Newbie engine question

If you look here and download the L engine calculator you can play around with different combinations for a close estimate of the compression ratio.

http://www.classiczcars.com/forums/showthread.php?s=&threadid=1292&highlight=L+engine+calculator

Looks like the E-31 with the flat tops L-28 bottom end should come out to about 10.25:1 or so. Not too bad, but you can lower it easily enough in a couple different ways. Beware though, the HKS head gaskets are pricey, like about 150 or so each....:cross-eye

I'd shoot for about 9.25-10:1 for a good street engine, but you'll need to upgrade the ignition for that to work reliably.

You could always use an N-42 head or an E-88 and save the E-31 as they are one of the rarer heads. N-42's are very easy to find as they were on the 280's and there are plenty of them so they are failry cheap. It's a good head, has larger valves already, and only needs a light shave to put up some good compression numbers.