Tech Tips
Part II
Buffing the Plenum Extension
Trans Am and Other Models

After you get your Plenum polished up the next area of concentration would be the Plenum Extension or Distributor Cover that attaches to it. This piece is plastic. If you were to use the stock plastic piece the best you could do would be spray it with a shiny silver paint like Eastwood Aluma-blast.....but there is a better alternative.

Go to GM Dealer and order or buy the following part numbers:

GM P/N 10108425 Aluminum Plenum Extension $ 19.50
14082425 Screws (for plenum extension) $0.42 x 3

This is the Plenum Extension from the Corvette models and it is aluminum. Follow the same procedures as you did on polishing the plenum. Be sure to get the three screws because they are different than the ones that hold the plastic cover.

Painting the Grooves in the Plenum and Extension

Now that you have your plenum and extension buffed out it sets off the finish if you repaint the grooves. You can choose any color to match your car or in my case I used Eastwoods Under Hood Black....which is a semi-flat.

I did my extension first with modelers paint and a small paint brush. This looked pretty good from straight down but what I noticed is the sides of the grooves were not covered. You rarely look at your plenum straight down from the top but actually view it from the sides. This makes the "sides" of the grooves the most important part of the visual so I came up with this idea.

The first thing we must do is clean the grooves. I use acetone and a q-tip to remove the buffing compound build up from the polishing process.

Next I shoot some compressed air to clean lint and any debris.

Use masking tape to establish a stop line for the grooves. Always use commercial grade painters masking tape for good results.

Repeat a guideline for both sides and don't forget the back, it is still cast and cleaning black from the cast would be difficult.

Wrap a tight weaved cloth (t-shirt or hankerchief, not towel) tightly around your finger. Put some oil on the cloth on top of your finger and blot this against somewhere else on the cloth. Then while keeping cloth tight rub oil onto the top......NOT in the grooves. This will keep the paint from sticking to the top. Do it a couple of times.

Go ahead and cover other non-spray areas with paint paper or newspaper.

Spray a mist coat from the left, wait a couple of minutes and repeat from the right, then the back, then a coat straight down from the top. Wait a few minutes and check the grooves for coverage. Repeat top coat if necessary. You may remove the paper to make the piece easier to move.....pull tape towards you. But do not remove the guideline tape for about 12 hours.

When you pull the tape off be sure to pull towards you or away from plenum.

I put some acetone on the rag and stretch it tight to remove black paint from the plenum ribs....just go slow here.

I retape my stop line and fill in details with a brush and let just have to play with your stop lines since the grooves are not deep here.

I do a quick re-buff with white rouge to remove handling traces and to buff out natural stop lines in the grooves and this gives you the completed project.

Here is a top view of the completed project.


[ Back to Part I - Polishing the Plenum ]

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