Mad Dog 401 cast hi-cp pistons

mika01

Any advice on the 401 hi-compression cast pistons Mad Dog has for sale? Is it worht it? Pros, Cons would be appreciated thanks.

82Waggy

The 10.5:1 compression ratio is probably high for street use on pump gas.

mika01

Would probably have to take some 58cc heads and unshroud them to say 60cc. That should lower the CR to below 10? What do you think?

82Waggy

Well,

I used the KB 354 with a 28cc dish - with stock 58cc heads and near zero deck clearance this would have made about 9.7:1 static CR. I opened up my heads to 65cc to drop static CR to less than 9.2:1.

Rule of thumb is that no more than about 9.2:1CR on pump gas with Iron heads and about 9.5:1 with aluminum heads (Alum sheds heat faster) - BUT, running ratio and good quench may alter this somewhat. Note that a later intake valve closing point could decrease running CR enough to keep you out of detonation with high compression pistons but if you get too carried away you may not like general drivability at lower rpm.

There is a compression ratio calculator under the tech section of this site http://www.kb-silvolite.com/index2.php

You might also want to scan some of the tech articles located there concerning quench and other topics of interest.