Choosing 3100/3400 Manifolds

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Choosing a lower intake is fairly simple. There are date stamps on them. This blank manifold came out of a minivan and should be avoided at all costs due to the injector boss design hindering the flow. Ported underflows a stock 2000+ manifold.
00 and 03 stamped lower intakes are the best as they have the same injector boss update from 99 stamped manifolds (2nd best), with a larger inside diameter near the top.
This is a pressed in coolant line fitting. Small port owners (94-99 3100) should have a threaded fitting where the tube goes into the manifold. Press in can be tapped for threaded but not the other way around.
This is an upper intake from a minivan. No 3100 or 3400 is on the manifold, which makes it nice for 3100 owners. The EGR type (top right flange in pic) is the major reason for using this type manifold. Its the worst performance of all upper intakes however
In 2000, GM changed the EGR mount to verticle, but the electrical connector is the same. Thats good news for 96-99 owners because you can just use the newer EGR without any adapters. These are the best upper intakes to use.
This is the same 96-99 minivan intake. 99 N body 3400s use the same style manifold unfortunately. The crease being pointed out is the culprit, restricting flow to the number 5 and 6 cylinders.
Looking through the throttle body port, you can see the restriction that crease present to the entire manifold. There is no reason for the crease.
Back to 2000, the crease is gone, giving this manifolds the best equal flow distribution potential.
Much better opening for the throttle body. The IAC (idle air controller) opening is also now connected to the main bore. This is something to be aware of but won't effect anything.
Older TB on the right with the square IAC passage, while the newer TB has it connected to the main bore. If you have a mismatched setup, its as simple as grinding a slot between the square and the main bore so that the engine can idle properly.
These protrusions are not killing performance, but can be modified to eliminate their effect on flow. Only 2000 and newer manifolds have these.


Product CodeArticle60V6Manifolds

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