Question about ported plenum
Thread Starter
Instructor
Joined: Jun 2001
Posts: 242
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From: Rochester New York
Question about ported plenum
Ok, I have large tube runners, big mouth manifold, and a 52mm throttle body. I just realized that I didn't do any porting of the plenum. How much of a difference would a ported plenum make and anyone have good directions to do it (or know of a good shop in Chicago)?
Drifting
Joined: Nov 2000
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From: Big D Tx
Cruise-In II Veteran
Re: Question about ported plenum (PylonBoy)
porting the plenum isnt going to make much of a difference at all. about the only two things there is to do, is grind down on the two "humps" at the bottom of the throttle body inlet. its difference will be very small, not noticeable at all. the other thing is to gasket match the openings to the runners. id recommend hourglassing the openings of the plenum if you got slp semi-siamesed runners.
Team Owner
Joined: Dec 2000
Posts: 90,675
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From: SE NY
Cruise-In II Veteran
Re: Question about ported plenum (88L98)
You need to port match to the TB & runners as well as clean up the TB interface opening. I ground away quite a bit of material from the sides and the center hump as well as remove the two bumps. Like 88L98 said, taper the openings from the runners for better air flow. My method is on my site.
You may not notice a big gain but they all add up and it's "free". So, definitely port the plenum; don't send it out just spend some hours with a Dremel.
[Modified by 65Z01, 6:44 PM 9/22/2001]
You may not notice a big gain but they all add up and it's "free". So, definitely port the plenum; don't send it out just spend some hours with a Dremel.
[Modified by 65Z01, 6:44 PM 9/22/2001]
Race Director
Joined: Aug 2000
Posts: 14,130
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Cruise-In II Veteran
Re: Question about ported plenum (65Z01)
Everyone nailed it...I agree with gasket matching the LT runners and gaskets to the plenum holes on the sides.
Very easy to do with a dremel tool and a metal cutter bit.
The GM holes arent always very round and have some sharp edges that stick out past the stock gaskets opening.
In fact, my plenum holes were a little smaller then the factory gaskets.
Depends on how the machining work came out.
I use thick duct tape around the areas I want to port after I make marks with a red marker using the bigger gaskets as a template.
The reason for this is the duct tape reduces the chance of cutting through or scracthcing the smooth areas the gaskets go over in case you "slip" the dremel tool when porting.
Ive done this several times by accident when I first tried simple porting or gasket matching.But the duct tape saved me the headaches of causing a cut or deep scratch or something that can lead to a vacuum leak.
To see a few pics of what Im talking about, go to this site.
http://community.webtv.net/TunePort28/
And you can see the size of the gaskets in relation to the GM plenum holes.
Very easy to do with a dremel tool and a metal cutter bit.
The GM holes arent always very round and have some sharp edges that stick out past the stock gaskets opening.
In fact, my plenum holes were a little smaller then the factory gaskets.
Depends on how the machining work came out.
I use thick duct tape around the areas I want to port after I make marks with a red marker using the bigger gaskets as a template.
The reason for this is the duct tape reduces the chance of cutting through or scracthcing the smooth areas the gaskets go over in case you "slip" the dremel tool when porting.
Ive done this several times by accident when I first tried simple porting or gasket matching.But the duct tape saved me the headaches of causing a cut or deep scratch or something that can lead to a vacuum leak.
To see a few pics of what Im talking about, go to this site.
http://community.webtv.net/TunePort28/
And you can see the size of the gaskets in relation to the GM plenum holes.
