Flathead 8 and power brakes.

[hammondite]

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?

[paul2748]

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

[Angledrive]

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

[petehoovie]

Originally Posted by Angledrive

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

Hella Street Vacuum Pumps 009428087

[shoe box Jack]

thank you petehoovie,

[tubman]

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Originally Posted by Angledrive

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

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?

[Randy in ca]

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.

[aussie merc]

add a vac tank even ford supplied these as an accessory

[Merc Cruzer]

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.

[petehoovie]

Originally Posted by Merc Cruzer

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.

[Ol' Ron]

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

[hammondite]

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.

[Merc Cruzer]

Originally Posted by Ol' Ron

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

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.

[cas3]

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

[Merc Cruzer]

Thank you, then goal accomplished.

[petehoovie]

Originally Posted by Merc Cruzer

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.

[Ggmac]

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.

[hammondite]

Thanks everyone for the answers.

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