What compression does your worked N/A engine have

Hi all,

firstly, I am not after your compression ratio at all.

I am just curious as to what compression your modified N/A engine may have, non turbo engine of course.

Mine has an average of 175psi.

Thanks, Kevin

Mine has 200.
You can advance and retard the cam and
note significant changes in the cranking compression.

Naturally a smaller duration cam, or more static compression will increase the number.

I always remember Mick Atholwood (RIP) used to say a good rule of thumb
for a drag engine was to adjust the cam duration and position to aim for 200 psi.

Just for comparison, and peoples interest, my old supercharged 1715cc engine with low 7:1 comp,
and large duration cam only had 100 to 110psi.

Thanks Dave for your input.

Gives me something to compare to and for others 👍

Any idea what your compression ratio was with the 200psi?

Cheers, Kev

Kev, your compression is fine 👍

What was the lowest and highest ?

My old 1500 single-port had 100psi in #1,2 and 4 and 70psi in #3. That thing had definitely been worked, very hard for about 40 years! 😂 Just for comparison. It still ran on all four just fine and I got it up to an indicated 86mph on a straight bit of road. Admittedly, it was slightly downhill! That was in a 1970 Beetle.

My 1835 has about 140 psi