Question about replacing rod bearings

[EL SHO]

hey guys... just wondering

If I were to change the rod bearings in my ATX SHO as preventative maintenance, before any sounds are heard (knocking, etc), this should be a really straight forward replacement of the bearings?

Does anything else need (if) to be machined, like the crankshaft?

Just order the correct parts, take off the Y pipe, oil pan and the rods will be visible?

you guys have any comments on this?

 

[msteiny]

Yeah, you pretty much got it. Dont forget to order the front and rear seals for the oil pan and the gasket for the pick-up tube. RCM has a kit with everything you need. You will need about a foot of plastigage for checking the clearances between the rod bearing and crankshaft. If you do it now before the knocking starts you should be good with no machine work.

Good write up here:
http://www.kurtmetros.com/bearings.html

Have fun.

Oh yeah, order an exhaust ****** gasket too.

 

[platoribs]

Sealing up the pan after can prove challanging, or so I've been told. I assume if you source a good RTV or whatever you like it'll be just fine, however I have heard of hanging the pan by a few bolts and allowing whatever you use to set up a bit, then snug it up to cure, then check your work...

 

[zak]

Plastigauge won't work unless the engine in inverted (e.g. on an engine stand). Assuming you are doing this in the car, and you have no knocking then I wouldn't bother with plastigauge, just visually check for scoring on the crank.

 

[EL SHO]

Yeah the engine would be in the car as I'm mostly interested in doing this as a preventative maintenance.

But... what is Plastigauge, never heard of that before. How does it work?

 

[JRA2000TL]

Never used plastigauge when I replaced the bearings on both my 89 and 95, and I did mine as preventative maintenance (with no noises/problems heard) rather than after the fact. If you buy the standard spec bearings, and you took off standard spec bearings; you should have no problem.

Plastigauge is this stuff that looks like dental floss. You remove the bearing, put a piece of it on the crank, torque the bearing down and it "smashes" the plastiguage. Then you remove the bearing, take the flattened plastiguage and measure the thickness against a chart that comes with it. I believe that's how it works. I've never needed to use it. I've put 8k miles on my 95 since the bearing swap and about 4k on my 89 since that swap and have had no issues.

If you had knocking/noises, then replaced the bearings, I'd want to plastiguage it to be sure.

 

[rubydist]

Plastigauge won't work unless the engine in inverted (e.g. on an engine stand). Assuming you are doing this in the car, and you have no knocking then I wouldn't bother with plastigauge, just visually check for scoring on the crank.

Actually, the plastigauge doesn't care if the motor is upside down or right side up. However, it is a pain to get it in there and cleaned up after when you are under the engine.

Just make sure all the rod journals are standard size, install the new rod bearings and go.

 

[jimtash]

Yeah I wouldn't worry too much about clearances if this is just preventative maintenance. Just replace them.

 

[sdpatt]

I replaced the rod bearings twice on mine for preventative maintenance and checked the clearances with Plastigage on the first few bearings changed, only to find them in spec. I was more concerned about the repeated r&r of the caps and the stretching of the studs. I passed on checking the remainder.

The sealing of the pan is a challenge only in that it is not an interference free reinstallation. Try a test fit without the RTV applied before the using the sealant.

The tighter lower end can be heard after starting the engine. It sounds like engine insurance.

 

[SHOdded]

How much time should be set aside to replace rod bearings? Sounds like you have to be meticulous and 99+% of the time you should be ok? Post-replacement, what to watch out for to ensure the replacement has "taken"? Thanks.

 

[jimtash]

At least two days minimum. You can pretty much take off everything and install the bearings in day but the RTV used to seal the oil pan should be allowed to cure before being put to use.

There is no way to ensure they are taken but to put the caps back in their correct position, which is tabs facing each other, the tabs in the bearings are seated, and make sure the oil hole in the bearings aren't blocking the holes in the rods. Use pre-**** on the surfaces and rotate everything around a couple of times before putting the pan back on.

 

[platoribs]

The sealing of the pan is a challenge only in that it is not an interference free reinstallation. Try a test fit without the RTV applied before the using the sealant.

not interferrence free = not, not, interference = interference, yes?

Which means it is an "interference installation" yes?

Having never reinstalled a pan, but knowing how it's done. Do you mean the rubber gaskets, fore and aft, can be crushed completely while squishing out all the applied RTV. Or in other words one has to apply the rtv, allow it to cure and then compress it just enough?

I'll be doing this sometime in the future and want to make sure I understand.

Please elaborate in your inimitable way Scott... Lol!

 

[rubydist]

no, you put the rtv on there and install the pan within about 5 minutes to make sure the rtv has NOT cured prior to the pan being torqued. then, you want to let the rtv cure overnight before exposing it to oil, etc. to ensure a good seal and no oil seeping out around the rtv.

I have had good luck using a little rtv to hold the front and rear seals in place to ensure that the rubber pieces do not shift while installing the pan.

 

[jimtash]

Make sure to scrape or use a wire brush on the pan to take off all the old RTV. It doesn't need a lot of it either when you put it on. A nice 1/8 inch wide line around the pan including the entire circumference of the bolt holes is plenty. Any more and you risk it getting squeezed into the engine and possibly blocking the oil pick up.

 

[JRA2000TL]

I did fine reinstalling the pan on the 95; but when I more recently did the bearings on the 89, I kinda screwed up the pan installation. I kept getting it hung up on the axle and other crap in the area. The rubber seal kept moving on me too. When I did finally get it seated with the RTV, apparently I crushed the seal and some of it "bowed out", I cut the bowed out piece and applied RTV there. (I was not removing that pan or buying another seal). I thought nothing else of it and drove the car around, including a 800 mile round trip to Nashville to the SESHO meet. About 2 hours from home, I stopped for gas and just checked the oil. I'd lost about 2 quarts!!!! I topped it off, got home, and checked the pan later. I found quite a few of the oil pan bolts were loose. Not sure how; that was rather scary. I thightened them up and haven't really had a problem since. I have a couple tiny droplets of oil from various places even though I've replaced all the seals except the rear main.

 

[SHOtime2511]

I found letting the RTV sit for about 4-5 min before install works well.
Just enough so it starts to kick off so it wont smear around as easy.
Make sure to be easy on the RTV,too much and it can clog up your pickup tube screen.
As others have noted,test fit first.
That way you get the feel of exactly how to position and move the pan first.
Make sure you have a good tq wrench for the rod caps and tq to spec.

 

[EL SHO]

wow.. never thought that the thing that could cause issues was reinstalling the oil pan. Good info here!
Thanks guys.. I guess I'll wait a couple of more paychecks to buy the rod bearings and install them in a weekend or so.

 

[luigisho]

wow.. never thought that the thing that could cause issues was reinstalling the oil pan. Good info here!

Those are the issues when everything goes well. With rust belt cars, exhaust manifold studs breaking off and trying to drill them out can be a real time killer.
Cover your eyes so you don't give them an oil bath when you're under there. It takes a while to drain all the oil so your face stays sorta oil free. Let it drip out for a long time after you remove the pan. You can get a plastic bag or something to cover the area if you have to worry about dirt/grit getting in there while everything is exposed.