Originally Posted by cdminter59
yankee phil, What octane gas do you plan on using with the 30cc pistons? A set of 27cc pistons using 781 heads with 119cc chambers would give you 10.3 compression ratio. To use 91 octane pump gas use a 18cc piston it will give you 9.5 compression ratio. I wouldn't go over 9.5 C.R. with cast iron heads if wanting to use pump gas. Some people recommend not going over 9:1 C.R. Big block are more prone to detonation than SBC. BTW if you do change rod bolts and do the honing on the rods they will have to be resized again.
Over here in europe the benzine is about 96 octane(regular unleaded) and we also have E-85 that they sell as super. The high octane,measured here in RON, is due to the addition of alcohol in all benzine products now. If you install a knock sensor with a timing retard function you can run almost anything. I work on BMW motorcycles with standard 12 to 1 compression on the normal factory sport street machine(180 horsepower,1300 cc) and the electronics take care of any detonation problems. If you have a MSD 6 AL there are attachments to give you a knock sensor function along with the automatic timing retard ,also available is a manual timing adjuster ( while your driving) as well. Its a bit expensive but with old fuel and other gas station tricks effecting fuel quality, it would be a smart move anyways(I knew a couple of gas station owners back in the day). You'd think with all the money they charge for gasoline now you guys would at least get a little higher quality product. I think ,no matter what I read on the net, that you gotta have at least 10 to 1 or more to approach 500 hp at the crank. I appreciate the advice and information,its a big help.