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intake port to intake manifold. match or mismatch?h

General engine tech -- Drag Racing to Circle Track

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dan miller

intake port to intake manifold. match or mismatch?h

Post by dan miller » Wed Jul 21, 2010 7:28 pm

You guys are doing great with the exhaust port to header flange question. How about talking about the intake side of things?

I'm from the "match it" camp.

I set the heads on the block (no valves, maybe a loose head bolt or two) and bolt on an intake manifold that has been dowel pinned. Then I remove the bolts from one side of the manifold, lift off the manifold and head, and reach up through the intake valve seat to scribe the manifold.

Danny

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Re: intake port to intake manifold. match or mismatch?h

Post by 1989TransAm » Wed Jul 21, 2010 8:02 pm

I'm from the school of getting the cross sectional area of the intake runner correct for the correct velocity. Then of course no lips allowed on the head entrance. :wink:

CHT

Re: intake port to intake manifold. match or mismatch?h

Post by CHT » Wed Jul 21, 2010 8:38 pm

For the EMC engine a match may work better. Do two intakes and evalutae A B A testing

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Re: intake port to intake manifold. match or mismatch?h

Post by cjperformance » Thu Jul 22, 2010 8:57 am

CHT wrote:For the EMC engine a match may work better. Do two intakes and evalutae A B A testing
X2 on that one. Comparisons are the best, leaves less to guess work.
Craig.

CHT

Re: intake port to intake manifold. match or mismatch?h

Post by CHT » Thu Jul 22, 2010 9:04 am

1989TransAm wrote:I'm from the school of getting the cross sectional area of the intake runner correct for the correct velocity. Then of course no lips allowed on the head entrance. :wink:
X2

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Re: intake port to intake manifold. match or mismatch?h

Post by Ted » Thu Jul 22, 2010 9:49 am

Recently dyno tested a street 454 BBC that had the 119 oval port heads with a variety of intakes. The rectangular port dual plane (factory Winters intake) easily outperformed the oval port Edelbrock Performer RPM. The intake port mismatch was beyond bad but both the lowend and topend numbers were better with the large rectangular port intake. Just FYI and shows that almost every combination has to be tested.
Ted Eaton

dan miller

Re: intake port to intake manifold. match or mismatch?h

Post by dan miller » Thu Jul 22, 2010 10:39 am

Hello Ted

I've heard variations on your findings many times. My partner, Gene Adams, has personally seen it on a Ford 460. Small port heads with a 4 bbl carburetor, verses Cobra Jet manifold with the same carburetor - the Cobra Jet manifold made 20+ more hp in back to back tests.

We figured that the manifold was the difference (a poor but correctly matched manifold would be beaten by a good but incorrectly matched manifold). But in this case, I suspect that the Edelbrock is at least as good as the GM manifold.

It's a mystery. lol

Test. Test. Test. Hey John, do we get a discount if we're on your pump over 100 hours?

Danny

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Re: intake port to intake manifold. match or mismatch?h

Post by promachine » Thu Jul 22, 2010 10:48 am

That depends on TWMIH (time with mop in hand). :)
h.p. peddler

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Re: intake port to intake manifold. match or mismatch?h

Post by cjperformance » Thu Jul 22, 2010 9:32 pm

promachine wrote:That depends on TWMIH (time with mop in hand). :)

:lol: beauty
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Re: intake port to intake manifold. match or mismatch?h

Post by 1989TransAm » Thu Jul 22, 2010 10:31 pm

Dan, it would be an interesting test to have the port of the intake manifold at the best cross sectional area and leave it as is at the head with no lips protruding from the head of course. Make a dyno run or two. Then blend the intake manifold port at the head end to match the entrance to the head intake port entrance. Then run a dyno test to see if there is any difference. Hey it is only your money and dyno time. :mrgreen:

CHT

Re: intake port to intake manifold. match or mismatch?h

Post by CHT » Fri Jul 23, 2010 9:15 am

It'd be interesting to see Dan do numerous intakes 1 matched, 2 +0.050, 3 +0.075, 4 +.100, 5 +.125, he'll be going for months. :lol:

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Re: intake port to intake manifold. match or mismatch?h

Post by Kdub » Sun Jul 25, 2010 12:20 am

The big mismatch made the oval port head think it was feeding from a larger plenum manifold? The bigger runners on the square port heads would make the manifold have more volume.

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Re: intake port to intake manifold. match or mismatch?h

Post by T-flow » Sun Jul 25, 2010 11:37 am

Kwilliams, hit it on the head! One intake has a bigger CS and feeds the intake track better. Even with the mismatch...
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Re: intake port to intake manifold. match or mismatch?h

Post by Ron Miller » Sun Jul 25, 2010 2:32 pm

kwilliams wrote:The big mismatch made the oval port head think it was feeding from a larger plenum manifold? The bigger runners on the square port heads would make the manifold have more volume.


kwilliams,

When you say big mismatch,,,,, did you leave the intake oval port shape oval ?? or did you possible grind a funnel shape(head side oval to square) to match the square port intake shape ??

I have seen this done before and wondered if this would help or hurt the air transition from the intake into the port.

Thanks for looking

Ron
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Re: intake port to intake manifold. match or mismatch?h

Post by Troy Patterson » Sun Jul 25, 2010 3:47 pm

Consider that the primary air stream or flow isn't spread uniformly across the port area, a majority of the flow occurring in a much smaller area and taking a path something like a string pulled through the port would take. Where the port mismatch exist may have a very small effect on the primary area flow area.

Troy Patterson TMPCarbs.net TMP Carbs

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