<VV> turboing a 95 hp engine

[Tony Underwood]

At 12:44 hours 08/09/2004 -0400, robert guerin wrote:
>I am thinking of putting a turbo on a 1965 95 hp engine presently in my
>corsa.It's there while the 140 is being rebuilt. 

snip  

.Are their major reasons for not doing this.Any comments will greatly
>appreciated. Thanks in advance.


You'll need to do a few things.   The turbocharger will need a drain for
the oil return.   A fitting installed in the right side head ala the stock
turbo head should do, a pipe nipple in NPT of the right size works well,
been there done that more than once.   I've seen people get away with
brazing a fitting on the valve cover to allow turbo drain oil back into the
engine.   

The 95 heads are *the* best heads to use on a turbocharged Corvair engine,
considerably better than the stock turbo heads.   The 95 hp cam is another
matter.   It offers up more cylinder filling at lower rpm than the 110 or
140 cams and is likely to cause mid-range pinging in a turbo engine.   A
little tuning trickery might make it livable but you'll need to use *The
Best* gas you can get if you wanna put your foot into it.   It should have
a really strong midrange punch.    

You will obviously need to do some distributor work via using something
like a stock 95hp or 110hp distributor and play around with springs to keep
it from advancing too quickly.  You also won't need to run anywhere nearly
as much initial advance as stock turbo engines used (24 degrees), likely
will be more livable with around 10-15 degrees initial advance tops,
DEPENDING on the distributor used... probably less.   Be sure to employ a
pressure retard and not a vacuum advance on the distributor.   

The engine internals in the 164ci 95 hp engine are pretty much the same as
the stock 164 inch turbo engine outside of the camshaft and valve guides;
guides are iron for the 95 and bronze for the turbo, likely you won't ever
see a dimes worth of difference either way in actual use.   The pistons,
rods, and crankshaft are all the same for both turbo and naturally
aspirated 164 inch engines outside of the surface hardening applied to the
turbo crank which simply makes it harder to scratch and does little if
anything to actually make the crank any stronger although the hardening
*will* make it more durable if you ever get any trash in the oil.  I've run
a non-hardened crankshaft in a turbo engine with good luck and that's
running it *hard*.    No problems.    

You might run into some carb issues if the car doesn't have a fuel return
line (turbos used it) and I'm still a bit "iffy" about running the 95hp
camshaft which is not a high rpm piece and may end up "arguing" with the
turbocharger which will likely really start to work at around 4000 rpm
which is about where the 95 hp cam starts running out of breath.   I've not
run an 889 camshaft (95hp) in a turbo engine so I'm not really sure what
you're likely to find when it's revving under a load.    


This sort of thing sounds a  bit like a hassle if it's only temporary but
if you have the time, go for it.   But expect to fiddle with it to get it
to run right, especially with the distributor and finding a happy medium
with  initial timing advance since it's gonna ping its brains out if you
try to tune it like a factory turbo engine and attempt to run 24 degrees
advance with the 95 heads.   

If you get it right, expect it to embarrass that 140 engine up through
around 4000 rpm or thereabouts, maybe higher although the 95 cam is still
likely to run down after 4k or so.    Or, if you swap out the cam for an
891 (110-140hp) you can expect some real performance especially with a free
flowing muffler and careful tuning.   



tony..