kgreen

The Green's will be there, sans Buick as it will be in for upholstery. I'm bringing sharp eyes though, to find the one part that I'm missing.

I’ve recently been struggling with a vacuum leak on a pneumatic convertible top mechanism. The vacuum cylinder is about 4 in dia by 18-20 in in length. That’s a good amount of vacuum loss when operating the top. It is not a closed system. The vacuum is applied to one or the other side of the cylinders position. Air from the opposite side of the piston is relieved through the valve.

Yes, but Pete is still around and better late than never was my view.

I found the bead breaker part of the Take-Off Tool, the large C-shaped device, in a flea market years ago. That would be parts T-129, 113, 114 and 130. It did not have the handle so I put a steel pipe in the threads. I've used it many times to break beads, then use the old hand techniques to get the old tire off a rim and a new tire installed. That effort can raise a sweat. Would be nice to have the rest of the machine, but then garage space?

Yup, and finally though I have a long way to go to wrap up details and get an interior. I might have overposted this topic, but I'm super excited by the progress.

No, looks like a dirty spot on the shaft. The shaft and the guide are not a close fit suggesting that a seal would or should go there. The valve has to perform two functions when either lifting or lowering the top. Pull vacuum on one side of the cylinder piston and relieve air from the opposite side of the piston. I'm beginning to wonder if the whole system is closed loop?

It took me an afternoon to clean up the seat frame and track. Seems that the the seat pivot point in the center of the seat commonly breaks. I have a list of things to start correcting including the brakes as the junction block is leaking. Still not keen on the engine operation, idling high and it has not smoothed out. Need to clean up and paint the air cleaner. Windshield wipers work great, I didn't realize that they are a single speed wiper. Oil spatter on the windshield got spread out nicely. Still have the trunk wood to finish as well. One of the parts cars had the wood for a pattern, but physical damage from drywood termites while the car was in South Florida converted much of the interior of the wood into dust. I finished the heater, but the defroster still needs cleaning and painting. Other than the junction block for the brakes, I don't see any other leaks worth fussing over. I have body color wheels with the pin stripes already painted. The wheel shields are safely tucked away for later. I'll get white wall tires as they were standard issue on this model car. Here's the dirty mechanics wave and the wife who has yet to learn how much she spent on this car.

Yes, I did. The engine had no problem with the hill but the very old (way too old) Montgomery Ward tires spun; left several thousand miles worth of rubber on the concrete. They are pretty slick since they have hardened. I'll get new tires this summer while Mr. Pruitt gets the interior and top installed.

Still a lot of work to do and many issues to be sorted yet, trial run because I couldn't wait to drive it. My retread Montgomery Ward tires are possibly 30-50 years old. Strictly rollers, and I'll have new tires by the time the car comes back from upholstery.

I'm looking for someone familiar with this valve to tell me how it is sealed. I don't believe it should leak in the neutral position. Has anyone attempted to recover one of these valves?

The vacuum valve leaks horribly in its three positions; up, neutral and down. There is no evidence that the valve ever contained seals internally or at the valve stem. The rear of the valve appears vented. The shop manual is of no help. The vacuum valve in this case belongs to a 2-door 1940 Buick Roadmaster. Only the 2-door models had vacuum actuators to lower and raise the top; not the 4-door models. I suspect that this valve was used for other years of GM 2-door cars such as the Cadillac, possibly from the later '30's through the late 40's? The following are photos of the valve: rear end of the valve: Front of the valve with the valve stem:

Good morning Pete. I wasn't around this forum in 2010, but found this post during my search for answers to a valve problem. This is not the convertible top valve. This is what the convertible top valve looks like:

Unless you want wall decorations in your garage, they are rather useless. What you are going through with his belongings is similar to what your kids and my kids will go through someday. This is a good time to make a future generation of our families happy and toss now rather than later or not at all.

This weekend is dedicated to searching for vacuum leaks in the pneumatic convertible top system, modifying the floor plate at the brake/clutch pedal and reinstalling all the cylinder locks that Frank Duval rekeyed for me. Thanks Frank! The convertible top takes a large vacuum line off the manifold. When I removed the connection on this line to take vacuum measurements, the engine performance improved dramatically: Leaks abound. I'll access the pneumatic cylinders and fill each with a little neatsfoot oil, not "prime" neatsfoot oil as that is a mix of other oils that could foul or bind the seals. The floor plate at the clutch and brake pedal is incorrect in that the plate has 5-inches center to center for the brake and clutch while my car has 5 1/2-inches ctr to ctr. I'll cut the panel and relocate the hole. Odd, I've asked others about this but all my linkage lines up straight. While I'm here, I'll share a "before" photo of the car. the initial car that I bought was missing numerous parts and had a 1941 engine. I was fortunate to find another of these fairly scarce vehicles so I chopped up the red primer and gray primer cars yielding one primary car. The chassis provided the later model year production engine, transmission and 3.6 rear end. The coupe was a gift when I bought the grey convertible. It provided a good number of detail parts such as clips, engine pans, extra carb, gages and some chassis parts. The coupe was ultimately sold. All other cars have been reduced to a pile of worthless parts. None of the cars had the correct 15-inch wheels, fortunately a donor car in Los Angeles provided them.

exactly

The darn fuel pump neck is supposed to seal around the lip of the filling point to capture vapors. I know the filler neck on pumps in CA are particularly touchy, other pumps elsewhere possibly less so.

The 1940 is different than the '41 at this location. If the keyed section below is worn or damaged, then you will have slop in the clutch pedal. The brake pedal has a return spring so that pedal is not affected.

Looks just like the "flipper" on 40-41 buick two-door convertibles, series 50 or 70.

Ah ha, the photo above shows your trick to eliminate the clang of the emergency brake hitting the torque tube on a road bump. I experimented by rotating the spring clip at the cable adjustment point into the upwards position. When inserting the spring, the tendency was to hold the mechanism downward. This spring position still seems to allow a good road bump to create the clang. Just a detail, but I wonder what the original configuration was?

Looks good in there. Thanks also for the PM on some of the research you did on fluid fill level requirements over the model years. I found similar paint on my torque tube as well as the axle ends. Mine was blue but I have no photo. The 76C parts car had red paint on the axle ends and torque tube:

The engine is running, though I think it could do better. Valve adjustment seems to have been a finicky sport on this engine. I appear to have a severe vacuum leak in the convertible top system; somewhere. I've disconnected the vacuum to the convertible top for this run. All fluids have been added, leak check for all fluids multiple times, all seems good. I'll set it back on its tires next and actually try to drive it. A little bit. But I'm not done. No, I'll wait. Face it, I need to learn all the bad news now.

Yes, it could. Since the starter is very accessible, take it off and disassemble it. Look for hardened grease, sticking parts, broken wires and bad contacts. In other words give it a thorough cleaning and inspection. If you have a short in a wire in the field, then the starter will need a rebuild for that part. The starter switch on the right (photo above) looks like it has had a long service life. You can clean that contact surface with a file - IF there is enough material left. Once you re-assemble the starter, you should be able to freely turn all parts. Opening up the starter is a quick and easy way to see more of what your problem may be.

I use a calculator to count the number of times I've assembled, disassembled and re-assembled each part on my car. The first time doesn't count, the second time is to break it, the third time is to verify that the NOS part is actually nonfunctional and the fourth time is to see if the reproduction part actually belongs on the car.

I've got a rough running engine after a total rebuild. Haven't run a vacuum gage yet, but will this weekend. In thinking of all the possibilities I wonder if the 320 cu in engine would even run if the timing chain was off by one tooth; anyone know? The engine starts, revs fine, but has a skip and occasional backfire and doesn't like to idle smoothly or at a lower more appropriate RPM of 650-700. New plugs and wires. Grounding the plug shows a great spark. New points and condenser, gap checks out at 0.015. Timing is close enough that the engine will start fairly easily and continue to run and adjusted so that I have a higher engine speed. I've improperly installed the flywheel with the timing marks off so conventional timing measurement is not available. The engine belongs on a convertible where there is a heavy vacuum demand when the top is operated and an improved chance for vacuum leaks. Carb was rebuilt, but by me so I could suggest that I goofed something there. Compressions on all cylinders is great and uniform. Valves adjusted correctly and checked. I've run the engine for a total of probably 20-30 minutes by now so some wear in has occurred. I'll run the engine with a vacuum gage this weekend as suggest by another member here; thanks Greg as always. I'm trying to think of all possible options before I dig back in this weekend. Any ideas that you think I should pursue?

Well, they gotta say something to make the article interesting.