3100 with 3400 top end questions

[n_c_mail]

I have a 96 3100 and i am going to get a top end off of a 3400 (UIM, LIM, TB, Heads, exhaust manifolds) do i have to get any certain year of 3400 to make it fit onto mine and what all else do i need to get to do it? And what set of gaskets do i need for the rebuild. And one more stupid question would it be worth shaving the heads and if so how much should i shave them down??? And sorry for all the stupid questions im kinda new to V6s and Chevy. My last car was a Saturn so thats all i really know anything about

[3100 MPFI]

if you pull the parts off of the vehicle yourself, when you remove the lower intake manifold, the coolant pipe that comes out the back of the thermostat housing, take that as well. When I replaced the lower intake on my 1996 Grand Prix with one from a 2000 3400, the pipe was completly different. I think the 1996 had a screw in fitting, and the 2000 had a pressed in fitting.

You don't need the heads, or the exhaust manifolds. Your 1996 will already have the roller fulcrum rockers, and the reason for swapping the heads is to get those. If you want to swap the heads anyways, look for newer 3400's. I think in 2001, or 2002, they got larger valves, or something. Just woke up, so my brain is still sleeping.

Only reason to shave the heads down would be if they were warped, or if you are trying to bump up compression. Someone else will have to chime in for info on that.

[Sidewinder]

I would get the 3400 heads as well, from what I've gathered they flow better than the 3100 heads anyway. You don't necessarily need to get them but you may as well. The cool thing about doing the complete top swap is that you are basically going to get 15hp and 10tq by doing the swap (give or take). The 2000+ 3100s are essentially 3100s with the 3400 top end swapped onto them and they put out 175hp and 190tq over the 160hp and 180tq made by just the 3100.

You could also do 3400 heads, 3400 lower intake and put a 3500 upper on it, but that does require some more work. Either way you go you should get the intakes ported if you have the extra in your budget before you put them on, and possibly even a bigger throttle body. This will save you having to take them off again to do the port work and get gaskets again, it just all depends on your budget and how much power you want right now.

Have a look around the store, got some great stuff here, and good luck with the swap with whatever way you decide to do it.

[IsaacHayes]

If you don't want to deal with the coolant line thing, you can tap the new manifold with 3/4" NPT (I think thats the right size) and it will fit your existing setup. Or get a 3400 lower from a 3400 van 96-98 or so I think is the era that already has it tapped. That's what I did.

1996 heads were not guaranteed to have roller rockers. Most had them but not all. Brad posted this info and 3400-modified's 96 car did not have them.

Exhaust manifold is a bit better in the rear compared to the early 3100's. The rear is has short short runners instead of a log. You will need a new downpipe though so be sure to grab the downpipe and flange from the 3400 car to fab up your existing one (and it would be good to just cut the flange off, and weld on new pipe as the stock is double walled and is 1.5" inside.. way too small)

As for heads, if you have roller rockers the intake will bolt up and clear, if you don't then you'll need to swap to roller rockers (only if your head has notches for them, it should) or grind the lower intake to clear the non-roller rockers.

The 2000+ 3100 heads had larger intake valves (just slightly) and all 3400 heads had the larger intake valves.

And yes porting them is a good idea, you can take your time and do it yourself being careful and at least just gasket match them all.

For the upper, if you get a 99 or older 3400 it will bolt up to your EGR. If you get 2000+ (which has a bit better neck on it, flows a bit smoother) you will also need a 2000+ EGR valve, and the tube that goes from the EGR to the exhaust manifold to fit the upper intake.

[n_c_mail]

Thank you for all the respsonses. I have been thinking it over and calling "junk" yards and i am doing a 3400 swap with possible a 3500 top end on it. depends on responses on other questions