oem specs for pistons and cam fred fellow corvette enthusiants i'm currently building a hp engine for my ' roadster i need to buy my pistons and cam shaft but i want to first know the correct factory standards where can i find this information things like cast vs forged piston weight lift and duration etc i'm also the guy who ask the question a few days ago about high compression vs octane thanks to all answered my message so i'm also going to investigate lower compression pistons as well as the standard any help in this area would be greatly appreciated thanks again fred
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Pistons, cams, and gasoline
pistons cams and gasoline jerry bramlett i don't know one source book that has all the information but it can be pieced together from several i use old gm parts books and modern soft cover books on rebuilding modifying chevy engines the cam was gm part the casting number on this cam was it has been discontinued for many years reproductions are available from several cam grinders i have used crane and engine service group probably wolverine brands the cam specs are lift int exh with lash and degrees of duration at lift the factory pistons were forged with a small about high domed area i've never bought any pistons directly from gm i have used cast and forged replacements from trw silv o lite and badger that all worked fine chevy advertised a compression ratio of with the factory pistons and stock cc heads but personally i have my doubts that it was really this high it certainly won't be if you use composition head gaskets rather than steel shim type i've never weighed a stock piston gram weights are probably published in the aftermarket manufacturers catalogs if you need to know this i always have the rotating assembly balanced by the machine shop the hp engine is a sweetheart to drive if you have the right combination of parts you can actually feel the loss in power if you use flat top pistons to lower the compression ratio with the stock cam same goes for retarding the initial timing to avoid using high octane gas a rear gear of or numerically higher helps the around town power a bunch make sure you have a vacuum canister in your distributor that requires very little suction the stock cam only generates about inches of vacuum at idle on a good day the original canister is available reproduction but i have never checked one for proper operation i use standard ignition's b a aftermarket canister the stock configuration will live okay on pure pump premium if you never floor your car or drive up hills i mix racing gas with pump premium in a ratio of and just don't worry about it i've never had much success with octane boosters racing gas costs a gallon here any speed shop or machine shop can probably tell you where to buy it in your town it is legal to dispense it to anyone with a proper gasoline container i refill a gallon plastic jug and pour it into the car at home burning it while driving on public roads is illegal but i can live with myself afterward however if i'd had an affair with a girl my daughter's age or lied to a grand jury i would be covered with shame i'm funny like that i have found some aftermarket internal engine parts that cost less than stock but give the same power and allow use of pure octane gas but i won't drone on about this on the board if you want to hear more of my opinions you can e mail me -
Re: OEM Specs for Pistons and Cam
re oem specs for pistons and cam bill clupper i have the tech specs filed with the ama autmobile manufacturers ass'n if you e mail me at slowmobile aol com i can scan them and send you a pdf file for your information i built a hp cngine last winter and without using the minimum specs i wound up with an honest to compression using a composition head gasket about thick the hp engine uses the same pistons forged and slightly more camshaft with larger valves jerry was right on the money as to the camshaft being discontinued but there are many options including reproductions as for gasoline i find for cruising i road toured last year any hi test unleaded will work unless you plan to stand on the engine at that point you will need a ton of octane booster or a mix of racing fuel or av gas let me know if you want the specs just remember the factory supplied these specs as representing the maximum to which the engine could be built in practice production engines usually will check out point or so below the published minimum or blueprint specsComment
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Re: Pistons, cams, and gasoline
re pistons cams and gasoline gene manno jerry makes a good point about using lower compression pistons with a hp cam the cylinder pressure will be lower due to the lower compression piston and the greater valve overlap of the hp cam better to use an after market short duration high lift or a little wider lobe centers cam to get back some of the bottom endComment
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