I have discovered an interesting thing. It appears that, although similar, the runners of a 2.8 and 3.1 are different. The 3.1 has larger diameter runners (I can prove it,, lol). when compared to a 2.8L, the runners are definately larger and slightly differently shaped. I will post a comparison picture of the two types of gaskets for everyones viewing pleasure. I was always told they were the same, guess I was misinformed...

 

Are you basing this off of gaskets alone or the actuall runners?

 

For now, just the gaskets, I should have true measurements of a 3.1 intake soon. Until then, it's just going by how the intake gaskets are (quite different). I'm hoping Matthewy will allow me to pull hi upper plenum so that I may measure it. I'll keep you informed.

 

Reason why I ask is because I "think" the spare middle and lower manifolds I have and ported already were off of a 3.1. They were identical to my original 2.8 middle that is currently still on the car.