The Stovebolt Site Forums The Shop Area Engine Shop 1952 GMC 228 crankshaft and bearings

I'm going to start working on a '52 GMC that has been sitting 10+ years. I know I'm going to have a lot of rabbits to chase, but #1 is the problem that helped lead to its long nap.

When it was driven until warm, and then parked, it would be hard to restart. My dad was told it had to do with the crankshaft being scored and / or bad bearings. At that time he was told the crank probably needed to be reground and the bearings replaced.

I'm not a professional mechanic but I'm pretty handy and have done the majority of the work on my vehicles over the years. I've done brakes, rebuilt master cylinders and carburetors, changed timing belts, replaced motor mounts etc on a variety of older Toyotas (1969 Landcruiser, 1989 Tercel, 1996 Tacoma) and a Volvo (1985 240).


I guess to start off I'm wondering how involved this job will be to under take. I'm thinking the crankshaft itself will probably have to be taken to a machine shop or replaced. I understand the GMC 228 has real bearings, not the poured in babbit type used on the Chevrolets.

Is this a realistic job to do in a driveway, or should I be thinking about paying a shop to do it?

Anything else I should be thinking about doing down there when I have it apart?

I would not jump to conclusions about bad bearings. There other more likely culprits to cause a no-start-when-warmed-up situation.

Overheating.
Dirty spark plugs.
Dirty battery terminal connections.
Weak starter.
Ignition timing off.
Coil going bad.
Carburetor out of adjustment or worn out.

Before you ever start this engine, make certain that you do not use the current gas tank as the fuel supply. There will be crud and varnish in it which will cause you some major headaches, if not nearly catastrophic engine damage. I small boat engine tank is very handy for supplying gas to the engine for testing. The priming bulb comes in handy too.

I would recommend checking all of these items in the order listed before ever dropping the oil pan to check the bearings.

Slow cranking speed when warm can be caused by lots of things, but a scored crank bad enough to cause that would have a lifespan of just a few minutes, and the engine would be knocking like a bunch of little guys with sledgehammers were trying to beat their way out of the oil pan. It's much more likely to be poor cooling system performance that causes the pistons to expand and tighten up in the cylinders. Try spinning the engine over with a good battery and with the spark plugs removed. A 52 GMC would have had a 6 volt Positive ground electrical system. Cranking it a little with a 12 volt battery won't hurt the starter as long as you don't overdo it. Cranking for 15-20 seconds at a time without the drag of compression pressure won't stress the starter at all. If doing that builds up good oil pressure, you probably don't have anything to worry about where the crankshaft and bearings are concerned. It's also possible to drop the oil pan and inspect the bearings without doing a complete engine disassembly.
Jerry

Good to know. I'm not sure how reliable the info he had on the crank was. I was under the assumption that a mechanic had looked at it, but it is possible it was just a mechanics guess hearing the symptoms described.

He was driving it occasionally for several years in that condition including freeway speeds, or at least what passes for freeway speeds with these trucks anyway. Based on what you say that would have been very unlikely.


I plan to replace belts, hoses, filters, fluids etc, who knows how long they had been on there before it was parked. It was never his daily driver.


Thanks, this is probably good news then. None of those options sounds nearly as involved as the crank and bearings.

if THE ENGINE CRANKS SLOWLY, CLEAN ALL THE STARTER TO BATTERY ELECTRICAL CONNECTIONS WITH SANDPAPER SO IT'S SHINEY METAL TO METAL INCLUDING A CONNECTION FROM THE BATTERY TO THE CHASSIS AND TO THE MOTOR. if YOU HAVE AND KNOW HOW TO USE A VOLTMETER MEASURE THE VOLTAGE AT THE STARTER AND IF LOW MEASURE YOUR WAY BACK TO THE BATTERY TO FIND WHERE THE RESISTANCE IS!

Before being cranked over, it would be best to check and see if any of the valves are rusted. Oil all the valve stems, then tap them all gently with a rubber hammer or block of wood to make sure they move, if they don't, there is risk of bent pushrods, or worse.

Ed

Roar, we're old not DEAF! Lose the caps lock!

His "ifs" are in lower case, HrL

His "name" is ROAR.

I would have also added in upper case: CHECK THE GAUGE OF THE BATTERY LEADS AND THE FRAME TO ENGINE GROUND STRAP. It was quite common to simply replace those cables/straps with whatever was available. 4 gauge or smaller size 12v cables/straps are too small for 6v systems. Use 2 gauge or larger size (smaller gauge number) cables/straps. I over-do it with 00 gauge cables.

Keep asking questions Aaron (and, keep posting your progress/questions/problems).

Nice catch on the proper use of caps there Tim! (I hope my exclamation mark wasn't to loud for those with sensitive "ears")
Carl