i have read of numerous people doing the 3.5 upper on 3.0 lower. i am wondering if we can integrate the 4.0 upper to our 3.5 lower. I am specificly interested in the plenum and throttle body. anybody think this would be worth while to look into.

 

We retro fit the 3.5 upper because it is a variable intake manifold. Your upper is already variable. So unless the 4.0 Upper is magical or ported better, I wouldn't see the advantage.

 

i am by no means an expert on engines but i figured since it is a 4.0 that the intake manifold would be bigger or at least the throttle body would.

 

But all the VQ40's that I know of are RWD, and that brings the age old topic of IM configuration once again. (ala 350z --> 3.5L Maxi/Alti mod)

Best bet would be something along the lines of the 4.0 heads.

Also, there are a few people using 00vi's on their 3.5L hybrids, so who knows ...

Personally I think the FWD 3.5L IM original design is made for torque(low rpm hp) ... and not high revving hp ..

 

the Z manifold fits fine......without the hood on

 

Would it fit the 6th gen? There might be more room under our hoods but im not sure.

 

bigger ports are not always better, although i'm not specifically familliar with the porting layout on the 3.5 vs 4.0. I've seen applications where the tuner FILLED the ports with epoxy, on a sport bike (which basically a racing engine), and gained power pretty much across the board (increased cylinder filling due to increased charge velocity). Or, the bigger heads may increase top end at the expense of low and mid range power.

How would the switch affect compression ratio? What about cams and cam timing?

 

The 4.0L is a truck engine. The intake manifold is prolly designed for low end torque and not high end power.

 

As the ports get bigger the air will come in at a slower velocity. There probably is a point at which the ports are so big that the air ivelocity isn't fast enough which would create a loss in power. But on the reverse side of things there is probably a point where there is the perfect size port that pulls in the air at just the right velocity which would give you optimal power. At the same time the length of the runners is a big part of it all.