Click on image for the lowdown. 
====
| | | Forums66 Topics128,023 Posts1,055,371 Members48,420 | | Most Online14,466
Apr 26th, 2026 | | AD Chevy Trucks  Over 6,000 pictures Brad Allen has an awesome collection of Chevrolet factory pictures that he has set up from film strips. Check them out!
Lots of work on Brad's part ... pure enjoyment (and references) for you!
| | THANKS!
For helping keep this great
old truck web site
on the Internet for over 30 years! and not clogged down
with Ads!  Again, thanks!
| | | | Joined: Dec 2000 Posts: 3,399 Gas Pumper | | Gas Pumper Joined: Dec 2000 Posts: 3,399 | I have been a Chevy guy forever now, but with some of the kits I sell, they are also compatible with GMC engines. Problem is, I know nothing about them. Can someone enlighten me please?
For example,
1940-1953 - Chevy made the babbit 216 and 235
1954-62 - Chevy made the full pressure 235 and 261
(close enough for my purposes)
During those same years, what were the GMC offerings? I know the distributors are compatible but my main concern is the
intake manifold vac fittings. I assume they are the same as Chevy, but I don't even know all the motor sizes. On the distributor, what was the last year they used a short cap/short rotor? | | | | | Joined: Sep 2001 Posts: 29,269 Bubba - Curmudgeon | | Bubba - Curmudgeon Joined: Sep 2001 Posts: 29,269 | GMC 228, 248, 270, 302 were common straight 6 engines (for the straight 6 smaller truck engines). https://en.wikipedia.org/wiki/Chevrolet_straight-6_engine#GMC_enginesBetween 40-62, GMC also made the following straight 6 engines: 236, 256, 426, and 503 | | | | | Joined: Dec 2000 Posts: 3,399 Gas Pumper | | Gas Pumper Joined: Dec 2000 Posts: 3,399 | So...
The 228 would be like our 216 (1939-1953) pretty sure that would have the short dizzy cap/rotor.
The 248 would be like our early 235 (1939-1955) same on the short cap/rotor.
Then the 270 could be like our newer style 235? that one looks like the year would matter as far as its evolution. (1941-1962)
Then the 302 is probably like our 261 (1952-1960) in that its the more highly coveted for its durability and power.
I still do not know what engines had a tall cap/rotor style distributor. Its amazing when you focus on one make how much you don't know about the others.
Thanks Tim! | | | | | Joined: Sep 2001 Posts: 29,269 Bubba - Curmudgeon | | Bubba - Curmudgeon Joined: Sep 2001 Posts: 29,269 | A GMC person would smirk at your analogies, Deve (as would a mathematician).
All the GMC engines (GMC 228, 248, 270, 302) were full-pressure/high-pressure engines.
I think all had insert rod bearings.
All would be considered full-pressure/high-pressure.
All were supposedly cast with a better/harder alloy/metal-mixture (I think more nickel).
All had superior carburetion, usually Zenith (or, Holley AA-1).
Comparing a 270 to a 235 is interesting.
The only "superior" technology that a contemporary Chevrolet engine had compared to the GMCs was the 58-63 261s had full-flow oil filtration (none of those GMC engines had that technology). | | | | | Joined: Dec 2000 Posts: 3,399 Gas Pumper | | Gas Pumper Joined: Dec 2000 Posts: 3,399 | Thus why I put the thread here, so a GMC person would post on some of the intricacies. I am sure we have a few people who know this stuff really well. Tall cap distributor vs short cap, bypass oil filter locations and NPT sizes on the intake are of particular interest. | | | | | Joined: Sep 2001 Posts: 29,269 Bubba - Curmudgeon | | Bubba - Curmudgeon Joined: Sep 2001 Posts: 29,269 | Have you checked out the GMC (vs Chevrolet) distributor caps listed for various years at vendors like Rockauto (if listed, the faster vendor-listings to peruse).
Keep in mind the GMC used positive ground until 12v-neg in 55/56 (depending on truck-size/engine). | | | | | Joined: Dec 2000 Posts: 3,399 Gas Pumper | | Gas Pumper Joined: Dec 2000 Posts: 3,399 | I don't even know how that would change the (stock) ignition system.
Good idea on RockAuto. But holding out for the GMC guru's here. | | | | | Joined: Sep 2001 Posts: 29,269 Bubba - Curmudgeon | | Bubba - Curmudgeon Joined: Sep 2001 Posts: 29,269 | "I know the distributors are compatible but my main concern is the intake manifold vac fittings. I assume they are the same as Chevy, but I don't even know all the motor sizes. On the distributor, what was the last year they used a short cap/short rotor?"
"I still do not know what engines had a tall cap/rotor style distributor"
"Tall cap distributor vs short cap, bypass oil filter locations and NPT sizes on the intake are of particular interest."
In an effort to keep this thread on-topic:
It looks like Deve is looking for the following information for 228/248/270/302 engines (throughout their life histories):
1. distributors: short-cap or high-cap and short or high rotor?
2. size/diameter/thread of vacuum port (and or PCV ports - see #4) on intake manifold
3. by-pass oil filter location?
- maybe he is interested in where the filters reside (right-front side of engines, usually); or,
- maybe he is interested in where the ports are located on the block
4. location of PCV ports/devices/fittings/hoses? | | | | | Joined: Mar 2011 Posts: 1,146 Shop Shark | | Shop Shark Joined: Mar 2011 Posts: 1,146 | I think this would help. 1929-1954 GM parts interchange manual buick chevrolet pontiac GMC (CD) in PDF format Product Description Vintage GM car and truck parts interchange manual on disc (CD) in PDF format, .Fully autorun, bookmarked with a master menu. 1929 to 1955 parts, there are over 5500 parts that interchange with Chevy, Pontiac, Olds, Buick, Chevy truck and GMC truck in this manual, NOTE, CADILLAC is NOT INCLUDED IN THIS MANUAL Also included is a 1929-54 Chevrolet illustrated parts manual Over 1100 pages of rare hard to find info It would be better if it covered more years. i.e. 1929-1975 | | |
|
|
