Ported Plenum
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From: Centerport NY
Ported Plenum
I want to start some intake mods on my '90 L 98 (auto. - 55K miles).
The car is set up with the usual minor mods, K&N, open lid, AFR, Taylor wires, TB vane, TB by pass - no frisbee - Hypertech Street runner, magna flows
With the stock TB, will a ported plenum provide any increased air flow/ performance improvements? Or would I really need to go the whole route ...... 52mm TB, port the runners, intake manifold and heads to see any improvements?
Flatbush862
The car is set up with the usual minor mods, K&N, open lid, AFR, Taylor wires, TB vane, TB by pass - no frisbee - Hypertech Street runner, magna flows
With the stock TB, will a ported plenum provide any increased air flow/ performance improvements? Or would I really need to go the whole route ...... 52mm TB, port the runners, intake manifold and heads to see any improvements?
Flatbush862
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From: altered state
St. Jude Donor '05
You could keep the 48mm TB, get some Accell runners, port the base youd see a difference. Just doing the plenum by itslefyou may pick up something but probably not SOTP noticeable.
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From: Athens AL
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port the base, or buy a bigger one like Accel or TPiS
buy some AS&M Runners or siamese your own as you port them
port the plenum
keep the stock TB, a bigger one isnt going to help you
buying the aftermarket parts will do better than porting your own because theyre capable of flowing more, but if you have to keep anything port the hell out of it
buy some AS&M Runners or siamese your own as you port them
port the plenum
keep the stock TB, a bigger one isnt going to help you
buying the aftermarket parts will do better than porting your own because theyre capable of flowing more, but if you have to keep anything port the hell out of it
Drifting
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From: The Motor City
Originally Posted by cuisinartvette
You could keep the 48mm TB, get some Accell runners, port the base youd see a difference. Just doing the plenum by itslefyou may pick up something but probably not SOTP noticeable.
The stock TB flows enough for a TPI 350 engine (it isn't until you get into bigger cubes that a larger TB is necessary). But just porting the plenum without doing anything else downstream will be waste of time. Larger runners (TPiS, AS&M, SLP, etc...) and a larger manifold (Big Mouth, Accel, Edebrock, etc...) will result in a slight bump in power (I'd estimate between 10-12bhp). Adding a set of 1.6:1 roller rocker arms will help too. But don't expect big numbers here. TPiS claims something like a 30hp increase using their Big Mouth intake, which is very misleading. Without some heavy-duty porting of not only the manifold but also the heads (AND maybe even a ZZ4 or 219 cam?), expecting a 30hp from just changing the intake is wildly optimistic at best.
The only way I would suggest porting the plenum without doing the runners and manifold is if you have it off the car for some reason, and you plan on doing this stuff later anyway. TPiS will port your plenum for $100+s/h. So if you have the plenum off the car, then it might be worth the $100. Otherwise, save the cash and do everything at once.
But that's just my $0.02.
Last edited by TheCorvetteKid; Jul 26, 2006 at 09:40 AM.
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Originally Posted by TheCorvetteKid
The stock TB flows enough for a TPI 350 engine (it isn't until you get into bigger cubes that a larger TB is necessary). But just porting the plenum without doing anything else downstream will be waste of time. Larger runners (TPiS, AS&M, SLP, etc...) and a larger manifold (Big Mouth, Accel, Edebrock, etc...) will result in a slight bump in power (I'd estimate between 10-12bhp). Adding a set of 1.6:1 roller rocker arms will help too. But don't expect big numbers here. TPiS claims something like a 30hp increase using their Big Mouth intake, which is very misleading. Without some heavy-duty porting of not only the manifold but also the heads (AND maybe even a ZZ4 or 219 cam?), expecting a 30hp from just changing the intake is wildly optimistic at best.
The only way I would suggest porting the plenum without doing the runners and manifold is if you have it off the car for some reason, and you plan on doing this stuff later anyway. TPiS will port your plenum for $100+s/h. So if you have the plenum off the car, then it might be worth the $100. Otherwise, save the cash and do everything at once.
But that's just my $0.02.
CorvetteKid has a good point, but I have seen in person with just an intake swap 22rwhp/22rwtq and no tune. This was an accel base/as&m runner/ported plenuem on a 88-90 vette. i forget the exact year. one would think the air/fuel might of been of a tad, so he might of seen a tad more. But keep in mind the tq/hp curves were very close to stock meaning it gave the same TPI characteristics, but there was more jam under the hood. If you can find these parts at a great price, It wouldnt be a bad idea. The TPI feeling on the street is fun. Throw in some 1.6's, and a set of pulleys, and 30rwhp would be the number.
Dont believe what TPIS says either!
Last edited by 88BlackZ-51; Jul 26, 2006 at 09:55 AM.
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From: Santa Maria CA
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Porting the plenum is important in that it becomes kind of a retsrictor plate if you've done the other mods. (base, runners, TB)
I would pull it apart and do it all at once. While your in there-Cam?
The LPE 219 is my favorite for a street driven 350.
Also consider the runners, I like the SLP because they are siamesed and let you rev a bit higher before you hit the "TPI Wall" In addition you can port them for even greater performance.
I mention this because I do this. Mike from corvetteplenum.com
I would pull it apart and do it all at once. While your in there-Cam?
The LPE 219 is my favorite for a street driven 350.
Also consider the runners, I like the SLP because they are siamesed and let you rev a bit higher before you hit the "TPI Wall" In addition you can port them for even greater performance.
I mention this because I do this. Mike from corvetteplenum.com
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From: MN
Originally Posted by TheCorvetteKid
: TPiS claims something like a 30hp increase using their Big Mouth intake, which is very misleading. Without some heavy-duty porting of not only the manifold but also the heads (AND maybe even a ZZ4 or 219 cam?), expecting a 30hp from just changing the intake is wildly optimistic at best.
But that's just my $0.02.
But that's just my $0.02.
