91 3.1 Port work

[Dave]

So some people were talkin' about portin' the heads in an other thread, but I'm wonderin' somethin' a little different...


I'm new here, tried a search, probably not lookin' for the right things..

I've got a 91 Beretta GT with the 3.1, I'm gonna be doin' the head gaskets, but was wondering, should I go with the newer year heads (3100/3400) or should I just do the portwork to the heads I have - Tryin' to figure out what would be more cost effective - I can actually get onto a flowbench for almost nothing, so I'm thinking if I port the ones I've got I should be a little better off.

any hints or tricks? I was thinking about takin' the head down enough to raise the compression up an other point and modifying the head to accept adjustable rockers. any help would be great!

--Dave
1991 Beretta GT (3.1 - 3T40)
1988 Regal Custom (2.8 - 4T60)

[akira]

The 3400 heads flow way better but... "These genIII cylinder heads are used on late model V6/60 degree engines for improved performance. They feature an increase of 0.040" in intake valve diameter and a reshaped port for a flow improvement if 16.7% at 0.450" of valve lift. The exhaust port has been reshaped into a "D" port configuration for a flow improvement of 31.7% at 0.450" of valve lift." That is a quote from the gm peformance catalog. But you need the 2 peice intake for it as well. Alot of people here have done the swap.

[v6h.o.]

the main gains from using the GEN3 heads on a 3.1L mpfiGen2, isnt just the heads. its the intake manifolds used on the GEN3 engines that bolt to the heads. the main restriction even with a good set of ported heads on the 3.1L mpfi is the upper and lower intake manifolds. they're piss poor.

[GRANDFURY]

so will the upper and lower intakes bolt right up to the 3.1 ? and if so then you could mount the heads right?

[SappySE107]

nope, you need the heads to make it an easy swap. The amount of work to make gen 3 work on gen 2 is pretty extreme for port matching.