<VV> Compression Ratio Question ??

[MarK Durham]

OK, this is for all of you guys that have cc'd your combustion chambers and
know how to relate that to compression ratios and performance.

Yesterday I was troubleshooting a engine related problem that I traced to
the '65 style carbs, so I put a kit in both of them and installed 53 jets
for what seemed a lean running condition and that's solved. The engine runs
smooth, accelerates great and is overall a strong performer with .030
cylinders and a Isky 270 Cam. It is running the best it ever has.

Background info: When I bought the car, it had Chevy 350 tapered seat plugs
in it. When I overhauled the engine and could take a look at the heads, I
found redesigned combustion chambers (they look like lower compression 150
turbo chambers). The spark plug holes had been welded shut and new ones
drilled closer to the exhaust valves.
(yes the plug holes are tilted to center in the tin openings for spark plug
wire and boot alignment.)

I presumed the engine would be a lower compression due to what I saw,
however, yesterday as a part of my troubleshooting, I did a compression
test for the first time since overhaul 8K miles ago and got these readings:

#1  - 195 psi                    #2  -  198 psi

#3  -  180 psi                   #4  -  187 psi

#5  -  190 psi                   #6  -  193 psi.

I was expecting compression readings in the 145 to 165 range. With these
high numbers, what could my compression ratio be?

Its obvious that the chambers, while they look like the 150 turbo heads,
have a smaller CC footprint.

I do remember going through several sets of normal temperature range plugs
(mild pre-ignition symptoms) , and finally found a set that works great two
temp ranges cooler than normal. Now its starting to make sense, some of the
issues I have had with this engine.

So, are these compression readings going to be detrimental to the life of
the engine?  Thoughts?


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