good morning today I'm installing a camshaft in a 1975 318 stone stock engine, after collecting the parts I have 2 question's the lift is 470/274 dur. I planed on breaking in the cam with the stock springs then switching over to the higher pressure springs tomorrow. will the stock springs coil bind at this lift, second is valve clearance to piston a issue with out valve reliefs in the stock pistons I usually work on engines with pistons reliefs cut and this is for a friends car who just wants that exhaust sound also going with the performer intake ,he already converted to duels . also is guide to retailer a problem with stock seals . I think this is too much cam for a 8.4 com engine so I also have a lunatti bracker master cam with 268deg with 464lift would this give it that cam sound in the tail pipes. thanks for your replies.
cam clearances
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fishy68
Tyr Fryr's Inc.
Due to the complex angles of the lifters to pushrods to rocker arms on a small block your .470 lift cam will only have about .450 lift at the valve, and that's with perfect geometry. Even with that said you need to actually measure your heads capabilities because they can vary a lot. I've measured some that bind up at .450 lift and others that will handle .500 lift before binding. Factory specs were far and wide. No valve reliefs in the pistons is the only thing I can say that shouldn't be a problem.
As for the cams, I can't fairly compare them by the information you've given. The advertised duration means little. Duration at .050" is the specification to compare by. IMO both cams are way too big for a 318 that "really" has only about 7.5~8 to 1 compression. It'll be a dog on take off with a cam that big. Yeah it'll sound nasty but when you get outran by some mom in her soccer van it'll sure be embarrassing. Gas mileage will be bad too as will cold starts
As for the cams, I can't fairly compare them by the information you've given. The advertised duration means little. Duration at .050" is the specification to compare by. IMO both cams are way too big for a 318 that "really" has only about 7.5~8 to 1 compression. It'll be a dog on take off with a cam that big. Yeah it'll sound nasty but when you get outran by some mom in her soccer van it'll sure be embarrassing. Gas mileage will be bad too as will cold starts
as for a note...went your cam is at max lift the piston is nowhere near the top of the cylinder...the Valve to piston clearance is tight during the over lap period of the cam....as the exhaust valve is closing the the intake is opening...and during the overlap period they are both open and the piston is dwelling near tdc...
Duration has a bigger play then the lift on the Valve to piston clearance....and the 318 pistons are down a ways in the bore...
Duration has a bigger play then the lift on the Valve to piston clearance....and the 318 pistons are down a ways in the bore...
moe7404
moe7404
you need this zinc oil additive. ZDDplus. [email protected]
fishy68
Tyr Fryr's Inc.
Or use a good break in oil with ZDDP already in it
btw: you may want to check that link cause it seems to be an e-mail address
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