So I am working on this truck that has a ford flathead. First time I have laid hands on one, so other than "4 stroke internal combustion works like a Brigs & Stratton"  I have no insight into the particular foibles of the breed. Don't ask me what happened to the pic!

The person who was working on this previous to me handed me a bracket with a vacuum pump on it and stressed how important it was that I run the vacuum pump with a big reservoir if I wanted the power brakes to work. This makes no sense to me.

Anyone with experience in this matter?

Digging deep into the HAMB is going to answer almost everything you could ever want to know. I have sporadic knowledge of flatheads. Specifically about trying to make power in them by slamming tons of carburetion on top.

In terms of power brakes, I have heard of good luck using the electrically powered ones that are hidden in more traditional builds that want power brakes. I have never put a flathead in anything that needed power ever. Most of the time you can lock the brakes up on even the big trucks with a good manual system.

In reply to wearymicrobe :

The HAMB scares the E36 M3 out of me when it come to posting. Those guys live in a pretty tight box. Feel like a cat at the pit bull breeders.

Shame cause there are some good builders there.

It also has an AOD with a weird EFI throttle body where there is not going to be any way to attach a TV cable. I am guessing that a carb is going to live on top of this thing.

Pete

I would love to do something with a flathead but don't know much specifics. However, I am currently, like today, working out a power brakes system swap for and older Ford I have. Engine vacuum is the power source for power brakes. Some higher performance engines don't produce enough vacuum to operate the brakes system. In those cases an alternate vac sources is needed. So one question is - how much vacuum does your motor produce? A small single carb doesn't seem like it would be a "high performance" engine. Another question is - what does the truck weigh and what brakes does it have. 

There ae various sizes of boosters and there are single and dual diaphragm boosters. There are calculations to determine how much a booster produces. Of the top of my head it is 14.7 (atmospheric pressure) x booster diameter x number of diaphragms. 

In reply to L5wolvesf :

This is a weird ass motor from what I can tell, they spent significantf $$$ on internals and nice Ofenhuser heads, but put like a stock cam in it. Never meant to be a real power house.

If I compare the stock straight six that came out of the truck to the stock flathead that was made in 1950, I would have to report to the owner that for all the time money and effort, he now has a truck with both less HP and less torque than when he started.

I will Google around and see if there is an expected vacuum range for a stock flathead, What I want to hear is that it is the same 19 inches of vacuum as any other internal combustion engine.

EDIT:

That did not take long. That should work just fine in my books.

They are based on some real old-school tech, so they'll never make a ton of power.  The chamber design  (since it includes the valve bowl) is not very resistant to detonation which is why the compression ratios are in the 6s and 7s.

They make plenty of vacuum, they just don't have much plenum space.  How it was explained to me was that they make vacuum, but it runs out kinda quickly.  That paired with old-school vacuum boosters makes troublesome things happen with braking assist.   I think people also tried to chase breathing (and choppy idles) with cam overlap.  Having said that, I think it was more internet lore than fact.

You need to just put it on a crate, send it to me, and I'll take one for the team. 

Which junkyard cars have a remote  electrically powered vacuum pump , 

and do you need a special one for drum brakes / drum+disc brakes / 4 wheel brakes ?

and yes the HAMB is  "interesting"  my problem is so much stuff gets posted everyday that its hard to keep up........lots of very smart people there....

In reply to Curtis73 (Forum Supporter) :

I might be able to make that happen. My pitch is going to be to junk the flathead and put in a 302. Why someone choose a flathead engine and then decided it had to power everything modern electronic amenity known to mankind is beyond me. The second they went with a TBI they lost it for whatever purpose a traditional engine was going to offer. Then they loaded on power steering and AC.

In reply to NOHOME :

Really?  Power brakes?  Honest?  
You  are aware that no race car uses power brakes?  Just match the size of master cylinder with the size  of fluid required to operate the wheel cylinders.   Too Complex? Call Wilwood. 

Weak  legs?   Go smaller on the master cylinder size with more leverage (longer pedal). Don't use 1/4" brake lines. 3/16ths only. 

I had a Mustang get converted from a 4 speed to AOD come to me because the power brakes didn't work anymore.  It had a tiny little booster like that one.

What was happening was, they were no longer letting off the throttle to shift, and the engine only made 7 inches of vacuum at idle in gear.  So it never made enough vacuum for the little booster to be useful.  Even rolling down the road, it'd drop into overdrive at barely over an idle.  If you shifted to Neutral and snapped the throttle and let the revs drop, the power assist worked just fine.  So the power brakes didn't work because the booster was now way too small, because the engine now never made much vacuum, even momentarily.

They did not like that answer.

My guess is the cam in the engine is hot enough that they anticipate the engine won't generate enough vacuum to properly operate power brakes without assistance.

edit: I now see where you said the cam is stock, so in that case I don't know why the vacuum pump would be required.

For context, this truck belongs to a septuagenarian who just wants to cruise around at a leisurely pace, The concept of race or performance does not enter into the story.

Pete's answer above re the AOD bears some consideration, I also learned recently that the flatheads do not harbor much vacuum in the engine. So there might be something to this.

Curtis73 (Forum Supporter) said:

  The chamber design  (since it includes the valve bowl) is not very resistant to detonation which is why the compression ratios are in the 6s and 7s.

 

You can't squeeze any compression out of them, and still have room for the valves to open, plus you need to leave room for the air to get over above the pistons.  Detonation has very little to do with it.

But yes, they have a lousy chamber design.  

Other than it's configuration the flat head was not much different than most engines of the time. 

 App .5 hp per cubic inch      Power brakes were a rarity. 

Vacuum pump for power brakes always implies big cam (lots of overlap / narrow LSA).  How's it idle?  What's the idle vacuum? What exactly does the customer want you to fix?  How are the brakes now? Is the booster too small (looks like it might be)? Do you have a brake problem instead of a vacuum problem? Where's the master cylinder? On the other hand, if the vacuum pump that you have gives decent brakes, maybe just do that. 

Ford flattys have low compression, lousy breathing, and are prone to overheating, but all the basics are the same as any other engine. 

Agree with posts above:  HAMB and Ford Barn are your resources. 

In reply to NOHOME :

I'm 72.  Not able to walk a block without a rest stop. 
 As you age your legs get weaker and weaker.  So I really do know what I'm talking about. 

Give  me an 85 year old granny  with a walker and you can make her car stop without power brakes. 

I mention race cars because there is no greater demand on brakes than racing.  Because of that racers know how to make cars stop. It's all about leverage. 

In reply to frenchyd :

I get that. But the car is not mine and it came with a paid-for brake setup that I am sure the owner does not want to scrap so that I can confabricate a new system. MY solution to the whole thing would be to get rid of the POS flathead and stab a 302 in the hole to accommodate all the modern niceties. Once again, not my car and not my call.

Some of the flathead fuel pumps had a vacuum pump on them. My dads '53 Mercury was that way, for the vacuum wipers. Now it has electric wipers. Might be a solution along with a vacuum cannister.

Don't be too afraid of the HAMB. A post stating what you're trying to do, and a request for links to threads that will answer your question should be all you need. 

NOHOME said:

In reply to frenchyd :

I get that. But the car is not mine and it came with a paid-for brake setup that I am sure the owner does not want to scrap so that I can confabricate a new system. MY solution to the whole thing would be to get rid of the POS flathead and stab a 302 in the hole to accommodate all the modern niceties. Once again, not my car and not my call.

I get that. You do what the owner wants.  Me?  I'd love a Flathead.   But then I grew up with them and spent a lot of time learning stuff about them all the time thinking about DOHC  and aluminum blocks etc. now in my old age and they aren't cheap and abundant anymore. Now I want one just to include in my engine display.   

stuart in mn said:

My guess is the cam in the engine is hot enough that they anticipate the engine won't generate enough vacuum to properly operate power brakes without assistance.

edit: I now see where you said the cam is stock, so in that case I don't know why the vacuum pump would be required.

I wonder if the PO just couldn't get the timing/idle right and never got proper vacuum.  It's also possible that whoever suggested the vacuum pump just received some misinformation.

Kinda like when I bought my 74 Maverick.  The guy I bought it from was the grandson of the original owner who had passed away.  He told me that I have to run premium gas in it 'cause grandpa always ran premium to keep the valves from ticking.

Streetwiseguy said:

Curtis73 (Forum Supporter) said:

  The chamber design  (since it includes the valve bowl) is not very resistant to detonation which is why the compression ratios are in the 6s and 7s.

 

You can't squeeze any compression out of them, and still have room for the valves to open, plus you need to leave room for the air to get over above the pistons.  Detonation has very little to do with it.

But yes, they have a lousy chamber design.  

Well, for modern priorities, they do suck.  In the late 20s and early 30s, more priority was given to simpler, easier to produce designs for this newfangled "mass production" thing. And the fuel quality was often abysmal.  An early Flathead, IIRC, would happily run on 66 octane fuel, and would even run on kerosene if warmed up on gasoline first.  Lots of mixture motion, and the spark plug was over the nice hot exhaust valve to get things lit off easier.

We're awfully spoiled with the homogenity of fuels we get to run nowadays.

Curtis73 (Forum Supporter) said:

stuart in mn said:

My guess is the cam in the engine is hot enough that they anticipate the engine won't generate enough vacuum to properly operate power brakes without assistance.

edit: I now see where you said the cam is stock, so in that case I don't know why the vacuum pump would be required.

I wonder if the PO just couldn't get the timing/idle right and never got proper vacuum.  It's also possible that whoever suggested the vacuum pump just received some misinformation.

Kinda like when I bought my 74 Maverick.  The guy I bought it from was the grandson of the original owner who had passed away.  He told me that I have to run premium gas in it 'cause grandpa always ran premium to keep the valves from ticking.

 

Never express doubt about the "wisdom" of someone else's grandpa.

1950 Ford V 8 (flat head)  had grown to 239 cu.in.  Had a 6.6 CR, for 100 HP at 3600 rpm.

As mentioned , fuel had effect on CR.    Later on, some still existing flat heads had hit 8.0 for high  altitude heads.

I have no experience with power brakes and a flathead Ford but I do have experience with vacuum wipers.  The issue with them is that you have to spend so much time with wide throttle openings that there's very little manifold vacuum.  I could see that being an issue with power brakes as well.  You typically only use the brakes at idle but without a good size reservoir the boost could be variable or nonexistent.