porting plenum quest?
Melting Slicks
Joined: Apr 2000
Posts: 2,793
Likes: 46
From: Elizabeth City, NC
Re: porting plenum quest? (DADDY D)
The biggest thing is to match the runner holes in the plenum to the size of your runners. Basically a useless mod unless you get larger runners. And there are a few things in the inside that can be smoothed out. Some even have some casting imperfections in the inside that leave lumps of aluminum just sitting in there. So just a basic cleanup is in order.
Team Owner
Joined: Sep 2001
Posts: 62,157
Likes: 1,732
From: Athens AL
C7 of the Year - Unmodified Finalist 2021
C4 of Year Finalist (performance mods) 2019
Re: porting plenum quest? (LPDesRoche)
you clean it out first, if your car has lots of miles on it, then it could have some carbon junk builtup in there. You then take a Dremel and make sure the holes on the plenum match up with the holes on the runners goin to the manifold. You can also take out whatever is inside the plenum too, as much as you want.
Melting Slicks
Joined: Apr 2000
Posts: 2,793
Likes: 46
From: Elizabeth City, NC
Re: porting plenum quest? (DADDY D)
Just make the openings behind the throttle body the same size as the TB passages. And make sure your gasket is the same size as well. No need to get crazy with it. If you have a 52mm open it to 52mm. There really isn't anything to hurt in the upper plenum so you will be ok. And when in doubt, leave it alone or ask lots of questions..... :D
Burning Brakes
Joined: Nov 2001
Posts: 812
Likes: 1
From: Sherman Texas
Re: porting plenum quest? (DADDY D)
I ported the plenum on my L98 GTA, it made a big throttle response difference. It had a "wall" just behind the throttle body that I basically removed, and smoothed out the air entrance of any other casting "flash". I don't know about LT1's, but I have heard that they don't have this "wall". Really woke up my old TA, and it was pretty easy too. I do recommend removing the plenum from the engine first though :eek:
:cheers:
:cheers:
Original Founding Member!
Joined: Jul 1999
Posts: 9,037
Likes: 88
From: Granby, MA
Cruise-In 1, 3, 9. 10 & 11 Veteran
Re: porting plenum quest? (thmupr)
i have also heard of doing this and siamese'n...the runners too.....my question is.....i have heard that a company does this....matches porter plenum to runners....and sells the setup for like 85 bucks or so.....any truth to this?....i don't remember exactly.....
my other question is.....on a stock L-98 does this really do anything?>......i have heard that you lose a little torque actually.......and gain a couple of ponies in the higher band.....?> opinions?
ttyl
jeff
my other question is.....on a stock L-98 does this really do anything?>......i have heard that you lose a little torque actually.......and gain a couple of ponies in the higher band.....?> opinions?
ttyl
jeff
Burning Brakes
Joined: Nov 2000
Posts: 1,040
Likes: 2
From: BowlingGreen KY
Re: porting plenum quest? (XtremeVette)
I ported my plenum last summer. I ground out the raised areas behind the TB, I also siamesed the runner holes, cut them and made two big ovals on the side instead of four separate holes. You can grind out a considerable amount of material in the plenum. I also smoothed out the initial entrances on the runners. There are little ridges in there that can be removed and polished. The process took a full two days work with a dremel and the flexible extension tool I bought for it. I ordered the larger plenum gaskets from TPIS. I would reccomend getting the gaskets before you do any porting so you can use the gaskets as a template. I also removed my frisbee at the same time. These mods really woke up the engine. It reaches much higher rpm's quicker. Seems to pull harder too. I don't have a before and after dyno, but definately think this is a worthwhile mod that dosn't hurt to try. I believe that anyone who tries it will be pleased. :cheers:
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