crank science

[dusterbd]

what crank should i use at what power level? i saw an article in a magazine that was putting out 670 horse with a cast crank. i mean, if thats ok, what level would you need to reach to necessitate a steel crank? what about 4 bolt mains? what power levels can the standard two bolt mains be used up to? the reason i ask is that im plotting the engine build for my duster. im wanting to run 11's on pump gas, naturally aspirated. you know, still be daily drivable, etc. oh yeah, with a small block, too. so whadya guys say? im just wondering.....

mike

[JVMopar]

Well from what I've heard. The 2 bolt mains are better in handling the high rpm horse power. But if your going to use the engine in a high torque application a 4 bolt main is better. The 2 bolt main has more main web to it because there aren't holes in it. Where as a 4 bolt main is better because it keeps the crank from flexing under the high torque loads. Now a splayed cap 4 bolt main (two outer bolts of the main are angled out) is the best of both worlds. To get 11's is gonna require a pretty stout motor and the ability to really plant the power. I would say spend the money and get the splayed caps and have them installed, cause who wants to spend $5,000 and just blow the dang thing up.

[dewme5]

a good difference in the cast and forged cranks, are going to be power adders and rpm's. Hitting a cast crak with a 250 shot of nitrous is probably going to cause some problems alot sooner then on a forged version. forged are also going to be stronger and lighter.

11's on a duster shouldn't be that hard, and shouldn't take 670hp. the mopar engine recipie doesn't mention a forged crank for running in the 10's or anytime before that. just some good flowing heads.

[451Mopar]

It should only take around 500 HP to go 11's unless you have a heavy car or high gearing.
The small block and cast crank should be able to handle 500 HP with the correct prep work, but when you start getting around 550 to 600+ HP you will have to be careful to use only the earlier blocks with the thick main webbing, and you may need to use hard block to support the cylinder walls. Aluminum rods and light weight pistons/pins will reduce the strain on the crank and block to where you may be able to run more power.

You may want to consider buying a mopar race block if you plan to spend the money to install 4-bolt mains anyhow?