Question - Oil pressure ?

You will usually loose a good bit of pressure, at least at idle, if you damage a rod bearing.

I've done it. Please try Castrol oil. My last Blazer, that's the only brand that quieted the rod knock.

Usually you will see a lowered oil pressure with a loose or damaged rod bearing. Changing the oil won't change a damned thing except MAYBE quiet it down a bit however if a rod is really knocking changing the oil will not stop the damage from getting worse. It will continue to do more damage and eventually spin the bearing. Changing to a different oil MAY lessen the sound of piston slap, which is an entirely different thing. Regards, JR

It's really getting loud, going to drop oil pan next week. Not a big job, six banger three speed. I'll probably pull rod cap off and shove piston up and pull rockers off that cylinder, and run it on five. The truck has a flat bed which I keep my trike on . I only move the truck in my yard . I don't drive it more than 20 feet. Hay Storman I got 55 gallon drum of 90 weight gear sludge , will that work ??? Jerry

yes, oil pressure is maintained by good cam bearings and good main bearings.

Might be easier to try a new rod bearing. Since you have the pan off, and all that work.

As to the gear sludge, just park the truck on a slight hill, so the fill plug is uphill on the differential. Then, you can get a couple more ounces in.

I really don't know the answer to this. But, doesn't oil pump into the crank shaft, to the rod bearings? If you take the bottom off the piston rod, won't oil spray out the lube hole? You could have even less oil pressure than before.

Maybe pull the spark plug and rockers from the top, and leave the rod berring attached. The rod berring will help hold the oil into the crank shaft. With the piston free wheeling, the spark plug won't be firing, and the piston won't be slamming the crank shaft.

Lot easier than pulling the oil pan, eh?

Whatever you do, please let us know how it works.

Removing the spark plug will result in a very noisy engine.

Removing the piston and rod will eliminate any remaining oil pressure, unless the oil holes in the crank are plugged.

Running gear sludge could easily cause the other bearings to fail because of the oil pumps inability to circulate it.

The only real good answer, if it is too noisy to be left alone, is perhaps drop the pan and change the bearing. If the crankshaft is not damaged to the point all high spots can be removed with emery tape.

If it's noisy, and getting worse, it may soon fail completely.

Removing the spark plug will result in a very noisy engine.

CY: Well, if the valves are opening. You'll get exhaust roar. But he mentioned taking the rockers off. So, less noise.

Removing the piston and rod will eliminate any remaining oil pressure, unless the oil holes in the crank are plugged.

CY: Kinda thought so.

Running gear sludge could easily cause the other bearings to fail because of the oil pumps inability to circulate it.

CY: I thought he wanted to put the gear sludge in the differential?

The only real good answer, if it is too noisy to be left alone, is perhaps drop the pan and change the bearing. If the crankshaft is not damaged to the point all high spots can be removed with emery tape.

CY: I do believe I suggested changing the bearing.

If it's noisy, and getting worse, it may soon fail completely.

CY: Agreed. My noisy bearing (Dodge van) turned into a thrown piston rod.

You get a real rush of air out the plug hole on at least the intake stroke either way. I have seen race cars loose plugs during a race, and you can hear the noise over their open headers. If he takes the rockers off, the cylinder will have to intake through the plug hole as well, so he would probably get even more noise.

I didn't see any mention of a differental. Running heavy weight oil will help with rod noises, especially if they are not too bad. I have an old fork lift with a loud bearing I have been keeping SAE 50 and STP in for many years. But I don't think he would get enough circulation to the rest of the bearings trying to run 90 wt gear sludge. Depends on how much wear the rest of the bearings have, how well it would lube the rockers if at all, and the ambient temperature. My guess would be he would kill the rest of the engine.

Oh yeah. Just for grins pull a plug sometime and start something up. It makes a heck of a racket.

Some loose tolerance racing engines run 60 wt, especially in the summer. I can imaging trying to run 90 to save an engine in his case. But if I had to bet on the result, I would bet on failure.

I was going to cut connecting rod close to crank and put cap back on. I forgot to put that in post . Gear oil was just a joke !! Like saw dust in rear ends . Do you remember in the " Olden Days " when you could make a four banger out of a 283 ? Maybe I should go with three cylinders. I thought with a rod knocking on a 78 six banger the crank would be scored beyond repair.

Jerry

I wouldn't try that either for a couple of reasons. First, how to make sure the piston doesn't shake back down, and leaving the right amount of rod to maintain any form of reasonable balance. A friend once installed the automatic transmission flex plate backwards on my race car, displacing the balance weight only a couple of inches, and the engine shook pretty badly. So I would suspect guessing how much rod to leave would be pretty hit and miss.

If you really want a cheap fix, you might try knocking the top out of the piston with a long steel rod. But you would have to retrieve all the pieces, and you might still have the rod knock. Also, removing a couple of rocker arms might make it impossible to keep those two lifters in position, and if they come out, you will probably loose all your oil pressure.

But there is indeed at least a good chance you could smooth the crank enough to install another bearing. Maybe not smooth enough to every drive it on the street again, but around the yard as originally planned. You can buy emery tape and sea-saw it back and forth around the journal, moving the engine a

1/4 turn at a time. Most bearing material is soft enough it can be removed. Then perhaps a 40 or 50 wt oil would save you.

Hard to say for sure, especially until you drop the pan and pull the cap, and see how badly you are really hurt. But I would sure try saving the crank, before I experimented with a more drastic attempt. Sometimes these old motors will really fool you. You just won't know until you get in there.

Oh no, very easy to do. Put a rod through the piston on lots of engines during tear down, due to extreme wear ridges or corrosion. Problem is sometimes the whole top of the piston comes off at the ring groove, leaving a bore size disk trapped above the skirt, which in this case you would be trying to keep. Punching the rest up enough to remove it could be a real chore. But if you started breaking the piston in the very center, with a small rod like 1/2", you could probably remove enough of the piston top to eliminate compression noise a lower speeds. But you are still gambling on the rest of the piston failing during operation, and punching the rod through the block.

But then you would still experience a lot of clatter or noise, and compression through the spark plug hole.

Depends on how badly it's damaged. Bearing problems are usually caused by heat, and the soft bearing material melts and begins sticking to the crank. Depending on how much the engine has been ran since damage, and how hard the engine was working when it failed, sometimes there is very little damage done to the steel or iron crank. But I have also seen some that almost cut the crankshaft in half, and they often damage the journal to the point it has to be welded before it can even be reground.

After polishing the crank, plastigage the fit and buy the proper undersize bearing. otherwise drive it until it breaks, all this other stuff, while amusing, does nothing to help you. Regards, JR BTW, before you remove the bearing cap, make a mental note of which side of the cap goes where. If you put the cap on backwards you're screwed.

Plastigage is pretty useless for measuring a journal unless you are certain it is perfectly round, and you already have a new bearing on a resized rod.

Did you read the stated purpose for the repair?

Yes I did. The OP has a rod knocking. The truck doesn't move much or operate on the road. Once you use emery cloth on a crank it is no longer perfectly round. How many rod to crank journals have you sized? In fact I'm curious to know just how many engines you have rebuilt? Successfully that is. Regards JR

Ok, so how can you measure a bearing clearance with plastigage if the journal and bearing are not perfectly round? How can you use plastigage to determine what bearing you need, if you don't have the bearing in your hand?

100s

In fact I'm

Dozens, and never had a failure. I have also built at least a dozen fully balanced and blueprinted racing engines. My father was an automotive machinest, crank grinder specifically, and I literally grew up in the business. Although I never worked full time, other than three summers through high school, I was alway working on my own race cars, and high performance engines for others. I actually learn to run a Storm Vulcan crank grinded my first summer in 1969.

But more importantly, if you want to join the conversation, then focus on what elements of the discussion you find invalid. Don't just make an abrasive blanket statement and expect to be take too seriously.

Ok Tim no problem. I really don't care if you take me seriously or not. You have vastly more experience than I. The OP had a rod knocking on a more or less junk engine he did not want to spend much money on. Sorry I offered a cheap fix. Now go tell more ppl how to knock a hole in a piston to quiet down the rod knock. I'm done. Regards, JR