The Stovebolt Site Forums The Shop Area Engine Shop crank counter weight rubbing...why?

I bought a spare block cheap a few months ago not sure if my original block was good.

The block I bought was a transplant 235 that came out of a 1952 GMC 3100 which was not the original. The numbers on the block were 072559 F55Y, 3836233 & C165. The numbers on the heads were B20 887, 3701187, & H123. He said heard a bang and the stopped and he shut it down and towed it home. He pulled out the spare runner he had and installed it.

I looked at the motor taking a chance that the block was good in case mine was trashed. I turned the vibration damper and it tured smoothly. I pulled the valve and push rod covers and everthing looked clean no sludge or gunk.

Now as the plot thickens, today I removed the head and I was suprised to find hydralic lifters. I thought he installed them because I knew the regular standard trucks did not have them. I pulled the oil pan and there is where I found the problem. On the little counter weight by #3 piston it was worn down looks like the cam lobe dug into it. It was also on the smaller counter weight by the #4 piston. I removed the timing gear cover and found another suprise, the timing gear was warn down and it was fiber so I am thinking this motor was from a 1955 car.

I have put some pics so you can see but why could this have happened? Was the cam bearings bad or main bearings bad? The cam shaft where I thought it might have rubbed on the lobe was not sharp or looked worn or damaged.

The pistons looked to have a lot of carbon on top of the piston and intake valve, the heads exhaust valves looked very white on the exhaust side. Is this normal or was the fuel air mixture not correct? The cylinder walls looked very good with no scrathes and smooth and clean.

My last question, should take what ever parts off I can salvage and boat anchor the rest? My original block was frozen and sat for about 20 years so it was very differnt situation. I just want to understand what happened to this one on the 55. This is my second 235 tear down.

http://i1291.photobucket.com/albums/b554/stovebolt56/55%20Spare%20Engine/55headview_zpsded81fa1.jpg

http://i1291.photobucket.com/albums...re%20Engine/55pistonview_zpsd7df6870.jpg

http://i1291.photobucket.com/albums...unterweightby3pistonpic1_zps7db4d48d.jpg

http://i1291.photobucket.com/albums...unterweightby3pistonpic2_zpsc0bbd59e.jpg

http://i1291.photobucket.com/albums...20Engine/55fibergearpic1_zps9b6161f1.jpg

http://i1291.photobucket.com/albums...20Engine/55fibergearpic2_zps77409944.jpg

http://i1291.photobucket.com/albums...e%20Engine/fibergearpic3_zpsbaede37b.jpg

The way the camshaft is made if the cam gear gives out and the cam gets out of time with the crank, the counter balance on the crank will hit the cam. The cam has a notch or relief in it that lets the crank counter weight go past.

Put a new cam and crank gear on. May have to remove the cam to do that. While it is out, have it checked for straightness.

I don't think you have a boat anchor there. But over the years the fiber gets old. You'll know when you pull the cam if there is any bearing tight. It should come out easily once the two bolts holding the front retaining plate are removed.

F55Y indicates 1955 car 235 installed with RPO313 Powerglide transmission. That engine would have come from the factory with hydraulic lifters.

3701187 & H123
Wait to hear from someone else, but could that block casting code be 3701887 (1953 235 truck), and H123 be August 12th 1953?

You posted that you have a GMC 3100. 3100 is a USA Chevrolet truck 1/2 ton designation. USA GMCs did not use the 3100 designation.

What year is your 235? Is it a 1956 truck 235 (mechanical lifters)?

sorry about the 3100 on the gmc it was a 1/2 ton whatever the number is.

my 1956 235 is the original motor I have checked all the numbers and it appears to be period correct. The 56 had an alumn cam gear and solid lifters.

it took me a week off and on to remove everything because of it being frozen solid at least last night i was ablbe to revoev everything in about a 1 1/2 hours with putting things and labeling them in baggies

I rechecked the numbers because knowing my eyesight the head casting # is 3701187 and the Engine block casting number is 3836233

Oh I did not mean to be insensitive to GMC owners I remember it was a a half ton truck but I did not know how called a 1/2 ton in the GMC world. I was thinking Chevy sorry.

I would guess that the timing gear failed due to lack of lubrication. If you repair that motor, you should take the front plate off to see if the oil supply to the timing gear is blocked.

What about the damage to the counter weights on the crank will it throw it out of balance? I am assuming the cam should be replaced, even though it had hydraulic lifters and fiber gear. I was thinking to replace it with alum. gear and solid lifters with matching cam shaft. I was reading in the patricks catalog, they did not recommend hydraulic lifters in the 235.

Lastly all the carbon build up on the pistons is that something to be cleaned or replaced?

if you are worried about balance have it checked and/or balanced when you rebuild it, they don't charge much as an inline 6 the crankshaft gets balanced alone without bobweights.

Those fiber gears dont hold up very well compared to the alum ones which will go on just forever nearly. Fiber gears were in there for the same reason the hyd lifters were-for quietness. Pickup motors never had them-the same reasoning is carried over into the 194/292 series motors,fiber for quietness in the pass cars and aluminum for durability in the trucks. Lubrication was not the problem, it was age.