Alright, this is for the ever lasting question of "what is the difference between 2.8/3.1 vs 3.4 heads"

Word is, that the 3.4 heads have more meat around the spring area. After having my 3.1 head on work bench, and 3.4 heads in the car, I compared.

You can NOT install a larger DIAMETER springs on the 3.4 heads. The area the spring SITS is not any larger. I measured both at approx 1.25-1.375 diameter.

What IS different, is the angle the material comes off of this "perch". It is more gradual (sp?). It appears the material on the top of the head is "slightly" higher, or maybe the "perchs" around the head bolt area is machined down more.

Valve size is same, bolt patterns all the same. I did find my 3.4 heads had more casting "flaws" that needed to be cleaned up then the ones that came off my 3.1.

So thats the difference. Hope everyone understands my ling.

 

Thanks for the info! So for all real "dyno" purposes, the heads are the same?

 

they should be "the same".

I think this less of a slope is to help prevent any possible cracking.