Hello everyone, I am throwing around the idea of doing a rebuild on my LT1 in the near future. I have all of the supporting mods and the bottom end is about the only thing still stock besides fuel system.

With that said I am looking to do a somewhat budget 383 build and I am hung up on crank choice. The plan is a 383 balanced bottom half with AI LT1 cnc heads, 58mm TB and AI's matching cam with LTs. From all I have read, this package peaks by 6500 rpm and makes around 420-430rwhp with an M6.

Would a prepped cast 3.75" crank hold up to this rpm and power level or would it be on the edge? Assuming its prepped correctly and all the flashing is cleaned up and polished to help avoid cracking. It would also be balanced.

Also I never heard much about the 4130/5140 cranks. Such as made by "RPM International". They advertise them as a forged nitrided crank and are on sale online for $275 at compititionproducts.com. Anyone know what kind of power levels these hold, or if they would stand up to low boost levels? Like less than 10psi.

And if someone is knowedgeble on these and could write up a comparision I would appreciate their opinion. We all know that 4340 forged is the way to go but my bank account wont allow it right now. Just looking for some info.

Thanks, Jay

 

A local speed shop in my area built my 383 with a cast 3.75 crank for my engine, Told me that it would be fine. The combo I had put down 385hp and 390 tq through a tremec tko and a 12 bolt and about 8 months later under hard launch the crank snount broke off, bent all my valves in my dart heads. 5g's down the drain. I was done at that point and parted the car out. So save up if need be and buy better stuff. Do it right the first time. I will never use cast again.

 

Trouble is, any cast crank from overseas isn't as good as stock parts. You can't count on their material spec, purity, or machining, or anything for that matter. Forged from overseas has it's share of problems as well - stronger, but undependable tolerances. Domestic cast steel is pretty darn good. Domestic forged is way better and won't leave your sht scattered on the starting line. Cheap builds usually end up posting on here with their tale of woe. Baby needs good parts, simple as that.