Cast crank rpm?

[Kevin D.]

I have stroked 340.With mopar perf. cast crank has been completely balanced externally including vibration dampner and flex plate.What would be the max rpm you would spin.Dont need to know ya get rid of of it and get steel crank.Just a simple street strip combination.Thanks for the input Kevin.

 

[360duster]

it depends on the used pistons. if i remember correctly a 4" stroke with hyper-u´s should not spin more than around 6300 rpm due to the piston speed. Forged pistons can go farther, stock ones below.

If the stroke is shorter in your case then the limit is even higher.

Michael

 

[RustyRatRod]

I wouldn't twist it more than 6500.

 

[85glht]

I run mine to 6000. Engine is done by then.

 

[BBBCUDA]

My guess would be something other than the crank will give you problems first. Not a SB, but I fooled with an old bracket motor (440), a friend bought. Ran 10 years with a ton of boost from a 6-71 supercharger. Ran another 3-4 with different heads, (10.6/1) in a bracket car, spinning 6,800 rpms. We detuned slightly, and it's still going strong. I bounced it off 7K a bunch. Cast crank.

 

[Locomotion]

A stroked street/strip combo should need to go over 6,500 anyway!

 

[Darter6]

For mine. 6-6200 no problem

 

[dusterdoug]

A stroked street/strip combo should need to go over 6,500 anyway!

What Myron said! Remember that's a full 1/4" longer than the OE 440 crank. Drive it as such...

 

[Locomotion]

What Myron said! Remember that's a full 1/4" longer than the OE 440 crank. Drive it as such...

oops - yea, should NOT need to go over 6,500!

 

[moper]

What you really want to do is determine what shift points get you the quickest. In most cases, shifting lower will get you there quicker. Most 4" arm engines that dont have more expensive top ends will be all done before 6500 and will want to be shifted between 5800 and 6100. You really needs some heads and carb to move enough air to make power that high.

 

[Guitar Jones]

Something that no one mentioned is I believe it's very important to get heat in the motor before you start spinning a cast crank to max RPM. I always liked to warm the engine to at least 180* then cool it down before the first pass. Heat will stay in there the rest of the night.

 

[BBBCUDA]

My point in mentioning the 440 I played with was the cookies probably won't fly out if it makes it to 6,600 by accident. Yes the stroke is longer than a 440, but it doesn't have nearly the weight, or forged 6 pack pistons swinging on the rods, or 13 yeas of steady abuse. I agree, shift it where it runs fastest. The aforementioned 440 got shifted at 5,500. If I binked it off 7K doing a burnout on the street, I didn't lose too much sleep over it.