am i in trouble?

L

larry harding

Senior Member
when i started in on my 31 pickup/money pit last fall, with a little tinkering and tuning the engine cranked and ran great. i put on a new muffler /exhaust the other day and found i have a knocking noise. i removed the oil pan and checked all the rods, no slack there then i was looking at the rear main and could see some cracking in the babbit in the thrust area at the back end of the crankshaft. i could move some of the pieces with a screwdriver. is there any short cut or am i looking at a complete overhaul and another grand or so down the tubes?
 
Best would be a complete overhaul. But you don't necessarily have to do best.

It may be a matter to replace only the thrust area of the rear main. The parts vendors now sell a brass shim that can replace the rather thin thrust surface once the existing thrust surface is milled off.

It may be possible to remove the original thrust surface using a lead file (coarse teeth similar to a rasp but designed to quickly remove lead based materials) but I can't say I have done it and I can see this remedy is subject to hand machining inaccuracies.

Still it may be simply a matter of "assessing" the condition of your engine. The issue may be limited to the thrust - or it may be a sign of a bent rod causing it to "flop" and this is the sound you're hearing (and possibly flopping the crank causing the thrust damage.)

Well, disassembly and restoration IS a big part of the hobby. If you wanted to simply drive it maybe a Shay or Glassic Ford would have been a better choice?

Sorry. That's hard. I know full well the disappointment of the unexpected.

Good luck with it.

Joe K
 
This is the option that Joe was referring to in post #3 above. It's not all that hard to do. I did have the engine out of the vehicle when I did that though.
 

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wow! there may be hope after all. if it is just the thrust and not the bearing itself worn out. there was some real banging especially if i shifted into second and lugged the engine a bit. if i can patch and get by for a while, at least until i finish the rest of the truck it sure would ease my discouragement. what else should i look for while i've got the engine apart? something about the rods? i could only find side to side play but no verticle movement. the engine runs great and doesn't smoke, so if i can buy some time before a complete overhaul i will be happy. thanks guys!!!
 
Joe K said:
Best would be a complete overhaul. But you don't necessarily have to do best.

It may be a matter to replace only the thrust area of the rear main. The parts vendors now sell a brass shim that can replace the rather thin thrust surface once the existing thrust surface is milled off.

It may be possible to remove the original thrust surface using a lead file (coarse teeth similar to a rasp but designed to quickly remove lead based materials) but I can't say I have done it and I can see this remedy is subject to hand machining inaccuracies.

Still it may be simply a matter of "assessing" the condition of your engine. The issue may be limited to the thrust - or it may be a sign of a bent rod causing it to "flop" and this is the sound you're hearing (and possibly flopping the crank causing the thrust damage.)

Well, disassembly and restoration IS a big part of the hobby. If you wanted to simply drive it maybe a Shay or Glassic Ford would have been a better choice?

Sorry. That's hard. I know full well the disappointment of the unexpected.

Good luck with it.

Joe K
Click to expand...
The thrust only works if the rear of the bearing is damaged. I suspect he is seeing the front of the thrust and it is broken. This damage is only repairable correctly by re-pouring the bearings and align boring them.
 
You said you heard the noise after putting on a muffler. Make sure the muffler isn't loose before rebuilding the engine. If you have the pan off, measure the forward and back movement. If it is excessive, then you can worry. Ron W
 
larry harding said:
how do i check it and what do i look for? tomorrow is going to be a busy " a " day.
Click to expand...

You can remove the main bearing cap, which means you need to pull the cotter pins from the nuts on top, and one is inside the valve chamber. Then you can fold aluminum foil to make a strip about 1/2" wide and 2" long and lay it front to rear on the bearing. Then screw the cap back on and see if you can still move the crank. If the aluminum foil is .0025 thick and you can still move the crank, then peel off a thin shim and try it again. If you need to peel off another shim, then take it from the other side, so you keep the shims about even in thickness. Try to get the main bearing clearance to .0015", as .0025 should be the max. Try to keep the clearance .0015" to .002".
 
I have said this many times. Never tear a engine apart until you know where the knock is coming from. It could be a loose flywheel timing gear, rod , main, piston, loose pulley, wrist pin and so on. If you take apart how are you going to know for sure what it is.

I do not think the end play is your knock.
 
i got it apart today. it is the thrust toward the crank (not toward the clutch) that is bad. i also am able to move the rear end of the crank up and down, meaning ive got some play in the center main. are there removable shims under this bearing? the main bearing bolts have square (9/16") heads. i have a few square sockets that were given to me years ago, but no 9/16", of course. where can i get a socket to fit these bolts? i have a grainger catalog but no listing for square sockets i may try mc master carr unless i get a better suggestion.
 
got one on the way from mcmaster carr. any chance i can get a little more life from this engine by removing shims from the center main or am i going to have to bite the bullet and go for a rebuild?
 
why not buy another engine to install, as many guys here do, for not too much and then give yourself time to rebuild your engine right.

Ive bought a couple of good engines in the 250.-350. range.
 
buying a good used engine sounds reasonable, if it is not another junker. i got a spare engine in the deal, i'm going to check it tomorrow to see if it is any better than the one i had in the truck. if not where might i find a usable, reasonable priced engine? i don't plan on using this for daily transportation, just parades, occasional rides etc. so i don,t need a perfect engine.
 
bought all mine on Craigslist

always from a guy rodding his car..................

within 150 miles from home
 
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