The Stovebolt Site Forums The Shop Area Engine Shop Need 1958 GMC 336 block cast #

I just bought a 1958 GMC 150 and am trying to ID the motor. The truck should have come from the factory with a 336. My cast number on the block clearly reads 523283. That number is not found on any chart. The closest number, one digit off, is 523293 which is the code for a 347. I tried to find a cast number for 336 on the internet, but no charts show it. I have seen other posts with guys having the same problem.
Does anyone have a 336? If so, what the hell is your cast number! It's on the passenger side, close to the dipstick.
Thanks! Dyno

the number should be stamped just above the oilpan, on the passenger side. It should start with 336. There are 2 different types of 336 motors, so the number after will identify it as an early 336 (based off the pontiac 370) or a later 336 (based off the pontiac 389).

I had an early 336 in my 59 gmc 1/2 ton longbed. I changed it out for a 59 pontiac 389 that I had bored and stroked to 447 inches. The 59 389 is virtually a drop in replacement for the 58 336. I had to have my flywheel bored to match the larger crank flange.

bigbad.. is looking for your engine serial number (right side, below manifold, in front of drain cock). Pretty straight forward. Starts with "336" you have a GMC/Pontiac 58' or 59' motor. Starts with "347" you have a GMC/Pontiac 347 cu in. a 57' motor.

I'm not sure Pontiac stamped them there. GMC definetely did.

I was trying to point out to dyno that these GMC years were Pontiac motors tweaked by GMC. Didn't mean to confuse the issue. Your nod to their Pontiac history is better than mine.

Thanks for the replies. I looked for a "stamped" number in that area just ahead of the drain cock passenger side. Can't see anything other than the cast number. I did find some stamped numbers on the front of the block below the head, passenger side:

Reads C757H 14287

The C apparently is the 3rd month, March 7, 1957. I don't know what the other number is.

No stamped number in that area could mean that you have a regular Pontiac engine instead of a GMC engine.
Let me throw out a couple of theories, you do some research on some web pages I will suggest and any of your own, and then you decide.
First, I believe your block casting number is 523293. What you think is an "8" is really a "9". This would mean that you may have a 57' 347 car engine. Please examine it closely again.
Second, I believe the "C757H 14287" number on the front of your block supports the "347" car engine theory.
Using info from the "1955-60 Pontiac Engine Component Interchange and Identification" pages bookmarked below, the number represents a serial number that would have been found on a tag inside the driver's door jamb and stamped on the front of the engine.
It decodes as
C = South Gate, CA, place where car was assembled.
7 = 27 Series car, 122 in wheel base (all Chieftains, Superchiefs and Safaris)
57 = model year of vehicle
14287 = serial number of car as it came off assembly line

I believe a 57' model year would indicate a 347 motor.
Please look at this info below closely. I trust others will
offer better info if they have it.


http://www.pontiacsafari.com/L1Garage/EngineID/index.html

http://www.pontiacsafari.com/L1EarlyV8Pontiacs/IdentificationTags/index.html

Very perplexing. I have looked at the engine cast number several times...it is very clean and readable. The "8" digit is definetely an 8, not a 9. I looked at the Pontiac Safari page several times also. They don't have a listing for a 336. Is that because it's a GMC motor? FWIW, Wikipedia states that it was produced by GMC:

336
GMC's own V8 was the 336-cubic-inch (5.5 L) OHV/pushrod engine. It used a 3.875 in (98.4 mm) bore and was produced only in 1958 and 1959.
While both the '58 and '59 GMC V8 engines were advertised as 336-cubic-inch (5.5 L), the '58 version was based on the Pontiac 370-cubic-inch (6.1 L), but with a smaller 3.875-inch bore giving 336.1 cubic inches (5,508 cc). The '59 version was based on Pontiac's 389-cubic-inch (6.4 L), but with a smaller 3.78-inch bore giving 336.9 cubic inches (5,521 cc).

Here is a short explanation by Bill Hanlon on the Safari site about the GMC 55'-59' V8's. (Look at the "GMC/Pontiac V8" section on this page).
http://www.pontiacsafari.com/L1EarlyV8Pontiacs/V8%20Engines/index.html

My take is that if you can't find the engine serial number that starts with "336" as illustrated here:
http://chevy.oldcarmanualproject.com/gmc/5559mm/5559mm0i05.html
and your block casting number is not "528456" (the Pontiac block used for the 58' GMC 336 or "532000" (the Pontiac block used for the 59' GMC 336) you do not have a GMC 336 engine. I do not know if any early 60' "536387" blocks were used for late GMC 59' 336 engines.

Please remember that any of the 55'-59' V8's produced by Pontiac or GMC could have been easily dropped into your truck in the last 50 some years. I still personally think you have a Pontiac 57' 347 for the reasons in my previous post.

For more informed opinions than mine I would suggest you register at this site http://www.oldgmctrucks.com/
and post your engine ID question there. Photos of your engine and its numbers would be helpful.

I believe the above mentioned Bill Hanlon is a member there and bigbadswingdaddy is there also. There are simply more people there interested in GMC engines. Good luck with your project.

Thanks for all your input, Randy. Will do more digging on the subject.

Most on the oldgmctruck site are interested only in 6 banger gmc motors.

Pontiac Safari and performance years offer the best tech info.

http://forums.performanceyears.com/forums/forumdisplay.php?f=426

Butler performance knows a lot about the early Poncho motors in GMC trucks.
http://www.jbp-pontiac.com/

Wallace Racing also has some useful pontiac information.
http://www.wallaceracing.com/index.html

A 1960 pontiac engine is easy to discearn from the 1955-1959 gmc and pontiac v8s. It is not reversed cooled, so there will not be any tubes coming out of the timing cover/ water pump housing going into the heads.

John
P.S. The oldgmctruck site will not give you any "bad" or "mis" information. If you get an answer on that site, you can rest assured it is the correct answer. I used all the above linked sites Randy has provided when I built my pontiac v8 for my 59.

Just curious... Does the water pump have 4 bolts or 6 bolts holding it to the timing housing? Larger GMC trucks got an Oldsmobile engine. Maybe your truck got one of those. The early oldsmobile engines had a round 6 bolt waterpump. The early Pontiac motors had a round 4 bolt waterpump.

Any pics of your motor?

Sorry to bring up an old post. Don't know if this will help. I have a supposed 336 out of a '58 GMC 2ton. There is a 336 by itself, no other #'s, stamped on a pad above the oil pan near the dipstick. Near the front of the block (think piston #2) is what looks like (cast) 533087. The pass head has 528511 on it. The engine has a 2brl carb with an adapter for small bolt pattern to big bolt pattern on the intake. Even has the spin on oil filter on bottom pass side.
This engine was definitely in a big truck. Huge frame, huge radiator, & huge generator. I still have the frame from cab forward & 4spd that used to have pto & drum parking brake.

Why not move this request for information to www.inliners.org. I know of many 336 owners on that site. There are a bundle of all kinds of inline owners on that site. I have a 302 built out to 320 c.i.but you are looking for another block type.
Normbc9