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I texted this to Kevin, but just for reference, the megathread is here:

packardinfo.com/xoops/html/modules/newbb ... 8299&post_id=272250#forumpost272250

Kev, you should be getting just a little less than manifold vacuum, and it should recover instantly when you push the pedal. I would not expect any less than 15 inches Hg. No wonder the brakes are terrible; you are getting no real assist.

Yes your hoses could be blocked or collapsed, but a likely culprit is the check valve. Of course, you can always test your manifold vacuum at the tube that comes out of the junction block between the carb and the check valve. I sure hope you have better than 5 inches there or you have a massive tuning problem to attend to.

Great advice everyone. I have some progress to report.

First I pulled the check valve off. Sprayed some cleaner inside and worked the internal mechanism back and forth. Everything seemed to work as far as I could tell, and the mechanism was free with no signs of restriction. Reinstalled and checked the vacuum, no change.






Next I removed the old vacuum tubing. Turns out it was fuel line, which is probably fine to use. It was old, stiff, and didn't appear to be sealing well.



I replaced all the tubing (from the check valve to the vacuum tank and BTV) with the correct vacuum tubing. I bought the last of Napa's stock. Installed it all and checked the vacuum again, no change.

Closer inspection showed this hose disconnected. It connects to the brass fitting on the back of the carb. I reconnected it, and while messing with all that I noted that the brass fitting to the carb was not tight. So I loosened the carb up (the mounting nuts are so much easier to get on these 4 barrels! The two barrels are the worst) then tightened the brass fitting an entire turn, which really snugged it up. This time when I checked the vacuum it was much improved, sitting at about 14 inHg and steady.






A video of the vacuum performance when using the brakes. Car is idling in Park, brakes applied and the vacuum recovers quickly. The "tick" at the end where it jumps from 13 to 14 is me letting off the brake pedal. Does this look like normal performance to you?



A short test drive showed the brakes are much improved, maybe 60-70% better. They are still not quite what I would expect from this system, but then again I have never driven a Treadle Vac car so I have no real comparison. I expect the rest of the improvement will come when a rebuilt BTV is installed.

Check out this 53 commercial which shows what Packard designed and advertised as the typical BTV brake pedal action. There may be a bit of over selling, particularly with the one finger steering on a stationary car but the brake demo starting around the 35 second mark with just the gentle touch and the pedal barely moving is usually about all it needs to come to a smooth stop. Typically the full pedal travel with wheel lock is only about an inch or maybe less. Pushing down hard like you had to do before would put you thru the windshield in a properly working system.

Your vacuum is still low. Have you ever checked the timing on this beast? Set the idle really slow and disconnect the vac advance line at the carb and then dial in 10 degrees.

Kevin,

For reference, the respective section is page 10 of the Engine manual.

Ross, I checked the timing yesterday as part of the whole vacuum saga. Cleaned the the points, reset the gap, checked rotor and cap, etc. I had the engine idling down low, but not sure how accurate my gauge is. I'm just using the tach feature on a cheap multimeter. Timing was already at 10 degrees. I did not disconnect the vacuum advance though. I'll do that and check it again.

PGH, thanks for the reference. I was reading through it yesterday as I worked. The Packard Club also has a a quick reference tune up sheet that is helpful to quickly find specs.

Kevin
Gotta cap off vacuum advance.

Watch the match marks. Vacuum on ,, vacuum capped.

Should jump up with vacuum hooked up