GMC 348? More likely a 248. I'll measure the plug in the back of my 302 head later tonight and verify that the 228-235-248-256-270-302 GMC heads all use the same plugs. Gotta go now.
'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.
Isn't there a GMC V8 (Pontiac) with 348 cubic inches? It's a downsized version of the Pontiac 370, so the same freeze plugs should work that fit the 370 engine. 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!
Pontiac Prior to developing its own engines, smaller GMC's used the Pontiac V8 engine. They used the Pontiac 287-cubic-inch (4.7 L) engine for 1955 and 316-cubic-inch (5.2 L) engine in 1956, but advertised the engines as the "GMC 288" and "GMC 316". They used Pontiac's 347-cubic-inch (5.7 L) in 1957. For 1958, GMC reduced the bore of Pontiac's 370-cubic-inch (6.1 L) to 3.875 in (98.4 mm), resulting in a displacement of 336-cubic-inch (5.5 L). In Canada. For 1959, as the Pontiac engine's stroke was lengthened to 3.75 in (95.3 mm), a further bore reduction to 3.78 in (96.0 mm) was done to keep the displacement at approx. 336 cubic inches (5.5 L) (336.7).
Yes, I know- - - - -probably a less-than reliable source! 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!
All 1939-1960 GMC six cylinder gas engines from 228 to 503 cubic inches use the same 1 1/4" plug at the rear of the head, GM part number 663032.
'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.
Don't know what to say. Below is from 1939-53 GMC Master Parts Book. 1955.2-1960 MPB reads the same. I don't have a 1954-1955.1 book, but I doubt GMC would have changed it for a year and then changed it back.
'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 GMC Master parts books say the 663062 1 1/4" plugs fit the back of the head on 228, 236, 248, 256, 270, 302, 360, 426 and 502 cubic inch six cylinder engines made from 1939 through 1960.
'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.
Start with the head, with one that shows the head casting number. Then a pic of the hole and the currently too large 1-1/4" plug in comparison to the hole.
Post what you have and then maybe we can better help out???
Hoping we can help you figures this out!
~ 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)
If the old one rusted out are you sure you got the remnant of the ring out?
Larry Old man᠁Old truck᠁neither one goes very fast. All you need in life is TIME, PATIENCE and MONEY. If you are missing one component, you'll need an abundance of the others two.
Here is pic of the head in question and freeze plug hole
where here?
'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.
Take a peek at this linked page of instructions to hopefully help you get a pic or two posted: Picture Posting Guide
If you continue to have trouble, feel free to PM me and we can talk further on trying to solve your picture posting problem.
~ 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)
I had to move my 302 head today to get into something stored beneath it, so I thought I'd prove my point that all 1939-1960 GMC straight six engines use the same size (1 1/4") freeze plug on the back of the head. My knowledge was strictly book learning as that is what my GMC parts catalogs say.
To quote Gomer Pyle, "Surprise, Surprise, Surprise!"
Pictures are from GMC casting number shown. The 3983 head was used on all 302 engines, 1952-1962.
Proper plug should be a Dorman 555-022.
'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.
