good day gents, I haven't posted here in quite awhile so figured I would throw question out there. For some reference I'm building a blown 270 GMC street motor for my '53 chevy truck. It was a built motor when i got it, sans blower, so i'm finally getting around to finding out what is in the inside. It was supposedly a 'race' motor( I know how many times have we heard that) from back in the day with a Fisher head and lots of other goodies. the head unfortunately did not come with it, with it does ahve some old , read heavy, Jahns forged pistons, Isky solid cam and other small things. The head is a run of the mill small port GMC with some very minor port cleanup and double springs with damper, stock valve sizes. I haven't pulled teh cam yet but seems to have appx mid .22x lift at the cam, so nothing too hairy.
SO, my first question mainly dealing with head gaskets...I know there are some on this board and other( I frequent the landracing.com forum as i'm a racer out there, not with a GMC) that have some very good knowledge of the GMC so was wondering when I should worry about blowing head gaskets due to boost...what exact type is recommended. Right now it has a FElpro 7391 installed. The problem(well not for me with a supercharger) is the flat top pistons where used with the special head which had to have those form what I have been told...but with a conventional 819 head which cc'd at 94.8cc you end up which a CR of about 7.24....and the previous owner said he had blown head gaskets recentyl in the front engine dragster....somethign doesn't compute there...or he just overheated it...this is not going to be a race motor(I've said that before) but just a very strong motor going in from of a WC T5 and 3.73 rear gear in my truck. Torque is of utmost importance, which the blower should provide. I know the head is a weak point but the blower can fool the head into thinking the intake is more efficient than it is and some bigger valves in teh exh and as much porting as allowed should make an OK driver.Would really like some roller rockers...hint hint Supercharger of choice is an Eaton m112 off a Jag. I have set up in my head a 5000 rpm max for the motor and 10psi max boost. this gives a pressure ratio of 1.68 and spinning the 112 to 10000rpm it is not near its max and should live a long time., but still in a fairly efficient area(85%, maxes at 90%). No intercooler, might impart some methanal injection at boost.
ANy comments questions or suggestions welcome.
Hans
