ir3333
Well-Known Member
Is it best to have the intake manifold port a bit smaller than the port on the head?
..or does it matter?
..or does it matter?
port matching heads / intake
- Thread starter ir3333
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twayne24365
Well-Known Member
if intake port is bigger than head the air/fuel mixture will hit the head...either have a real nice smooth transition into the head or have the intake port a tat smaller
moper
Well-Known Member
It is never good if the intake port exit is bigger than the head's intake port entry. It will run, but the more air that tries to get through there, the worse things get screwed up. It is fine if the head's intake port is smaller than the intake's exit. In some cases it will help with an engine that is overcammed. When I port match, the priority is always the roof, the long side, then the short side. The floor I don't really care about as long as there's not a step there.
With a smaller port on head, it will create a ledge/wall so turbulence would be created. I would think you would want a larger port on the head.
ir3333
Well-Known Member
i have installed a few aftermarket aluminum intakes and the castings are terrible.
I've taken 3/16's off as many as 4 intake ports on a single aluminum intake
and always leave them rough...never polishing them.But i have taken
intake manifolds with poor castings off of some very strong running 340's.
..that's why i wondered if it made much difference
I've taken 3/16's off as many as 4 intake ports on a single aluminum intake
and always leave them rough...never polishing them.But i have taken
intake manifolds with poor castings off of some very strong running 340's.
..that's why i wondered if it made much difference
From the Racing Manual, matching the top and divider wall is the most important. I usually gasket match the top, and sides on the intake. Then the top, bottom, and sides on the head to leave a step for anti reversion on the bottom.
moper
Well-Known Member
Sorry - I was tired when I posted that... It is NOT fine if the head port is smaller than the intake's port. What I meant to type was "It's fine if the head's intake port is larger than the intake's exit."
.............I have wondered if in the real world if in fact the so called anti reversion effect actually affects the performance of a mild engine ot that it is even worth trying to measure it......years ago I have had many 318s and 360s with the 318 head on them with the 340 intake on them that went very good for what they were..............kim.......
I'm only here for confusion so here i go
I have heard of stories told that when they installed a smaller intake mouth then head there was a performance gain. My theory on this, is that the wet fuel on the side of the manifold was pulled back into the air stream by the sharp edge that is created. It may be B.S but it's my BS
If you have a smaller intake port then the head, yes it could help with reversion, if that was an issue. But now your intake is the flow restriction.....Or maybe not if you're not demanding all the air you head is capable of.
Myself, well, i'm with Moper, roof and dividing wall is my most focus, in matching.
Now how much power will you make from this effort......Most cases, not much, but a bunch of not much, make for one of those eng that "just runs good"
I have heard of stories told that when they installed a smaller intake mouth then head there was a performance gain. My theory on this, is that the wet fuel on the side of the manifold was pulled back into the air stream by the sharp edge that is created. It may be B.S but it's my BS
If you have a smaller intake port then the head, yes it could help with reversion, if that was an issue. But now your intake is the flow restriction.....Or maybe not if you're not demanding all the air you head is capable of.
Myself, well, i'm with Moper, roof and dividing wall is my most focus, in matching.
Now how much power will you make from this effort......Most cases, not much, but a bunch of not much, make for one of those eng that "just runs good"
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