<VV> Advice on a '65 Turbo?

[Tony Underwood]

At 11:40 AM 6/25/2011, Frank DuVal wrote:
>My mountain story is when I first bought my 64 Spyder convertible in
>1976. I was taking friends on a drive around Charlottesville and went up
>the east side of Afton mountain on US 250.


Oh yes...  the Afton Mountain grade will do it just as well as 
Christiansburg's hillclimb.


>I was in 4th and nothing
>seemed odd to me the driver. Pleanty of power. Just chatting away with
>the top down in the fall of the year. Then the guy in the backseat asks
>"Is that pinging I hear?". I look down and the temperature gage is
>pegged past 600! So I downshifted to third. I couldn't hear the ping in
>the driver's seat.
>
>Yes, later the engine dropped many valve seats. It is why it is
>currently parked awaiting a engine build with different heads.



95 heads with deep seats?   :)


Now...   Ladies and gentlemen:

People are always talking about how 140 heads "work well" on a late 
turbo engine.   We keep hearing about how the wheelers and dealers 
run modified 140 heads on turbo engines making a bunch of 
power.   Let's get real here.


You can, with minor mods (ignition, camshaft, exhaust, mild whittling 
on ports) to a late turbo engine, use 95hp heads and get a 
dyno-proven 230hp out of an RL engine.   There was an ancient hotrod 
magazine engine buildup that did this and they dyno'ed the 
result.   They still had an engine that would idle fairly decent at 
800 rpm and was docile enough to drive grandma to church.

230 hp is more than enough to yank a Corvair around with a 
vengeance.   If this is going to be a street-driven Corvair, you do 
NOT NEED 140 heads on it, with all their associated compression 
problems and rickety valve seats that simply do not much like being 
subjected to boost since there's less actual meat around the seats to 
keep them anchored.  Even with deep seats, there's still the 
compression issue which means you have to either cut pistons or cut 
the heads... and that usually means you end up opening up the squish 
area which plays havoc with flame travel, which is where the 95 heads 
work out nicely because they have a squish area (kinda a bit less 
than what would be best, but it's there) and they're already the 
right compression.

And with 95 heads you don't need to deal with that MORONIC 24 degrees 
initial advance along with the flaky compensation advance curve 
necessary to make those open chamber heads work... and they don't 
work very well under the best of circumstances and in fact are pretty 
sorry excuses for a cylinder head for ANY Corvair engine, much less 
one with forced induction.   I'm frankly surprised GM ever used them 
in the first place.   With 95 heads you won't need to run anywhere 
near that much initial advance because flame travel with the 95 hp 
head's confined chambers will be better and your fuel mileage might 
even perk up a bit.

If you're going racing and you need every last drop of chewy 
goodness, then use the 140 hp heads with angled port exhausts, deep 
seats, cut pistons, etc ad nauseam and after you spend a grand on 
them before you put them on the engine you can go out and run pretty 
strong if you have a source for avgas or race fuel... but if you 
don't have access to exotic gas, and the car isn't going to be raced 
and you don't need the last fraction of power you can extract, run 
the 95 heads.   You likely will notice hardly difference at all on 
the street.

...just my opinion.




tony..