Ok, I can't find a shop manual or any info on the web about the specs for this engine, as far as tune up parts go. Does anyone know what specific points, condenser, cap, rotar, oil filter, etc. I need? Also the point and plug gaps? I can't believe I can't find any of this info anywhere. Any help appreciated.
I believe the same points and condenser, and possibly the distributor cap and rotor will interchange with a distributor for a 235. The 426 is the smallest of the "big" GMC engines, with the 503 being the largest one. Ed Pruss has a 1954 630 series truck with a 503 in it. You might want to send him a private message to see what information he might be able to provide. I drove that truck from south Tennessee to the reunion in Kansas city a few years ago after Ed broke down on his way from Cullman Alabama to Denver. Quite a trip! I changed the points partway, and the ones I used were identical to points for a 235. A point gap of .016" and a plug gap of .035" will get you on the road- - - -not sure if that's perfectly accurate, but it's in the ball park. 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!
On a big, low-compression engine like the 426, about all that a spark plug needs to do is light the fire. As long as the thread diameter and length is correct, there should be a wide range of plugs that will work, especially if you're not planning to do a lot of hard pulling at max RPM and wide open throttle like these engines were designed to do. As long as the plugs don't foul out from being too "cold" of a heat range, you should be good to go. 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 kid raised on Hotwheels, Matchbox and Tonka cannot be reasonably expected to own only one vehicle as an adult.
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Hy Guys, I know we are talking about the medium and heavy duty truck engines here, but the smallest displacement of that design of engine, manifolds on the right side of the block and removable cylinder bank was a 278 I believe and there was a 308 as well, I have a 308 in a 1948 500 series GMC.
I think there was some kind of break as the engines got larger, no clue where it was, but somewhere they looked the same but got physically larger, perhaps larger than 308?
Ed
'37 GMC T-18 w/ DD 4-53T, RTO-610, 6231 aux., '95 GMC running gear, full disc brakes, power steering, 22.5 wheels and tires. '47 GMC 1 ton w/ 302, NP-540, 4wd, full width Blazer front axle. '54 GMC 630 w/ 503 gasser, 5 speed, ex fire truck, shortened WB 4', install 8' bed. '55 GMC 370 w/270, 420 4 speed, grain, dump bed truck from ND. Works OK.
I seem to remember a late 1940's/early 50's GMC road tractor owned by my uncle that had a big gasoline engine with the carb on the passenger's side. I believe it had some sort of updraft carburetor, but that might not be the case. It was a conventional cab rig, not a cabover. He used it to pull a trailer for the big freshwater boats he repaired at his shop near Old Hickory Lake, near Nashville. 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!
My spare 503 distributor is driven by a rectangular shaft crosswise through a vertical 3/8" pin that extends out the bottom of the housing. The rectangular shaft is offset slightly from the center of the 3/8 shaft, one must be careful when inserting in block.
Innards of distr. are probably same as other GM distributors, however.
Ed
'37 GMC T-18 w/ DD 4-53T, RTO-610, 6231 aux., '95 GMC running gear, full disc brakes, power steering, 22.5 wheels and tires. '47 GMC 1 ton w/ 302, NP-540, 4wd, full width Blazer front axle. '54 GMC 630 w/ 503 gasser, 5 speed, ex fire truck, shortened WB 4', install 8' bed. '55 GMC 370 w/270, 420 4 speed, grain, dump bed truck from ND. Works OK.
1950 was the year GMC Heavy Duty Trucks, introduced the new style Cabs. Along with the new cabs, came the new engines. 318, 360, 426, 503, and 707. Before 1950, the Heavy Duty gas engine group, consisted, of these engines. 308, 361, 451, and 477.
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GMC 630's came with 503's, which are just slightly larger, similar engines. Parts and service manuals are frequently available on EBay, that is where I got mine.
Ed
'37 GMC T-18 w/ DD 4-53T, RTO-610, 6231 aux., '95 GMC running gear, full disc brakes, power steering, 22.5 wheels and tires. '47 GMC 1 ton w/ 302, NP-540, 4wd, full width Blazer front axle. '54 GMC 630 w/ 503 gasser, 5 speed, ex fire truck, shortened WB 4', install 8' bed. '55 GMC 370 w/270, 420 4 speed, grain, dump bed truck from ND. Works OK.
Be careful, head gaskets and gasket sets are hard to find for 426's or any other big blocks, makesure your head bolts are tight (80 ft. ft. pounds for .437 bolts, if .437 bolts less, ) ARP has.437 head bolts, slightly long, but OK.
Ed
'37 GMC T-18 w/ DD 4-53T, RTO-610, 6231 aux., '95 GMC running gear, full disc brakes, power steering, 22.5 wheels and tires. '47 GMC 1 ton w/ 302, NP-540, 4wd, full width Blazer front axle. '54 GMC 630 w/ 503 gasser, 5 speed, ex fire truck, shortened WB 4', install 8' bed. '55 GMC 370 w/270, 420 4 speed, grain, dump bed truck from ND. Works OK.
No known head gaskets, there was a fellow in WA a while back that had some 'space age material' that he made head gaskets out of, Stewart or Stevenson or something like that was his name.
Ed
'37 GMC T-18 w/ DD 4-53T, RTO-610, 6231 aux., '95 GMC running gear, full disc brakes, power steering, 22.5 wheels and tires. '47 GMC 1 ton w/ 302, NP-540, 4wd, full width Blazer front axle. '54 GMC 630 w/ 503 gasser, 5 speed, ex fire truck, shortened WB 4', install 8' bed. '55 GMC 370 w/270, 420 4 speed, grain, dump bed truck from ND. Works OK.
Ditto on Gasket City. I got the last valve grind gasket set he had in stock for Ed's 503 about 3 years ago, but at that time he had ONE head gasket left for the same engine. I believe the 426 and the 503 use the same head gasket, but I'm not sure of that. 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!
