jct404

I've been looking at some performance crate motors to swap out my current motor. I have a 496 w/allison in a 3/4 ton right now and want to put a higher HP crate motor in its place, either another 496 or maybe a 502. My question is are they going to be the same block (bolt patterns) or are these crate motors an older version to the L18. I am going to call a couple places monday but I thought I would get a jump on it today. Programing will not be am issue for I have EFI live.

Thanks, Jon

Shawn MacAnanny

iTrader: (12)

Keep in mind the Allisons MAXIMUN input shaft rpm is 4800rpm. Atleast thats what its rated for. I have a Duramax/Allison. This Gen3 forum is for LS1 series engines. They are on an SBC format, your 496 is a BBC format and not compatible with much. Has a different firing order than BBC, but from what i understand with a little tuning can be made to run a BBC cam from what ive heard. Read the conversions and hybrids forum there are a couple threads with info on them.

The bolts pattern will be the same. The allison trans has a BBC/SBC bolt pattern believe it or not, even on the Duramaxes. The only difference will be the crank spacing. I am unsure of the crank spacing with the 496/allison

jct404

Thanks Shawn, I guess my main concern would been the EFI bolting up, Alot of the motors I have looked at are pre 1976 emmisions...so I wasn't sure what they were meaning.

Yeah I have read about the 4800 +/- rpm deal on the allison its got alot to do with the torque converter. I'm not out to have a big block turning 6k, just good low to mid range power.

I'll go dig in the other forum. Thanks again.

Jon