| mzahorik | -- 07-13-2019 @ 9:32 AM |
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Well... I think I have repaired the back fire problem on my 1937 Ford. I had a tremendous vacuum leak, the windshield wiper motor and the vacuum brake on the distributor were leaking badly. I plugged them up and then I had a bad back fire through the muffler. Well, this turned out to be I had the mixture so rich, in order for the engine to run with the bad vacuum leak, now filled the muffler and pow. After lowering the carb float level the engine ran a lot better, but I only had about 17" of vacuum. After advancing the timing a little the vacuum, is now almost 20" and the engine runs very good. Now for the distributor vacuum brake. I can not hold any vacuum on the piston and using a vacuum pump the piston will not move away from the distributor plate. Since the engine runs good, I am questioning the function of this brake. The brake stops the mechanical timing advance. So does this addition resistance on the fly weights tend to retard the timing, under low engine vacuum. Then under normal driving the brake is released and the advance works normal? How can a guy repair this brake vacuum leak without getting a new or different aluminum distributor casting? Thanks Mike
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| deluxe40 | -- 07-13-2019 @ 10:01 AM |
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The vacuum brake's function was to eliminate sharp pinging under load. I believe it has been made obsolete by today's better fuels. Plug the leak and you will be good to go.
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| mzahorik | -- 07-13-2019 @ 10:29 AM |
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From what I see over the few miles I have driven without the vacuum brake, I agree. Thanks Mike
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| TomO | -- 07-13-2019 @ 5:43 PM |
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The purpose of the vacuum brake is to keep the mechanical advance from advancing the spark too fast on sudden acceleration. This gives a better throttle response and faster acceleration. If your housing is worn so much that the vacuum brake cannot work, you should replace the housing. A rough setting of the brake can be done by backing off the adjustment screw until the spring is at its full length, then turn in the screw until it contacts the spring. Next add 3 turns in and lock the adjustment. The housing seat on the distributor and the seat on the large nut should be free of burrs. Coat the vacuum brake metal with a light coat of a thin high temperature grease and add a little to the seat area. Tighten the spring nut as tight as possible with an 8" wrench. Tom
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| tabrecheisen | -- 03-30-2020 @ 8:46 AM |
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I answered my own question. This message was edited by tabrecheisen on 3-31-20 @ 7:40 PM
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