3400 top end swap on a 3100 block

[mograndam]

I am in the midst of an engine rebuild with a 3100 engine for a Pontiac
1995 Grand AM. Block and cam stuff are stock 3100. Top end has been
replaced with 3400 heads and intake manifolds. My problem is what push-
rods do I go with? I presently used the 3400 set and they have issues!
The Intake pushrods are causing the Intake valve to hit the pistons and exhaust seem to be ok for now. I don't have the oilpan or oil pump in yet so I can't pump up the lifters. I curious with the lifters pumped up will the exhaust pushrods give me problems too with too much lift??

[RebelGT]

If you are using 3400 heads with 3400 pushrods, you shouldn't be having any issues. The lift on the 2 cams is the same. The only difference would be the rocker arms. But since you are using 3400 heads, that shouldn't be an issue. Perhaps you put the pushrods in the wrong spots? The intake pushrods are 5.75" long whereas the exhaust pushrods are 6.00" long. That would cause the intake valve to hit the piston.

[RebelGT]

I double checked the pushrods and I am aware of the different lengths. I have had these heads milled and a valve job done on them, nothing fancy! I'm still getting intake valve interferance. When I loosen the intakes a couple of turns, the crank turns fine. I still stump! I rechecked timing gear alignment and that all seems to be ok! I can't run with my intake not torqued. Helpful suggestion, please.

Suggestions... perhaps take a head off and see if it is just one side or not? Then try the other head? I'm not sure the status of the engine (in car, on a stand, etc) but that might help lead you into a direction.

Right now engine is in the stand and it is both sides.

Hmm... ok. How much were the heads milled? And has there been any other internal work done (replaced pistons, etc..)?

[mograndam]

rebuiling 3100 engine with 3400 topend

stock pistons and stock cam and lifters. Could shimming correct this problem?? Also, noted when I stuck two pennys under each corner of head and german torqued head. Noted piston valve clearance was fine.
I am also considering adding a supercharger in the the future, so this may be an added blessing. I believe to solve this mystery I will have to
go with copper head gasket for the extra strentgh and durability when
adding high performance bolt ons. Any yeahs or neahs from the peanut
gallery

[Compufreek]

I have heard that the '97 Venture/Transport 3400 is the best donor. Is this true only because of the EGR valve placement? I have also read the article on 3100 to 3400 swap were it is explained that the '99 3400 has slightly bigger intake valves, is this true and will it make that much of a difference and does anyone have the adapter plate diagram still? They also talk about using 24lb Mustang injectors that match with the 3100 harness is that true and what years?