Hello. I have a 290 hp crate gm 350 sbc with a broken crankshaft. Rather than just patch it up I have opted to do a full rebuild. I want to put a little more performance into the engine without going too crazy; my target is somewhere around 320 hp or so. The heads on this engine are 1.94" intake 1.50" exhaust with 76cc chambers. Are these adequate heads or should I change them? Thanks
Real HP is in cylinder heads. Having said that, those valve sizes will support your goal. The weakness of factory heads is in the port work. In today's world it's easier and usually cheaper to buy aftermarket heads than to have a guy do port/chamber work on your heads. Your goal can be met with pistons that bump up compression to about 9 to 1 and a 270 or so duration cam with a decent intake manifold/headers. With decent heads the number jumps up to 400/425 HP without breaking a sweat.
I'm not sure if the block is damaged or not. I'm hoping not, since there was no oil leaking from it but we haven't took it apart just yet. I've never dealt with this problem before, does it usually ruin the block?
I personally would use one of the extreme energy cams with longer duration favoring the exhaust, but your combination of parts will easily hit 325 HP. I also prefer the performer RPM air gap style although the air gap thing appears to be more form than function....but I live where it's pretty hot in the summer.
I had a customer drive his 1990's TPI Camaro to my shop with a broken crank. The break was near a main and the crank just stayed wedged together. We put a crank and oil pump in it.
several years ago we pulled a 350 from a 78' Z28. Rebuilt with new bearings, rings, light cylinder hone, decked block .013 to square it, milled heads .030, mild 278/288 split duration Summit cam and Edelbrock RPM intake with a 600CFM Eddie carb. That motor put out 362HP at the crank.. Got great gas mileage and perfect street manners.
Thats a very budget minded build.. We spent less then $600 only reason we spent so much was one head was cracked and we went ahead to have it repaired.. i did however reshape the guide bosses in the runners..
Well come to find out after taking it apart, the motor had been rebuilt poorly at best and 1 rod didnt match the others. It was there that I decided the break originated. And it just kept coming apart from there.
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