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L28- 3.1 Liter, main bearing issues. Harmonics?


gira

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There was an entire thread on oil, it dealt with rounding off cams.

At least it is a very interesting read. Even the synthetics were subject to the new restrictions.

I'm not saying this is your unlined problem, however, it is worth looking into to protect your investment.;)

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I doubt it's an oil issue. I would first suspect an oiling issue if mechanical or assembly flaws are ruled out. This hasn't been a recurring issue for you, I assume, so the likelyhood of it re-occurring on the next build, is slim. If it does re-occur, then we have two data points and can diagnose it much more accurately.

 

Especially lately, I have learned that things are often more simple than they seem. Don't try to out-think the problem. Step back and go to basics.

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The thing that bugs me somewhat, is the fact that the crank seemed to form a jump rope, due to the center bearing toasting.

So would there not be any opposite force exerted on the opposing force exerted from the center, if it was an harmonic issue?

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My comment on the external oil modification was the relocation of the pickup to the side of the oil pan, then routing that externally via a -10 hose to a specially modified L-Series Pump Cover, through the pump, and then to the block via another -10 hose.

This totally bypasses all the restrictive gun-drilled galleys in the block, which can be restrictive. Stock pickup and feed to the filter galleys are plugged in this modification. The B-Car doesn't have it, but Sho-'Nuff did, an under 3L Hydro in the midwest that ran 9K+ rpms under marine loading conditions...far more serious duty than our land cars will see!

 

You mention oil pressure going away---is it possible there was a drainback issue causing the pump to pass aerated oil? high rpom engines use that larger sump as much for keeping the pickup submerged, as to give you a ready reservoir for higher rpm operation when you are pumping a lot of oil to the top end...and it takes the same time to drain back at 9000 as it does at 4500...problem is you have 2X the oil you're pumping.

 

This was the largest recommendation for the external routing of the pickup, to increase the volume moved.

 

I know I answered this in a PM earlier in the week, but for the rest of everybody who thought I was a butt for not responding...LOL

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What TonyD says is a good idea. If you're not up for that, or a dry sump, make sure you "blueprint" the oil system, i.e. remove all the sharp edges everywhere the oil has to turn to aid in eliminating cavitation and restriction. Bad spots are typically in the timing cover, and filter boss area- especially where the oil galley enters the boss area. Grind all that out smooth like you were porting a head.

 

I think the crank probably wasn't heavy metal balanced properly, wasn't a straight as you thought it was, or wasn't a good choice to start with. Every engine builder has their secrets to determine if a crank is going to "be happy" and not move around alot. Some guys "ping" them. Torsional twisting turns into radial deflections because when torsionally displaced the balance is thrown off. Likely a harmonics problem IMHO. Like John says, the right ATI can go a long way.

 

We may never know, especially without actually seeing the parts, but I think your shotgun approach is the right idea in this situation. Best of luck with it.

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I was reading these posts and mentioned harmonics early on. There has been much speculation as to the cause but I think I may have stumbled on the answer. I was over at my engine builder's shop dropping off 12mm head bolts for my L6 project. We started discussing crankshafts, preparation, modifications, etc. He pointed out that Nissan and Toyota plug the cross-drilled holes in the crankshaft with slugs of aluminum. He described bearing failure on some rebuilds many many years ago that sounded just like the photos indicated here. Turned out that sludge and bearing material would build up behind those plugs over time. When rebuilt, the cranks would get the total treatment including rodding the passages but it wouldn't get to the trash behind these plugs (not realized by the builder). Once installed, this trash would dislodge and score one or more bearings on some engines. He now removes those plugs for a proper cleaning then fits threaded plugs (note: Jaguar has always fitted threaded plugs just for this purpose). The shop has never experienced failure due to this issue since changing their methods. Could it be the cause of this engine damage?

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The pictures posted were from my customers U20 motor that he brought in. I don't know if I want to accept this idea really because of the fact that there is a pattern. The worst is in the center and gets better as you move towards the ends. I still don't know if I like the oil idea either but it plausible IF the thrust/center main bearing has a different oil hole or something in it to make it unique compared to the rest thus making it fail while the others weren't hurt so badly. The dirty crank and the oil issues are causes for bearing failure but like I said, to produce a pattern seems like it bumps those ideas down a little bit. Maybe we should look back at the history of other builds. If it was Greg's first 3.1L perhaps theres still a learning curve but if he had previous strokers which made it out fine, what happened differently on this on then? Thats all I can think of really.

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Hey folks,

Can anyone out there tell me the exact recommended ATI Superdamper. I am going to take your word for it on this and try it.

BTW, we set a new track record this past weekend at VIR by beating the old one by 1.5 secs. That ought to stand for awhile. 2:06.3

 

Thanks

Greg Ira

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Congrats Greg. Thats some margin! Any vids?

 

Dave

 

Yeah, got some vids of a seriously ill handling car. Heim joints were worn out and we baked a LR tire trying a new thing. Car had about 2" of stagger and it was noticable. My camera uses a card and mega memory so I don't post that often.

 

G

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Josh,

How fast are you? LOL just kidding.

 

G

>_> Made a steady 2nd and 3rd when I use to kart race back in the day but thats because 1st and 2nd (when he actually finished) place kids were running new motors and had a larger budget allowing them to go to nationals, now all I do is play computer simulations... :icon56: Grand Prix Legends 3rd place at Watgens Glen on pro mode? Haha, give me your car for a weekend, lets see what can happen. :flamedevi

 

2h3ucgn.jpg

 

Oh and I checked out the ATI site but they name everything with Super so I'm clueless, however I would say the "race" damper for a race motor right? I reread over the previous posts and I'm kind of confused now. Are you still getting the same power band but this time with the 3.1L rather than the 2.4L? I bet if you lighten things up so they are more similar to your old EP engine (like reciprocating mass, knife edge the crank as said in the previous post), things may be better, plus the damper, plus any finds you may run into if you check out the harmonics. I'm curious if there is any sort of electric motor that you could bolt up to the rear of the crank while its in the block (I guess with pistons and everything else that spins and thats balanced together) and see if you can spin it up to some high RPM's without actually having to bolt a head on and run the motor. I've seen some engine builders throw the motors on a break in machine for several hours at like 1500 RPM drawing lets just say 3 amps through the motor. They come back a couple hours later and the RPM's have bumped up to 1800RPM's with only 2.6 amps so that tells you the motor is breaking in. Get something like that but have a motor that can spin pretty fast, maybe setup a pulley like an air compressor. Those run at 3000 RPM off that motor but you also remember you aren't compressing anything without the head on the block so it should be easier to hit higher RPM's. That way you don't have to do a full assembly, you don't have to go out and run the car, and you can sit inside the shop waiting for **** to happen at whatever hypothesized RPM you think you will have problems with.

 

It all makes sense in my head, maybe not in real life though. Just a thought.

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Yeah, got some vids of a seriously ill handling car. Heim joints were worn out and we baked a LR tire trying a new thing. Car had about 2" of stagger and it was noticable. My camera uses a card and mega memory so I don't post that often.

 

G

 

I think ill-handling might be a relative term. I.e. consider your answer to this question: wanna swap? :D

 

Dave

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Greg, I also find it hard to believe it's harmonics. Seems impossible to destroy one bearing without at least wiping the coating off of others. It is a 7 bearing motor so it seems hard for the entire crank movement to be limited to the center bearing. It's possible harmonics contributed if the oil film was marginal, but not the root cause.

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Greg, I also find it hard to believe it's harmonics. Seems impossible to destroy one bearing without at least wiping the coating off of others. It is a 7 bearing motor so it seems hard for the entire crank movement to be limited to the center bearing. It's possible harmonics contributed if the oil film was marginal, but not the root cause.

 

Hey Clark,

Yeah, we're starting to believe there is another issue. The cam showed oil starvation. We know we ran the engine hard with low oil pressure. Once the center bearing started to go the oil pressure went way down. The crank was quite "not round" when checked post issue. The crank turned by hand and was checked during the build. We'll get it right.

 

I still need to know if anyone out there has a model number for the ATI damper.

 

Thanks

Greg

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BTW, we set a new track record this past weekend at VIR by beating the old one by 1.5 secs. That ought to stand for awhile. 2:06.3

 

A 2:06 is cooking around VIR. Greg, congrats on the new record. Nice job.

 

jt

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