Well, it's not completely done right now, but you get the idea. My digital camera is really showing its age in these pictures, so forgive the quality (or lack thereof). So far, I have concentrated on the throttle body inlet ports. I removed the EGR wall, ground down the side walls a little bit, smoothed out the hump between the two ports (IAC passage?), and opened up the ports a little bit (I didn't increase their diameter, I just removed some of the flare). Tell me what you think thus far.

We all know what the stock plenum looks like...





The first stages of EGR wall removal:



The port on the left is the more-complete version. It's hard to tell in the picture, but notice how the side wall is much smaller and there is less of a flare around the inside of the port.



I'll appreciate any comments. If you've ported your plenum, post some pictures! I'd like to compare mine to someone else's. I'm going to post more pictures as I progress.

 

Thanks for posting pics man! I plan on doing this when I get into the cam swap later this spring. I need to find a stock FPR to modify first though since I have a need for more fuel after the first round of mods. I'm also going to be powder coating everything while it's off too. Should be a nice gain visually as well as seat of the pants. Have fun!

 

http://home1.gte.net/res0t8sj/inj/

There are a few pics that you can see some of how i did mine on there. Like the shots into the side show a decent bit of how to cut a good radius on the runner openings. Word of advice. Do not waste your time with siamesing it like i did. I didn't see anything out of it, and it took a good amount of time. It's not a bad idea to port match the runners to the plenum. The kinda sidish shots on the runner show how you can smooth out that lip as the flange proceeds to the tube. You don't need to go nuts opening it, just smooth it out and match it. Rememeber you can put a runner on the plenum and look through the other side to check the match. You can even put marks on the plenum/runners so you can make sure it's lined up the same way on the car.

 

Thanks for the pictures, Ed. What else should I remove besides the stuff that's immediately behind the throttle body ports? I read somewhere that I should remove the vertical "line" that's between the runner ports on the inside of the plenum, and also to smooth out the runner bolt bosses.

I'm glad you mentioned port matching because it reminded me of a question that I had. I bought new runner gaskets (Fel-Pro, OEM style), and they match up perfectly to the runners and also to the plenum. In other words, there's nothing that I can really grind away to make the ports match up with the gasket. Should I remove a runner, like you suggested, and see for myself just to be sure? Should I have bought larger-diameter gaskets?

 

Dont do that unless your running aftermarket siamized runners. Those dividers induce a smooth flow of air to each stock runner. If you remove them, the incoming air will hit the flat runner flange. You could always round off the runner flange as well, but its really not worth the effort.

 

I think that you're referring to what I'm talking about, but after reading what I wrote, I didn't do a very good job of explaining it. I'm not talking about the actual cast aluminum between the holes, I'm referring to the thin, protruding line on the inside of the plenum between the holes. Perhaps this picture will help... it's taken from MikeInAZ's Tech Tips.



Just wanted to make sure that I'm clarified .

 

the peice in the pic above, what u basically want to do is knife edge that spot. on my setup i siamesed the plenum and the tops of the runners and removed any/everything that looked like it shouldnt be there.

Blue86IROC, im from pittsburgh too, what part you from? maybe we can meet up sometime.

 

Murrysville, PA. I'm about 15 minutes away from Monroeville. How about you? I've been talking to burnouts4ever through PMs and he mentioned that you and him are going to the Thirdgen Nationals together. I'm going to see if I can make it; I'm already planning on going to three car shows in Carlisle this summer.

 

Huh I grew up in Moon so I know where your talking about. Anyway heres mine with just the one side done. I finshed it I just have not taken a pic of it yet.

 

im in Hazelwood, like 2 minutes from the waterfront, Ill be attending the shows at Carlisle also, and yeah we are gathering a small army to head to 3rgden Nats.

back on topic, the plenum is looking good, are u going to siamese your intake base while your at it?

 

hey Rosco, where is the IAC passage on your plenum? did u weld it shut or something? ive never seen a plenum like that before.

 

That's cool, the Waterfront isn't that far from me at all. Maybe we can meet up sometime.

Nah, I'm just doing the plenum right now. I had thought about siamesing the base since I have the plenum off, but I really don't think I'd gain much right now with a stock cam and heads. Also, that's a pretty big change for me right now. Last summer I blew out my tranny drag racing, so I never had "accurate" times because it was pretty screwed up to begin with. I installed a new one in the fall but never had a chance to run it... I don't want to make too many changes because I won't know what mod helped or hindered -- and I've heard that siamesing can sometimes decrease performance if you don't have the right parts (or don't go deep enough). It may be a while before I siamese the base... I want to try to make it into the very low 13's without doing anything to the engine internals. I think it's possible. My friends think that I'm probably already in the high 13's now with the new tranny (the old one slipped so badly it wouldn't even shift manually), and with a little chip burning and some headers and weight reduction I could probably shave off a few tenths. We'll see .

As for my porting progress: I have the TB ports complete, and one side of the plenum is mostly done. Like you suggested, I knife-edged the sides. I still have to polish it up with a buffing wheel on my Dremel. I'll post some updated pictures later.

 

just clear cut like I did...I still have my stock runners to...No clue on performance gain though cause my IROC is in storage right now sittin for the winter...But I decided to just cut out every thing.. so there would be barley any restriction. All gaskets and ports are all matched up... on my runners I rounded off the edges between ports so it would be a smooth ride in...Also on the TB side I brought everything to the floor and did some real big radis cutting on the side wall. and if you notice the taper goin into the plenum from the TB I flatten that out to..well just let ya know what I did..

 

I pulled off the runners last night and I think I'm going to smooth out the walls a little bit. I figure the car is just sitting there, I can't drive it in this weather anyway, so I might as well do a little more. This also gives me an opportunity to get my injectors cleaned, as I pulled off the fuel rail while I was at it.

Fbirdta878787, I did just about everything that you did minus the siamesing. The pictures that I have (which aren't uploaded yet) will show that... I'll do that when I get back from church this morning. That TB-to-plenum taper is a pretty big one; I wonder how much restriction that caused.

 

Here are the completed pictures... completed in the sense that all the grinding and "polishing" is done; I have yet to clean all the metal shavings out .









A friend of mine suggested that I sandblast the inside of the plenum to further smooth it out -- would that be a good idea?

 

Lookin good blue86iroc, with the same frame of mind you are in, thats how i ended up doing all my porting /head/engine rebuild last winter,as well as my clutch/trans/rearend/suspension work this winter, sandblasting should work well to clean out the inside and probably smooth it out a little bit more but the way to go would be extrude honing which is pretty expensive , or carbide blasting which will smooth the inside quite a bit more. There is a machine shop right by me that I know the owner of ,he does carbide blasting. If you interested send me a PM or an E-mail and ill give you his info. Hes a real good guy and his prices are amazing, The quality of his work is awesome. He does everything from setting up rears to building race motors and custom fabrication. definitely makes my life easier to have freinds like him

now that you have decided to port the runners , I assume you are just gonna remove that small ridge inside the openings where the tubing meets the casting. I did this also, with all this work you should have a noticeable improvement in throttle response, etc.

and since u have the fuel rail off now would be the time to modify your FPR to make it adjustable, Vaders tech article is the way to go. For the $1-$2 cost of parts to do it you cant go wrong.

Matt

 

I'm not much of a mechanic......but..I would LOVE to port my plenum too.....on a scale to 1-10....10 being the hardest....how hard is it to take the plenum off?

 

removing the plenum is pretty easy, id say its like a 8.5 for the beginner and a 10 for anyone who has done it atleast once

IMHO the hardest part is hooking the connector on the IAT sensor on the underside, because the wires are so short

 

man I wish I could post some pics ..... I don't know how to format my pics to jpeg ....and get them to a nice size . I am doing this as well ......I am about to have the inside of the plenum glassbeaded. and the runner holes enlerged to match the new edlebrock runners.........some one Pm me on how to convert picks ...and I'll post a bunch ...if ya want

 

I think you got that backwards. Being easy, as you stated, would be at the opposite end of his "10 being the hardest...." scale at a 1 to maybe a 2 rating. 84customZ28, it's easy! Just don't take any chances and make sure you get all new gaskets on hand and be sure all gasket surfaces are clean before you put it back together. The rest is just nuts and bolts!

 

lol yeah i did have it backwards i was thinkin 10 being the easiest

 

that dosen't sound to bad..so....is it really worth taking it off...porting and polishing it??

 

Fastcamaro87, a PM is on the way regarding that machine shop. You're right about the ridge in the runners, that's exactly what I'm going to remove. I read on Ed Maher's Website that he used something called Castrol Super Clean to etch the runners... basically he soaked the inside of the runner in this stuff. He said that it might open it up a few thousandths of an inch, so I might as well try it. Can't hurt. I had thought about making an AFPR using Vader's article, but I didn't know if it would be any less reliable than buying one. I have access to an acetylene torch, so building it shouldn't be too hard. Have you done this?

Yes, removing the plenum is easy. The only annoyance that I've run into is pulling off the TB coolant hoses before I did the bypass mod -- it gets a little messy. Other than that, it's basically ten bolts for the runners and four for the throttle body.

84customZ28, I've read a lot about people porting out the plenum. I don't think that it's supposed to give mad gains in horsepower, but every little bit helps... especially on these relatively restrictive TPI intakes. I'm anxious to see the improvements this summer at the track.

 

i can't wait to start porting mine.......

 

The AFPR mod is so easy and cheap to do, all you need is a torch that gets hot enough to use a brazing rod, I have done this mod on my car as well as my freinds 86 iroc, Both have yet to have any problems, to justify spending upwards of $50 for just a peice thats adjustable that replaces the stock one i cant justify the cost of buying one versus making one (which will only cost $2.50 tops). Just follow Vaders tech article and its a breeze.

As for the Castrol Superclean, i didnt have much luck cleaning the runners out with that stuff, i managed to find a brush at the hardware store , it looks like a giant pipe cleaner with a handle, i used that and a combination of Purple Power and Castrol super clean (Grease Lightening works really good for this), and i eventually got them cleaned out. As for them etching the metal a few thousandths i think he was just kidding, that stuff is pretty caustic but i dont think it will remove material, Carbide blasting on the other hand though will definitely take care of that.

Matt

 

******* hope this works guys .....took 2 hours to upload to the server ! ( DAM dail up !!!!! )




[url]



Hope it works .....and helps ..........here is the plenum

 

k...here it the mat .....DIRTY !!!!!!!!

 

I got a question about removing the plenum... Do u have to remove the runners to get it out,or can they be left in place and the plenum slid out? Cause a couple of the bolts on the bottom of the runners look pretty tough to get to...

 

The plenum can be removed with the runners still intact. I thought the same thing about some of those lower runner bolts, but they actually look worse than they really are. I had the runners off in no time.

 

Im thinking about porting out this fall. This stuff has been very helpful, but theres so much talk of what you guys are porting out and not enough talk of what shouldnt be ported out... What dont i want to port??? I figure if i know what i dont want to do, then i cant mess it up....

 

The only thing that I've really heard *not* to do is siamese the plenum-to-runner ports... there's no benefit. See Ed Maher's post further up this thread. Basically, you want to go inside and smooth out everything that you can -- no rough edges, casting marks, etc. Just take a look at my pictures. You might also want to sandblast the inside of the runners and plenum. I read that a slightly rough wall actually causes airflow to increase than a perfectly smooth wall.

 

So theres no sensors in there im gonna cut into? And im not suppose to change the diameter of the tb passages right?

 

You're correct about the diameter of the TB passages; you'll end up opening them up a few thousandths of an inch when you smooth it out, but don't purposely enlarge the holes unless you have a larger throttle body.

As for sensors, there's really only one... the intake air temperature sensor. I unscrewed mine before I began the porting. It's located on the bottom side of the plenum and can be removed with a deep-well socket (I forget the size).

Check out this link for some techniques: http://www.gmtips.com/3rd-degree/dox...-port/port.htm

 

Formul8 just ported a plenum for me to match my slp runners. He did a pretty darn good job. If I can I will try and get some pictures of it.

 

The casting in that plenum looks terrible.

Here is a pic of my plenum when I matched it to my slp runners. I didn't cut that much out, but I did make it perfectly smooth and exactly the same shape as the runner ports. It's kind of a bad angle, my brother took it.

 

You're absolutely right. I sandblasted the plenum and the runners, both inside and out. I'll post some new pictures when I get home.

 

Just thought that I would share some pics. Back when I was running AS&M's Semi-Siamesed Large Tube Runners I modified them further by chopping off more of the runner inlet on the plenum by making it more of a 'B' shape instead of an '8' shape. This might be useful for some of you guys still running the tube-type setup on your TPI motors and want to get the most airflow possible ...



Check the whole directory for more pics:
http://www.celligent.com/tim/iroc/asm_runner/

Tim

 

Tim, is that bolt in your IAT sensor hole part of a relocation kit? Do '90 IROCs use MAF or MAP?

 

My IAT is relocated - however, the bolt wasn't part of a relocation kit. I just carried the plenum to the hardware store and found a plug that fit. 90 IROC's are Speed Density.

Tim