3500 heads on a 3400?

[ProjectMM]

I'm just wondering what modifications would bw needed to do this swap. I've been looking into this for much better flow numbers, but I'm going to keep my upper intake.

would i want to use 3500 head gaskets? or are those to thin?
i think i read that you also have to move the coolent temp sensor.
also did anyone figure out if it lowers or raises compression?

[black05gt]

Assuming that you're considering this mod for your 2002 GAGT1, MOST of your changes will be related to changed sensors and their connectors - not difficult, just need to find some parts - this topic has been thoroughly covered in several existing threads .
In answer to your specific questions - yes, you can use the standard GM head and LIM gaskets (the head gasket kit part number is in one of those threads (look for one started by onefastv6) ), and since you're planning NOT to use a 3500 plenum, the number of changes is further reduced. (But I would still recommend that you consider using a ported 3500 plenum on a ported 3500 LIM).

It's not that you move the ECT- the ECT from a 3400 and from a 3500 are not the same (IIRC), what is different is its location (in the LIM on a 3400, and in the rear head on a 3500 - the connector is the same, but you'll need to extend the sensor wiring harness to reach the 3500's ECT , since it's now lower and to the rear of its current location in the LIM near the thermostat housing.
Referring to existing threads, IIRC , there was some minimal reduction of compression when replacing the 3400 heads with 3500 heads.
And, just for clarification, the 3500 heads and the 3500 LIM must be replaced together. The UIM's and LIM's can be mixed & matched, however. You'll also need an adapter plate to mount a 3400-style TB on the 3500 plenum