The Stovebolt Site Forums The Shop Area General Truck Talk Considering a '51 GMC

Hello all - new member here. Did not know whether to post this in the general forum or here, but chose here since this is my intro...

Considering the purchase of a relatively clean and complete truck. It looks and drives well and the ask is $16k. No rust, but its definitely a 20 footer since the PO painted it in his garage, over the dings and scratches previously present. It's on consignment, and is presented as a 1951 100. Reason I'm here is that the serial shows a 1 ton (code 25) long bed (code 3), which it clearly is not. The serial indicates it would have been originally equipped with a 228, but I did not have the ability to verify on site. It has a four speed, floor mounted shift, which I am really happy about. It also has a curious park brake handle that I have not seen in other photos of 100 series trucks. I honestly don't care about matching numbers or originality, but would love to know what to look out for if this was indeed converted from a one ton, and also wondering if market value may be affected, and I should use that in negotiation.

I am in California if that makes any difference as far as price comparison, and have attached some pics for what they are worth.

Welcome.

Step 1: check the vin on the title against the tag on the truck. If they don't match, run for the hills.

Step 2: Those look like 6 lug rims. A one-ton would not have had those.

Step 3: I am pretty sure the one-ton had wider fenders than the smaller trucks, but that might not be universal

It would not be uncommon for a cab to get swapped and move the vin from a larger truck to a smaller frame, but make sure the vin on the title matches the truck.

A lot of older trucks were titled based on the engine serial number, which makes them extremely hard to legally title if that engine needs replacing for whatever reason.

As far as what it is worth, that is something you have to decide for yourself. You can look at auctions and other trucks for sale. Combine that with what you are willing to pay to decide what it is worth to you.

Things to consider for the value to you:
-Are you going to leave it basically stock or modern it up?
-Are the brakes, steering, and suspension in good condition?
-What is your long term goal? Fix the body and paint? Enjoy as-is?

The more work you intend to do to it, the less it is probably worth to you as-is.

Im guessing its either a vin swap or just a cab swap. The first thing that jumps out at me is its not 8 lug like a 3/4 or 1 ton would be. Its obviously a shortbed now but just glancing at the rear bumber brackets it looks to be a 1/2 ton frame. The 3/4-1t rails would be closer together. Dosent look like its a “bad” truck….just make sure you know what your buying for that kinda $$$. Also a truck with “no rust” could be easily patched up junk. If you slather bondo over anything it could be considered “rust free” in my experience.

Thank you, Fibonachu - that is extremely helpful, especially the cap swap bit, which would make more sense than a frame shortening, axle swap scenario. It's currently California titled/registered, and I can easily ask the dealer to confirm the serial plate for me (it's two hours away).

I want to leave it stock for the most part. A little body work, a color change, interior work, get the trim back to where it should be, and use it for farm/feed runs. $16k seems reasonable given the comps - just want to make sure I'm not buying a Frankenstein. So yes, I want to do very little, and this seems like a great starting point as its not rotting in a field, and it's not a full concourse restore with a $50k+ ask!

Thank you as well, Barnfind. I did take a look under the floorboards, the floormat, the frame and in the fender wells. There is nothing but surface rust visible, and the serial indicated is was built in Oakland, so it may well be a west coast lifer. It does have an interesting band of metal bolted/riveted to the bottom of the front fenders at the lower rear, which I have not seen in other photos (and they don't show up in mine). I am assuming there may be some rot there. I was previously hunting for a squarebody truck, and the wife fell in love with this, which allows the pocket book to open faster and wider, so I'm doing my best to research!

Chevy engine, too!

Those doors are earlier than '51 (no vent windows).

It has been converted to 12 volt (has a ballast resistor).

What is that thing that looks like a radiator cap about 12" to the passenger's side of the ignition coil?

Handbrake indicates earlier than 51 cab.

As Ed pointed out, a Chevy engine. The Chevy engine is about 1 1/2" shorter back to front, so the fan will be further from the radiator than stock. If you do a lot of low speed driving in a hot climate a fan shroud may be necessary to keep the coolant temp down.

Using your cab's serial number and the table below, which year would your cab be?

My 51 GMC (Canadian) one ton has a parking brake handle in the cab.

I believe the half tons had this option in 47/48, but went to a foot operated park/emergency pedal in ‘49.

Small (half to one ton) Canadian 47-55 ND (New Design=GMC. Aka Advance Design) trucks used Chevy engines, whereas American counterparts did not.

I also think it’s been subject to a cab swap. Do your homework on this one. You don’t want to get burned.
47/48 1ton GMC CAB, Chevrolet half ton frame, would be my guess. Do your research.

Gas tank under the frame and the filler below the bed says it's not a '51 either. That was a 47-48 feature. It seems to be a bit Frankensteinish. Maybe a big bolt cab swapped to a 1/2 ton frame. Floor shift would be a 4 speed or a 3-speed ('47 feature). Looks like it might have a 235 as well, from the 4-bolt valve cover and short pushrod cover.
It won't win any prized for originality, but looks like it might be a solid truck (from the pics, anyway.)

You all are a tremendous resource. Thank you for your time and knowledge. Looks good for a pretty version of the farm truck we want, but I'm looking to give less than asking on this one. All that said, I'm pretty interested in the odd features this has that I like - underbody fuel tank, floor shift, full windows (my preference is to hang my arm out easily). Originality aside, those all seem like plusses. It is a bummer that it is in fact a Chevy motor and possibly frame (I dig the uniqueness of the GMC models of this era), and I have no idea what the "remote" rad cap neck is all about. Don't want to offend the owner, but I think I'll offer $12k here and see what happens.

Bill Hanlon - if I'm reading that table and serial correctly, the regular production number (1694) would make it a '48? The full serial is 25322C1694.

If this is a 48 I thought I could share a couple photos of the 47-48 front grille with a three bar front grille and broader grill surround (mustache) used during those years. Perhaps, GMC modified the grille design later at some point in 1948 to the 4 bar grille that is on your truck. But the 4 bars appeared in 49 for sure. The three bar grilles define the rugged GMC look. Always liked those.

I understand that originality isn’t a priority- but for others this may be interesting.

As the others suggest, do your homework and look it over. It’s exciting to find a truck you want / there is always always another and perhaps better deal to be found too - to keep it in perspective. First sightings can be wicked exciting, but now that you found something that interests you - expand your search along with this one.

Keep us posted!

I see it has a short cap distributor... original to 6 volt applications. 12 volt systems use a tall cap distributor.
Which questions the 12v ballast resistor. Soooo which is it... 6v or 12?
If it's 12v then it would run really crappy with a 6v distributor cap.

The way I read the table (which is from the 1939-53 GMC Light Duty Truck Master Parts Book) is:

25322C1694

25 One ton
..3 137" wheelbase
....22 228 engine
.......C built in California
.........1694 Chassis serial number

So it would almost fall into the second to the bottom line EXCEPT C1694 is lower than the published numbers C1775-C2495. I'll check with some of the guys over on the OldGMCtrucks forum to see if maybe the 3rd line from the bottom actually should include a P, C or S "Plant identifier".

Staggerlee -- kudos for doing your homework!! You have presented us an interesting case here...

On the grille .,.. didn't the Big GMCs have a 4-bar grille?

Definitely a Frankentruck... Needs to be checked over *very* carefully to ensure all these different year components were assembled in a professional and safe manner.

Also ... the fact that it *is* a frankentruck should work in your favor pricewise. Unless the seller is thinking if you can be scared off, a more gullible buyer will come along ...

Last note -- welcome to the old *truck* hobby ... The whole "numbers matching" thing doesn't mean to us what it means to the muscle car folks ...

Good luck with your endeavors!
John

staggerlee 1976 It looks like parts of several trucks assembled into one to sell. Body work is expensive and often disapointing,I would check the fit and closure of the maiin door that you are going to use every day,hers too. Seems like a lot for a truck that doesn't appear to be a survivor ( whole truck that just lived thru the years with what it left the factory with) Another thing is not push button door knobs like 52 on up had. I use pull downs every day and am happy that the doors fit as well as they do. Another thing is the glass,it's just hard and expensive to change,door glasses often cracked from slamming are a fairly easy home repair job. Would mostly go by how good the body is California truck might be clean,magnet it all over with a rag hunting for bondo. Good Luck !!!

A picture of the ID plate on the left door hinge pillar would help. If the rivets holding the plate on don't look "right" it could be that the plate and the serial number do not belong to the cab.

Another question: I can't tell from the driver's side picture you posted. Is there a vent door on the outside of the cab forward of the left door?

Staggerlee,

I wouldn't pay $10 grand for that truck. Much nicer and correct trucks can be bought for that money with a little patience and searching.

My primary concern would be trying to register it if the title and door jamb plate don't match or if the id plate has been removed and re-installed. Many states will not title a vehicle that has been altered in such a way. It might slip by for you but selling it in the future, especially to someone out of state might prove difficult if the identification on the body doesn't jive with the title.

Anyway, what else is "wrong" with the truck? The previous posters discovered all kinds of anomalies in just a few minutes from five photos. Who knows what other problems are present that can't be seen in these pictures? Who did all the work? Was it done correctly and in a workmanlike fashion?

The ballast resistor and 6 volt dizzy cap are a red flag. Was it actually converted to 12volts? If so was it converted properly? It doesn't appear so at first glance. You don't want a pile of electrical problems down the road.

Don't worry about offending the owner. If he can't or won't answer legitimate questions about the origin of the vehicle concerning who cobbled it together, how the work was done, why the mish-mash of parts, its mechanical and physical flaws, then you don't want to buy the truck anyway.

And what the heck is that tube on the passenger side of the engine bay with a radiator cap on it? Maybe the engine came from a stationary industrial unit or something and that's an oil filler neck?

Good luck, don't fall in love with it and proceed with extreme caution.

The ballast resistor (signifying a 12v battery) and a short distributor cap are not a problem if done right. My '52 GMC had those when I bought it in 2013. Worked well.

Look at the area near the water pump outlet. There is a red lever ball valve from Home Depot. I assume it is a heater shutoff valve. Who knows?

Number 2 plug wire is different from the others. Why?

And what are those hoses down low on the passenger side going toward that mystery tube with the radiator cap?

Just more questions that need answers before moving forward.

Wrong taillights.

Do you have more photos of the engine bay from other angles?

Also missing the upper radiator support.

And probably the biggest red flag of all, it's equipped with a Rochester B!

That's a joke son, why aren't cha laughin'?

I will add my Welcome to the Stovebolt this morning.

Just back from travels so missed the start of this conversation.

Lots of very good info and feedback from everyone on your potential purchase. FWIW, after getting to look at your pictures, I will offer a bit more info and details that I see (or in some cases don't see in the pics).

That "remote radiator cap thing" appears to be someones contrived radiator overflow catch device as it is plumbed into the overflow spout on the upper radiator neck (clear-ish plastic tubing). Willing to bet there is some kind of closed container that neck is joined to that catches antifreeze overflow during possible overheating conditions. Mounted that low, wonder how effective (or problematic) it may be???

There are also a number of missing pieces in the engine compartment, most notably the upper radiator 2 piece shroud (see attached engine compartment pics form another '51 GMC - Not Mine - that I found through a quick web search).

Also missing is a required safety device (horn). At least none is visible in it's normal location. Perhaps there is one, but the absence of the horn button on the steering column may indicate not.

Missing the foot stomp starter entirely and looks like an after market ignition switch. You may or may not care on that feature, but just wanted to note it's absence.

Another indicator that a 12V conversion has been done (not necessarily saying it is correct or not) is the absence of a "voltage regulator" (black box on upper firewall area in my added pic below). Would indicate the original generator was probably replaced by an internally regulated alternator. A common change for many these days.

As several have mentioned, you are clearly looking at a "Frankentruck" put together with lots of "unique" aspects, parts, you get what I mean.

In the end, your choice on if you decide to pull the trigger. Just know what you are getting yourself into up front and go from there.

Keep us posted on what happens!

Dan

EDIT: Bill Hanlon caught the missing shroud before I could post my reply - haha!

You can almost bet that truck is on a 1/2 ton frame. 1ton would be 137 inch wheelbase and those rear wheels would not be centered in the wheel openings of the short bed. John

1 ton frame rails will be flat on top all the way to rear where 1/2 and 3/4 ton will have a ‘hump’ over axle. John

Well, as you can see, this truck is anything but stock and is indeed, a Frankenstein's monster. It also doesn't seem to have been cobbled together very well at all. Missing parts, title doesn't jive with the truck, improperly installed add-on parts, incorrect parts, etc.

It's certainly not worth $16k based on all this and it doesn't look like it meets your expectations based on your posts. All of this information can be used to to bargain the price down - I'm saying $8k but that's just my opinion.

My feeling is that this truck was hastily cobbled together for a quick sale and profit. With that little care and attention to detail visible in just these few photos, I wonder what kind of work was done on the brakes and steering components?

Thanks, all! Lots of great info and I'm armed with load of questions for the seller. Will keep you all posted on which way this goes.

Dan / Gdad,

In the photo of the engine you posted, the draft tube looks like it has a removable cap on it. Is that what it is? Does the filter element come out with the cap for cleaning or something?

And now that you are past "moderation" status, you can fire away at will!

(Wanna give a little more to your location in your profile? Even if it's just So Cal or No Cal or near a city, or county. It'll help people who may be close enough by know ... some of those guys could be of help. That's what we do!)

Otto,

If you note on the GMC valve cover, there is no "oil filler" provision. The removable cap on the draft tube (correct me if I'm wrong GMC guru's) is for filling ye 'ole crankcase with fine motor oil.

As to how the underside of that cap looks, I can't say as my x-ray vision stopped working decades ago - haha!

How about it GMC guys??? What's under that cap? My best guess is just a simple baffle plate a bit down the throat of the tube???

Dan

Feel free to ask them to confirm it before you go back, but 100% check it for yourself before you agree to anything. I have seen plenty of super-sketchy and/or straight up illegal old vehicles sold and certified by dealers both in and out of California.

All things considered, given your statement that you don't want a franken-truck, this is probably a hard pass.

There is an oil filler with a filter breather on 'Bolter Crenwelge's '51 GMC parts truck that I stole the oil pan from while he was in Germany a week or so ago.

GMC sported a closed crankcase breather system. here are a couple photos from my 46 resto. Note the breather tube plumbed into the intake from the valve cover. The moisture and crankcase gases pass through an evapotransfixerator (PCV valve) just before the intake where they are recycled that also includes a disposable baffled filter inside the canister on the upper breather tube.

This would be the same principle as found on 261’s and correct for a 6 cylinder GMC 228-248-270 and possibly but unsure a 302 (military 302’s also had a closed system where a snorkel was added with a similar but more robust down tube canister.)

The last picture shows the builder in fast action mode. Note the blurred hand movement. This comes with practice (some humor to add some brevity to this outstanding message string )

(Look what you started Staggerlee… it can only get better, or worse depending on you point of view… welcome aboard)

Otto,

FWIW, here are some pics that add info to the "filler cap" mystery. Thanks Bill H. for your input!

1st pic is noted to have been for a 1931-42 Chevrolet cap with the handle, which is what was apparently used on the '51 GMC I grabbed a pic of. Would not have been a "stock" item on the '51 GMC engine.

2nd pic is of two slightly different GM NOS oil filler caps noted to be 1931-62, GM part number 836450 which I confirmed using GMpartwiki search as the same number for both Chevy and GMC.

The 2nd pic shows the cap with just a cork seal. Whatever baffle material was down inside the draft tube itself remains a mystery to me at this point.

Dan

EDIT: Tom's pics of the "Closed" road draft tube system was an option to the open road draft tube setup on these engines. Thanks Tom for your input too!

This is the system used on a Chevy 6’s. The experts can correct here - but I have not seen this on a 235 but rather, on 261’s.

I don’t see any reason why they were not installed on 235’s unless the application or use of the engine demanded these on the the 261 and not 235. ?

Not the best picture but you can use these to compare and contrast.

Note: there was no filter element in this system but just the evapotransfixerator (PCV valve) nearest the down draft tube head. .

The last picture shows the end that would tie into the intake manifold. The tube went up and over near the middle of the valve cover…that seems sort of inconvenient if the cover needed to be removed, but it was as a direct routing as possible I suspect to avoid condensation and cooling if the tube was re-routed.

I don’t intend to go down a rabbit hole here, considering the intent of the original posting… but inquiring minds might want to know how Chevy / GM addressed crankcase ventilation and recycling gases (seeing that it was brought up here) on these Stovebolts.

I can digress further and go into a lengthy powderpoint discussion on gearing ratios used in 1951. Let me know.

LOL, this thread has been a compendium of changes to our trucks over the years.

Zooming in on that driver's side picture reveals a side cowl vent. The feature went away on '51 trucks.

So now we see that the cab, at least, isn't even a 1951 truck and probably not even a 1 ton cab.

That leads me to believe that if the door jamb plate matches the title, it has been illegally removed from a 1951 1 ton cab and placed on a 1947-1950 cab.

The plate may have been removed altogether and the title is using some other id method. Either way, it's not good.

Thanks, Peggy. I updated my profile to show I'm up in Petaluma (30 minutes north of San Francisco).