I have this spare plenum/runners. Im gonna polish it. Runners are getting painted same color as my body...(I was told it doesnt get hot enough to hurt the paint) I want an intake that will atleast pull a little more than the stock TPI I have

here is the plenum


If I knock out the walls between the runners like this

and kinda make the area on the runners between each tube more aeodynamically friendly w/ each other will I notice a difference without touching the base. I dont want to get that deap into it.

and also. while porting or whatever do I knock out this entire wall (except where studs go) I have highlighted in green in the last picture


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Fire fighting, Scuba Diving, and Fast cars.....Does life get any more exciting

WwW.Generation-3.com
'86 TPi T/A L98
Mods:
Borla 3" Adjustable Cat Back
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Catco High flow Cat
GT Auto Ram Air Hood
4th Gen. Spoiler
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AOL Screen Name, Madbiker1

 

This is how I did mine:




I don't think I would have noticed any difference without the SLP runners. Porting helps a bit, but siamesing the runner openings without siamesed runners probably won't make much difference. The throttle body opening only needs to be opened to match the throttle body. Any more is a waste of time.

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Bob '89 Ram Air Formula 350

And until that time when death won't wait, let each man rage against his fate. (O'neill)
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Yeah i really wouldn't worry about siamesing the plenum with stock runners unless you are really bored. I was really bored the day i did my injector swap so i took my already heavily ported plenum and siamesed it as well as siamesed the stock runners through the flange. I don't think there was any point really though, like i said i was just bored. pics here - http://rain.prohosting.com/imwhom/junk/inj
Your best bet is to slightly open and make sure all the runner openings are round (there are a few that have overhangs), then radius (make aerodynamically friendly) all the openings as heavily as you have time for. I spent an entire day on just this phase for my first pass (was bored that day too.)
As far as the TB inlets, there is really no point in knocking divider out of there. The best you can do is to slightly open it up and radius the entry here too to give the air a smooth transition.

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Ed Maher - Moderator @ The TPI & Carb Boards
92 Z28 Convertible - Quasar blue / Tan top
305 TPI A4 2.73 - 14.7 @ 93.6
Stock except ported plenum and dual cats
-=ICON Motorsports=-

- Definitely prototypes, high powered mutants of some kind. Too weird to live, too cool to die

 

Looks vaguely familiar You can see pics of mine on my homepage: http://temp.corvetteforum.net/bss/romeobarrera

 

1st of all I doubt any porting of the plenum will net you more than 2-3 hp and I strongly doubt that. You forgot to tell this guy however the main place to port are the walls just pass the thottle body openings, that shroud the EGR holes. That's where you will find your biggest gain if any is to be found at all. I know I didn't notice a damn thing, but it was easy if you are bored. Most people that cut out the divider between runners is b/c they have SLP or another brand of siamesed runners that aren't seperated when they join the plenum. Hopefully someone can post pics on what I'm trying to explain. Don't waste your time on what you showed removed in the 2nd pic if you plan on putting the stock runners back on. Do a search for porting plenum and you'll see what is best to remove.

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14.62@96mph headers, muffler, chip, ghetto stuff, duct tape
89 GTA 305 TPI 5 speed 3.42 gears

 

I was assuming that he had already looked around a little bit and knew that the main restriction is the EGR walls behind the TB holes. I figured he was just looking for something extra while he was there.

 

Yeah I knew that one, but thanx for lookin out!

 

anyone know what I can expect if I buy a set of siamesed runners then port and siamese my plenum. Will I notice SOTP horsepower. times drop, speeds rise?

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Fire fighting, Scuba Diving, and Fast cars.....Does life get any more exciting

WwW.Generation-3.com
'86 TPi T/A L98
Mods:
Borla 3" Adjustable Cat Back
Edelbrock Headers
Catco High flow Cat
GT Auto Ram Air Hood
4th Gen. Spoiler
4th Gen Seats and center console

AOL Screen Name, Madbiker1


[This message has been edited by 86FyrBrd (edited November 01, 2001).]

 

Well you should notice your useable power rpm (ortherwise known as a power band) to go up to around 5000 to 5100 rpm. My engine pulls pretty well past 5500 with all of the mods I have made, but I don't have dyno results to show me exactly where it drops off. I would guess that it actually starts to drop off around 5300 but just doesn't drop off as quickly as a stock TPI setup does.

I ported the SLP runners down about an inch from the way they come, and did the mods to the plenum like everyone does, including siameseing the runner openings like your picture depicts. I also port matched, or double checked the componant for it's port match, everything I could get my hands on (TB, plenum, runners, base, heads, headers). There is a lot of crappy interfaces and transitions with mass produced componants so give everything a look and clean them up - it's 'free' power!!.....

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1987 GTA L98 MD8
355, TFS Heads, LT4 Hot Cam
My GTA

The Minnesota F-body Club