are manganese steels and aluminum bronzes which a far closer to the CTE of aluminum than the OE seat material. 
4. Seats not well retained. Now this one is open as to the best way to do this. But a step machined on the OD of the top of the seat allows the head material to be staked well into the seat. Or threaded seats. Or setscrews (not my fave). Or if someone had a huge budget, electron beam welding of the seats into place. Yes, you CAN weld steel to aluminum by this method. There are also brazing alloys suitable for this as well. Or some other method I haven't thought of yet... 
5. Engine not properly tuned/syncronized. Detonation, one side running hotter than the other, too much retard, et al, all can exacerbate the problem. 
6. Valve train not properly set up. When the valves clatter like hell, it's a sign that the valves are slamming into the seat, as compared to landing gently, as designed. This will hammer the seats loose more than one might think!

Now, as far as what to do about this, my best idea is to pull the seats, weld 'em up, and put in nice deep ones. Also, make sure the guides are in good shape. 

So, there's my start on this thread!! 

 

John Roberts
 

 

-----Original Message-----
From: shortle <shortle556 at earthlink.net>
To: virtualvairs at corvair.org <virtualvairs at corvair.org>
Sent: Mon, May 10, 2010 10:18 am
Subject: <VV> Corvairs


My nemesis with Corvairs (lately) seems to be with their valve seats coming 
loose from the heads. This has happened to me twice in about 25,000 miles. First 
was with 140HP heads (intake seat exploded) and then it was with 95HP heads. The 
95 was an exhaust valve. Both of these heads were very deflashed long before the 
seats came loose. Neither of these were ever overheated in the time I owned them 
(don't know about previous history).What is the solution to this? Can something 
be done to keep this from occuring? Neither time was it warm outside nor was the 
engine under any extreme load. The vehicle is my '63 Rampside with a 1965 RN 
engine, 3.55 diff. and a PG.I am using the 12 plate oil cooler with both side 
covers and the OTTO parts pan and valve covers. I hope to get some answers and 
suggestions from ALL members regardless of race, sexual orientation, age, 
political beliefs, education, life experiences, etc.
Thank you in advance for what I hope is an interesting thread.
Timothy Shortle in Durango Colorado
Getting ready for our tri state meet next weekend
 _______________________________________________
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 
 _______________________________________________