Flathead Power brakes

[47merc]

I want to fit power brakes (vacuum) to a Flattie engine that has an Offenhauser triple carb manifold on it. The manifold has 2 vacuum ports on it. One off the front carb on the left hand side for the vacuum to the distributer and another off the rear carb on the same side which I presume is for the vacuum wipers.
I don't need the rear one as I have electric wipers but it doesn't look big enough for the vacuum brakes as they require an 3/8" line.

I have considered blocking the rear hole and drilling a new one for the 3/8 line on the right hand side of the manifold so that when the brakes are applied it doesn't effect the vacuum to the distributer as the 2 sides of the manifold appear to be separate but am not sure. If anyone else has done this or has some thoughts on the matter I would be most interested.

[GigglingMonkey]

I want to fit power brakes (vacuum) to a Flattie engine that has an Offenhauser triple carb manifold on it. The manifold has 2 vacuum ports on it. One off the front carb on the left hand side for the vacuum to the distributer and another off the rear carb on the same side which I presume is for the vacuum wipers.
I don't need the rear one as I have electric wipers but it doesn't look big enough for the vacuum brakes as they require an 3/8" line.

I have considered blocking the rear hole and drilling a new one for the 3/8 line on the right hand side of the manifold so that when the brakes are applied it doesn't effect the vacuum to the distributer as the 2 sides of the manifold appear to be separate but am not sure. If anyone else has done this or has some thoughts on the matter I would be most interested.

I haven't done this my self but it seems logical and bypasses the problem of low vacuum from a lumpy cam.

Add a vacuum pump and storage tank connected to your brake booster, it could be hidden under the floor or in the trunk.

Some one else might have a clearer thought on this idea.

mick in glen innes

[MickD]

I put a booster on my flathead, but it's only a single carb. On the standard manifold there's a 3/8" hole in the manifold just under the carb. My booster works fine, but I suppose if you've got a lumpy cam your vacuum might be a little on the low side. I sort of like the idea of drilling a hole in the manifold like you said. Even with multiple carbs I would have thought you'd still get vacuum when you lift your foot off because all carbs butterflies would be closed. I Think I'm right in saying that.....?

[Twin Spinner]

The 351 clevo that was in my F100 when I got it years ago had a GTHO Ph 3 grind camshaft and was very poor on vacuum so I made an extra vac tank to use inline with the booster, it was an improvement for city driving but that cam was a bit too crazy for an auto so I went back to a standard.