Thread: Got a question for the racing gurus ?

Tweet

Guys:

I built a chevy smalll block for my 51' chevy truck. The usual. .030 over, flat top pistons, mechamical cam (.050 dur 254/254) mechanical lifters. My heads are power pack heads. They have had a valve job. 650 cfm carb. headers. 4-speed manual trans, 4:10 rear limited slip auburn rear. Guys, what can I expect from this set-up. Im pretty "dumb" when it comes to engine/horsepower. Need some tech advice.

Well, assuming you're being real here and not just jerkin' our chain, I'd say you're in for a rude awakening and ya ain't gonna like it.

If the cam you have chosen truly is 254 degrees duration @ 0.050" lift, the motor will need somewhere between 11.5:1 and 12.5:1 static compression ratio to support it. If you have that much c.r., (trust me, you don't), the cam will make power between 4,000 and 7,000 rpm's, so it won't be much fun on the street.

Now, if you had said that the cam had those specs at "advertised" lift, I would have said that you were on the right track except that you might have been better off to use a dual-pattern cam with OEM heads in order to crutch up the exhaust side a little.

Yeah, I'm being real here. This motor was built with a compression ratio of 10:1. Valve size was increased (1.94 and 1.60). What is "advertised lift" Richard ? Maybe I'm not reading something right.

Look at this application chart from Comp Cams. You'll see duration at "advertised" and duration at 0.050" lift. Advertised duration is checked at a tappet lift of usually around 0.006", while 0.050" lift duration is checked at....you guessed it....0.050" tappet lift.

I don't know what size motor you have there, but my best suggestion would be to call your favorite cam grinder on the phone and talk to one of the tech guys there. Have him recommend a cam for you, 'cause the one you have is gonna be a nightmare.

Richard,

Thanks for the help I appreciate it. I will follow your advice. Btw, it's a 350.

Thanks for the help.