I'm going to do the coolant bypass when the engine goes back together and since I have everything off I am doing a little clean-up porting on the intake but have a quesiton about bump behind the throttle body opening...

I did a lot of searching here but couldn't find any info on it - How much of that bump can go away? Even with the port opening or will it get into the old coolant passage and create a vacuum leak? If so what has everyone done to solve that? (have a welder TIG it up?)

Pictures would be greatly appreciated too!!

 

I took out the front bumps and the ones around the ports, then port matched it. The MAT sticks up in front of the rear port so I relocated it to the air box.

 

I ground mine down to be even with the bottom of the plenum. Very similar to Andrew's.



I also opened up the sides and ported the runners to match.

 

Yep,,,cut it all the way back. Match it to your TB opening or even a bit more as long as you make smooth transitions into the plenum walls.

You don't need to make the walls thinner and the IAC will still work pretty well. (Hard to say for sure when the backside of my mod included a cam but it should idle fine.)

FWIW, I think that hump is designed to create a small low-pressure area to improve idle air to enter thru the IAC passages. There it's a bit more evenly dispersed.

No biggey....Lots of people run other intakes that don't even have it!

 

Take a look at this; it was very helpful to me.
http://www.gmtips.com/3rd-degree/dox...-port/port.htm

 

Took it down and shaped it, didnt remove it completely

 

this far GL

 

very good info helped me as well.

 

DANG good information there - and the pics helped a lot - the intake still has the throttle body on it and I didn't realize it was more of a vertical dam than a wide coolant passage...

Going to be doing some porting and if I get ambitious going to try and do some polishing (haven't done that in probably 15 years since I did a 22R valve cover and I just remember it taking quite a while to do...)

 

Youll spend a bunch of time on it so be ready....on the base just paint it, the casting is real porous and doesnt polish out real well, besides you dont even see it once assembled if that helps.

 

I wasn't planing on polishing the base - a simple trip through the glass bead blaster and a good wash down and coat it with either a catalyzed clear that I've got laying around or just some spray bomb engine paint...

I may see how the top is going and if it's not turning out the way I want it to I'm wondering how just polishing the tops of the ribs and painting the whole rest of the manifold and runners would look...

 

Question. The two holes in the floor of the plenum at the front as seen in ch@Os photo. What purpose do they serve and are they necessary? I think I filled them when I did my plenum. Didn't notice any difference!?
Something to do with idle air? Thanks.

 

The cast humps create turbulence to mix EGR gases that come through the two holes shown.

IAC air comes out the back of the TB
On 85-88 there is a matching hole in the front of the plenum that directs IAC air to intake ports. Air goes through a passage cast on underside of plenum and down the tube on the drv side of runners to CSI .There is a hole in each port in the intake base
Later years drop the IAC air at rear of TB

 

Thanks for the explanation.

 

Lot of times clear will make the aluminum look like a darker grey and may yellow over time. Mid America sells (or used to anyway) a real nice paint just for the TPIs, laid down real nice and looked, I thought just like fresh cast aluminum, nice stuff. Didnt have that cheap fake silver paint look to it. Havent used it in yrs not sure if they still have it. Used multiple coats, wiped clean real easy with a soft rag and windex.

 

I painted mine with Duplicolor cast aluminum engine paint then clear-coat.
The valve covers came out really nice then they didn't work with my rockers.

 

I ported the plenum on my previous car when I upgraded the runners and intake. It wasn't as difficult as it was time consuming, but it's definitely worth doing if you're upgrading everything else. If you're just porting the plenum itself and leaving everything else stock, it's not worth the effort IMO.

The "Big Tube Runners" were made by Arizona Speed & Marine. The Intake base was "supposedly" an Accel base but as I quickly found out after opening the box, it was actually an Edelbrock unit instead. Edelbrock was (at that time anyway) the only supplier of TPI bases.

Anybody that spent the big bucks on a Lingenfelter, Accel or TPIS base got royally scammed when all they received was an Edelbrock intake instead which they could have bought directly from Edelbrock for about $180 less.

Good thing I got my "Accel" base on sale at the "Edelbrock" price otherwise I'd be pissed!

Basically, there was no point in spending the "big bucks" on an intake base by Accel, TPIS, or Lingenfelter because they were actually all the same by then. They were all made by Edelbrock.

Still, the Edelbrock was a nice piece but definitely had room for improvement. Porting it out definitely took a long time, but the end result was well worth it.

Here are some pics I took of the work I did on the plenum and intake.

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What I found to be absolutely idispensible when porting is a sanding drum. Get a 1 inch, and if available, a 1 1/2 inch as well. It fits on any 1/4 inch drill, and the drum discs come in 80 to 120 grit. They can cut a lot of meat rather quickly, and allow you to easily make a clean perfect and professional looking circle for the ports.

 

It would look VERY good. I've seen several pics of this combo on this forum. It also looks good to polish the ribs and runners while painted/powder-coating everything else. (IMO, it looks best with the runner flanges painted/PC'd too.)