Custom Brake Booster

[Yadkin]

I've got a pair of Offenhauser valve covers that I've wanted to use on my 390, but my OE booster is about 1/2" too long. Not wanting to cut the cast covers, I'm looking to "shrink" the booster instead. Since the old booster is original, one of the only parts of this car that has not been replaced, it's now time for it to go.

I found a Tuff Stuff 2131 "slim line" that looks like it will fit. No one has dimension drawings for this or can tell me what the bolt pattern is, so I had it delivered to see if I can modify my existing bracket.

The MC looks smaller too, so that should eliminate the interference with my diagonal brace on that side.

[Yadkin]

I measured up the parts as best as I could and it all looks like it will fit, so I went ahead and started modifying and fabricating.

Here's the old booster. There is 2-15/16" between the bolt flange and the center of the 3/8" diameter rod end. The aluminum cylinder protrudes exactly 2".

[Yadkin]

The new cylinder is a larger diameter and some type of plastic. It fits inside the bracket but I had to cut it to length. I used a Dremel cut-off wheel and wore a paint respirator. Whatever that stuff is gives off smelly, irritating fumes. I used tape to make it then cut away.

[Yadkin]

After cutting:

[Yadkin]

Next was to cut the threaded rod to the right length. I'm using a spherical rod end to mimic the fitting on the bracket, which fits a 3/8" diameter rod. Measure both the rod and rod end. My rod end is deep to allow for adjustment; I had to cut it down to fit. As long as you have 3/8" depth of threads for a 3/8" rod you have full strength. Measure twice, cut once!

[Yadkin]

Like I said, measure twice. Here I'm using the cut end of the (male) rod to check the available rod end (female) depth.

[Yadkin]

I don't have room for a lock nut so I used a big ol' blob of RED lock-tite. AFTER measuring again, of course...

[Yadkin]

Inside the cylinder is a two-stage air filter. The soft foam is pictured in the last post. The outer part is a dense felt, which I had to remove and enlarge the center to fit around the rod end. Then I threaded it on one final time over the red lock-tite.

[Yadkin]

The rubber bellows didn't fit over the rod end, since this steel insert was inside it. I just removed the insert and stretched the bellows over the rod end.

[Yadkin]

The bolt pattern on the new booster is slightly smaller (in both directions) than the OE bracket. To make it fit, I just enlarged the holes. Progress 1/32" at a time to keep the new hole centered at the original location. For this application, a 1/2" final hole size was perfect.

[Yadkin]

Bolted up, everything fits. I have one, maybe two toothpicks clearance.

[Yadkin]

As my last dual master modification, there is interference with the OE diagonal brace. Last time I modified the cylinder cover, which took a lot of time and looked terrible when I was done. Since I have a parts car available, I went ahead and modified the brace this time instead.

A little cutting, bending, and finally hammering a little bulge to just clear the edge of the cover.

[simplyconnected]

Holy shock towers, Steve... What happened to this one?

[Yadkin]

That's just some red primer under the bracket that I removed for access.

[simplyconnected]

That's just some red primer under the bracket that I removed for access.

You might consider welding a heavy plate on top, then buy new front shocks. Is the other shock tower the same?

I'm worried about the spring coming through... - Dave