Port mathing question
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Elder User
Joined: Apr 2002
Posts: 533
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From: Texas
Port mathing question
I know there is tons and tons of info on port matching heads headers but my question is about port matching the intake manifold to match the heads.
I bought a Edelbrock manifold and the ports are smaller then the ports on my d0ve heads should I grind the ports out to match or not? would it make any difference? any help would be awesome
I bought a Edelbrock manifold and the ports are smaller then the ports on my d0ve heads should I grind the ports out to match or not? would it make any difference? any help would be awesome
Hotshot
Joined: Dec 2003
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From: iowa
honestly on a typically street driven engine you won't notice any difference, it usually takes a dyno to measure the increase gained by port matching the intake when the intake ports are smaller (it does make more of a difference when it's the heads that are smaller but even then not a lot)
You could do it IF you really felt the need but as long as the difference isn't so far off as to cause a vacuum leak I personally wouldn't bother on a typical street or even a street strip motor.
You could do it IF you really felt the need but as long as the difference isn't so far off as to cause a vacuum leak I personally wouldn't bother on a typical street or even a street strip motor.
Temporarily Deactivated
Joined: Apr 2008
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Ok, the 429/460 heads most of your porting needs to be done on the exhaust side..intake side is not really necessary. there may be some dyno time so show what does what as far as intake vs exhaust but its a well known fact that the exhaust side bbf heads are a bottleneck. the intake are on the big side for street use kind of killing port velocity. you'll even see that with the way cams are cut for them with the longer duration, lower lift on the exhaust side. they slow it down to try to promote nice even flow and keep away from eddy currents in your exhaust ports. where as on the intake side they try to speed it up to increase port velocity, higer lift, little bit less duration. exactly how much they differ is going to depend on what your application is. if you are trying to get every last hp out of the engine then go to the intake after touching the exhaust. so basically if you port match the intake you likely wont see any noticeable gain, possibly on a dyno, but not likely driving it.
ah monster scooped me when i was typing this long winded answer!
ah monster scooped me when i was typing this long winded answer!
Last edited by northern 7.3; Aug 23, 2008 at 02:33 PM. Reason: i was too slow
Laughing Gas
Joined: Dec 2007
Posts: 796
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From: Minnesota
I matched ported my intake and heads for the 460 in my 73 tbird. I agree that the exhaust side would make more difference. Just seemed so mismatched. I had extra time on the rebuild. Just used the intake gasket as a reference and matched it to that. I don't know if it made any difference, but it still has a lot of power.
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Elder User
Joined: Apr 2002
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From: Texas
Well I saw this guy use poster board, he laid it on the heads then lightly tapped with a hammer around the port holes then punched out the bolt holes and had a perfect template to match the ports by, but he did it on the heads I was thinking of trying this with the intake..
Here is the video that audio sucks but its cool how do makes the template.
YouTube - Hot Rod TV Head Porting
Here is the video that audio sucks but its cool how do makes the template.
YouTube - Hot Rod TV Head Porting
Junior User
Joined: Oct 2007
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hi, yes most port work is on the exhaust side, but port matching the intake simply using your intake gaskets is easy and promotes smooth flow into the head. if your RPM is below 5000 keep the small port manifold for better low use. if above 5000 rpm think about a different manifold . have fun !!!
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Post Fiend
Joined: Mar 2004
Posts: 6,056
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From: Union, Washington
With street motors , on the intake side it is a good idea to have the intake ports smaller than the head ports so as to create a revision pulse dam. This keeps the pulse create when the valve close from reaching the carb. Two strokes are real bad about spitting gas out the carb because the reeds (valves) are so close to the carb. But it happens with 4 strokes too. In the spring and fall you can see a little fog cloud over the carb from this and it isn't good for efficiency. Port matching is really for race only engines on the intake side.
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Hotshot
Joined: Dec 2003
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From: iowa
1/2" what are you talking about, you grind that much off a head or an intake and you better have a welder handy cause your going to hit air or water.
also in most cases the amount of gain on a dyno is so small that only the people looking to gain every single hp would benifit and honestly if you mess up like grinding the port 1/2 bigger you will probably hurt yourself a whole lot more then you will ever gain. (that much grinding will almost certianly kill low end power)
also in most cases the amount of gain on a dyno is so small that only the people looking to gain every single hp would benifit and honestly if you mess up like grinding the port 1/2 bigger you will probably hurt yourself a whole lot more then you will ever gain. (that much grinding will almost certianly kill low end power)