I'm working on a bit of a Frankenstein project so bare with me please. I have a 261 that I'm building into a Turbo Charged engine. The turbocharger will require a good bit more oil pressure than the stock Chevy pump is capable of supplying, the GMC pump is rated at a higher pressure and I assume volume.
I have an oil pump from a GMC 270/ 302. How difficult will it be to adapt the pump for use in a Chevy block? I anticipate some modification to the oil pan and mosst likely the internal oil lines.
Has anyone had any experience with such a modifications? Are there somethings I need to focus on?
Last edited by TUTS 59; 08/25/202612:41 PM. Reason: Add info
~ Craig 1958 Viking 4400 "The Book of Thor" Read the story in the DITY 1960 Chevrolet C10 "A Family Heirloom" Follow the story in the DITY Gallery '59 Apache 31, 327 V8 (0.030 over), Muncie M20 4 Speed, GM 10 Bolt Rear... long term project (30 years and counting)
If you don't like driving yourTruck, you won't drive yourTruck..| Living life in the SLOW lane
I spun the oil pump on a 270 with a 1/2" drill motor. The oil was cold, probably 10w30. Air temp was in the mid 40s. Pressure regulator (relief valve in the pump) held the max pressure at 57 PSI from about 1200 engine RPM to 1700 engine RPM, as fast as the drill motor would turn. This was using a 4" calibrated 270 degree sweep pressure gauge.
'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.
That is exactly what I'm looking for with this engine combination.
~ Craig 1958 Viking 4400 "The Book of Thor" Read the story in the DITY 1960 Chevrolet C10 "A Family Heirloom" Follow the story in the DITY Gallery '59 Apache 31, 327 V8 (0.030 over), Muncie M20 4 Speed, GM 10 Bolt Rear... long term project (30 years and counting)
If you don't like driving yourTruck, you won't drive yourTruck..| Living life in the SLOW lane
What year is the 261? If it's the newer type with the offset in the oil pan rail beside the pump, there will be a bit more room for a bigger pump than the 54/early 55 engine. Either way, you'll probably need to do a little surgery on the oil pan sheet metal, as the GMC pump is MUCH larger than even the bigger oil pump used on the later model Chevy engines. Have you considered the added load on the distributor drive gear the extra volume pump will create?
I think I'd choose to use an external, belt-driven oil pump like the dry sump oil systems on NASCAR engines use. They're driven off the crankshaft snout by a toothed belt. There is also a way to put the taller, high volume gears from a Chevy V8 oil pump into a stovebolt pump housing by adding a spacer plate between the pump body and the base plate. 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!
I don't believe the added load will effect the distributor drive that much. It's basically the same configuration as the distributor in a GMC. The engine will be running a modified GM 2.8L small cap HEI .
~ Craig 1958 Viking 4400 "The Book of Thor" Read the story in the DITY 1960 Chevrolet C10 "A Family Heirloom" Follow the story in the DITY Gallery '59 Apache 31, 327 V8 (0.030 over), Muncie M20 4 Speed, GM 10 Bolt Rear... long term project (30 years and counting)
If you don't like driving yourTruck, you won't drive yourTruck..| Living life in the SLOW lane
Firecracker 400- - - - -Daytona July 4th. 1963- - - - -Chevy didn't believe their new 427 "Mystery Engine" (first of the straight valve cover big blocks) would have oiling problems- - - - -Until NONE of them finished the race because of sheared-off oil pump drives. 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!
a turbo of the size to be on a 261 shouldn't need excessive oiling. you'll most likely need a restrictor in the line to the turbo to keep oil pressure up. i'm in the process of putting a turbo on a 270 GMC in a 31 chevy pickup street rod. i had Comp Turbos spec a turbo for me. i also bought the oilless model that is also water cooled. i also went to a ware cooled waste gate. first time for a turbo so i'm hoping it works good. https://compturbochargers.com/
That is a beautiful setup. I not working towards anything that elaborat, I'm using a small Trubo fronm a Cummins 4 cylinder. I have a waste gate with 8 and 10 lbs spings, leaning towards the 8.
The plan is to run a Holley 300 CFM 2 barrel jetted back. The engine is bored .080 over with dished 231 Buick pistions and 302 GMC rods. A mild Melling CCS1 cam with an "848' head, 1.94 intake valves and stainless 1.50 exhaust valves. The Turbo will mount on the passenger side of the engine with exhaust crossing under the oil pan.
This is going in a truck, I just want a few more Ponies, nothing race ready.
Last edited by TUTS 59; 08/25/20265:57 PM. Reason: Add Images
~ Craig 1958 Viking 4400 "The Book of Thor" Read the story in the DITY 1960 Chevrolet C10 "A Family Heirloom" Follow the story in the DITY Gallery '59 Apache 31, 327 V8 (0.030 over), Muncie M20 4 Speed, GM 10 Bolt Rear... long term project (30 years and counting)
If you don't like driving yourTruck, you won't drive yourTruck..| Living life in the SLOW lane
With a little bit of creative machining, it would be possible to adapt a pump for a big block Chevy V8 to a stovebolt engine. I've also done that with a 230/250/292 6 cylinder oil pump.
"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!
My driving gear is 1.635" across the teeth. My driven gear is 1.638"
Last edited by Bill Hanlon; 08/31/20263:35 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.
