Vacuum brake "again" !!!!!

BUBBAS IGNITION

BUBBAS IGNITION

Well-known member
Guys , you got to help me out here a little bit !!!
In the last few weeks there has been quite a few no starts and hard starts etc on the forum. As usual we always try to help in any way we can ( thats kinda what we do).
Just this week alone i have tested 5 crab distributors and a couple helmets that had a problem or two each concerning starting and just plain ole not running right.
This morning two out of three had the brake spring removed .
You really need to run this spring in the distributor for a number of reasons.
In the factory set up the spring would push the piston into the retard ring when the engine was shut off causing the engine to start slightly retarded and then pull away for advance as soon as the engine starts with manifold vacuum on the brake unit.
As the engine accelerates the manifold vacuum drops allowing the piston to move in against spring tension retarding the spark to prevent spark knock.
We have found that the brake steadys the spark output at wot as well..
Bubba Bulletin # br549 says leave this sytem in the unit.......:eek:

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Thanks for the vacuum brake info Bubba. We had a '35 Pheaton on the cross country tour that suddenly developed a gas ping during acceleration. This was with a stock '35 helmet distributor. We tried tightening the vacuum brake adjustment and that seemed to help some but we finally had to set the timing fully retarded to get the pinging to stop. I suspect the brake stopped working and caused this to happen.
 
As long as we're on the distributor subject...I have a 1936 40-B (I'm the guy with the lubrication question.Thanks for the answer). You said that sticky advance mechanisms are a common problem with these distributors so I cleaned mine with Chemtool and lubed it.What a difference!Now I understand why the engine would idle good but lousy at higher RPM's,and if I advanced the timing it would run good at cruise but poor at idle.Jim,you're my hero.Thank you.In the past,I thought these distributors were magical and they scared the dickens out of me.But after taking it apart a dozen times,I'm understanding how they work and how simple they really are.What a clever design.By the way,I still can't get it to ping with the vac brake so I left it screwed in two turns.I'm just pretending that it's perfect.
 
You may not be able to get it to ping because todays fuels are much different than the fuels used in the 40s. It is best to leave the adjustment out all the way ( by hand do not force) and then screw it in 1-1/2 or 2 turns and lock it down.
 
A minor tech: On fleamarket distributors, frequently the piston is stuck, making disassembly difficult. Run in a suitable tap to catch the inner cavity of the piston and pullitout. I use a filthy, rusty old tap with unreadable numbers, but I think it is likely 1/4 pipe.
 
Thanks Terry,I'll do that.
JM....I might be wrong here but I'd let the engine idle and pull the vac hose and reconnect it a few times.You should hear the plunger bounce back and forth.If that's not the problem,check the distributor for stuck advance.
 
This might be a dumb question but should the vacuum brake cylinder have in lubrication put on it? Or should it be completely dry?
 
JM, the leather may be all worn out on the vacuum piston. I've seen them worn out and the advance or retard plate would be worn right into the piston. Walt
 
Not to hijack this thread - but I think it will serve a purpose to fellow members here. Does anyone have a source for the leather in the vacuum brake? I have one here that is toast..
Thanks,
Tom
 
NH Ford nut said:
Not to hijack this thread - but I think it will serve a purpose to fellow members here. Does anyone have a source for the leather in the vacuum brake? I have one here that is toast..
Thanks,
Tom
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I think Ken ct has them, but I am sure Bubba would. Or, you could cut one out of an old belt. I have done that before.
 
I try to explain to the readers that the brake is very important to proper operation of the distributor. But it has to be checked every so often for hanging up and warn leathers. I use Vaseline to lubricate the piston.
 
NH Ford nut said:
Not to hijack this thread - but I think it will serve a purpose to fellow members here. Does anyone have a source for the leather in the vacuum brake? I have one here that is toast..
Thanks,
Tom
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We make up the brake out of some old leather and cut with a harbor frieght set of gasket punches. I bought the leather at a antique store ( a weight belt i believe). Glass bead inside of piston and jet glue new leather in.:)
 

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ccnelson said:
MAC's lists the brake plunger with leather and spring under part # 18-12220-S in the distributor section.
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Another beware of what you buy from Mac's,! the spring that comes with his plungers are tooo big in diameter and dont really slide in the piston like they should,this impeades the action of the plunger. You are better off using the originan spring in it if you can. Also dont like the curature of the contacting part of the pad. A flat surface will last much longer. Lube up well. OMO. ken ct. There is also a big fiber gasket that goes under the big nut,they dont provide one. Have thoses too. ken ct.
 
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