Big truck motors in lighter vehicles

I have the chance to get a Pontiac motor out of a 58 GMC for my 37 Chevy p/u that came out of a fire truck,is there anything I will need to change except to get rid of the governor to get it to run right in a lighter vehicle.

 

The '58 Pontiac truck motors were very tough with forged crank and rods with a reinforced block. If you choose to, you can install later heads that breath much better but, will have to watch to valve to cylinder wall clearance.
The engine should work fine for what you are doing. Save all the related Pontiac mount stuff if you do not use it.

 

Usually, removing the governor from a truck engine is a bad idea, as the truck internals and valvetrain are not intended for high RPM, and spinning them up usually results in bad noises followed by terminal silence- many truck engines have been blown up because the owner did not know how to rebuild a Holley, balked at the price of a rebuilt gov carb, and put a car carb on it- a couple 4K plus shots is usually all it takes for boom to show up

 

If I do this swap I doubt the motor will see high RPMs and will keep it geared reasonable,just what is different in the truck motors then the car versions that will go kaboom if taken over 4000.

 

The big difference is that it's in a truck, hauling a lot of weight.

 

So would it be better for me to p*** on this motor and just stick with a car motor.

 

I don't see any issues with using the GMC/Pontiac engine. The factory camshaft in it may be designed for low rpm / high torque use, but it's not going to blow up.

 

You might check in a truck forum but I was told that the V-8 in GMC trucks was the same as the 347 V-8 in the Pontiac Coupe I had. Great engine

I think it was a case of them putting a car engine in a truck instead of the other way around -- pull the pistons out of a big block GMC V-6 and you'll find long pistons with 4 four piston rings and a super heavy crank, none of which will want to move very fast.

Friend of mine had '56 shorty PU with that engine and man it could run!

 

The governor on HD trucks with gasoline engines is there for constant load operation. I drove a 366 gas motor in a 26,000 pound truck for years. The governor was there to keep you from blowing the engine up in 2nd or 3rd gear on a hill with your foot planted on the floor for 15 minutes straight.

You might have enough horsepower to easily hold 4,000 in 3rd. Shift to 4th and you will be downshifting in a minute. With no governor you can probably run 5200 on the floor - and blow it up in a week.

That engine will be built & cammed for torque where you need it in a heavy vehicle. Put any kind of induction you want on it - just watch the tach, and short shift around 4,000. WOT > 4k> Shift > WOT > 4k> Shift...

B.

 

No mechanical skills? How in the hell did I ***emble this 37 by myself with only the front end alignment farmed out,never messed with known big truck motors before even though the 235 I have in it now could be considered one. Just want to know what I will be getting into with a big truck V8.

 

It's a 336 if it's the original 58 engine. Only up to 57 did GMC use the same size engines as the Pontiacs. The 59 gmc was also a small bore 336, not a 389.

 

Refer to pot 10 he said it like it is. The governors were put on those engines exactly for the reason he mentioned. Drivers would drop down to low or second gear and wind the things out for miles on end climbing grades (and still do) or wind them out way too high going through the gears and blow them up.

I would go through it and put new bearings in it if it has been setting for a long time though as old acid etched bearings are a really killer of old engines. The same reason many of us in our 60's blew up that first car that our dads just thought was perfect for us because old lady or old man _______ had driven it for years and never went outside the city limits and only drove it to the market and church.

I wouldn't be afraid of it one bit if it is a solid engine now.

 

JEFF instead of telling you it wont work, there are easier ways to make good power! iam not a big high post # **** that has to belittle you for your question good luck with your project. Mark

 

Run the damm thing ! The truck specific things cam designed for torque usually lower compression.Good truck things, normally better valves and higher quality/duty bearings and timing components. Sold auto/truck parts for years and most internal stuff was the same. This is a CAR motor adapted to medium duty truck usage, not a purpose built TRUCK engine. GMC also used Olds engines in the heavier medium trucks.

 

Jeff,
Do some research on the consumables (bearings, etc.) to see if they are different / still available. If so, go for it. It's just an engine. You already said you aren't going to rev the snot out of it. Ditch the governor and have fun...

 

Upgrade the valve train and you should be fine.

Elwood

 

Jeff
The 1st and real question is........ just cruising, or wanna go fast? Is it a 4 barrell with the back 2 governed? If your just cruising, who cares, run it with the governor. You need to find a good motors manual for trucks, it will give you the specs of that motor. Just like ford, it is a car motor that has had the compression lowered, slower speed rockers, and a torque camshaft. It may have a dropped forged crank, especially if it has HD rating on the motor. The flywheel will be a heavy monster. Since it was in a firetruck, low mileage, but lots of idling time. Have you seen it run?

 

Ring ridge at the top of the cylinder can & will break up pistons in an engine that runs faster, even a little faster, than it generally has before.

You probably know that already!

 

Its not running at this time but is not stuck and the seller has not heard it run,I forgot about the truck motors having lowered compression that makes them run not as good as a car motor so I might have to p*** on it. It would be just like the 352 that was in my 66 F250 that had no guts and no matter what I done to it I could not get it to get decent gas mileage.

 

I know of a GMC ex- firetruck with a 401 in it. I've often thought about puttin that motor in a rod.

 

Did you change the rest of the drive train already ? If I was going to run a truck engine it would probably be a "W" block, but mostly I would run something that's easy on the wallet. Not great milage per say but something easy to get parts for and run on current pump gas.

 

Jeff, its just daring to be different!! Do more investigating. Truck motors weren't designed for mileage, they were designed to start a heavy load from a dead stop, and keep on pulling. I checked the truck motors manual I have, it only goes back to 1960, it only lists the spec of the V6 GMC motors. Since your motor is a Pontiac block, I bet you can get a car flywheel (presumably lighter) and a 4 speed car ******, or automatic maybe. Fix the compression issue with a blower.

 

I will try to get more info on the motor before I decide to get it.

 

Jeff i say use it would be cool and different.yes truck motor internals are heavy and most likely not like alot of rpm but i would approach the build as if it was a diesel and not expect a ton of rpm use low rpm torque and strong engine to make a small car haul with a little boost from a blower i think it would perform well

 

I think one of those supercharged 3.8 Buicks might have a part I could use.

 

this is a great engine for your project...if it was in a truck pulling a lot of weight, it'll be on easy street in your pickup...I had a sbc 350 from a schoolbus swapped into my cj7 jeep...still had low compression pistons and small valve heads...ran a 2gc rochester carb and dual ramhorn manifolds...this engine was really a strong runner...unmodified!

 

Here is the thing... leave the engine alone... don’t screw with the governor...

Just put in some TALL *** highway gears in your rear end and ****** and
You’ll be driving a rocket... use the torque not the rpm and you will
Have a monster.

 

I got a dollar bet saying if you had this Pontiac truck engine or the same size Pontiac car engine with the same intake and exhaust...Be hard pressed to tell the difference in performance.

 

In the 50s GMC used Pontiac engines in their light duty ie 1/2-1 ton and Olds in the 1&1/2 to 3-4 ton trucks. No real difference from a car engine. They may have better quality valves ,bearings,heavier flywheels and in some cases governors. Bottom line change cams and intakes to more car type stuff and run 'em. Chevy "W" engines were orignally TRUCK motors EH!! Seems they did real well in cars too, same with big blocks orignally 366 CID TRUCK motors.

 

Save your dollar, you'd have to go a little deeper to "equalize" them. I actually knew a pair of brothers in the early 70's who had one of those GMC trucks, a 10 whl dump, would you believe Southern Tier NY (Steuben County). The original truck engine was shot, so they found a Poncho car engine and bolted it in, but didn't change enough stuff- worst part was they kept the car cooling setup, and it would puke water going up any serious hills, and the car cam & compression were incompatible with the loading, pinged like crazy and didn't live very long. You could take that truck engine as-is, run it in a car, should last forever, run on any gas you could find, and be fine as long as you didn't care that it wasn't fast or throttle-responsive.
Your usual truck g***er has a very small cam, low compression, heavy reciprocating ***embly, many times heavy, large-stem valves with springs appropriate for low rpm, and high-capacity cooling systems. My gramps had an International dealership in the 50's-early 60's, and had several farms, lime spreading and general trucking companies, had my hands in gas truck engines since I was 5- REO, Binder, Ford, Chebbie, GMC, whatever- the gas truck engines are meant to grunt and get reasonable mileage while lasting a long time, and are pretty lethargic compared to a car engine. FE and FT Fords are similar but also very different, and very different states of tune. We used to have a Binder Fleetstar 10-wheeler with a 549 g***er in it, and along with the guys with the 534 Fords, would keep right up with or outrun the Maxidynes and 6-71's that many were running if you stuck your foot in them- but would drain the tank pretty fast if driven that way. One of the guys had an F800 with a 534 and had cutouts in the exhaust with 3" pipes sticking out from behind the cab on the right side and angled up, if one of the diesel guys p***ed him on a hill, he would let it eat, p*** them back, and open the cutouts right in their open window as he p***ed- nobody p***ed him more than once
And the REO OA331 was hands-down the saweeeetest sounding six truck g***er ever- we had a trio of deuce-and-a-halfs, along with a bunch of regular REO's, and they would howl pretty good

http://www.youtube.com/watch?v=k5jSWhzG3D4

And here's one with the "Fording Kit"- sealed ignition, fuel, intake & exhaust

http://www.youtube.com/watch?v=W**ZRzAh4bg