High/Fast Rev SB

erich · 06-23-2002, 01:35 PM

I am building a Porsche 944 with a small block chevy (BTW, I also have a 95 Z28). I'm looking to make the engine suit the nature of the car. My first thought was a flat/180-degree crankshaft. Unfortunately, I haven't been able to find out much about building them. Any thoughts/references would be appreciated.

The second option was a quick revving, high-revving sb. My thought was to get a 400 small block and de-stroke it to 348 cubic inches (327 crank?). My main concern was the heads. I figured if the stock heads could handle 6000 rpm for 400 cid, they should be able flow enough to accomodate a 350 at 7,000-7,500 rpm (without any head work). Of course, it will have appropriate cam, roller rockers, lightweight pistons, etc. Does this make sense or is there a better way? Thanks.

BamaZ28 · 06-23-2002, 02:16 PM

I am not real technically educated in strokers but I havbe a friend from IL that races a 355 SBC he tops the RPM's around 10G. I have been in the car to prove it. Of course it is a pure drag, not street car. Only thing special besides a huge cam and stuff I know he has is a thing called a "rev-kit", which is a special set of springs and spacer type things that prevent your drivetrain components inside the engine from scattering. He also went from gas to alcohol, but it ran the same rpms on gas. If i find anything else out i will let you know.

BamaZ28

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1981 Pontiac FB originally V6, converted to SBC (HEI), Performer RPM, Holley 750 Vac Sec., Chrome Dress up, True Duals

racr4jc · 06-25-2002, 01:19 PM

The flat-crank would be sweet, but you would need a custom billet crank with some really special balancing. this means dough $$$. Then you need a custom ground camshaft with lobes in different places. Other than that, you just switch some wires around on the distributer and it's about ready to go test...who knows what other problems you will find when you turn the key!

High revving motors are fun. To do it on a SBC, your first concern is getting heads that flow. Your #1 best bet for RPM is a NASCAR SB2.2 motor which would prolly want to tach around 8500-9k and make in the neighborhood of 700-800hp @ the crank depending on the compression ratio and type of fuel. That would probably be way expensive too, but more feasable. Your next best option would be some 18* or 14* heads which would be less expensive, but still expensive compared to the regular SBC stuff. You will run into valvetrain problems next, so start out with the good stuff unless you want to spit out valvesprings and what-not. With the 18* stuff, you have to run a shaft-rocker system. A solid roller cam is a must.

Now you could go with the new wave of technology in your SBC or you could throw it all away and do it like Smokey Yunick used to. Start off with a small displacement motor. You can get a 327 crank from eagle, 3.25" stroke. Then get the biggest set of heads you can find on EBAY (aluminum is optional). Slap 'em on there and throw in a huge solid flat-tappet camshaft with matching lifters and pushrods. tighten it all down with a set of suggested valvesprings, retainers, etc. and roller rockers. cover it all up with a Victor series manifold of your choice and put some big tube headers on it and it should rock.

Greybeard · 06-27-2002, 10:52 PM

There were some 180 cranks in engines in the late '60s. The engine builder I think was Fischer and the crank supplier Moldex. One of the problems with 180 cranks is they are prone to some harmonics, and tend to unbolt everything. Safety wire is a must "through" the entire drivetrain. NEAT sound though.

If you decide on a 353 style engine, and are going to use a 400 block, use the Clevite thick bearings. Bearing spacer engines tend to have a higher "thrust" failure. Aftermarket blocks are available with 350 main bore for this style engine.

Sounds like a great project.

IrocSS85 · 06-29-2002, 08:56 PM

Id go w/a 377" eng. a friend of mine has one and it revs to 9K. its a 400 block w/350 crank I believe. I have read about this package in the mag.s lately and they liked it too. bigger piston gives you more torque and shorter throw crank gives you higher rev.s ability. If your going for high rev. power, forget the stock heads. get some afr's. like maybe 220 or 235's and port them. on top of that, get at least a solid cam, but if you got hte bucks, get a roller solid cam. it'll give you much more lift at the same duration as a flat tappet cam.
as for the revkit, thats for high reving hydraulic cams. it helps control valve float.