56mm TB on 3500?

[hookdonspeed]

3500 with 56mm TB? should i use a 3400 upper plenum and match it to the 3500 lower? or will the 56mm be enough for the 3500 plenum untill i get a larger one?

im eventually getting the 65mm TB, but dont have the funds for it at the moment with the rest of the swap.

is there a huge difference in flow between the 2 upper plenums?

[IsaacHayes]

If you are getting the CNC TB you'll need the adapter for the 3500 plenum, so just run a 56mm for now. The 3500 plenum has a few different design changes that make it beneficial. However port it and the lower to the gaskets (at least 3400 gaskets) as the ports are rather small stock. It's not all about flow, the 3500 has more plenum space, and more "equal" air distribution.

[hookdonspeed]

kk, i already have the adapter for the 3500 manifold, so im good there for now.
ty.

[SappySE107]

no it does not have more equal distribution. The 3400 flows more evenly across all ports. The 3500 broadens the powerband so if you care to fit it, then by all means use it.

[Barry]

I ran a 52mm tb on my 3500. Even with small 3100 exhaust manifolds I couldnt hold 100 kpa until red line.

52mm is just too small. 56 is probably not bad though.

[IsaacHayes]

Ben, so having the neck dump in the center actually hurts flow to cylinders 5 and 6?

I bet the 3400 equinox 3500-ish plenum where the neck actually enters the TOP of the plenum would be more equal.


--
Ben, is the 3500 plenum lower in peak power than the 3400 one? There has to be a trade off??

[SappySE107]

I don't recall what other changes were made, if it was TB included or not, but the powerband was more noticable than peak numbers (i know it wasn't a loss). I have the equinox upper to flow test once the new bench is built (working on it this week).

[torq455]

anyone notice there is a difference in some years of the 3500 UIM? the plenum shape by the 1-2 runners is square on the older ones, and the newer have a heart shape to them. better flow?

[SappySE107]

pics?

[torq455]

haha! i was just going to say that!

[IsaacHayes]

The heart shaped ones are the VVT 3500.

Also did you know the 2009 Equinox UIM now has a 77mm TB and neck? I'll have to verify from pics, but it sort of looks like the neck no longer comes directly down top like previous years, but more like the 3500 style... Hard to say though the only pic I saw had an engine cover on it.

[torq455]

geezz, the LS1 TB is 78 mm!