I had my local machine shop build me a high performance street stock motor... 350, 4 bolt main, bored 60 over, flat top pistons, performance cam, and high volume oil pump... 305 performance heads, with enlarged intake and exhaust valves, hardend valve seats, heavy springs, screw in studs, 11.5 compression, Overall performance... good... and lots of power... :7 BUT... it has a noise that has been sometimes called a spark knocking... a slight noise somewhat like a ticking or knocking slightly when acelerating... have been using at least a 91% octane... plus have been adding a octane booster... also have tried to adjust the timing but noting so far has reduced or elimated this noise... any ideas? Also I keep blowing the valve gaskets... any ideas? Motor has less than 500 miles on it and is already smoking (oil burn) out the exhaust... this bothers me ... I have a lot of time invested... and $ but no satisifaction :-( runs great but want it to run without slamming oil in it everytime I drive it... Any ideas or hints would be great... Hurry I can't keep my favorite toy sitting idle for to long... I might get lonely on these cold winter nights coming up without my baby to keep me warm ;-) Hey don't tell my wife I said that
howziit Chris! sounds like several problems in your engine...most of them due to your unusually high compression for a street engine in a heavy truck. JMO, you should rid yourself of those 305 heads; they're one reason for your high cr and detonation problems. also, 327-350 heads have a more efficient combustion chamber, and larger valves. if you choose a 76cc head, that may drop your cr down to 10:1 or less, without having to change to lower-compression pistons. although 10:1 is still high for an engine with cast-iron heads, your engine may be able to perform well, if equipped with aluminum heads. BTW, what IS your deck height? also, how thick is your head gasket? what is your "quench"(piston-to-head clearance)? if the deck is still at factory .025", a .015" shim gasket would produce a .040" quench, which would really help with your detonation problem. next issue is high pressure in your crankcase, causing your valve cover gaskets to blow out. my guess is improper ring seal(or, hopefully, oil leaking through the valve seals/guides). if it IS leaking past the guides, that will be solved, when you replace those 305 heads. hope this helps; good luck. Myron
Thanks for the great information... I took your reply to my local machinist and he recommend a machanic who works on high preformance engines... All he did was listen to it for a couple of minutes and figured out exactly what was wrong... and fixed it in 10 mins. for just a few bucks... phew... He removed one pcv value and replaced it with a breather to releave crank case pressure... and that fixed the gasket probelm... "oil leak" and he fixed the spark knock by disconnecting all my vaccum lines, set the timing and the idle speed then he reconnected the vaccum lines and finished fine tuning the timing by road testing... which didn't releave all the spark knock but help quite a bit... But to get the spark knock to stop entirely he disconnected the vaccum advance... which solved the probelm... All he said about the spark advance was "Us big boys don't need the spark advance anyway" :7 That solved everything... including the gaskets leaking... Thank you for helping me out... My 77 baby is back and bad as ever... }> Thanks Chris
