The Stovebolt Site Forums The Parking Lot Big Bolts GMC 450 curb weight needed..... now with pictures

My truck has (F453 30 1023) on the ID tag in the driver door jamb. I've never seen a letter after the initial series no. ie: 452 except once, & it was a "x" after (HF 602x 31 1245) This was a 600 series "Cannonball" COE I once owned, & the "x" in the ID number denoted it being a special order wheelbase. Your "a" has me puzzeled. I saw a air over hydraulic '54 GMC 450 series once with "Hyd./Air" on the glove box lid plate, nest to serv. brakes.

I looked at the drivers door jam to see if the a is on it, it is not. There is a 452 a large space then 30 another long space followed by the 4 digit serial number. The glove box tag lists the model as 452. There is no A on the glove box tag either. On the center of the dash there is a large nomenclature tag that lists the empty weight, payload max weight and the combined maximum weight, plus the contract no. date of delivery, where it was built, who it was built for USAF and the make - GMC and model - 45230A on the same line. Model 45230A is also on my paperwork needed to receive a title. On the bottom of the tag are the large letters PMS with an insignia next to it. I don't know what that is about.

The Hyd./air would be the accurate notation on the glove box, but it only says AIR

K9, my 450 is air over hydraulic also, and states air on the glovebox tag. The booster for this system is known as an air-pack.

I'm in my diesel mindset, air-pack for diesel, hydrovac for the gassers.

I'm wondering if the compressor is the same for air over and full air.

Looking in my maintenance manual, I see one compressor listed. Midland steel products, model N-4098, so should be the same compressor for both setups.

Maybe the compressor is the determining factor then.
Is hydrovac a brand name or a descriptive name?
Vacuum isn't used is it? I certainly don't know how they work.

Tonight I pulled the plugs squirted alittle oil down each cyl and thought I'd crank it with the plugs out. There was nothing. Not a click, no sound at all from the starter. If the engine was stuck I thought I'd hear something from the starter, but don't know because I've never tried turning over a stuck motor before. Tomorrow I'll try to turn it over by hand to find out if it is stuck. The battery is good. The headlights did come on, but somewhat slowly. I'll have one of my boys push the floor starter button while I watch it to see if that is working right too. Anything I'm missing?

Hydrovac is a descriptive name, I believe Bendix made them and yes they are vacuum actuated. Many other brands used them as well like Ford and Dodge.

Turn the head lights on and see if they dim or go out when you hit the starter. If they do then the battery is weak.

Put the truck in High Gear and gently rock the truck back and forth and see if the motor turns. Make sure to have wheel chocks on both sides of the tires (about 6" away so the truck can roll, but not get away from you if the motor breaks free.

Mike B

you may want to pull the button assembly off top of starter and clean contact on top of starter and inside button assembly. don't lose the cardboard inserts inside starter button housing ,it prevents accidental arcing. might want to remove valve cover and spray around valve stems and make sure they are free. cool truck.

K9, the hydrovac uses vacuum, while the air pack uses air pressure, since you have an air compressor then it must have the air pack system?

I don't know how either system works, but since this truck has a compressor, I didn't think it used a hydrovac, unless hydrovac was a brand and not a descriptive name with vacuum use. Gas engines produce vacuum to use a vacuum system diesels don't produce enough vacuum so air pressure is required, basically it's push rather than pull. Being a tractor it's intended use is to pull trailers and they need air.

I was wondering about the button assembly needing cleaning or the contacts need replacing. With the oil filter located directly above the starter something has to be moved..... unfortunately.

I was going to try to turn the engine over by hand. If it's not stuck it should move. I hope.

I haven't taken the truck off the trailer yet. I was hoping to get it running so I could move it around my driveway as needed. Having bought the truck from uncle sam, you get paperwork to obtain a title and you must bring the truck to the DMV for the VIN inspection to get a title. If I drive it there it costs for trip permits and insurance. That's why it's still on the trailer and unable to rock it as suggested. It's a pain to work on being up so high but the trailer provides a nice platform to crawl under it on.

I had my son help me push the floor starter while I watched the headlights. !st off the headlights wouldn't work and then after trying to figure out why for 10 minutes they came on. With the headlights working they immediately go out and won't come back on if the floor starter is pushed. I'm guessing there is a ground issue, because if there was a dead short the wires would start to cook. I put a meter on the lead to the starter and I couldn't get a steady reading. The voltage was bouncing around from 2 to 3 volts. If I could get that to stop and give a steady reading the headlights would come on again until the starter was tried and then nothing would work again. The hot wire to the cab comes off that starter connection. I'm guessing that is where one of the problems is and the other is where the cab electrics ground. I think I'll check the engine grounds too. Maybe the engine is stuck and the contacts to the starter burned. I wasn't able to try to wrench the engine over. I'll try that tomorrow. Whoever was working on this truck before looks like they were holding a hot wire to the coil wire with there fingers to move the truck around. If it sounds like the wiring is a mess.... it is.

I need to get it running soon and when it gets to that point where it might start, I'll twist one of my sons arms to make a video of it.

The truck came from a dry climate and smelled bad enough from mice living in it for 10 years or more, but now since I brought it home to this wet rainy climate it is the worst smelling truck interior imaginable !!! I have smelled bad mice infested trucks before and this one is easily the worst. I can't put it into words how bad this is but I do know that the truck will rust out in short order if I don't get it cleaned soon.

You might want to take the cover off the flywheel and turn it with a large screwdriver or a pry bar. Is it possible that the starter drive is stuck engaged into the flywheel? Might want to loosen the starter mounting bolts and see.

I'm guessing you had the plugs out trying to rock motor, otherwise compression could be holding things up. You may want to go ahead and take it where you need to to get title and get it off trailer easier to work on. Suggest pulling seats out and power wash interior. Let oil soak in cylinders awhile. You can disconnect all the other wiring and hot wire the truck that might eliminate some of the draw in wiring harness. Clean the connections at battery, starter and engine and chassis grounds.. If cables have been chaffed and patched you may have a corrosion issue within the battery cables themselves. If the battery is not new have it tested it may not be up to snuff, I even have had a brand new battery fail to hold a charge.

I took the plugs out to put some oil in each cylinder in case they were dry and possibly sticking. I left them out to try to turn it over by hand. There is a bolt on the end of the crankshaft and the fan was already off when I got it, so I thought if I moved it even a small amount that would tell me it was free. Taking the cover off the flywheel would be a better idea because I could turn the engine more and in the right direction. I hope the rain stops today and yes I've got to get those seats out right away.

The battery shows almost 13 volts and it's the same battery I used to pull the truck up on the trailer with, it should still have enough to crank an engine with the plugs out. I won't ignore the possibly it is now weak, and I'm going to put a charger on it.

Thanks

Since someone has already been messing with it it's hard to say what is going on with it.

I took off the flywheel inspection plate and with the plugs out the engine spins by pushing with just one hand on the gear. The starter gear is where it should be

The truck is full of small white bugs they were up in the clutch and on the flywheel teeth. I woke them up when I turned over the engine about 30 or 40 immediately fell out, some fell on me. They were under the mat in the cab too.

With the engine spinning so easily I'm going to turn it some more to make sure the valve train is smooth. It looks like the starter needs to come out.

Your right, that makes it all more complicated.

When a truck is given to a local volunteer fire dept by the feds they are going to use it and spend little to nothing on maintenance. Can't blame them, they don't own it Then when it quits and/or no longer meets their needs they park it. If they don't use it it goes back to the feds. If no other fire dept or agency wants it, it gets auctioned.

I'm developing an opinion of what happened the more I work on this truck. Right now I'm thinking the electrics went bad, the truck was hard to start or hard to keep running and the starter was over used and being 6 volt, with a 12 volt battery it couldn't take the punishment. Then the mice took over and it was never going to get fixed.

One thing I didn't know until I bought this truck is that these federal vehicles are given to ranchers that form their own volunteer fire dept's and they are encouraged to do so. They have the ability to be first on the scene after a lightning strike and get the fire out while it's small.

I removed the seat and while the seat looked good on the outside, no rips or tears, inside the bottom bench was one big huge stinking mouse nest. The cardboard bottom held it all in. There was no space in the springs, it was totally packed full, and that's why my son who was helping me yesterday was saying the longer I sit in here the worse the smell gets. Everytime he moved he pumped out more smell and man did it ever stink.

Glad to hear the motor turns ok. I would remove valve cover you are likely to find crud on top of head and around valve area. you want to clean that up so it doesn't block oil drain holes and spray lubricant around valve stems and push rods. Starter may be ok once you clean everything up and clean contacts.

I took the starter out. The contacts looked good. It may have a dead spot. I'm going to have it tested. For some reason the fan was removed when I got the truck. I'm wondering if they were trying to turn the starter off a dead spot by turning the bolt on the end of the crank. They have this bubba installed battery cutoff switch in the cab too. Probably had a battery drain at some point but I didn't notice one when I hooked up the battery.

What lubricant do you recommend?

Thanks

Around the valve stems and push rods the penetrating oil of your choice. Kroil, marvel mystery oil, pb blaster. You want something that will lubricate and penetrate any sticky deposits. Even on modern motors people have been having problems with varnish from old gas, causing stuck valves ,bent push rods carb problems. You might do a search in the engine forum for advice on reviving engines with least amount of damage and ways of determining the polarity of you r truck as they were positive ground from the factory.

The truck had a battery in it. It had 2 positive battery terminal cable ends. I think it was changed to negative ground when an alternator was added. I don't think there ever was a positive ground alternator, but don't know enough to say for sure. I hooked up a battery negative ground.

I want to eventually remove the alternator and put in a 12 v generator. I'm going to need the mounting brackets too. The alternator that's in it isn't lined up very well and probably throws belts. The starter shouldn't care about the polarity should it? I believe it would run with either polarity.

Not having messed with the positive ground systems I don't have a ready answer. With some electric motors you reverse the wires they turn backwards. I don't know about starters. You would be doing yourself a favor to post a question in the electrical bay forum.

The starter doesn't care about polarity. If they converted it to negative ground, and they knew what they were doing, the negative side of the coil should go to the distributor. A positive ground would have the + side of the coil going to the distributor. However, there is a good chance that whoever converted it was clueless that coils have polarity. Permanent magnet motors care about polarity, and so does the radio and the ammeter.

I checked the coil and they didn't change it. They should have changed it for a better spark. I think it would still run but maybe be harder to start and not run so good.

The starter is totally shot, even needs field coils. $310.... ouch. I had it changed to 12v since it was only $15 more.

I hope you had your original starter rewound to 12v, not just putting a 12v starter on. There is not a 12v starter gear with the correct teeth on the drive gear. Both 6&12v have the same number of teeth, but the pitch is wrong on the 12v. It engages the teeth on the flywheel too shallowly. Also, the 6v gear won't fit on a 12 v starter. The 12v starter that was on my truck was chewing up the ring gear pretty bad. The 12v starter would occasionally hang up in the engaged position. To make matters worse, a 12v ring gear won't fit the 6v flywheel either.
What I ended up doing was using a key start 6v starter from a chevy car. (COE's are push button start, rather than stomp start). My starter repair guy installed the correct drive gear for the original starter. He also installed a 12v coil, leaving only the motor itself as 6v. I should have written down the part number for the drive gear, but didn't. My starter's O.E. Part number is 1107960. The starter guy could look up the correct drive gear from there. I had to buy the starter, drive gear, coil and pay to have the guy cobble it all together and still only had $160 in it.
So, I would recommend sticking with the 6v starter. If, you find a way to make the 12 v starter work let me know. I couldn't find it. I had a thread going here and a the old gmc trucks site about this. I'll give you the link to both. You have to be a member to view the old GMC site, which I would recommend if you aren't already. Sorry about the long winded post.
Scott

https://www.stovebolt.com/ubbthread...Main=113543&Number=776311#Post776311

http://oldgmctrucks.infopop.cc/eve/forums/a/tpc/f/4101021591/m/28620585763?r=63620916763#63620916763

I'm having the original starter converted. Thank you for posting. That is very good info to know. I always seem to pay twice as much.

I was hoping to have a good attempt at starting the truck today but Napa's books don't go back far enough. The spark plug wire set I got for a 270 is not going to work. It may be for a different distributor location. Napa doesn't have any info on a 302 inline 6. Seems odd, was this engine limited production? I'm going to see if I can scratch around for the ID pad to see if it really is a 302 or what is in it now.

perhaps a universal set that you cut to length would work.

Hmmm, I haven't had to cross that bridge yet. I was able to get a fuel pump by crossing out a '57 400 series at Carquest. My local Carquest has been there for about 30 years and have some paper books in the back room that go way back. I think GMC used the 302 from '52-59. They were also in military duece and half truck during that time. 302's are also popular with the hot rod crowd, so spark plug wires are out there.
Perhaps some one who knows a part number will chime in soon.
Scott

I found a set that closely matches what was on it. I should have gone with a universal set, but thought that buying a set meant for the engine would be good enough and save some time, but after returning the 1st one, and all the running around, it didn't save any time. I would recommend cutting a universal to fit for anyone needing new wires. You can get an exact job doing your own.

The napa spark plug wires I ended up using were 700126. They matched better than the set that fit a 1955 270ci engine. 1955 was as far back as the book went.

I ran out of time before the rain storm came so I hope to get another try at starting it tomorrow.

I scraped the pad. It starts with 302 so it probably is the original engine.