The Stovebolt Site Forums The Shop Area Engine Shop Horrible Sound from my 261. Part 2.

I'm back to continue with my 261 after exhausting all other diversions. To review, it Idled beautifully but the knock/scrape noise started at 1300 RPM. The oil pressure was good at speed and idle. Previous thread at:

Horrible Sound. Part 1. (Previous thread.)

Knock w/o fan belt.
Knock from inside.

I've ruled out (to my amateur satisfaction) the water pump, generator, fuel pump, harmonic balancer, timing gears, rockers, throw out bearing, flywheel hitting cover, maybe more.

There was no metal whatsoever in the oil pan when I dropped it. The oil was new and clear and I saw no metal. It's not running now since the oil pan is off and various other things off, damper off.

1. Would there be value in looking at the hydraulic lifters and pushrods after removing the side cover? If so, what would I look for?

2. Removing the front main bearing cap like HL suggested would make me uneasy to say the least. Is removing those 2 big bolts the thing to do? Will everything else stay up there like they belong? Will shims fall out? What do you look for?? Would it be Plastigauge time?

I have to get out of Mrs. Wally's garage before the snow flies so any further help and instruction would be helpful. Thanks!

You actually need to remove 4 bolts, not 2. The two big ones that hold the cap to the block will be TIGHT- - - - -use a long handled 1/2" drive breaker bar and a 3/4" socket, but remove the two small bolts that go forward into the timing cover first or the cap won't come off. The crankshaft isn't going to go anywhere- - - -there are three more main bearings holding it up. Unless you've got a 1954 or early 55 engine with the high-mount water pump, there aren't any shims between the cap and the block to worry about. Even some of those early engines didn't have shims - - - -they were only needed if the bearing fit was too tight.

Unless you're willing to break some eggs, you'll never be able to make an omelet. Get busy and inspect that front main bearing! You're looking for score marks on the crankshaft surface, discoloration of the bearing material, debris imbedded into the soft metal at the top surface of the bearing where the crankshaft contacts it, or any other indications that there's not enough clearance for the crankshaft to ride on a thin film of oil instead of actually touching the bearing. Now, that clearance needs to be between .001" and .003"- - - -the thickness of a very fine strand of hair, to a maximum of 3 of them stacked on top of each other. That's where the Plastigauge comes in- - - - -use the green colored PG. The red or the blue will be too thick to work well.

Jerry

Big bolts are out w/help from 14" breaker bar and 24" cheater pipe. Gear cover bolts already out.

The cap is stuck. Do you try to pry it off? Tap it? With what?

Am I cautious or what? Thanks!

Tap it from side to side, and/or pry it front to back. DO NOT try to drive a chisel or something similar between the cap and the block. It's a precision machined fit, but it's not impossible to get the cap moving. The lower part of the timing cover gasket is probably holding, and don't be surprised if it tears. It's easy to fabricate a replacement from gasket paper.
Jerry

Prying front to back loosened the bearing cap. The next problem (necessary, right?) is the metal shell of the front motor mount extends to the rear too far and the cap won't drop free. It hits that motor mount metal shell. (The engine is still installed.) Can't see the surfaces of the crank or cap. Trying to bend it back a bit with a hammer, careful not to hit anything important, doesn't work. Any ideas?

Normally I would get under there with a grinding wheel but I'm leery of that with important surfaces close by. I think that metal shell acts as a big washer but I might be wrong. Maybe it's time to pull the engine.

Thanks for any advice.

Bolt the cap back on, and use it as a fulcrum to tweak the motor mount shield a little with a pry bar, or just unbolt the mount and jack the engine up a little. Maybe we need to send Larry the cable guy over to give you some moral support! "GIT 'ER DONE!"
LOL!
Jerry

How about turning the crankshaft to create more clearance toward the back of the engine so you can tilt the cap?

Send Larry. And his brother Darryl and his other brother Darryl. Sorry for going off top.

The general rule of thumb when doing this type of diagnosis is simple- - - -if something gets in the way, move it, bend it, take it off, or deal with the situation in such a way that the job gets accomplished. Early in my career the facts of a mechanic's life got explained to me pretty plainly- - - - -"Son, there's only two 'caint's' in the mechanic business- - - -if you cain't do it, you cain't get a paycheck!" I got paid!
Jerry

I found the sweet spot for the crank with the counter-weight part of it out of the way and the bearing cap came off. The crank surface is smooth as a whistle. Can't feel anything at all.

The bearing surface has some grooves. My fingernail catches in a couple of them. It makes sense they would make the crank out of harder metal than the bearing.

What's next? New bearings since it's open?

One other question. Will it ever stop dripping oil?

Personally, if you haven’t done already,.. for the amount of effort and good work you are doing, consider taking it one more step, ... pull the motor, put it on a stand, read the manual on your bedside table, and systematically tear it down, clean, inspect, measure, and inventory. Bag and tag, photograph, and organize a work space.

Check flywheel, replace soft parts like clutch friction plate, grind flywheel smooth, replace seals, gaskets and replace throw out bearing. Install new rear and front motor mounts.

Take the block and head to machine shop, shake/bake, measure bores and think about reassembly with new bearings, polished crank, and/ or rebuild. A fun and do -able project. My two cents...

That’s me though... just being thorough and complete.

If that were my engine , I would be concerned with the damage done to that bearing surface . Also I see the rod bolts have no lock nuts (pal nuts) on them .

I'm inclined to go with tom moore suggestion .

Just a FYI, Chevrolet stopped using pal nuts when they went to full pressure engines.

That bearing isn't badly damaged, but the wear pattern is all wrong. It would be interesting to see what a piece of Plastigauge would show in the way of clearance. Now, to be thorough, there are three more main bearings and six rod bearings to inspect. That engine was designed to be able to change main bearings "in the frame"- - - - -notice the small anti-rotation tab on the bearing that's up in the block? It's possible to loosen the other bearing caps a little, insert a home-brewed tool made from a cotter pin into the oil hole of the crankshaft, and roll the top bearing shell out by turning the crankshaft. Earlier engines with dowel holes in the block and corresponding nibs on the main bearings required the crankshaft to be lowered 1/2" or more to change mains. That modification to the block and the bearings happened about mid-year 1955, the same time as the change to the low water pump position.

So far, I haven't seen anything bearing-related to cause your squeal. I was expecting to see much more damage to the front main bearing, and possibly a badly scored crankshaft. the surface of the bearing that rides on the crank is made of soft metal, a lead/tin/antimony/copper alloy. "Babbit" metal is one type of bearing material, but there are others as well. The next few layers of the bearing will be copper, and then a steel backing shell. The soft metal is there so debris can score, or "imbed" into the bearing with little to no crankshaft damage. It looks like your bearing has done its job of protecting the crankshaft quite well. Now- - - -slip the lower bearing shell out of the cap, look at the back side, and see if it shows an "undersize" It will probably be marked "STD", .010, .020, or .030, indicating the size of the crankshaft. Reground shafts have been ground down to a smaller size to make the shaft round again, and eliminate out of round or tapered wear. As long as a shaft is round, and not scored or tapered, new bearings can be installed without regrinding the shaft. You're getting close to the point where removing the engine will let you do a better repair job, although untold thousands of stovebolts have been rebuilt with the engine "in the frame" under the old shade tree in the back yard!
Jerry

Wrist Pin knock?

I have a '53 W/Powerglide 235 (Chevrolet's first full pressure engine) which has pal nuts. (A little off topic since it is not a truck engine. Just thought that I would share some trivia since a lot of car engines end up in trucks.)

Did you ever inspect the thrust plate behind the camshaft timing gear? You can see it through the holes in the gear and maybe from the side with a flashlight.
You need to make sure that the screws which hold it in place are there and tight and actually going through the holes in the thrust plate.
I just got done tearing down a 235 which was parked by the previous owner soon after a re-ring job because of a "horrible noise" (his words!).
I removed the 2 screws which hold the the thrust plate to the block and removed the cam to find that the screws had not been installed through the holes in the thrust plate! The ears of the thrust plate were completely broken off. No wonder it made a "horrible noise".

How do you slip the bearing out of the cap? Tool required?

That one has a dowel built into the lower bearing shell to keep it from moving, so rolling the bearing out of the cap isn't possible. I use a sharp instrument like a gasket scraper or a pocketknife blade to lift one end of the bearing away from the cap.
Jerry

10/02 (date?) 0.010
Clevite, etc.

0.010 means it's smaller in diam by 0.010" than stock?

It was rebuilt in 2003-2004. Has about 30,000 miles on it.

OK, you need to order .010" undersize bearings if you choose to replace them. It's not a particularly difficult process. Simply remove the main caps one at a time, and loosen all the others a couple of turns to let the crankshaft drop down a little. Then bend a cotter pin into a T shape that will slip into the oil hole in the crankshaft journal with the cross piece of the T lying flat against the shaft. It won't be a perfect 90 degree angle since the oil passages are drilled to point toward the rod journals. Roll the crank against the bearing shell and keep turning to push the bearing out of the block. Be sure to push the anti-rotate tab out of the block, not force in tighter! Roll the new bearing into the block the same way.

I'd suggest checking the oil clearance with Plastigauge, using the bearings you have in there now. Pay particular attention to the front to rear clearance, as the bearing in your picture appears to have more clearance at one end than the other. That's not a good thing! The only way to correct a tapered crankshaft journal is to regrind it to the next smaller undersize, .020". That requires a complete engine disassembly.
Jerry

A lot to think about for sure. We're heading out of town for a few weeks so I'll have to hit the pause button on this. I might pull the side cover first and look around. That's about the last thing I can do before going deep.

Thanks all. I'll be back.

I was shocked it wasnt your balancer, but I have been thinking about this over and over again. We havent given up on you. Worst thing is it comes apart for a complete look see, which I assume others have said and you are now contemplating

Steve

Another thing, I just went through a 261 and a complete rebuild was cheap cheap cheap. Magnufluxing Machining Boring Honing the block and crank turning was very reasonable here in Gig Harbor Washington. You will like a new Best rear main seal too. Does the engine owe you anything at this point? If not, give it a go through. Rod and main bearings are $150 PISTONS $260 SET, RINGS $60, cam bearings $30 gasket set $50

HRL, Don't they make those tools for rolling out main bearings anymore? Mine are a shaft the size of the oil hole in the crank with a flat tee head at an angle to match the oil hole. They're made of aluminum. If they're no longer made, I'd better treat mine real well. I imagine I'll do an in-frame again before I die.

I’ve used a 16p nail , just the head and about 1/4” of the nail shank. True hillbilly, shade tree there,man

Just for git’s and shiggles now that you have the pan off, check the bottom inside surface of the oil pan, in the front section, like where the 2nd 3rd or 4th rod would be possibly hitting the pan?
I once bought a car REAL CHEAP because of that one day.
Took it home, hammered out the pan, and drove on,,,,,,,,,,,,,

Tommy, I've owned a couple of sets of those main bearing roll-out tools over the past 50 years, and about the time I need one I find that the one with the correct angle to fit the crankshaft oil passage I'm working with has been misplaced, or borrowed and not returned. On the other hand, I've got a bin full of cotter pins!
Jerry

I agree, a dented oil pan can create a heck of a clanging sound. Put a 261 on the stand to run it in, and whoa... overlooked that when I changed out an oil pan.