Bearing Failure?? - Team Camaro Tech
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post #1 of 19 (permalink) Old Nov 4th, 00, 02:30 PM Thread Starter
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Last Christmas I built a 400 sb for my '69. Within a few hundred miles I was hearing a faint rattle/knock by the #2 cylinder. It's gradually gotten worse so today Shawn and I yanked the motor and dissassembled it. The #2 rod bearing was shot - it had eaten well into the copper and the crank journal is damaged as well. In addition, all the other journals show excessive wear to varying degrees.

I had a rebuilt stock crank (.020 over on both rods and mains) and rods with Clevite bearings throughout (I verified they were the correct size). I checked every rod and main for clearance with plastigage and by measurement. I used new ARP bolts and studs, assembly lube and carefully torqued everything with the proper steps checking for binding along the way. The block was squeeky clean, I used fresh Valvoline racing oil and changed it several times on the way to 1000 miles.

So what gives? What could be the cause of this failure?

------------------
Scott
'69 400SB, Richmond 5-speed; '99 HD Road King Classic
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post #2 of 19 (permalink) Old Nov 4th, 00, 03:09 PM
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Scott,
1. You said that you used ARP bolts, did you install them yourself, or have a machine shop do it ? ARP bolts are a very tight fit in the rod and require the big end of the rod to be reconditioned when they are installed.
2. Did you have your crankshaft reground, or did you buy a "crank kit" ?
In my opinion most "rebuilt" cranks that you can buy are not suitable for any type of performance use. About half of them are welded up on one or more journals, and it has been my experience that the finish and sizes, taper, out of round etc. are just not acceptable for anything but a bone stock daily driver, and only as a last resort.
Short of some type of lubrication failure, these are the two things that come to mind right away. I am sure I will get some arguments, but personally, I do not think it is possible to properly measure rod bearing clearance with plastigage. The rod moves around too much when tightening it and also when removing the cap to look at the plastigage. Plastigage also only tells you the amount of clearance you have at the top and bottom of the bearing. It could be tight at the sides and you would not know it. The only way I know to properly check rods is to bolt them together with the bearings, measure the inside dimension of the bearing and compare it to the diameter of the crankshaft.
I know this does not tell you why the bearing failed, but its a start so you don't have the problem again. If you have any other questions, you are welcome to e-mail me.
Hope this helps,

------------------
Bill Koustenis
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post #3 of 19 (permalink) Old Nov 4th, 00, 03:58 PM
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When you tightened the rod bolts did you use a torque spec or check for bolt stretch? If the torgue wrench was not calibrated you could have under torgued them or over torgued them.. just a thought
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post #4 of 19 (permalink) Old Nov 4th, 00, 04:18 PM
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Scott,

I agree with Bill, and what I will add, is did you use a crerry ball hone on the cylinders, and if you did what cleaning procedure did you go through?

Larry
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post #5 of 19 (permalink) Old Nov 5th, 00, 03:19 AM Thread Starter
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Thanks for the replies.

I bought a kit (406 Strong Arm) from Speed-O-Motive. Reground stock cast crank, rebuilt 5.7" rods with ARP bolts already installed (and clearanced for the cam) and Silvolite hyperuetectic pistons.

A local machine shop with a good reputation did the machine work and measured the pistons prior to doing the honing. I know they checked the rods and said they looked good except that they were all slightly bent and/or twisted (very small amounts). They straightened them with a long steel bar thru the wrist pin hole and said this is fairly routine. I watched them do it - they got them all right on the mark.

I agree with the plastigauge comment - it's tough to do it without the rod moving all over and when you tap the rod apart I have to believe it affects the reading. I did measure the crank and assembled rod and as I remember the clearances were right on, however, I didn't use an inside dial indicator - I used a precision inside/outside caliper with a digital readout. Maybe the reading isn't as accurate that way?

I will also admit that I didn't think about my torque wrench calibration - I wouldn't be surpised if it's off after 20 years - I should have considered that. I just torqued everything with the torque wrench - do I need to use a rod bolt stretch measurement tool instead?

I keep coming back to the crank - but I don't understand why it wouldn't hold up and where all the scoring comes from. Is the surface just not hard or smooth enough after being re-ground and maybe welded? Does this cause the bearings to start to score right away? What happens to all the millions of other motors with re-ground cranks out there?

Besides getting the measurement and torquing right this time - where do I go with the crank and rods? I'm thinking it may be time for a better crank and rods - but I don't want to drop too much on them - any suggestions/

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Scott
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post #6 of 19 (permalink) Old Nov 6th, 00, 05:44 AM Thread Starter
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I talked with Speed-O-Motive this morning regarding this problem. Their tech guy asked which bearings were bad and I realized they were the worst at the front and were less damaged going to the rear of the motor - which, according to this guy, means I likely had an oil starvation problem that resulted in low oil at the front of the crank and a slow death for the #1 & 4 rod bearings.

I have to confess I didn't hook up my pressure guage and I remember the (idiot) oil light coming on during a high rpm run once (maybe twice) but by the time it registered in my brain the light was out.

So - the culprit here may very well be oil starvation. I'm running a Z28 oil pan and windage tray along with a Summit high volume/standard pressure pump. I set the pickup height correctly with a wad of clay. All oil passages were thoroughly cleaned with the plugs out.

So, what's wrong with this setup? Do I need restrictors to keep the oil from building up on the top of the motor?

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Scott
'69 400SB, Richmond 5-speed; '99 HD Road King Classic
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post #7 of 19 (permalink) Old Nov 6th, 00, 05:52 PM
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Scott,

The first thing I would check is the 3 oil gallie plugs behind the cam gear, if the machine shop had these out and did not stake them back in properly they will come out. I always tap these holes to 1/4 NPT, just be careful not to go to deep.

As for the restrictors, I never use these except solid roller cam, not even on hyd roller.

I always use Melling M55HV oil pump. This pump comes with extra spring, use the extra spring as it lowers the oil pressure, but the volumn is not affected. This set up has always worked for me on engines from stock to others turning 9000.

Larry
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post #8 of 19 (permalink) Old Nov 7th, 00, 10:06 AM
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Standard solid lifters with the flapper valve metering and snap ring on top pass a lot of oil to the top end.
I use the older Corvette orfice type with no snap ring, they pass less oil and are good to use with roller rockers. Otherwise use restrictors with a solid lifter cam.
With hyd lifters you can't restrict the oil flow or they won't work properly.

I used to lose oil out of the valve cover vent before switching lifter type.
David

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post #9 of 19 (permalink) Old Dec 28th, 00, 11:22 AM Thread Starter
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Well - it's been a slow process but I finally got all the parts checked out. My machine shop said the rods were terrible and the crank not much better. The problem was the quality of the work done when they were rebuilt the last time. Apparently, there was quite a bit of taper side to side in the rod bores and the crank journals were not finished well either. In addition, the sides of the rods were fairly rough. The shop owner (and chief engine builder) said he wasn't a bit suprised that the bearings failed given the poor quality of the prior work.

The shop rebuilt all the rods and reground and polished the crank. It all looks much better and is now at the balancer's shop. I also swapped in flat top pistons this time which turned out to be over 60 grams lighter than the dish tops so they have to take weight out of the crank and get it all balanced up again.

Anyway, I wanted to let you know what I found and say thanks for all your suggestions.

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Scott
'69 400SB, Richmond 5-speed; '99 HD Road King Classic
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post #10 of 19 (permalink) Old Dec 28th, 00, 01:11 PM
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Just a reminder, I have found SEVERAL things wrong with the Speed-O-Motive kits and/or engines. Their prices are good but you MUST have a good machine shop check everything BEFORE you assemble it. I would not consider buying an assembled engine from them; did that, had BIG problems.

I've still bought stuff from them; just not anything they machine themselves. They have far too much production to have time to thoroughly check things.

Jody
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post #11 of 19 (permalink) Old Dec 28th, 00, 01:36 PM
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Glad to hear you have things rolling on your car. Hey, I thought shawn was in some different country or something. Where's he been? And, will your new motor be a threat to the green meanie? We'll stay tuned.

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Steve
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post #12 of 19 (permalink) Old Dec 29th, 00, 02:42 AM
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just a quick note. have you checked the alignment of your main bearings. if you're going through this much work?
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post #13 of 19 (permalink) Old Dec 29th, 00, 09:11 AM Thread Starter
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Scott -

Yes - if you mean check the main bearing bore alignment? I swapped in ARP main studs so the shop checked out the alignment and pronounced it in good shape.

Stevo -

As far as Shawn is concerned - he's in the country but just too busy to check the site and find out all the things I'm doing so my car will be faster than the weenie mobile! He swapped in AFR 195 heads also recently and is really happy with them. I think with my new combo (AFR 195's, a little more compresson and a CC hydraulic roller cam) we'll be dead even on power - the only difference will be my manual vs. his auto. Depending on how much power his auto is taking I may have him. However, he's now making grumbling noises about a new bottom end and a gargantuan roller so you just never know!

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Scott
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post #14 of 19 (permalink) Old Dec 29th, 00, 07:51 PM
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Scott,
While at a speed equipment show I talked with an Eagle rods rep.

He had a small magnetometer on the table and I asked what it was. He said it was to measure magnetism on the cranks and rods.

Many parts are magnefluxed either by a small electromagnet or by magnetizing the whole crank, checking it, then de magnetizing it, and sometimes when that or machine work is done, some small amount of magnetism can remain.

When you wash the parts off, they can pick up metal filings and even hold them inside the oil passages inside the crank!

They can be flushed out by the oil when the engine is started and damage bearings and cylinder walls, etc.

Just something else to worry about.
David


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post #15 of 19 (permalink) Old Jan 1st, 01, 11:35 AM Thread Starter
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David -

OK - so it's not enough that I have to worry about the machine work from Crap-O-Motor, now I have to worry about magnetism attracting various bits of killer metal! It seems like it used to be easier than this!

David and Bill -

I've been thinking a lot about this bearing failure situation. I also re-read an ancient Smokey Yunick book and picked up a few tidbits.

Here's my new and improved failure analysis:

It seems that the lousy machine work and resulting rough and uneven bearing bores caused poor contact between the bearings and the bores - thus keeping more heat in the bearings instead of transferring it away. Since I was thrashing the car at the time it went south, the motor was already hot and excessive heat in the rod bearings could easily have started to make the oil wedge thin out. Then, since I was hammering it through an uphill turn and running higher rpms, I believe the oil both stacked up against the side of the pan and built up in the valve covers. This allowed the pickup to suck air for a heartbeat, and the excess heat in the bearings eliminated any margin for error. The result was fried bearings and enough debris to spread the misery around a bit.

So - assuming this is a correct analysis - then this time around:
- I've corrected the machining problem and should have better bearing-to-bore contact - plus the clearances are now on the tighter side so I'll get more consistant bearing crush - improving the contact even more.
- I'm considering swapping in a Milodon performance pan with some baffles to keep the oil in the right part of the pan.
- I'm still unsure about how to keep excessive oil from collecting in the valve covers unless I use restrictors, which I don't think are a good idea on a street motor - any ideas? (I wasn't running either a HV or HP pump - just stock Z-28 with a standard pressure spring)

Thanks again!



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Scott
'69 400SB, Richmond 5-speed
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