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Jul 21st, 2025 | | | | Joined: Nov 2020 Posts: 754 'Bolter | | 'Bolter Joined: Nov 2020 Posts: 754 | I took a long look at a stock ‘54 3100 today, mostly to expand my knowledge of the original mechanics. (I’m one of those HotRod guys᠁shudder᠁)
Everything made sense to me , as simple and straightforward as those machines are , except for the vacuum line leading to the fuel pump and from there through the firewall to (presumably) the vacuum driven wiper motor.
- Is the fuel pump not mechanical and driven off of the crank or cam?
- Why doesn’t the vacuum line for the wipers go directly to the wipers?
I know that these are pretty basic questions, but I’m asking because (as Red Green said - those three little words that men have such a hard time saying -) I Don’t Know.
Age 68 is not too late to start hot rodding , right?
| | | | | Joined: Oct 2021 Posts: 5,686 'Bolter | | 'Bolter Joined: Oct 2021 Posts: 5,686 | Fuel pump is mechanical driven off a cam. The diaphragm in the pump also creates vacuum which assists the windshield wipers. The fuel pump provides a steady source of vacuum as opposed to the on again off again wiper operation you get from manifld vacuum.
1950 Chevrolet 3100 (Ol' Roy)
1939 Packard Standard Eight Coupe (The Phantom) | 1956 Cadillac Coupe de Ville (The Bismarck) | 1956 Cadillac Sixty Special Fleetwood (The Godfather) | 1966 Oldsmobile Toronado (The Purple Knif) | 1966 Ford Mustang (Little Red) | 1964 Ford Galaxie 500 coupe | 1979 Ford F-100 | 1976 Ford F-150 (Big Red) | 1995 Ford F-150 (Newt)
| | | | | Joined: Feb 2004 Posts: 28,675 Kettle Custodian (pot stirrer) | | Kettle Custodian (pot stirrer) Joined: Feb 2004 Posts: 28,675 | Vacuum wipers slow down, or usually stop altogether when the vehicle is pulling a hill or passing. The vacuum booster pump is in line with the intake vacuum to prevent the wipers from coming to a complete stop- - - - -if it works as designed. Most don't. Chevy was too cheap to put in a reserve canister with a one way valve to be a backup for the intake vacuum.
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!
| | | | | Joined: Jan 2022 Posts: 1,987 'Bolter | | 'Bolter Joined: Jan 2022 Posts: 1,987 | It is a second diaphragm on the pump that provides the vacuum for the wipers.
'57 GMC 102, Original 347 V8, HydraMatic, 3.08 rear gear, added A/C, disk front brakes, HEI, AFB carb, '98 Honda Black Currant paint. T-boned and totaled 10/12
'52 GMC 152 Stake Bed, Original 228, SM420, added A/C, HEI, disk front brakes, '67 Chev 3.55 rear gear. Gets used as a real truck.
| | | | | Joined: Dec 2020 Posts: 1,731 'Bolter | | 'Bolter Joined: Dec 2020 Posts: 1,731 | My 58 panel came with a vacuum pass thru bolt that mounted the
fuel pump. That line ran to the bottom of the fuel pump
with 2 vacuum ports underneath.
~ BD.
You won't find me in an old folks home | | | | | Joined: Nov 2020 Posts: 754 'Bolter | | 'Bolter Joined: Nov 2020 Posts: 754 | I am familiar with the wipers slowing or stopping or stopping when manifold vacuum drops ᠁ I am old enough that such things were common knowledge in my formative years.
I even understand the function of the vacuum advance!
Now that I think of it , such things were taught in hands- on shop class back then.
Ah, the good old days᠁
So there is a second diaphragm in the fuel pump , and it’s function is the produce vacuum for the wipers. The fuel pump itself is driven off of the camshaft.
I am a little smarter now than I was when I got up this morning,
Thank you.
‘Ski
Age 68 is not too late to start hot rodding , right?
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