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Re: delusions of grandeur: porting and polishing
>would like to raise my compression ratio as well for some added oomph. i
>would like to impose upon my fellow listers for some advice. i have
>heard that my 1990 80Q has domed pistons. how much (if any) can i shave
>off of my head before my valves and pistons collide? also, i am concerned
>that if i shave too much, my knock sensor will retard the timing to the
>point where performance is adversely affected. is this a valid worry?
>how much can i shave off, and what would be the resulting compression
>ratio? another worry i have is the effect on my timing belt with
>the decreased space.
You'll have to measure the clearance yourself, between the piston tops, and
the valves, using Plasigauge.
For compression ratio, you'll also have to measure the combustion chambers,
add the compressed volume of the head gasket, and also the piston dome deck
Head volume plus gasket volume minus piston dome deck haight volume equals
combustion chamber volume, or "dead volume".
Next "live volume", which is also known as swept volume. Measured bore
squared, times .7857 times measured stroke equals live volume which is
compressed into the combustion chamber.
Add the dead volume and live volume together, and you get the total cylinder
volume. Divide by the combustion chamber volume, and you get the compression
Reference: Racing Engine Preparation: A Complete Performance Guide From
Building to Tuning, by Waddell Wilson and Steve Smith.
Winston Cup Grand National stuff, but the theory is the same...and this guy
has built a _whole_ lot of successful engines.
Lots of good ideas....like using Dow Corning RTV foam to make moulds of your
ports for external inspection.
BTW, the 2.3 litre _is_ the high performance version....130 BHP verses
101-110 for the rest of us mooks.
1984 5000S " Audrey"