bearings

[trainguy1989]

I have a friend who has owned 3 SHOs and I asked him about the rod bearings. He said by replacing them you are more likely to cause engine fail sooner. He told me if you do replace them that you might as well take the crank to the machine shop and have it cleaned up too otherwise the new bearings will not help much. Is there any truth to this? I have 180,000 on my engine with original bearings and I still build great oil pressure every time I start her.

Thanks,
David

 

[Eric VerValin]

He needs to stop smokin that crap. The only time I've ever heard of someone turning a crank was if it was scratched... there are quite a few SHO's on here over 250,000.. **** some over 350,000 on the stock crank.

And you say you have 180,000 on it? Mine spun at 189,161... will never forget that number..

 

[yamahaSHO]

Don't assume that because someone has owned a few, that they know what they are talking about. Unless done incorrectly, it will prolong the life of the engine.

 

[sperold]

If your engine has great oil pressure, you don't have to worry about changing any bearings.
Not knowing everything that has been said, it is hard to comment on your friends statements. Your engine wont fail sooner if you replace your rod bearings before they get to an advanced stage of wear. If you do the bearing swap and don't do a thorough job (and happen to miss torquing the rod bolts), then you would have been better-off to leave it alone. The comments on turning the crank rod throws do make sense if the crank has suffered damage. Often they can be polished in place with emery cloth, but it is time consuming. That would be the case if a small piece of casting went through the bearing and left a mark on the crank. If it is hammered or out-of-round, it can be machined to a smaller diameter, and rod bearings can be bought to match the new size. So there is nothing wrong with that statement. Taken generally, if you have ignored the low oil pressure light and have delayed the bearing swap, and serious crank damage results, then there is no sense just changing the bearings.

 

[SHOtime2511]

how is anyone to know what there oil pressure is?
installing and oil pressure gauge is more of a PITA than changing the bearings...

 

[trainguy1989]

I do live on my own. I told my father about the bearings. He thinks I am blowing things out of proportion and this is not that big a deal. He says I worry to much about this car. He keeps telling me that this is "just a car". How could I tell him otherwise? I love my SHO....

 

[elarm1]

New rodbearings, new piston rings, new life!

 

[SHOtime2511]

I do live on my own. I told my father about the bearings. He thinks I am blowing things out of proportion and this is not that big a deal. He says I worry to much about this car. He keeps telling me that this is "just a car". How could I tell him otherwise? I love my SHO....

its your car,do what you want with it.
why do you need your fathers approval?
were simply providing infomation based on what we know about the SHO.
IMHO at 180k you should change your rod bearings,simple as that take it as you will.

 

[Bob Gervais]

This is one of those subjects, that if mentioned to a mechanic/machinist, they will look at you like you have three heads.

It's not normal practice on many engines to swap out rod bearings as preventive maintenance. Most other engines fail long before the Yamaha does, for other reasons, so it never gets to the point of rod bearings.

There's many arguments as to what makes them fail in our cars. Improper maintenance, lugging the engine, etc. Point is, we know it's an issue so we do them before they fail, to avoid having to do machine work to the crank and rods.

To educate the OP on the subject:

Rod and main bearings are made of a softer material than the crankshaft, which makes them the sacrificial piece in the puzzle. Normally, when rebuilding an engine, the machinist would measure the crank journals (where the rod and main bearings ride), look at their condition, and machine them as necessary. This may be a simple matter of polishing a few ten thousandths of an inch off and installing new bearings, or if the journals were damaged he'd have to machine the journals undersize and install oversize bearings to take up the gap. He'd also measure the rod bores to see if they're out of shape or oversized, and machine those if needed.

After all this is done, he would use a material called Plastigage upon reassembly, to check the clearances between the rod and main bearings, and the crank, and compare them to the factory specs, as a double check to his work.

All of this is expensive though, and really not worth it on our engines at this point. There's a lot of 3.0 and 3.2l engines to be had in junkyards, SHO vendors, parts cars, etc. so it's easier and cheaper to swap engines if there's substantial crank damage because of failed bearings.

Basic rule of thumb when doing rod bearings in our engines: if the journal is not scored, doesn't look worn, and you can't catch a fingernail in a scratch, it's OK to simply replace the bearings and call it a day. You can Plastigage upon reassembly if you'd like, just to see what your clearances are, but 99% of the time if a bearing hasn't already spun you'll be fine.

 

[Bob Gervais]

If your engine has great oil pressure, you don't have to worry about changing any bearings.

Not completely true. My 3l in my old 93 ran great and made good oil pressure, right up until the point of rod bearing failure.

 

[NEp8ntballer]

how is anyone to know what there oil pressure is?
installing and oil pressure gauge is more of a PITA than changing the bearings...

I disagree as long as you understand wiring it isn't hard at all. You don't have to remove the starter, y pipe, miracle the oil pan off, remove all that crap. The only hard part is planning it out and carrying the plan out.

 

[SHOtime2511]

I disagree as long as you understand wiring it isn't hard at all. You don't have to remove the starter, y pipe, miracle the oil pan off, remove all that crap. The only hard part is planning it out and carrying the plan out.

im not saying its hard really,just IMHO its quicker to swap out the bearings so long as your car isnt a rot box. I think it took about an hour for me.

 

[STL. SHO]

what is normal oil pressure on a stock 3.0?

 

[NEp8ntballer]

what is normal oil pressure on a stock 3.0?

8-10 PSI at idle when hot.

 

[STL. SHO]

thanks

 

[SHO_91]

Replace 'em. They may not be bad - mine came out at 215k miles and looked okay -, but you will sleep better. It's not that hard of a job. Typically, once you hear knocking or the low oil pressure light flickers, it may be beyond simple rod bearings R&R. The majority on this forum has done it. Just be careful and torque everthing to spec. Look at http://shophoenixproject.com for a really good write-up. And, but that's just me, I prefer not to plastigage to avoid putting unnecessary stress on the rod bolts. Oh, and the bearings set (includes gaskets, RTV, and plastigage) can be had from http://rcmautomotive.com for around 60 bones.

 

[jmpSHO]

im not saying its hard really,just IMHO its quicker to swap out the bearings so long as your car isnt a rot box. I think it took about an hour for me.

I did the rod bearings in two different SHOs and I have an oil pressure guage that i want to install but it seems more of a pita to do than the bearings.

 

[SHOtime2511]

I did the rod bearings in two different SHOs and I have an oil pressure guage that i want to install but it seems more of a pita to do than the bearings.

try using one of the oil filter sandwich blocks.
it fits between the engine and the oil filter and it has a few ports for connecting oil pressure feed lines.
you can pick them up on ebay for a few bucks.

 

[trainguy1989]

I am going to replace my bearings. I just have no place to work until spring. It is very cold now in Kansas and leaves and dirt are blowing around now. I have no garage to work in. It should be as clean as possible from what I read. To tell you guys the truth, I have a very subtle knock on cold starts, but give the engine one minute the subtle knock goes away like it was never there. I have had people tell me the noise I hear is from that thin mobile 1 10-30 I run. I have not been able to confirm that the very subtle knock is from the bearings. I am just under the influence as the car warms up the metal expands making the knock disappear(tolerances change as car warms up). This is my daily driver, so I will be real easy on her till spring, unless you guys have any suggestions, ex. thicker oil?

Thanks,
David

P.S. had her at 6000 RPM's the other night without any problems.

 

[matt59]

My 93 3.2 rattles for a second if it hasn't run in a couple of days, The Oil light goes out quickly when started. My concern is if I run 10/30 Synthetic on a hot day the oil light flickers at idle but with 10/40 Dino oil it never even flickers. I like to run synthetic oil because it has better lubricating properties (slippery). But when that light flickers I grind my teeth. Is it too late for my bearings?