What is the name of the flare fitting on the front of the block, I am referring to the port which supplies oil to the cyl head. It is a 90 deg fitting with 3/8 npt on the end that threads into the oil gallery on the front of the block. The threads for the line fitting are damaged, So I will have to source a new fitting, thing is I don’t know for sure what the thread for the line end is called ??
Just checked the 1939-53, 1947-54 and 1955-60 GMC Master Parts Books. No description of of the size or type of the connections are given.
Last edited by Bill Hanlon; 06/23/202611:10 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.
Dave - I found the same issue as Bill reported, with the part identified as GM# 6107373 - Fitting, oil handler (picture from the Book of Parts I found it in below).
Knowing this was a component of a GMC 302 which Uncle Sam bought lots of, I figured it's most likely still listed in Mil Spec records. A web search turned up the below data on the basic Mil Specs for GM# 6107373 and the refined specs of the same part under the National Stock Number assigned to it (collected from multiple sources). If you can decipher the details in the specs, I hope you can figure out what you need to replace your fitting.
If not, I'd suggest you post an ad in Truck Parts Wanted. There may be someone with an old scrap block that would give up a fitting?
Last edited by Gdads51; 06/24/202611:38 AM. Reason: spelling
~ Dan 1951 Chevy 3 window 3100 Follow this story in the DITY Gallery "My Grandpa Carl's Truck and How it Became Mine" 1966 Chevelle (Wife's Hot Rod) | 2013 Chevy Silverado (Current daily driver) US Army MSG Retired (1977-1998) | Com Fac Maint Lead Tech Retired (1998-2021)
The 1947-54 GMC Master Parts Book has a fair drawing of the T. Question is what is a 2 way and what is a 3 way. I'm guessing 6107373 is a 2 way, 1 way in, 1 way out. I believe the drawing from the MPB shows a 3 way (1 in, 2 out) with the second output line ending up behind the generator in the drawing. I've never seen one of those and don't know what that line hooks to.
My other two GMC Master Parts Books also show all 3 numbers.
The description of 8.4550 is shown below. Not much help.
'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.
Do the 248 and 270 engines run the same type of oil system as the 302? I've got both of those engines handy for pictures and/or measurements if needed. The circuit can be duplicated easily with commonly available brass fittings- - - -there's no need to source scarce OEM parts. A street tee and NPT to inverted flare adapters would serve the same purpose as the original part.
"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!
Do the 248 and 270 engines run the same type of oil system as the 302? Jerry
Same part numbers for 228, 248, 270 and 302.
'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.
The parts book shows a 2 way tee. One to the head and one to the oil gauge. The 3 way is the same but you have one more leg for the oil filter.
Both the GMC 228 and 302 engines in my garage connect the oil pressure gauge to the main oil gallery on the lower left side of the block about 5 inches from the rear. The place on the front of the block that the Tee threads into has a small hole at the bottom, restricting oil flow and therefore reducing pressure into the Tee. My 2 way Tee feeds the oil filter and the head.
I'm guessing that the 3 way Tee is for some accessory on larger trucks. The drawing you posted shows a 3 way Tee with the 3rd line ending in an upturn right behind the generator. I'll bet Kenneth (GiantMountainClimber) knows what it connects to.
Last edited by Bill Hanlon; 06/24/20262:20 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.
I think the 3 way tee shown in Bill's diagram with the line going back to the rear and up behind the generator mount is actual a line for an air compressor on many of the larger trucks.
I did some more snooping with the added info you guys posted above and here's a screenshot from a 1963 Master Parts Book indicating the model applications for the 3 way tee.
~ Dan 1951 Chevy 3 window 3100 Follow this story in the DITY Gallery "My Grandpa Carl's Truck and How it Became Mine" 1966 Chevelle (Wife's Hot Rod) | 2013 Chevy Silverado (Current daily driver) US Army MSG Retired (1977-1998) | Com Fac Maint Lead Tech Retired (1998-2021)
Hallelujah ! The threads in the fitting are fixed. If anyone is interested, the threads on the inverted flare fitting are 3/8 - 24 tpi Commonly known as 3/8” fine thread. Thanks for the advice / suggestions !
Both the GMC 228 and 302 engines in my garage connect the oil pressure gauge to the main oil gallery on the lower left side of the block about 5 inches from the rear.
That started in 1951
Originally Posted by Bill Hanlon
The place on the front of the block that the Tee threads into has a small hole at the bottom, restricting oil flow and therefore reducing pressure into the Tee.
That depends on the flow rate of the pump. If its 5 gpm the pressure drop will be minimal. I would say less than 0.1 psi.
Originally Posted by Bill Hanlon
The drawing you posted shows a 3 way Tee with the 3rd line ending in an upturn right behind the generator.
The drawing is an exploded view from a military CCKW350 parts book. When you move the tee fitting back to the block the tube will be at the back of the block not the generator. Here is a drawing from a 1939-1947 MPB 100-900 and the CCKW350 engine side view.
'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.
