NC-car-guy Posted September 14, 2017 Share Posted September 14, 2017 I'm sure it's been discussed before, but the search function has yielded nothing. How does one verify that the vacuum advance is operating? Is a hand vac pump the only option? Link to comment Share on other sites More sharing options...
Fr. Buick Posted September 14, 2017 Share Posted September 14, 2017 Put a section of rubber hose on it, and suck out all the air you can. Set your tongue on the tip, and it should hold a vacuum. 3 1 Link to comment Share on other sites More sharing options...
NC-car-guy Posted September 14, 2017 Author Share Posted September 14, 2017 I'll try this over the weekend, thanks Link to comment Share on other sites More sharing options...
JohnD1956 Posted September 14, 2017 Share Posted September 14, 2017 Or manually rotate the plate it is attached to and then put your finger over the inlet and then let go of the plate. If the plate returns to the original position then the vac advance is not holding. 1 1 Link to comment Share on other sites More sharing options...
old-tank Posted September 14, 2017 Share Posted September 14, 2017 3 hours ago, Fr. Buick said: Put a section of rubber hose on it, and suck out all the air you can. Set your tongue on the tip, and it should hold a vacuum. or blow... 2 Link to comment Share on other sites More sharing options...
avgwarhawk Posted September 14, 2017 Share Posted September 14, 2017 2 hours ago, JohnD1956 said: Or manually rotate the plate it is attached to and then put your finger over the inlet and then let go of the plate. If the plate returns to the original position then the vac advance is not holding. Tastes better this way than the alternative presented by Father Buick . lol 2 2 Link to comment Share on other sites More sharing options...
Beemon Posted September 14, 2017 Share Posted September 14, 2017 My favorite is hook up a vacuum line to the T at the intake manifold, and then, with the car running and timing light in hand, connect the vacuum line to the vacuum advance. The rest is self explanatory. I'm personally not a fan of sucking or blowing. 2 2 Link to comment Share on other sites More sharing options...
NTX5467 Posted September 14, 2017 Share Posted September 14, 2017 This is all pretty elementary. If the diaphragm is "good", the idle speed should significantly increase under Beemon's suggestion. All you're trying to do is determine if it "works", not how much advance it has in it (number of distributor degrees usually stamped in the arm to the advance plate). Or if you disconnect the line to the distributor, with the engine running about 1500rpm or so, the idle speed should drop with no vacuum advance. Whether you pressurize or de-pressurize the advance can yourself, using a reasonably sterile tube is a plus. Enjoy! NTX5467 Link to comment Share on other sites More sharing options...
Smartin Posted September 15, 2017 Share Posted September 15, 2017 The bummer about a 54 is that it isn't simply a rubber vacuum line. It's one of those horrible steel lines with a threaded fitting at each end...so it would be tough to simply attach or detach at a moment's notice. I would do the suck test, or pull on it manually...then hold my finger over the opening to see if it holds. If it holds vacuum, then it will release when the finger is released. 2 Link to comment Share on other sites More sharing options...
EmTee Posted September 15, 2017 Share Posted September 15, 2017 11 hours ago, Fr. Buick said: Set your tongue on the tip, and it should hold a vacuum. I triple-dog-dare ya! 4 Link to comment Share on other sites More sharing options...
Beemon Posted September 15, 2017 Share Posted September 15, 2017 48 minutes ago, Smartin said: The bummer about a 54 is that it isn't simply a rubber vacuum line. It's one of those horrible steel lines with a threaded fitting at each end...so it would be tough to simply attach or detach at a moment's notice. I would do the suck test, or pull on it manually...then hold my finger over the opening to see if it holds. If it holds vacuum, then it will release when the finger is released. For my own testing purposes, I've gotten some hose that slips over the fittings when disconnected from the carb base, and attached with a barbed fitting at the intake. I can see why this method would be much more tedious to do, but you get immediate feedback results. 2 Link to comment Share on other sites More sharing options...
Fr. Buick Posted September 15, 2017 Share Posted September 15, 2017 Oh come on guys, If you have ever put your head under a car, then you have worn, smelled and accidently tasted at least a few automotive fluids. Do what you have to, spit it out, and go on. But I stand corrected, there is no nipple for a vacuum hose to draw air on. Take the mechanism off, and suck on it directly. If it is clean enough, you get to taste good GM cad plating. It has a certain je ne se qua. I do this at swap meets to be sure a unit is good before I put my money down. I am off to the garage, good night! 4 3 Link to comment Share on other sites More sharing options...
Frank DuVal Posted September 15, 2017 Share Posted September 15, 2017 Blowing only work to test a vacuum advance if it happens to be a pressure retard unit, like on turbocharged Corvairs! Sure if there is resistance to blowing and you hear no air leaking the diaphragm is probably good, but I want to see the arm move. Only pressure retard units will move the arm with blowing. I use a Mighty-Vac so I can see just how many inches of vacuum are needed to make the arm move. I have had to "adjust" several vacuum advance units to make them apply at the right time or maximum pull, but not on Buicks yet.... Link to comment Share on other sites More sharing options...
old-tank Posted September 15, 2017 Share Posted September 15, 2017 Those early nailhead units either work or they don't. Disconnect and see where the timing is at 1200 rpm; connect and it should show an additional 10* advance. Link to comment Share on other sites More sharing options...
Beemon Posted September 15, 2017 Share Posted September 15, 2017 15 hours ago, Fr. Buick said: Do what you have to, spit it out, and go on. I was going to write something about the old lady but I'm refraining myself. What? I'm talking about the car, of course. 1 Link to comment Share on other sites More sharing options...
NTX5467 Posted September 16, 2017 Share Posted September 16, 2017 On 9/14/2017 at 8:55 PM, EmTee said: I triple-dog-dare ya! IF one can do that with the distributor still in the engine, go for it! PICTURES/video needed, though. In order to compress the plunger on the canister with it removed from the distributor, a particular level of dexterity is needed. Doing the "evacuation" method is much easier and quicker . . . if it moves at all, it's probably working decently good enough. If one keeps the engine clean and somewhat nice in the distributor's region, with all of the heat in there, what "bad" stuff might stay in there for very long? On those with that neat-looking tube, make sure there are no leaks at that connection, too. Of course, if your highway fuel economy is lower than what it used to be, with all other things being in good shape, you'll probably need a vac advance unit, by observation. NTX5467 1 Link to comment Share on other sites More sharing options...
KAD36 Posted September 16, 2017 Share Posted September 16, 2017 Vacuum pump with gauge and this info from second change garage, which sometimes needs doublechecking, has worked for my 55. Seems reasonable: Vacuum Advance Data: Inches of vacuum to start plunger movement: 6.5 - 8.5 Inches of vacuum for full plunger travel: 11-1/2 - 15 Maximum vacuum advance, Dist. degrees: 9 - 10-1/2 3 2 Link to comment Share on other sites More sharing options...
lancemb Posted November 23, 2017 Share Posted November 23, 2017 Run a tee off the vacuum advance with 2 hoses. Connect one to the frammistan, and the other to the connuter valve. Then, tap three times on the front bumper while the engine's running and listen for a whistling sound! Link to comment Share on other sites More sharing options...
Beemon Posted November 23, 2017 Share Posted November 23, 2017 I don't think we're in Kansas anymore 1 Link to comment Share on other sites More sharing options...
NTX5467 Posted November 23, 2017 Share Posted November 23, 2017 Wasn't "Knock three times" on the ceiling? NTX5467 Link to comment Share on other sites More sharing options...
1956century Posted November 24, 2017 Share Posted November 24, 2017 I hooked mine up to a vacuum pump when cleaning up the distributor. Here is a video. I also did the tongue-on-hose check (it's not that bad). Link to comment Share on other sites More sharing options...
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