Bearing inspection

[GWDriver]

OK, I need help on this one.

Can bearings be inspected from underneath and if so, can they be changed as well if all else is ok?

[talntar]

uuummmm what bearings are we talking about?

[GWDriver]

Sorry,

Rod and crank

[GWDriver]

Main

[talntar]

i am told it can be done,but i think i would pull it if i could.you will need to unbolt the motor mounts and lift it to get the pan out.by that point you may as well take it out.

[andy d]

uhhmn, if you jack up the front end of the wag until the wheels are fully off the ground and then put jack stands under the frame, you can wiggle the pan out. i did it on my 88.

[Knucklehead]

if you only remove the Main caps one at a time and DO NOT disturb the placement of the crank. And do the rods one at a time with the main caps in place and torqued to spec.

You can get the pan to clear with out raising the motor. Just jack it up at the frame rails.

You will only be able to see the bottom half of each main bearing and won't be able to "mic" the main journals, which is the whole point.

Get some 5/16 ID fuel line on put over the rod bolts to protect the rod journals.

If you pull the crank you will be cussin a blue steak tryin to put it back in with 8 con rods hangin in the way.

Don't scratch anything and good luck.

[talntar]

Originally posted by andy d:
uhhmn, if you jack up the front end of the wag until the wheels are fully off the ground and then put jack stands under the frame, you can wiggle the pan out. i did it on my 88.my bad.you can do this as well.but like the next post says you wont be able to do much with it in the rig

[carrotman]

According to the 76 TSM, the V8 and six engines must be pulled from the vehicle and separated from the transmission prior to changing the main bearings. It also says that the rear main oil seal on both engines can be changed with the engine in the vehicle. If you pulled the oil pan you could measure the crankshaft end play. Are you hearing main bearing noise?

[GWDriver]

I'm not SURE where the knocking is coming from, except that it seems to be in the bottom end somewhere. That's why I was thinking of checking it out. I've read in the Haynes manual that it is possible. The degree of difficulty is not mentioned.

My kid brother (yep, kid at 50) is a trained auto mech and he seems to think it could be done providing I do only one at a time and don't mix things up.

I'll take all of the feedback I can get. Thanks.

Would like to hear from anyone who has done this.

[Knucklehead]

If you got knocking form the rotating assembly, You got a spun bearing then the crank will have to be removed and turned down and polished. It is easy to get the crank out but you have to remove the transmission and timing cover and all that is associated with them.

It will be next to impossible install back into the block unless you remove the heads to allow removal of of the pistons. You have to remove the pistons to get the rods out of the way of the crank throws. It is easy if the block is on an engine stand and up side down.

It won't hurt anything if you pull the pan and look around, but, I would plan for pulling the engine. You really should do the top end (pistons, rings, heads) at the same time as the bottom end anyway because when you do these you will have do redo the bottom end again.

[kenny1221]

I replaced the main bearings on a 302 Ford truck by pulling the caps one at a time and using a piece of copper tubing that was pounded flat and curved to push the top of the bearing out. My 89 GW did what yours is doing but mine lost oil pressure first. I swapped engines because I bought mine with a spare engine . If yours has over 80K miles on it the engine probably has a lot of blow-by and could use a rebuild. However, if all you want to do is keep it on the road, Discount Auto parts only wants around $60 for all the main and rod bearings.

Ken

[GWDriver]

Got a bit over 85,000 miles on it.

[tgreese]

Failed rod bearings are much more common than failed mains. First thing I'd do is pull the pan and plastigage the rods and inspect the mains. If you have the pan off you may as well do the rods anyway, so I'd plan on replacing the rod bearings no matter what.

I've never changed mains with the block in the car - if it were mine, and the mains needed changing, I'd pull the engine and inspect everything. JMO.

[ January 03, 2004, 03:40 PM: Message edited by: tgreese ]

[Crazy_Jeepman]

Oil Pressure would be low or poor if you have an audible knock caused by a Rod Bearing. You will not hear a Knock from a bad main. You can change rods and mains without pulling the motor or heads. I would isolate the Knock before pulling anything apart. Can you hear the knock at idle? Whats the Oil Pressure? If you have a knock at idle.......I would idle the engine and pull on plug wire at a time. Pull one, knock still there? put back on and pull the next and so on. Untill you hear a change in the severity of the knock. If no change at all then I would look elsewhere. Flex Plate, fuel Pump, Water Pump.

[GWDriver]

Thanks,

Oil Pressure is good. That's what has me wondering because it does knock at idle, sometimes worse than at others. Sometimes it's almost quiet .

After what I've read on this site about oiling problems, I figured I was just one of the unfortunates.

As you look at the engine bay FROM the radiator, the noise seems to be coming from YOUR right side (drivers side).

[GWDriver]

Crazy_Jeepman,

What you have said pretty much goes along with what I'd been thinking. It would seem that if the bearing has not scored the crank, I should be able to replace the bearing itself. That's probably a long shot but worth a try anyway. Somewhere I read of it being done and the engine going strong for 5-10,000 more miles

???

[GWDriver]

The main thing right now is to keep it on the road until I will have the time to do either a rebuild or swap. When I get back from overseas, time will be critical for getting the house in order and ready for the winter. I will have an addition to put on to the house as well as a new garage.

I'll be busy for awhile.

[Knucklehead]

I would do what Crazy Jeepman said. The sparkplug thing is a good way to diagnose individual rod bearing as well as exhaust leaks around the individual eshaust ports.

You say drivers side. Is it comming form around the fuel pump. They make a noise sometimes when they are about to fail. Smog pump make some strange noises.

YO might try taking off all the belts and run it for a short time an listen to it. THis gets rid of all the other noises from the excessories.

Get under it while it is running and listen to the oil pan. A rod knock will sound like hitting a 2x4 with a hammer on a soft surface. If you got good oil pressure at idle and hear no knock at idle, I doubt that you have a bearing problem.

[GWDriver]

66HD

If it were a rod knock, is there a way to correct the problem without a full scale teardown?

[Crazy_Jeepman]

Depends on damage, usually with the rod knocking you need to have the rod resized and crank reground to correct surface and diameter specs on the crank. This would involve pulling the motor and at least one head and crank, at the least. Some say you can just put a new rod bearing in on the knocking rod.........I do not beleive this and do not advise it.

[Knucklehead]

Yep, I have never seen a crank that had spun a bearing and did not need the crank turned. When you put new bearings on an old, out of round journal, you are asking for a spun bearing right away. And if the bearing spun it spun because it seized to the crank journal enough to spin off the tangs that hold it in place in the con rod.

Without spun bearings, it is advisable to at least repolish the crank. But that is just me. I hate to do things half-assed.

But from what you said earlier it may not be a spun bearing and may be something else. I would remove the belts and listen (for short amount of time). If you got oi pressure It is not likely you have a bottom end problem.

[tgreese]

Dick Datson tells a story in one of his books of his Lark that spun a rod bearing on a long trip. He tells how he removed the pan and rod cap by the side of the road and worked the journal over with crocus cloth, then put it back together with one new rod bearing and drove every day for 6 months without a teardown. His main point was to make a case for steel crank and rods, which the Studebakers had - but it illustrates the kind of repairs that today are uncommon but didn't used to be.

Not saying this is good practice in all cases, but you can do a lot of such things to get by if you know what you're doing. The old mechanics did this sort of stuff a lot, like replacing one used piston with another or adding one new rod bearing, to keep cars running on the cheap. Nowadays it seems like the standard response to any major engine problem is a complete rebuild with reground crank and rebored cylinders ... doesn't have to be. No wonder there are so many 401 blocks that need sleeves, engines junked at less than 100K miles, and a shortage of boreable blocks.

[Knucklehead]

AMC 360 and 304's use cast (soft) cranks and ductile cast iron rods. A tuftrided (nitrided) crank will not suffer as much damage as a cast iron crank will when a bearing spins. Cast cranks and not tuftrided (nitrided).

Older engines of the 50's and up to the mid 60's (67 for chevy) were most if not all forged steel rotating assemblies. That is why you can spina 327 or 283 to 8,000 RPM safely in these small blocks. Chevy never used a cast rod but did use cast cranks.

The last 360 I tore down had spun rod bearing. Was shut down when the driver heard the knock. The crank was trashed and thus pitched. This is not the case every time, but I think that is there is spun bearing the crank will need to be turned.

However, I have not seen oil pressure and a spun bearing in the same engine.

You have good oil pressure, yes?

[Crazy_Jeepman]

Short and simple if it is a Rod that is knocking (Doubt it is) you will be pulling the engine taking the crank in to be checked reground or polished. Rod resized and then from there ya can do what you want, complete rebuild or put it back together. To pop in another rod bearing on a knocking journal is just silly. Lots of stories about the olden days don't fly in real life, lots do but not all. At anyrate........I doubt you have a bad rod.

[GWDriver]

66HD,

Yep, Oil pressure is fine and consistant. It's got me baffled but I'll try the tech tips if heard so far when I DO get back stateside.

I just need the beast up and running as soon as possible.

Thanks guys,

LarryD