Compression question...

[ITLBTU]

I seem to remember seeing a chart years ago that gave ball park numbers for compression test numbers to compression ratio. I know it's not that accurate because of cam timing but I'm curious as to what ratio my 400 sbc is. I'm running "292" iron heads that have been shaved some, but I don't know how much. My cam is around 250 deg duration, .530 lift and a 110 lobe centerline. The pressure on the cylinder cold cranked is around 235 psi.

[MarkM66]

I don't think it'd even be close enough to give it any consideration at all. An educated guess would get you closer.

Do you know what pistons are in it.

[ITLBTU]

It's been 15 years since I had the heads off, but I'm pretty sure they are flat tops with the valve reliefs.

[MarkM66]

Does it run okay on pump gas?

I used this and came up with a little over 10.5:1 , but had to guess on some figures.

http://www.csgnetwork.com/compcalc.html

[ITLBTU]

Thanks... that calculator was cool. I think I must have around 12.3:1. I have to mix 5 gal of 110 race gas per tank for it not to ping.