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Friday, June 25, 2010

1952 Chevrolet Pickup Truck

Mine looked something like this (if you squinted your eyes), except the wheels were white, the running boards were black and the bed was eight foot long instead of six. Mine had numerous flaws, but this gives you an idea.

I found this disaster when I was living in Houston many years ago, probably around 1975. I needed a cheap car and I found this thing advertised for $400. It was night when I went to look at it. The six cylinder motor was knocking. It had new red paint and good, late model bucket seats. I talked it over with my girlfriend at the time, but she didn't have a clue. I may have known something about mechanics, but I sure didn't know what the heck I was doing. I bought it. It must have been in a flood. The entire floor of the cab was rusted out, and the wood in the bed was half gone. The engine was a GMC 270 straight six that someone had transplanted into this vehicle. I pulled the engine and rebuilt it in the single car garage attached to our rental house. I think it must have cost me close to $600 in parts and machine shop work.

One of the first things to do when reassembling the engine was to put new freeze plugs in. These are little sheet metal cups that are a press fit in holes in the side of the block. The idea is that if someone doesn't put anti-freeze in the coolant, and the engine coolant ever freezes, the expansion of the ice will force these plugs out and save the block from cracking. The auto parts store didn't have the right size freeze plugs. They were some weird size like 1 21/32", only used on this particular engine. I didn't have time for this. I got the next size up, put a punch in the center, and beat on them until they were cone shaped and the diameter had shrunk enough for them to fit. What a pain.

I was trying to be methodical when I put it together. I even went to the trouble to plasti-gauge the main bearings on the crankshaft. This is a somewhat involved procedure:
  • guess-timate the amount of clearance there should be,
  • obtain the correct size of plasti-gauge,
  • cut a length of plasti-gauge slightly shorter than the length of the bearing journal (not the diameter),
  • assemble the bearing and cap,
  • torque down the bolts to their specified values,
  • take the bearing back apart, and
  • compare the width of the now smushed plasti-guage to the chart on the package.
They were all a little on the close side. Now what do I do? I hadn't thought this far ahead. Well, phooey, I'll just bolt it together anyway.

Got the piston, rings, connecting rods and bearings all assembled. Now for the head. Everything goes well until I try to torque down the last head bolt. It's stripped. Great. That's just great. Pull all ninety zillion head bolts back out. Lift the hundred ton cast iron cylinder head off. Go to the auto parts store and spend another $20 for helicoil kit. Drill out the hole. Retap it with the special heli-coil tap. Screw the magic helicoil into the newly rethreaded hole. Put it all back together again. I suspect I used my new head gasket a second time, even though proper protocol says otherwise.

Get down to the very end, and I have two bolts left over that screw into two holes at the bottom of the timing chain cover. Problem is, they don't hold anything together. The threads are in the cover itself. The holes behind the cover have no threads. I already had the oil pan on or I might have figured out what the problem was. As it was I left it, and it leaked, which was no big deal. All of my vehicles had always leaked. It was just a fact of life. It wasn't until a couple of years later that I figured out that the bolts were supposed to be inserted in their holes from inside the engine. The clear holes were in the front main bearing cap. The bolts went through these holes and screwed into the special tapped holes in the timing chain cover and pulled the bottom of the timing chain cover up against the front main bearing. Once I did that, which required removing the oil pan, the leak stopped. Huh, imagine that.

After I got done putting this monster back together, I painted the whole thing Caterpillar yellow. It was sort of impressive, if you are impressed by that sort of thing. I also hooked it up and ran it while it was sitting there in the garage. Just to make sure that it was going to work, you know. Here's a picture of a real Caterpillar engine, so you can get some idea of what it looked like. Getting the right shade of yellow on a computer monitor is a bit of a trick. I think this one is pretty close, at least on my screen. Stolen here.

This page has some good illustrations of old Chevrolet 6 cylinder engines, both external, exploded views. They are very similar to my GMC engine.

Eventually got it back in the truck and got it running, which was great, for about three minutes. I figure that's how long it lasted before something else failed. I ended up replacing or repairing the:
  • wiring
  • transmission
  • rear wheel bearings
  • front wheel bearings
  • steering joints
  • tires
  • front springs
  • support frame for seats

I think I must have had to do something about the brakes because at one point I was having to fill the master cylinder with brake fluid every day. I left work one day in Austin and didn't have to use my brakes until I came to a stop sign at a major street and then I suddenly discovered I didn't have any brakes. That was exciting. I managed to slow down enough to make a right hand turn onto the street. Fortunately there were no cars coming. Eventually I was able to pull off the road and come to a stop. I must have fixed it because I kept driving it. I am pretty sure it wasn't the master cylinder. The master cylinder is mounted on the frame underneath the drivers feet. Crawling underneath wasn't a problem, it's a pickup truck after all, put the whole thing was completely corroded. Getting it apart would have been short work for a cutting torch, but I didn't have one of those. But evidently the master cylinder, in spite of being really ugly, wasn't the problem, because I didn't have to touch it.

The transmission was another learning experience. The first problem was the column shifter, never great to start with, it was completely hosed by the time it came to me. Fine, replace it with a floor shifter. The floor of the cab has plenty of holes, one more isn't going to make any difference. That worked for a bit, but then it started popping out of third gear. So I dropped the transmission and took it down to the junkyard to get a different one. Got one and put it in, and, great. This one pops out of first gear. Well, that sucks, but we can live with it for a bit. At least this stays in gear on the road.

I took both of them apart and reassembled them a couple of times, looking for something wrong, but never could find anything. I got to be pretty good at it. Manual transmissions are relatively easy, except for this one bearing in very center of things. It is an uncaged roller bearing, meaning the rollers are just in there loose. They are just enough to completely fill the space so they hold each other in alignment, so to speak. When you pull it apart these rollers fall out all over the bottom of the transmission. Putting it back together is a bit of a trick. The loose roller bearings that ride in a cup in the aft end of the input shaft and on the forward end of the output shaft. The trick is to pack rollers into the cup in the input shaft using really thick grease. The grease holds them in place while you slide the input shaft into position.
The problem with these transmissions was that the corners of the engaging teeth were just too worn. If I had both of them I could have probably made one good one, but I had to leave mine with them or pay the core charge. I never found out just what that was.

A year of two later I glommed onto a four speed from a friend who had an old Chevy that died. I took it to a shop and asked them to swap it out. I fully expected them to have to cut the driveshaft and weld it and balance it and all sorts of mystical stuff, but they just bolted it in. The U joint didn't even fit the yoke on the axle, they just tightened up the caps until it was secure. I was surprised. It worked fine.

This truck had a rear bumper made out of an old roadgrader blade edge. I needed a trailer hitch at some point, so I got an 18" long piece of 6" angle and welded it to the vertical face of the bumper. Some old geezer told me it wasn't going to work, the grader blade was hardened steel and would snap when I put a load on it. Yeah, sure, old man. Turns out he was right. Fortunately it didn't turn into a disaster, just another minor annoyance in everyday life.

Update: a couple of items I forgot that show just how old this truck was.

Timken Tapered Roller Bearing
Ball bearings in the front wheels. I wasn't long after this that everyone had changed over to Timken tapered roller bearings. The rear axle used rollers, but the front still had ball bearings.

Single Leading Shoe Drum Brake
Single leading shoe brakes. It would be decades before disc brakes became standard, but I thought all drum brakes had always been double leading shoe. With drum brakes, if the actuator pushes the shoe in the direction of rotation, then there is a kind of wedging action that makes the brake more effective. Going in the opposite direction you do not have this advantage. The brake had fixed pivots for the shoes at the bottom, so only one brake shoe got this mechanical advantage. Not long after this, the fixed pivots were replaced with a floating link, so both shoes were pushed in the direction of rotation.
Worm and Sector Steering Box
I suspect the steering gear was a simple worm and sector (above), not the fancy recirculating ball (below) that was the standard for a long time before rack and pinion took over.
Worm and Nut Steering Box
Update July 2015: Replaced original with copy from Google Drive that still had pictures.
Update November 2016 replaced missing pictures.


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Old cars said...

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John said...

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GMC Dealership Cincinnati said...

Love the look of this classic truck. It's very distinct looking and vso unique; got lots of character.