VIN M to VIN J Questions

[ryansm1]

My brother has a 95 GP with the VIN M 3100 that we are going to replace, but we haven't been able to find any lower mileage/reasonably priced replacements. We've found several VIN J 3100s, but I wasn't sure if it could just drop in or not.

What are the differences between the J and M motors? I've tried searching around and have at least found that the plenum is different, and the J motors were the more recent/powerful builds, but that's about it. Are there any fitment or computer issues to worry about (EGR?) or can this basically drop in and go?

[tractorman]

I own both versions of the 3100, and there are differences with the EGR mounting. I've heard of people making adapters, but I don't know what all that involves. If you have a '95, I assume you have that 3-solenoid EGR. My 01 lumina has a different setup, and the upper intake probably wouldn't swap. However... I used to have a '96 achieva that had a very early VIN J motor. I THINK its upper intake had the same mounting setup for the EGR as my old '94 VIN M motor. Not positive about that, but it'd be worth checking out.

Other than the EGR mounting, I think all the sensor locations are pretty much the same, so your '95 sensors could be swapped over if they're different.

The newer J engines have roller rockers, better flowing heads (I'm told), aluminum valve covers, and a slightly different intake arrangement. I don't think it'd be too hard to make one work in your '95.

[bszopi]

https://www.3400swap.com

Pretty much explains it all right there. Check out the manual over there for the swap and you will be able to see what all is involved.

[ryansm1]

Thanks I thought there was something out there like that, but wasn't having any luck finding it.