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| | | | Joined: Sep 2010 Posts: 1,715 back yard wrench turner | | back yard wrench turner Joined: Sep 2010 Posts: 1,715 | I'm looking for a listing from a supplier for an oil pump for my 1955 GMC 270 CI. motor. I've checked Jim Carter, Chev's of the 40's, Napa, and O Reilly's.
No one has a listing.
Who knows where I can get one?
Wayne1938 1-Ton Farm TruckStovebolt Gallery Forums1989 Silverado 1996 Mustang GT convertible When I die, I hope she doesn't sell everything for what I told her I paid for it! | | | | | Joined: Feb 2004 Posts: 29,852 Kettle Custodian (pot stirrer) | | Kettle Custodian (pot stirrer) Joined: Feb 2004 Posts: 29,852 | Here's a used one on Ebay- - - - -"make offer". www.ebay.com/itm/187287251005?TRW NOS: www.ebay.com/itm/296933253335?I think I might have one stashed away somewhere- - - -gotta find it first. PM me. 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: 2,482 'Bolter | | 'Bolter Joined: Jan 2022 Posts: 2,482 | The TRW NOS part that Jerry pointed at has a bottom cover designed for a large truck with a deep oil pan. You'll need to change that with a cover designed for a smaller truck with a shallower oil pan. If you have your old one (and it's not badly worn) you can swap it onto the new pump.
'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: Sep 2010 Posts: 1,715 back yard wrench turner | | back yard wrench turner Joined: Sep 2010 Posts: 1,715 | I was hoping Hot Rod Lincoln would chime in. I know Jerry has been playing with these 270's for a long time.
What's happening is my oil pressure is dropping to almost 0 when at idle. I am thinking with a fresh pump I could get it up and not starve the bearings.
I'm not wanting to refresh this motor. It runs good, and doesn't burn oil.
Wayne1938 1-Ton Farm TruckStovebolt Gallery Forums1989 Silverado 1996 Mustang GT convertible When I die, I hope she doesn't sell everything for what I told her I paid for it! | | | | | Joined: Oct 2021 Posts: 6,932 'Bolter | | 'Bolter Joined: Oct 2021 Posts: 6,932 | How are you measuring the oil pressure? If you're relying on the dash gauge, I would plug in a temporary gauge under the hood to the port and see what it says. Your oil pressure might be just fine.
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)
| | | | | Joined: Sep 2010 Posts: 1,715 back yard wrench turner | | back yard wrench turner Joined: Sep 2010 Posts: 1,715 | How are you measuring the oil pressure? If you're relying on the dash gauge, I would plug in a temporary gauge under the hood to the port and see what it says. Your oil pressure might be just fine. I have an after market gauge that is plumbed to the motor.
Wayne1938 1-Ton Farm TruckStovebolt Gallery Forums1989 Silverado 1996 Mustang GT convertible When I die, I hope she doesn't sell everything for what I told her I paid for it! | | | | | Joined: Oct 2021 Posts: 6,932 'Bolter | | 'Bolter Joined: Oct 2021 Posts: 6,932 | You might plumb in another one just to test the accuracy.
The thing is, if your oil pressure really is low, you don't know if the oil pump is the reason.
What does the gauge say the pressure is while driving?
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)
| | | | | Joined: Jan 2008 Posts: 4,962 'Bolter | | 'Bolter Joined: Jan 2008 Posts: 4,962 | This is a Melling replacement M-23b Melling. I don't think
they make them any more, but they appear on eBay quite often. | | | | | Joined: Jun 2003 Posts: 565 'Bolter | | 'Bolter Joined: Jun 2003 Posts: 565 |
Last edited by Gdads51; 09/19/2025 11:18 PM. Reason: remove tracking junk form link
"Do not walk behind me, for I may not lead. Do not walk ahead of me, for I may not follow. Do not walk beside me either. Just leave me alone, you're starting to freak me out."
1957 GMC 150
| | | | | Joined: Jan 2022 Posts: 2,482 'Bolter | | 'Bolter Joined: Jan 2022 Posts: 2,482 | Specs from 39-54 GMC Maintenance Manual calls for a minimum of 5 PSI at idle for a hot new or rebuilt engine and a minimum of 2 PSI at idle for a hot "used" engine. The 55-59 manual doesn't show a spec, but uses the same oil pump.
'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: Oct 2021 Posts: 6,932 'Bolter | | 'Bolter Joined: Oct 2021 Posts: 6,932 | That sounds like your engine might not have an oil pressure problem. You said hot idle is "near 0 psi". 2 psi is pretty near 0.
I'm thinking you'll go to the trouble replacing the oil pump and have no improvement in oil pressure.
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)
| | | | | Joined: Jan 2022 Posts: 2,482 'Bolter | | 'Bolter Joined: Jan 2022 Posts: 2,482 | Specs from 39-54 GMC Maintenance Manual calls for a minimum of 5 PSI at idle for a hot new or rebuilt engine and a minimum of 2 PSI at idle for a hot "used" engine. The 55-59 manual doesn't show a spec, but uses the same oil pump. I should have added that my GMC with 40,000 miles that I've put on it and unknown mileage before that, but it had a badly burned #5 exhaust valve when I bought it, idles at 425 RPM and about 12 psi in the Texas summertime with the A/C running.
'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: Sep 2010 Posts: 1,715 back yard wrench turner | | back yard wrench turner Joined: Sep 2010 Posts: 1,715 | With the above statements I'm wondering am I wasting my time. I'm using 10w-30 High mileage oil. Should I go to a heavier weight?
Wayne1938 1-Ton Farm TruckStovebolt Gallery Forums1989 Silverado 1996 Mustang GT convertible When I die, I hope she doesn't sell everything for what I told her I paid for it! | | | | | Joined: Oct 2021 Posts: 6,932 'Bolter | | 'Bolter Joined: Oct 2021 Posts: 6,932 | Yes! Use 20w-50 or 15w-40 at the lowest.
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)
| | | | | Joined: Jan 2022 Posts: 2,482 'Bolter | | 'Bolter Joined: Jan 2022 Posts: 2,482 | 15w40 in mine.
The same GMC manual calls for a minimum of 25 psi at 2750 rpm warm on a used engine and 40 psi on a new/rebuilt engine.
My measurements were taken using a 1% accuracy 270 degree sweep 4" diameter gauge.
Last edited by Bill Hanlon; 09/20/2025 3:45 PM.
'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: Feb 2004 Posts: 29,852 Kettle Custodian (pot stirrer) | | Kettle Custodian (pot stirrer) Joined: Feb 2004 Posts: 29,852 | Oil pressure is inversely proportional to bearing clearance- - - - -the wider the clearance, the lower the pressure will be. A new set of rod bearings will probably raise the pressure more than replacing the pump will do.
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!
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