<VV> Compression Ratio Question ??

[Jay Maechtlen]

wow - that's impressive static compression, especially with a non-stock cam.
Lifespan/durability - I'm not a real Corvair guy, but seems to me if it 
runs well and doesn't ping (no preignition, no detonation) it should be 
great.
Assuming the beast is timed well, and not terribly retarded - the 
exhaust temps should be reasonable.
(It would be interesting to measure that somehow - got pyrometer?)
How about head temps and oil temps?

Regards
Jay


On 9/7/2014 6:17 PM, MarK Durham via VirtualVairs wrote:
> 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
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-- 
Jay Maechtlen SoCal '61 2-dr modified w/fiberglass skin, transverse 3.8 
Buick V6 TH440T4 trans

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