Modifying the firewall for HEI clearance

When I initially installed the engine combo for mock up, I had intended to use a small cap HEI distributor. However, as things often do, plans changed and I decided to go with a remote coil large cap HEI distributor. This meant that I would not have sufficient room to remove or install the cap with the engine in the vehicle, nor would I have proper clearance for the remote coil cap adapter.

So this required some modification to the firewall, and cutting up of fresh paint. It ended up going pretty smooth and was well worth it.

First I had to decide just how much I was going to remove, this required some measuring and measuring again to ensure I didn’t remove too much, or even worse, not enough.


Then, with the area marked out using painters tape, I used an air powered cut-off wheel to make the initial cuts where clearance allowed, then followed up using my air powered metal cutting saw.


Here you can see I had to cut into part of the wiper arm support. Cutting this section out made the entire cowl area quite flimsy and removed a lot of strength.


After the material was removed, I began mock up using cardboard to create the templates for the box that would ill the cutout. After it was properly fit, I was left with a tight 1/8″ of clearance, but that will be sufficient.


Now comes  the sheet metal patch I cut out and welded up out of 16 gauge sheet. It was quite sturdy.


Then began the slow process of welding in the patch. This took quite some time as one of my cuts was not perfectly square and required me to fill in a gap that appeared.


This is NOT how you are supposed to weld, but I was in a hurry to get it done, and the engine back in. lol


Once the welding was finished, the inner cowl area was sealed along the weld using silicone, and covered with a coat of etching primer to help prevent rust.


With the welding finally done, a light skim coat of filler was used to fill in any scratches from grinding the welds. It too was sanded.


The entire area was masked and taped off and a coat of primer was laid down.


Followed by two coats of color and two coats of clear.


With the engine back in and everything reassembled, you can see the clearance I now have. Which is plenty to remove the distributor cap and to service the distributor.

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