PG Turbos?? Re: <VV> Re: TURBO BENT VANES

[Tony Underwood]

At 09:43 AM 9/11/2007, Mark Corbin wrote:
>A GM engineer who worked on the Corvair and addressed the CORSA convention
>one year responded as to why it was never offered. He said that they found
>that with just two speeds in the Corvair's powerglide, the situation arose
>that when the trans shifted, you were running high boost and suddenly also
>had low RPM. What happens then is that you tend to blow the heads off the
>engine. With a three-speed, they might have gotten away with it, though.


I suspect the fellow was speaking whimsically.   I've seen tweaked 
'Vair engines that were overboosted and thus break, and the heads 
never failed.  Pistons would perforate or collapse and/or break 
apart, connecting rods would bend, or bearings would mash out causing 
the rods to beat up the crank journals and heat up the big end and 
possibly toss a rod, but I've not seen heads blow off, ever.

Too many other parts will fail first before the heads manage to pull 
the studs out.    Of course, I've not seen everything either.   But 
I'd put money on piston failure first, then rods, before I'd wager 
the heads would blow off.


By the way, IMHO it takes a special kind of lead foot to load enough 
boost to bend connecting rods.   ;)    ...and I still have some 
pistons with the top ring grooves so tight against the compression 
rings that they won't come out or even move at all... piston crowns 
slightly dished... and they weren't dished pistons when they went 
into the engine AND the dishing wasn't from being squashed, it was 
from heat erosion.

...crowns looked like asphalt.    Good place for ceramic coating, I 
bet, and an educational experience in how not to load up a 
turbocharged 'Vair engine beyond reason.   Junk happens.



tony..