My vacuum advance on a 54 235 went bad so I got one from Chev of the Forties. The vacuum line fitting from the old vacuum line does not fit into the vacuum diaphragm. Does anyone know what thread size it might be?
1946 1/2 ton Chevy Pickup 1954 235 cu in 3 speed on the floor
The normal fitting for that vacuum advance is a 3/16" inverted flare. If the replacement was made in some offshore sweatshop, there's no telling what thread it might have. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
The normal fitting for that vacuum advance is a 3/16" inverted flare. If the replacement was made in some offshore sweatshop, there's no telling what thread it might have. Jerry
I don't know where they have made things. thanks. 'm going to go to Grainger in the morning to see what they can do for me.
1946 1/2 ton Chevy Pickup 1954 235 cu in 3 speed on the floor
If it's got a 1/8" diameter tube, it's the only stovebolt vacuum advance in the world like that. The original vacuum line was 3/16" OD. Can you post a picture of the unit you've got, showing good detail on the threads? Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
If it's got a 1/8" diameter tube, it's the only stovebolt vacuum advance in the world like that. The original vacuum line was 3/16" OD. Can you post a picture of the unit you've got, showing good detail on the threads? Jerry
What would the stock size be? This was my Dad's project before he passed 10 years ago and towards the end he "modified" some things. I'll post a photo tomorrow.
1946 1/2 ton Chevy Pickup 1954 235 cu in 3 speed on the floor
Like I just posted- - - -the distributor vacuum line is 3/16" OD steel tubing. The gas line is 5/16" OD steel. Both lines have male inverted flare fittings on both ends. The gas line uses 1/8" NPT male to 5/16" female inverted flare adapters at both the fuel pump and the carburetor. The vacuum line has a 3/16" to 1/8'" pipe brass adapter at the carburetor, and the advance has a 3/16" inverted flare thread in the vacuum chamber- - - -no adapter needed. Jerry
Last edited by Hotrod Lincoln; 03/07/202310:02 PM.
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
They were no help at all. I was very disappointed! What is V.A.
Vacuum Advance
1950 Chevrolet 3100 (Ol' Roy)
1939 Packard Standard Eight Coupe (The Phantom) | 1956 Cadillac Coupe de Ville (The Bismarck) | 1964 Ford Galaxie 500 coupe |1966 Ford Mustang (Little Red) | 1969 Pontiac GTO (The Dishpit) I 1979 Ford F-100 | 1976 Ford F-150 (Big Red) | 1995 Ford F-150 (Newt)
The vacuum advance has had the same design for decades. Its actually comprised of two parts. The Octane Selector Plate/distributor clamp, and the vacuum advance canaster. The vacuum advance canasters are all about the same design, the Octane Selector Plate/clamp arrangement has a couple of different variations but all look and work the same. The port where the vacuum line enters into the canaster, if you look into the port, you will see that it is a flare arrangement like a wheel cylinder, or brake line distribution blocks. And they all (as far as I have seen) use standard 3/16 flared brake line. So if you have a compression fitting on yours, that was added to the system by a previous onwer. Frankly, its not all that uncommon to see these kinds of modifications. These motors were installed in everyday man's car and/or truck and in those days, every single dollar counted so if you could make repairs with what you had on hand, rather then pay a mechanic do it, then that is generally what you did. So it appears that a previous owner fixed the vacuum advance line with what he had on hand.
If you want to make this right, get it back to what the engineers originally specified for the advance system, remove the line and fittings, and make the installation as the engineers designed it. Direct install to the vacuum advance with the flared 3/16 line. At the other end of it, at the carb, there should be a fitting. I want to say 1/8 npt at one end (carb) and inverted flare for the line at the other.
The vacuum advance has had the same design for decades. Its actually comprised of two parts. The Octane Selector Plate/distributor clamp, and the vacuum advance canaster. The vacuum advance canasters are all about the same design, the Octane Selector Plate/clamp arrangement has a couple of different variations but all look and work the same. The port where the vacuum line enters into the canaster, if you look into the port, you will see that it is a flare arrangement like a wheel cylinder, or brake line distribution blocks. And they all (as far as I have seen) use standard 3/16 flared brake line. So if you have a compression fitting on yours, that was added to the system by a previous onwer. Franklly, its not all that uncommon to see these kinds of modifications. These motors were installed in everyday man's car and/or truck and in those days, every single dollar counted so if you could make repairs with what you had on had, rather then pay a mechanic do it, then that is generally what you did. So it appears that a previous owner fixed the vacuum advance line with what he had on hand.
If you want to make this right, get it back to what the engineers originally specified for the advance system, remove the line and fittings, and make the installation as the engineers designed it. Direct install to the vacuum advance with the flared 3/16 line. At the other end of it, at the carb, there should be a fitting. I want to say 1/8 npt at one end (carb) and inverted flare for the line at the other.
A little history of this truck. It's a 1946 Chevy pickup with a 1954 6 cylinder. It's originally from oklahoma. My father bought it 23 years ago here in Pennsylvania. The guy's wife wanted a new kitchen so he had to sell his truck.🙂 My dad passed away about 10 years ago so I have the truck now. I promised him it would stay as stock as possible. As I go through the truck, I see where he modified some things. The vacuum advance line being one of them.
I've got it all sorted out and will be hooking things up tomorrow. It's too cold in the barn today to work for very long. I am hoping that this will solve the noise that I've been chasing for months. I thought for sure it was the valves but now I think it was misfiring. Thank's to the wealth of knowledge in this forum. I really respect all of you.
1946 1/2 ton Chevy Pickup 1954 235 cu in 3 speed on the floor
Dragsix is correct. Both the carb and vacuum advance on the distributor have 1/8” male pipe thread on on end and a 3/16” inverted flare fittings on the other. I used CuNi (copper nickel) brake line to plumb mine. It bends easy and flares easy. You will need a flaring kit to install a double flare on each end of the tubing. You can buy a flaring kit, tubing and the fittings at your local auto parts store on on line.
Phil Moderator, The Engine Shop, Interiors and Project Journals
1952 Chevrolet 3100, Three on the Tree, 4:11 torque tube Updated to: ‘59 235 w/hydraulic lifters, 12v w/alternator, HEI, PCV and Power front Disc Brakes Project Journals Stovebolt Gallery Forum
Dragsix is correct. Both the carb and vacuum advance on the distributor have 1/8” male pipe thread on on end and a 3/16” inverted flare fittings on the other. I used CuNi (copper nickel) brake line to plumb mine. It bends easy and flares easy. You will need a flaring kit to install a double flare on each end of the tubing. You can buy a flaring kit, tubing and the fittings at your local auto parts store on on line.
Advance, Auto Zone, OReilly, etc will loan you the flaring kit for free. You pay full price use the kit, return it, and get your money back. It's not a brand new kit. They keep all kinds of tools like this on hand specifically to loan out to customers.
1950 Chevrolet 3100 (Ol' Roy)
1939 Packard Standard Eight Coupe (The Phantom) | 1956 Cadillac Coupe de Ville (The Bismarck) | 1964 Ford Galaxie 500 coupe |1966 Ford Mustang (Little Red) | 1969 Pontiac GTO (The Dishpit) I 1979 Ford F-100 | 1976 Ford F-150 (Big Red) | 1995 Ford F-150 (Newt)
Like I just posted- - - -the distributor vacuum line is 3/16" OD steel tubing. The gas line is 5/16" OD steel. Both lines have male inverted flare fittings on both ends. The gas line uses 1/8" NPT male to 5/16" female inverted flare adapters at both the fuel pump and the carburetor. The vacuum line has a 3/16" to 1/8'" pipe brass adapter at the carburetor, and the advance has a 3/16" inverted flare thread in the vacuum chamber- - - -no adapter needed. Jerry
Thanks. I guess my dad just made something work with whatever he had laying around. I appreciate your help. I got a 60 in brake line and did some pretty good pipe bending to replace what was on the engine. Worked great. Thanks again Jerry
1946 1/2 ton Chevy Pickup 1954 235 cu in 3 speed on the floor
