I once saw an article posted on the board about porting the plenum. It was pretty detailed with lotsa pics too. I think Vader posted it, but I'm not sure. Does anybody have it?

Do I have to port the runners too? I took the whole thing apart today to see what i would be getting into. The plenum definitely does have a restrictive design but the runners look decent to me. The gaskets don't obstruct airflow and the internal diameter of the runners matches the openings in the plenum too.

I hope I don't have to match-port the intake manifold to the runners - that thing's a bitch to remove.

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'88 IROC 305 TPI
Crappy 700R4 slushbox
Gutted airboxes
180 degree T-stat
Advanced base TPS voltage
Relocated IAT sensor
Momo steering wheel
Ram-air setup coming soon
Flowmaster muffler
Taylor SpiroPro wires
Accel cap and rotor
Kills: '94 Z28, Olds Aurora V8, bunch of Mustangs, T-birds, ricers, and others who thought they could trounce a 'lowly' 3rdgen.

 

You dont have to port match anything, for the most part everything is port matched from the factory. The main thing you want to do is take down the wall behind the plenum openings. Thats the biggest obstacle.

Start with a dremel. Put about 4 or 5 cut off discs on at once and take down the wall. Dont worry about not having it smooth, that does not matter.

You can also radius the "side" walls but be careful not to go through.

As for polishing, this is a lot more work and requires alot of time and patience.
If you look at your plenum you notice it has a cast /rough finish. Start with 80 grit and sand until it is smooth and there is no cast (look at it in different lighting at different angles). This stage is very critical. Then move on to 120, 220, 320, 400. 400 is the most critical. Spend a lot of time here. When you're done buff out the plenum with a terry cloth and 3m marine aluminum polish (found at parts america or advanced auto). That was your test buff. If you still see a lot of "scratches" keep going on with 400. When you feel the finish is ok, move on to 600, 800, 1500. Now buff out again with 3m polish. Take notice of the finish. Now, wetsand with 1500. You may want to spray some WD-40 on there for lubrication.

Buff out again with 3m. Follow with MOTHERS aluminum polish. And buff the hell out of it. It should be a mirror shine.
In the event where there are a lot of fine scratches, go back to step 400. Good luck. Heres a link where you can find an article about porting.
http://www.tribal-treasures.com/cars...-port/port.htm

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91 Formula
305 TPI 5speed
1LE/G92/WS6
Custom K&N cold air intake, SLP airfoil, ported & hi-polished plenum, March pulleys, TB coolant bypass, 180* stat, Crane AFPR (47psi),94 octane,Crane Extruded Alum. 1.6 full roller rockers, Timing set from 4*BTDC to 10*BTDC,MSD coil,MSD6AL, Holley 9mm Annihilator Laser shot 50 wires, Ac Delco cap,rotor and plugs, Bosch O2sensor, SLP 1 5/8 headers,SLP catback,3:73s,JET 195* fan switch, Macewen white face gauges, Autometer gauges, Zoom hi-performance clutch.
Street legal with stock throttle body, runners,intake manifold,cam, and heads.

[This message has been edited by theformula (edited January 06, 2001).]

[This message has been edited by theformula (edited January 06, 2001).]

 

IROC,

Another porting guide is located here:

Plenum Porting.pdf

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