Flathead 8 and power brakes.
 

Howdy all.

I have a 30 Model A I bought off an estate a while back. The owner was going for a 50's 'ish' build.

Why am I here rather than the Model A forum? The car came with a 48 truck flathead V8 (that's why i bought it) and a Speedway brake/clutch master cylinder kit. Which has a power master cylinder.

Question - Can the flathead provide enough vacuum for the master cylinder? If so, are there any tricks/mods needed to do so, or can I just run the vacuum from the intake manifold?

Re: Flathead 8 and power brakes.
 

Really need a power brake with a Model A/flathead combo

Re: Flathead 8 and power brakes.
 

I would not use engine vacuum. If 12volt car use this..........
https://www.summitracing.com/parts/h...RoC1hgQAvD_BwE

Re: Flathead 8 and power brakes.
 

Hella Street Vacuum Pumps 009428087


https://static.summitracing.com/glob...-009428087.jpg

Re: Flathead 8 and power brakes.
 

thank you petehoovie,

Re: Flathead 8 and power brakes.
 

I'm curious; what is your reasoning behind this statement?

A good running flathead makes plenty of vacuum (>20 inches). Is there a difference between 6 volt vacuum and 12 volt vacuum?

Re: Flathead 8 and power brakes.
 

In the "notes" section for the above pump it states:
"This is not designed for use with power brakes; it is designed to control vacuum operated accessories. If used in conjunction with power brakes, it may not be sufficient as the main vacuum source".

Summit has other pumps recommended for use with power brakes:
https://www.summitracing.com/parts/a...9308?rrec=true

I kind of agree with tubman above - what vacuum is your engine producing?

No matter which way you go, the use of a vacuum reservoir (lots of different ones available) is a good idea in my opinion.

Re: Flathead 8 and power brakes.
 

add a vac tank even ford supplied these as an accessory

Re: Flathead 8 and power brakes.
 

Yours is a 48' engine and mine is s 53', but yes the flathead provides enough vacuum for a power brake system. Mine is a factory Treadle-Vac, power brake booster, with a factory vacuum tank, under the driver side floor, bolted to the frame.

If you are still 6 volt pos ground you can always find and install an Electro-Vac unit.

Re: Flathead 8 and power brakes.
 

https://www.fordbarn.com/forum/attac...9&d=1713618487

https://www.fordbarn.com/forum/attac...0&d=1713618487

https://www.fordbarn.com/forum/attac...1&d=1713618487

Re: Flathead 8 and power brakes.
 

I only saw one that comes to mind. It was on a 52/3 ford and had an adapter under the carb with a larh (1/2") line to the master cylinder vacuum unit. Not sure how it worked, it waz along time ago!!
Gramps

Re: Flathead 8 and power brakes.
 

Thanks everyone.

The car was converted to 12v Neg ground, so it looks like, if needed, one of the aftermarket units should work. I'll check the engine vacuum first.

Re: Flathead 8 and power brakes.
 

This is how mine is routed, from the back the manifold, to the booster, on my 53' Merc, with a check valve at the booster. The last picture shows the hose coming from the vacuum tank mounted under the car.

Re: Flathead 8 and power brakes.
 

That sure is a tidy lookin engine bay there Mr Merc Cruzer !

Re: Flathead 8 and power brakes.
 

Thank you, then goal accomplished.

Re: Flathead 8 and power brakes.
 

Re: Flathead 8 and power brakes.
 

Check the amps required to run an electrical vacuum pump . I would just run the engine vacuum with a extra holding tank. Easier and probably cheaper . Just my opinion.

Re: Flathead 8 and power brakes.
 

Thanks everyone for the answers.

I'll check the vacuum and decide whether to use a tank, pump or both.