What would be better 5.7" or 6" rod 383



I'm in the process of deciding how I want want my 383 built. I'm trying to decide weather a 5.7 or 6 rod would be better. Mainly because of the availible pistons that could handle spraying a 350 shot. Most of the pistons that I have found for a 6" rod 3.75" stroke claim to be good for a 250 shot. I haven't found any heavy duty nitrous pistons listed in the catalogs that I have for this type of combo.

The machine shop that I was talking to said a piston for a 6" rod was pushing the rings up towards the top of the piston and cautioned me about using the longer rod.

I'm leaning towards using the callies compstar series crank and rods but I'm not really sure what brand of piston to run. The shop that is going to build it is always busy so since they are only workin ng on my heads at this time I can't get much info out of them.

I hope to reach about 600 fwhp on the motor and spray a 250 shot safely. Im want to have about 11.5 or 12 to 1 compresion.

 

Your shop is correct - the 6" rod puts the pin too far up in the piston, limiting how much they can drop the ring pack to get the top ring out of the intense heat generated by the nitrous. Also limits to some extent the thickness of the crown, which is typically increased on a nitrous piston. I opted for 5.85" rods, which still require a ring rail. BME will make you any "nitrous" piston you want.

 

I disagree. Like you said, the 5.85" rods still require a ring rail and I personally have not, nor have I heard of, anyone cracking a ringland on a forged piston, even a 6.0" rod piston with the slightly thinner lands. If you've gone that lean, you've probably damaged other things that would require a rebuild anyway. Most of the 6.0" rod 383 pistons will handle a 200-300 shot if tuned properly. If you are wanting to spray more than that, than you should have a professional decide on the internal parts and would not want to likely use a 6.0" rod. The 6.0" rod makes for much easier balancing and ends up being cheaper in the long run in most cases.

In the end, it likely won't matter much for performance or reliability.