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I know it's possible to replace the rod bearings on my '91 olds without removing the engine. Is there a proceedure I should follow and what is entailed with this that I need to be aware of? It appears once the pan is removed the access to the crank is wide open.

dandyd wrote:I know it's possible to replace the rod bearings on my '91 olds without removing the engine. Is there a proceedure I should follow and what is entailed with this that I need to be aware of? It appears once the pan is removed the access to the crank is wide open.

It is possible, but not advisable to replace the bearings in this way.

The procedure is simple, drop the oil pan, rotate the crank by hand to bring the rod down to Bottom Dead Center (BDC). Use a feeler gauge to check the side clearance on the rod. It must fall within 0.003" min to 0.015" maximum.

NOTE: You may wish to do all of the rod side clearance measurements first, before you replace any bearings...If one of the rods is out of spec, then you will need to replace the rod or the crank...at which point it has to come out. If the side clearance is Ok on all the rods, then you can replace the bearings. (Too much side clearance will allow the rods to tip & twist..destroying the new bearings. There's no way to correct side clearance issues without replacing or reworking the crank & rods.)

Mark the cap to indicate the direction that faces the front of the motor, then remove the connecting rod cap. Protect the crank journal by slipping rubber hose over the exposed threads of the connecting rod, then use a piece of oak to shove the piston & rod up the bore to get it out of the way. Remove the old bearing halves and note the part number on the back (should have "STD" stamped on it to indicate a standard thickness bearing.)

Clean the crank journal with acetone and a soft cloth.

Take your new standard size rod bearings and install them in the cap & rod. Pull the rod down until it is in contact with the crank journal and remove the rubber hose from the bolts. Lay a stip of Plastigauge on the rod cap bearing and gently install the cap on the rod. Torque the bolts to 43 ft-lbs. DO NOT ROTATE THE CRANKSHAFT...you will smear the Plastigauge and not get a good reading. Loosen the rod bolts, remove the cap, and measure the Plastigauge mashed on the surface of the crank. If it falls between 0.0003" and 0.0026", then it is good to go. If not, you will need an oversize bearing (0.001" or 0.002") to correct the clearance back into the proper range.

Clean the crank journal with acetone and a soft cloth. Clean the rod cap bearing with acetone and a soft cloth. Lubricate the bearing with engine assembly lube and reinstall. Torque to 43 ft-lbs.

Take a break...One down, five more to go.

Now, At the begining I said this was possible, but not recommended. Here's why: You are installing brand new bearings on a worn crankshaft. Not exactly a good idea. The correct method is to remove the crank from the engine, then turn/grind/polish all the journals to the next size down. That removes all wear, taper, and damage from the crank so the new bearings have a perfect surface to ride on.

It's been a while since I pulled the pan on my 3800, and I can't remember. Is it possible to lower the crank w/o removing the engine? It's seems that once you remove the bolts from the flywheel, there should be nothing else in the way. I know this is the lazy man's way of doing things, but my time is really at issue here while working 2 jobs to put gas in the car.

dandyd wrote:It's been a while since I pulled the pan on my 3800, and I can't remember. Is it possible to lower the crank w/o removing the engine? It's seems that once you remove the bolts from the flywheel, there should be nothing else in the way. I know this is the lazy man's way of doing things, but my time is really at issue here while working 2 jobs to put gas in the car.

There's a lot that has to come off before you can lower the crank with the motor in the car. All of the accessories, Harmonic balancer, water pump, timing cover, flexplate, oil pan, oil pump pickup, & starter. That will clear the area around each end of the crank, and all the main cap bolts, allowing it to drop out the bottom of the block.

If time is the issue, do the entire motor as a replacement. Yes, buying bearings, gaskets, and seals are cheaper..but you are going to do a bunch of extra work just to get the crank out of the block while the motor is in the car. Plus, you will probably have oil leaks when you are done. Considering the cost of a fold-up engine hoist and stand..they are worth their weight in gold when it comes to working on cars. Even a handy tree and chain hoist is going to be better than trying to do the crank in the car.

co-worker of mine likes to say "If you don't have time to do it right, when will you find the time to do it over?"

unless this is going to be a VERY short term solution for you, I cant see the benefit of doing it with engine in car

You'll save a lot more time if you simply separate the trans from the motor and yank the motor... It will make this process much easier..

If you do this have the crank checked and turned.....

That is exactly the conculsion I have come to. I have a friend how has a hoist and stand that he lets me use at any time. I can't afford the entire re-build, but turning the crank and replacing the bearings I can deal with. The car has 237k on it....and it still runs good, just in the last month or 2 I have started hearing a 'clatter' at about 2,000 rpm, and then right as I turn the engine off. It does not sound like a cam lifter clatter as much as worn crank bearings. What I may do is head down to our local Pick and Pull and snatch another 3800 out of a wrecked car. I was down there 2 weeks ago, and they had several w/ 75-100k on them, the body just wrecked. The ol' 3800 is a work horse engine (wish the tranny in them were as strong...had mine rebuilt at 100k and still going strong.). The Pick and Pull engines run about $100 plus core.....you have to pull it, but I'm in no hurry with this. It's an option to consider.