I have recently removed my upper plenum off my 86 IROC and am looking to port out a few things. Now when you look into the plenum from the throttle body spot on each side there is a rectangular bar that runs across the bottom. Now can those be removed or should I leave those. Also the 2 throttle body holes they have a taper to them could I match them also?? what else could be done to not have my engine fall flat on its face at 4400rpm?? I'm lookin into the SLP siamesed runners. Good idea???

 

http://www.slponline.com/view_produc...RTNUMBER=20002

runner are suppose to give alittle more top end.

 

siameseing your runners over the upper 1/3 to 1/2 of thier internal length when combined with a ported base does raise the rpm levels your engine will effectively make power in by about 500-700rpm (a worth while gain ) but I would NOT ADVISE SIAMESEING the base as just the upper runners show the gains from my testing
http://www.eecis.udel.edu/~davis/z28/buildup/plenum/

https://www.thirdgen.org/newdesign/t...meseport.shtml

things to read

https://www.thirdgen.org/newdesign/faq/thirdgen.shtml

https://www.thirdgen.org/newdesign/tech/tpimod1.shtml

 

Yes you can remove those boxes. Anything that makes the transition of air through the plenum smoother.

 

when porting the plenum you can also remove some of the side walls to make it smoother there is a pic on this sith that will show you
http://www.geocities.com/tpiecology/

 

Thanks for the helpfull site both of you!!!! Well I noticed that you both ground down the taper to the throttle bodies...Should I leave mine or should I also grind those down? Does it do anything into air removal. Stock throttle bodies are only 40 some mm big... I thought they were 52mm WTF????

this is how far I am!!! just the front boxes behind TB ports I marked what I'm talking about in red...Sorry for the blurry pic

 

Never mind!!! I just went ahead and clear cut the whole deal. I cut out the boxes inside the TB and the TB Taper. I need to know if cutting off the reinforcements in between each runner will cause the plenum to crack or break. Because of the reinforcements not being there? I have seen people do this and I wanna know if it should or shouldnt be done. I'm also using a dremel for this job and so far it is working great!!! just bought a carbide bit, 80 grit wheels,120 grit wheels and some WD-40. And everything eats through it like there no tomorrow only took me an hour to do what I have done so far!!

 

Taking out those two big chunks of metal in the front of your plenum will not give you a noticeable "horsepower" gain. It does however seem to slightly improve the throttle response.

Those "blocks" are put there to create a vacuum behind them for the purpose of the EGR passage. However on most mid 80's cars your EGR passage is 100% blocked from carbon and soot ..... the passage and it's purpose has been long since non-functional.

The plenum derives the majority of it's strength from the four corners plus top and bottom and realistically it is not under a great deal of stress.

The caution you should use is in radius-ing the side blocks on the front of the plenum. It is possible to grind away into daylight.

~~~~~~~~~~~~~~~~~~~~
Red 86 T/A 5.0 TPI (LB9/WS6)
~HyperTech Cap/Coil/Rotor/AFPR
~Derale Adjustable Fan Switch ~ 170° Stat
~Flow Matched Injectors ~ K & N Air Filter
~Ported Plenum ~ Pirelli 245/50/16
~SLP TB Airfoil ~ All Else Stock

 

yea I noticed how thin the side walls are there!!

can you just removed the EGR completely?? is that good or bad idea...

Cause if its already block or probably will be I think it would be fine right anyone done this??

 

You can get a few ideas here: Plenum Porting.pdf

You'll need Adobe Acrobat Reader to open/print the file.

 

If it were me I would get some carb cleaner and a long pipe cleaner and clean that puppy out with this plus some air pressure.

What???? Vader???? No Hidy Ho from you........ no wonder you're sitting alone............LOL.

Happy New Year dude.

 

the way I clean the ports that fill with carbon is bake it at 350*-400* until it stops to smoke then hit it with airpresure and it all blows right out if it all does not come out stick the nozal of your sand blaster in the hole for a few seconds then hit it with the air presure again it should be clean as new