Direction flow question

[1988GTU]

If you have a set of heads that you are porting the exhaust to and want to mate up a manifold to the exhaust in the best way possible for flow direction purposes, should you angle the port upward, downward, or straight off that port? This would be for a couple of different heads, but we'll use the lx9 3500 as an example.

I am thinking for stock heads it would be best to come straight off of and if ported, angle upward a few degrees (nothing drastic) .

Is this correct logic based on the design? Will there be a common thing to note/look for in making this decision?

[1988GTU]

nada?

[ericjon262]

really depends pn the shape of the port, if it approaches the flange at an angle, then angled, if straight, then straight.

[1988GTU]

3500 looks like it approaches it at an upward angle.

[SappySE107]

It doesnt.

[Superdave]

You aren't going to gain anything by angling the port shape in the direction of flow for a manifold. Just clean it up and polish the crap out of it.

Headers man... manifolds suck.

[1988GTU]

You aren't going to gain anything by angling the port shape in the direction of flow for a manifold. Just clean it up and polish the crap out of it.

Headers man... manifolds suck.

Headers should still be provided the best initial direction of flow to enhance there efficiency

[Superdave]

With headers you don't have pulses from other ports interfering with the flow though.

When you build the headers you would follow the angle of the port out for a little bit before changing direction. Doesn't have to be much but you don't want to turn it right at the flange. Makes for a bad hot spot and will fry header coatings plus not good for flow.

[1988GTU]

When you build the headers you would follow the angle of the port out for a little bit before changing direction..

And that is exactly what got this thread to be created!

[SappySE107]

20140625_122654 (Medium).jpg

WOT-Tech port mold of the 3500 exhaust.

[1988GTU]

Untouched port correct?

[SappySE107]

Correct.