Originally Posted by 396Rookie
, I've been reading forums on this site for quite a while, but first time posting anything. I'm deployed to Afghanistan right now and just looking for some ideas and/or help on this build. The block is out of a 1970 chevy pickup(2 bolt mains), and the heads are coded for 1969 SS Chevelle/Camaro(375hp rectangle port). I've had all the machining work done on the block(.060 over), and had hardened seats and everything else done to the heads. It came with a forged crankshaft and pistons(flat top). I bought some nice forged I-beam connecting rods for it. I have a hydraulic cam for COMP Cams rated for 1500-5500 rpm, switching this out for the Big Mutha Thumper Hydraulic Roller Cam from COMP Cams rated for 2500-6200 rpm if I remember correctly, with their steel roller rockers. I was looking at the Demon Carbs, but have read all sorts of forums on the right cfm rated carb for my size motor(any ideas?). I plan on puting the motor in either a chevelle or nova that came with the 396. I plan on using the car for the car shows, cruise nights, and some decent time spent on the drag strip. One thing dishearting about my motor though is I read a lot of people dissing it and saying "IF YOU ARE GOING TO BUILD A BIG BLOCK BUILD AS BIG AS YOU CAN." Something has just always caught my attention with the 396. One other radical idea I had was swaping out the rotating assembly and throwing in a 4.250 stroke crank with 6.385 rods. That would make it a 461" monster. I seen it on CarCraft's website. Although the guy kept complaining what he had to work with. Money isn't really a big problem for me so anything really goes, I just want to use the block and heads. I'm looking to keep a stock look under the hood too, make a "mega sleeper" out of it. Sorry for such a long post, but I figured I'd try and put as much info I could in hear so you don't have to ask a million questions to figure out what I'm aiming for.
Thanks for your service to the country and welcome aboard.
The engine with flat tops and the closed chamber heads will be around 8:1 compression ratio. Fine for a mild camshaft or forced induction, but you'll need more CR to run a "choppy" cam w/a lot of duration/overlap.
Use that mother cam if you feel you must, but there are better cams for power out there- that sound less radical. Remember, the choppiness you get from a radical camshaft is a result of the inefficiency of the cam at low RPM. You will need more CR than FT pistons will give you to run that cam, I believe.
I'd rather see you use a set of pistons like the TRW L2240NF. They have a short dome and will get you about 9.5:1 CR, give or take, depending on the head gasket thickness, amount the head's been milled and deck height.
Before I would throw a 4-1/4" stroke crank into a 396 block, I would use the 4.250" nominal bore block from a 427/454 engine. At 0.060" over, a 427/454 block w/a 4-1/4" crank will get you almost 500 cid, plus even more gain from the valves not being shrouded by the small 396 bore.
AFA keeping it stock looking, a 454 looks like a 396 to many guys and the ones who are REALLY sharp won't be fooled anyway.
If you are sold on a 396 block, I'd keep it w/a 3.76" crank and live w/it.An engine in the 400 cid range will run fine w/a carb in the area of 750 CFM.