Rod Bearings Again?

[Tmade]

Ok,
I had my first engine replaced about 3 months ago. The engine that was replaced due to the rod bearings going out. I had consulted with several people and that was the case.

Well now I have the second engine in the car, and I was told it had about 40k miles on it. Now I have been getting that same rod bearing noise again. It's very mild, and hardly noticeable but I know it's there.

I have talked with a friend of mine, who has 3 sho's and he says that it's very odd that they both would go out like that.

I had a different mechanic, very experienced and knowledgeable about Sho's and race cars in general and he has confirmed that it appears to be the rod bearings again.

Ok, how can the rod bearings go out twice on 2 different engines?

I had only gotten near redline about twice, and really hadn't been pushing the engine a lot since it was put in.

OK, now this is not a slam, but I noticed the sound after my wife had drive the car for a couple of days. Can stalling a car cause that problem to come up?

I'm kind of clueless as to how this can happen twice. My father in law and I are planning on replacing the rod bearings, but I want to make sure I get the problem rather than just bandaging it.

I know a lot of you guys are experts on these engines and I really appreciate your input!!!

I have also been reading a lot of the posts on rod bearings, but found nothing that can indicate why they may go bad.

Thanks,
Doug

 

[Slo-Sho]

First off you need to get an oil pressure gauge on the motor ASAP. It doesn't matter if the motor is a different one, if the bearings are gonna go then they're gonna go. Lugging the motor or taking off from a standstill w/ the rpm's at like 1k is bad for them. High load/low rpm is a on any motor. Do yourself a favor and buy the bearings ~$60 at NAPA (CB1435P) and swap them out. Since the motor has been out recently the Y-pipe should be a cinch to drop. But DO get an oil pressure gauge on the car now! Should see atleast 10 PSI at HOT idle running 5w-30.

 

[luigisho]

That is very irregular but it is a failure in two different motors so you can't really compare the two. Causes range from driving style to correct/incorrect oil pressure, to maybe a flaw from the start like an unbalanced rotating assembly. Check the crankshaft for any damage. If there is very minor wear you might be able to smooth it out with just a little emery (sp?) cloth. If there is really noticeable wear you might have to get it machined or swapped out. If no visible wear just replace the bearings. Testing oil pressure might be a good idea to see how efficient the oil pump is at this point. Did you reuse the one from the first motor on the current one?

 

[Tmade]

The mechanic that switched out the engines said that he used the "best" of both engines. So I'm not sure if he used the same oil pump or not.

 

[Cobraii976]

Replace the bearings and get the oil pressure gauge on it. As for being told it had 40K on it well it's quite possible it was a HARD 40K engine. I know in the last 20K with mine I've been to readline over 365 times atleast once a day if not more.

 

[sdpatt]

One stall should not **** the bearings on a 40,000-mile young SHO engine. I would ask the mechanic who did the engine swap exactly what parts were used from the original engine. I seriously doubt, however, that he would have used anything from the bottom end of an engine that succumed to rod bearing failure.

Running the SHO engine near redline is NOT a hazard. My engine touches the rev-limiter nearly every day and my original bearings were replaced at 268,000 miles as preventative maintenance. The Yamaha was designed to survive at the high revs that let it breathe.