<VV> 110 vs 140 heads,

[MarK Durham]

Cliff, I agree with all you said. My experience is with air cooled aircraft
engines and we expected CHT's to run in the range you are running, and oil
temps as well. 150 to 200 hp engines ran in the 325 to 350 cht and 180 to
200 oil temp, Very high horsepower engines ran 375 to 425 CHT and up to
225-250 degrees oil temp all the time.

My point was that the small valve engines cannot flow enough air/fuel
mixture to get themselves in trouble, unless you add the turbo. Where, the
140 heads can flow enough under heavy driving use to get hot. Your engine
with shrouds on may not be able to flow the necessary air to kept temps in
your range when conditions are less than ideal and its smart of you to take
them off when temps get higher. I do that on my 110!

I would suggest that where valve seats are coming out, they were probably
installed a bit loose to begin with. I know there have been seats installed
by very reputable corvair mechanics that have come out, too, and that is
probably due to the method of install (following GM's instructions), and
age of the heads. The resistance fit we used on seats to seat bore in
aircraft cylinder heads were up to several thousands tighter than what the
corvair spec is.  When I installed a seat, it was frozen, and the head
heated to 500-600 degrees, then quickly installed and let cool. It took a
special tool to even get them out after heating the head up, and shock
cooling the seat with water.

So, from my perspective, the issue of seats coming out is a loose GM spec,
and lack of the proper tooling/technique to install in heads that run much
hotter that water pumpers do, that GM was not accustomed to and regardless
of the engineering they did, they did not fully comprehend the
situation. Today, 50 some years into aging aluminum that has endured
countless heat and cool cycles, here we are.

What to do? Install the deeper seats keeping the interference fit as tight
as possible, de-flash the heads, and watch your temps.

Regards   Mark Durham Hauser, Idaho

Mark Durham
Hauser, Idaho
62 Monza coupe Red/Red 4 speed


On Mon, Mar 24, 2014 at 6:12 PM, Cliff Tibbitts <cliff at tibweb.com> wrote:

> Regarding 95 vs 110 vs 140, I can only speak from my own experience.  I
> have a 66 Monza.   I am using an engine that began life in 66 as a 110, and
> now wears 65-140 HP heads.  The car is air-conditioned with the condenser
> in the stock location, (aided by two auxiliary fans)
>
> My car runs cool.  I do remove the lower shrouds in the summer.  With the
> A/C on, the car typically runs 375 degrees, (Corsa dash)  Granted the
> nearly 50 year old gauge and thermister could be off.  However, when I stop
> the car the engine is still relatively cool to the touch and my 3 year old
> oil temp gauge says the oil temp is right around 200 degrees.
>
> Maybe I'm just lucky, but I think 140's can be made to work well.  But it
> is imperative that you have the heads rebuilt with the deeper seats
>
> Just my humble.
>
> Cliff Tibbitts
> 66 Monza 140/4-speed A/C
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