Help with manifold matching

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jsgarage
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Re: Help with manifold matching

Post by jsgarage »

I know that everyone (including me) port-matches heads and intake manifolds by scribing our chosen gasket size onto the port openings. Its always bothered me that head & intake manufacturers develop a port to the best of their ability. Then we come along and change possibly vital airflow dimensions based on what a gasket manufacturer builds...
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Re: Help with manifold matching

Post by groberts101 »

jsgarage wrote: Wed Mar 21, 2018 7:46 pm I know that everyone (including me) port-matches heads and intake manifolds by scribing our chosen gasket size onto the port openings. Its always bothered me that head & intake manufacturers develop a port to the best of their ability. Then we come along and change possibly vital airflow dimensions based on what a gasket manufacturer builds...
That's just it. They don't develop it for all combinations having various and differing airflow requirements. It's a happy medium based on market shares. On the plus side.. there's almost always room for improvements on more highly developed parts combo's.

Ever measure gasket openings of all stamping before starting the layout/scribing? I've seen mismatches of gasket openings exceeding .040" difference in widths. Seems rather silly to go to all the trouble of blueprinting an engine and porting heads and inductions to gain more consistency.. then piss it all away by matching a $2 gasket.
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MadBill
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Re: Help with manifold matching

Post by MadBill »

it doesn't take long to use a ball peen hammer to tap out a cardboard pattern to transfer exact dimensions from head to manifold or vice-versa, rather than grinding an 'aneurysm' into the joint to match an oversize and/or mis-located gasket....
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Re: Help with manifold matching

Post by FC-Pilot »

MadBill wrote: Wed Mar 21, 2018 8:33 pm it doesn't take long to use a ball peen hammer to tap out a cardboard pattern to transfer exact dimensions from head to manifold or vice-versa, rather than grinding an 'aneurysm' into the joint to match an oversize and/or mis-located gasket....
By no means am I a real head porter, but knowing that I have a pushrod pinch further down stream from my intake face I always make the intake and head as small as the castings allow. If my heads are sized pretty close to begin with I try to match up the ports so there are no hard lips without any issues in the head or intake. I hate the idea of port matching to a huge gasket and then have a pushrod pinch that is much smaller. By keeping it smaller before it I can keep the pushrod pinch as smooth as I can. But then again I am a backyard hack that has the time to do it this way. I can see how guys doing this as a profession have to do things to maximize their time and dollars.

Paul
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Re: Help with manifold matching

Post by Mikej26 »

FC-Pilot wrote: Thu Mar 22, 2018 3:39 pm
MadBill wrote: Wed Mar 21, 2018 8:33 pm it doesn't take long to use a ball peen hammer to tap out a cardboard pattern to transfer exact dimensions from head to manifold or vice-versa, rather than grinding an 'aneurysm' into the joint to match an oversize and/or mis-located gasket....
By no means am I a real head porter, but knowing that I have a pushrod pinch further down stream from my intake face I always make the intake and head as small as the castings allow. If my heads are sized pretty close to begin with I try to match up the ports so there are no hard lips without any issues in the head or intake. I hate the idea of port matching to a huge gasket and then have a pushrod pinch that is much smaller. By keeping it smaller before it I can keep the pushrod pinch as smooth as I can. But then again I am a backyard hack that has the time to do it this way. I can see how guys doing this as a profession have to do things to maximize their time and dollars.

Paul
I do this same thing. I focus on the actual pushrod pinch as being the actual narrow point so I try to widen it rather than the port opening itself in order to get a straighter line. Widening the opening along with the pushrod pinch seems to in my mind at least to be working against you
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Re: Help with manifold matching

Post by F-BIRD'88 »

I also don't see any thing in ,his, on this motor. Other than increasing the chance of a gasket leak at the manifold.
Raising up the manifold a bit, as said is as far as i'd go with this one. There is more in the cam and carb.
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Re: Help with manifold matching

Post by gmrocket »

A dual plane on a jet is kinda odd to start with...unless it's a really low rpm big block in a heavy boat with something like an A2 or bigger cut impeller, a single plane is always better

Look for a single plane and chuck that dual plane ...or you will kill all the good flow in those heads

like you said, the impeller acts like a small diameter converter.

Ive run mild small blocks in jets with single planes ...that's the ticket
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