Bearing damage analysis

[Cammer]

The only facts you have are that you ran a dyno test!

You do not know if engine was assembled correctly.

You do not know what clearances engine was assembled with.

Your responsibility rests only within the confines of the dyno test.

It is much easier to build an engine correctly than figure out what killed it!

[roger]

Just out of curiosity, how many above that swear to the clearences being .0012 per side on the rod (.0024) and .0014 per side on the mains (.0028) being just perfectly fine, have actually built or build Pontiac and Oldsmobile engines that dyno out at 500 plus HP and see frequent bursts of rpms in excess of 5000?

Clearances killed my last engine , my builder stated that regardless of bearing diameter rod or main an .002 rod and .0025 main was suitable.
Side clearances was another matter altogether, I am looking for another builder .
Does main and rod journal size dictate how large a clearence there should be as well as side clearance?

[Engguy]

Just out of curiosity, how many above that swear to the clearences being .0012 per side on the rod (.0024) and .0014 per side on the mains (.0028) being just perfectly fine, have actually built or build Pontiac and Oldsmobile engines that dyno out at 500 plus HP and see frequent bursts of rpms in excess of 5000?

Clearances killed my last engine , my builder stated that regardless of bearing diameter rod or main an .002 rod and .0025 main was suitable.
Side clearances was another matter altogether, I am looking for another builder .
Does main and rod journal size dictate how large a clearence there should be as well as side clearance?

Yes it does. For granny engines (everyday drivers zero performance)
around .001 per inch diameter of journal. For performance
engines .0015 per inch diameter of journal. This can vary per application and the oil used.

[toddcalo]

Make sure you have the pickup tube coverd good, you stated the oil pressure dropped at higher rpm, Ive seen this happen when the the pickup isnt coverd good enough some of the after market stuff dosent do a very good job covering the pickup.

[Greenlight]

How much oil did you have in the engine?

Too much oil will cause aeration and allow and oil/air mixture to be pumped to the bearings.

[R.Brown]

Great discussion! Thanks for all the comments. I dyno'd another engine for the same shop yesterday, so I have a couple of updates.

The pickup was .375 from the pan bottom, it is a stock oil pan for a 79 trans-am... if that matters. Now whether the pan is flimsy under the pickup I don't know.

Sleeper Sedan, thanks for the ideas! They say that no plugs were left out, but they are going to run the oil pump primer with the pan off and see if anything is bleeding off / leaking. One of the first thoughts I had was that the lifter oil band may be uncovering during the lobe lift, but this is a popular combination for the pontiacs... no reason not to check it tho.
Regarding your query on the oil pressure, yes it started out at 20PSI, hot oil idle, then jumped up to 60 as the revs increased, then went back to 58 at the end of the pull.

Nich: that is a VERY interesting post, thanks for sharing it!

Tuner: One of the first things I asked was if the bearing radius' cleared... I was told yes.

Strange Magic: I appreciate your suggestions!! Your procedure is the exact one that they already do. The block had been line honed the first time, and now since the crank was ground again, they now have .0037 main clearance and .0032 rods. The crank grinder indicated the # 2 and # 3 mains had .001 runout before grinding. If that was from the heat, I have no idea... but I was told they had NOT checked that before assembly. ... this is a major development, as if it had that runout from day one.....

Also to Strange Magic (or anyone) Do you have a particular part number for the H or V series bearings? I do not have my clevite catalog handy, and this shop tells me that V's are not avail.

Also, what oil pump would you suggest with those clearances?

Hardcore, I value your input!! I will find out exactly the parts in the oil system, but the parts I do know of is the oil pan is stock '79 trans am, I believe the pump is a mellings, but will find out the p/n. The screen is stock replacement.

Ron C. - just as a side note, do you consider a 15W-40 with .0024 rod and .0028 main clearance to be to heavy weight? Thanks for your input!!

Engguy: The engine ran very smooth, in fact I commented on it before the trouble! The bearing wear definetly looks odd. I am still at a loss for the rod bearings on #1 and #2 looking so good... As I typed earlier in this post, the #2 and #3 mains were found to be .001 O.O.R., and whether this was before or after the bearing damage, I can't say, but I am not sure of any bearing damage issues what would CAUSE a crank to have runout.

thanks for all the ideas so far!!

rb

[R.Brown]

toddcalo & greenlight:

It took 5 quarts or so, and the dipstick said 3/4 full, and this is a stock pan / pickup arrangement, 1979 trans-am.

thanks!

rb

[Strange Magic]

R. Brown here is a few reads for you. This should help you understand the Pontiac and Olds engines:

http://www.oldsperformanceproducts.com/techarticles.asp

[rmbuilder]

R Brown,
Here are two files I have uploaded to Mediafire to help you determine the root cause. The are PDF versions of Bearing Failure Analysis Tech Papers.

http://www.mediafire.com/?cmzmjnwmngz
http://www.mediafire.com/?5jmzymlt4qm

Bob

[toddcalo]

When I say make sure you have the pickup tube coverd good what I ment is make sure you have a shield over the top of the pickup tube if its not coverd in some cases Ive seen the oil pressure drop like a rock at high rpm Ive seen the oil pressure in my buddys big block chevelle drop from 60 to 20 like you hit it with a hammer at high rpm all because the pickup tube wasnt shielded good enough. Took the motor out built a custom windage tray to completley cover the pickup problem solved.

And he was running a moroso pan, but the pickup tube was'nt coverd good enough (just somthing else to check)

[Maximum Race Engines]

Being a Pontiac guy myself, I will say this. The oil pressure sounds way too low to start. Pontiac oil pumps are high pressure, not high volume. As many Pontiac engines I have done, regardless of power, They were all 60-80 lbs cold. Hot never dropped 20psi, let alone 40lbs+, and with rpm will come back up. When an engine loses oil pressure at rpm, you have an oiling issue. Maybe running out of oil up top or the clearances are too loose, bearings going away, or the pickup is too close to the pan and sucking it up into the pickup shutting off oil, which I have seen, or too much cleanrance running out of oil, etc.. I normally stay at .0025" on these, rods and mains, and do not go .003" or more. .002"-.0025" is more than fine. As for cross drilled cranks, yes they have gotten a bad reputation, but they are fine and will only start to give you problems at higher rpms. I do not use them in anything 7,500 or more. Keep it below 7,000, and I do loosen the clearance a little, and they do live. I also run the 3/4 groove stuff bearing, as the lower bearing tends to acts as a wiper. The tails on the lower part have a smoother transition. If you run fully grooved, you will not have to open clearances up as it gets the volume it needs, but at high rpm it will still shut off oil to the rods, and will usually kill 7/8 rod bearing first. I try not to use them if I have to buy the crank new, but when the customer brings you a crank he feels was alot of money, and wants to use it, and you tell him no, then you just lost a customer. As for cutting a brand new crank, well if it has run out, which should be checked, ESPECIALLY with an Eagle crank, but really should be checked with any crank, if it needs it then it needs it. People have to realize just because it is new out of a box, regardless how much you pay for it, doesn't mean it is perfect. EVERYTHING needs to be checked. Pontiac's don't have the greatest oiling system, but for this to happen within a few pulls, there was an issue right off the bat, and only got worse the more you pulled it. Has nothing to do with type of oil. There was an assembly error from day one, that was overlooked while building it. I will not begin to try to give an opinion as I would need to see all of the parts, but Cammer hit it on the head..you do not know and may never know what the guy who built it did at the time of assembly. Everyone swears they did everything correct, but something caused this, it is not a parts failure. A good builder can look in all the right areas and the engine should be able to tell him but, sometimes it won't and you have to go on instinct and experience. Something went on not allowing the engine to rcve. proper oiling and can be a number of things. I would hope that when it was disassembled, that it was disassembled just like it was assembled, as you can't just throw parts over your shoulder and expect to see what happened, because you will miss all the signs. Pontiacs rcve. oil at the lifters first and mains last. The clearances were not an issue, although maybe a little on the high side, not enough to cause this. I am sure if they retrace their steps they will find it.

[Barry_R]

I've been watching this one. I was something of a second hand bearing guy for a while. Crank looked bent to me (likely your out of round). Since I've only "watched" a Pontiac motor being built I did not want to add any comments that I could not support.

Regarding clearances - - my old bearing engineer used to say that he got a lot of phone calls when they got over .003. If you got good info the clearances were not to blame. Serious race engines with lightweight cranks and such need added clearance due to the deformation of the crank and rods under pressure & RPM. This Poncho does not sound like it fits into that realm.

Too late to check it now - but some of those import cranks don't have a very good surface finish...could cause trouble too...

[putztastics]

I'd have to agree it is not a bearing clearance issue if the numbers were right.

Built a low dollar IMCA mod 3.9L V-6 Dodge with very tight bearing clearances, less than .001, it ran many laps at 6500+ without bearing problems. It was set up with a remote filter lines right out of the in/out holes under the oil filter base plate (a few 90 degree turns can be eliminated with this setup). After about 1/2 season and a couple seasons off the owner decided to put it in a new car and wanted to run the filter in the normal location. He put the plug under the oil filter base plate back in - in the WRONG hole - which should have shut off all oil flow. The engine was run that way testing the car ripping around in his corn field. When he started it at my place the engine idled but quit in a very strange way, like it was getting "tight". We pulled the oil filter base plate and put the plug in the right hole, restored oil flow, started the engine, it runs like nothing happened.

The point is engines can take a lot sometimes, if tight bearing clearances kill engines that V-6 should have died on the dyno. But it's still running.

I don't know Pontiac but every small block Mopar gets a drill bit through every oil passage, if nothing else this will verify the passages are full diameter their entire length.

I'd study the oil system from pump suction to bearings, you'll see where problem areas are.