Sunyi

Recently, I had my 383 engine built by a machine shop based on a rotating assembly from Eagle

Went to the track this friday and on the end of the first pass, the engine started to make knocking sound.

Pulled the pan and found a spun bearing on the third journal from the front of the engine. The engine only has 140 miles on it and this is the second time i have to pull it.

The first time was because the same machine shop did a terrible job mounting the core plugs, the rear left one simply poped out during the camshaft break in:shocked:

I strongly belive that they did not check the bearing clearences, and just simply slaped the engine together.

What do you guys think that could have caused this faliure.

I now that I did not loose any oilpressure because I monitored the oil pressure guage during the whole run.

This is what it looks like:






[Modified by Sunyi, 9:58 AM 7/7/2004]

Corvette0096

Oil starved or the bearing where set up wrong or touqed down wrong.

FD2BLK

There are several reasons it could have hapened but most point to the motor assy. Improper cleaning would be a posibility that I would think of first. If you had a new rotating assy then I doubt it was a clearance problem. If they installed the cam bearings wrong then that could also cause a oil starve situation. I hate to say this and I know you probably already know but the whole thing needs to be torn down and cleaned before re-assy.


[Modified by FD2BLK, 6:51 PM 7/4/2004]

Sunyi

I do not think its oil starvation, the oilpressure did not drop during the run.
The rest of the bearings look just fine. Shouldent they also be badly damaged by starvation

The fact that the shop did a so so job with the core plugs tell me that the rest of the engine was done in the same manner.


[Modified by Sunyi, 1:58 AM 7/5/2004]

Sunyi

How can the cam bearings affect the oilflow to the main/rod bearings?

tjwong

The cam bearings are fed by the main bearings so even if the cam bearings we done wrong they would have went away long before the rod bearing. And there would have been problems before going 140 miles. I would be will to think that it was improper clearances, or contamination that caused the failure. What did the other bearings look like? You mentioned it was the third journal so that means it with either number 5 or 6. Which is close to the rear main cap. What did number 1 look like? If that one is wasted as well, it would be a sign of oil starvation as it is the furthest crank throw from the pump.

Sunyi

The bearing spun on cyl no. 3 (second on the driver side, from the front ), The Cylinder no. 1 bearing looks just as fine as the rest of the bearings.


[Modified by Sunyi, 4:54 AM 7/5/2004]

FD2BLK

Let me clarify "wrong", what I am saying is if they got any contaminants into the oil galleys while they where installing the cam bearings or cam then it can cause starvation problems. I have seen several problems with people posting a spun rod bearing after a cam install particularly with the LT1s. I still would be surprised if you had a clearance problem with a new crank and rods. I always check clearances on every motor I build and while I have only built 12 motors I have yet to see a problem with a set of bearings being out of spec. I did have a situation on one motor where the clearances where a little on the loose side but it was still with in spec.

tjwong

Contaminants, foreign material is the number one cause of bearing failure in engines or industrial bearing situations.

silver84

That picture is of a main bearing cap, or what?
How are main / rod bearings keep from spinning,
a mounting peg-hole, or just crush force, or whatever.
Sorry for bozo questions.

rick lambert

I feel your pain. Happened to me once-and once is one time to many. I suspect a bad rod journal. Usually contaminats will affect the bearing surface-but aren't normally the cause for a spun bearing. The other thing would be improper torque. Then again I usually put on a few more miles and changed the oil before putting the hammer down.

Sunyi

It is a picture of the rod cap.
The bearings are secured by a mounting peg-hole combined with crush force.

0ski_dwn_it

Good oil pressure doesn't mean good oil flow. Something people VERY often misunderstand.

If you have a bearing too tight, it will increase your pressure. Since pressure is just a reading of restriction.

Oil volume is a whole nother game. You can have very high pressure, and not any oil volume. And visa versa.

Also all too often people think a good machine shop can build a good motor. Most of the time these guys know how to machine a block, but can't put one together.

In this case with the freeze plugs, I would say they can do neither. I would get your money back and take it to a well known engine builder and have them do it after they check EVERYTHING.

Sorry to hear about your troubles.

Sunyi

I picked this particular machine shop because they do all the engine work including the assembly for the Swedish supercarmanufacturer called Koenigsegg. Took it for granted thar they knew what they were doing

The ting is that it was this new young guy in the company that did the assembly work on my engine.
When it was time for the pistons (hypereutectic) to be mounted, they called me and said that i got the wrong rings for my 0.030 hypereutectic pistons from Eagle, that the ring gap was to large

When I left the motor at the shop, I gave them the ring gap chart that i got from Eagle. It clearly stated that the ring gap should be no less than 0.0060" in a N/A street engine.

It was the right rings they had, but they wanted to install them with a 0.0025 gap and the rings were gaped to 0.0050". That is why they called me to say that i should order a new set of rings :shocked: :shocked:

I bet they also torqued the caps wrong as well :mad

By the way, what is the right torque setting for the rod caps? (Eagle I-beam rods whith ARP studs)


[Modified by Sunyi, 4:15 PM 7/6/2004]

Bruthish

Please excuse my ignorance on this subject...but if it had only 140 miles on the motor, shouldn't there be a "break-in" period before doing hard runs like that? Just curious....

jefft84

my vote is the rod is on backwards. If the rod/piston is in backwards the bearing will get crushed when torqued down causing premature failure. Could happen in 50 miles could happen in 500 miles depends how tough the bearing is. check the side of your rod for any scuffs from rubbing the crank or adjoining rod, that would indicate severe side load and explain it. This problem will not show up as an oil pressure loss at all.

Sunyi

The shop claimed that the engine could take full load after the initial camshaft break in because of the special cylinder henning process
Very well, I thought. It is their butt if it breaks.


[Modified by Sunyi, 9:12 AM 7/7/2004]

Sunyi

I have studied the rod cap and found that the metal is blue on the sides. I have also found traces of wear on the sides but when i took it of the rod, it was is in the same position as the other 7 rods.




[Modified by Sunyi, 9:38 AM 7/7/2004]

jburnett

I'm going to go with improper bearing setup... Did they mic the rod bores with and without the bearings? Did they torque the bolts or stretch them... Did the load and unload the bolts two or three times before they checked the clearances? And another important question: these are new rods, correct? New rods will shrink .0005" or a little more once they're run which if they're improperly set up (ie., too tight) they will certainly cause that problem.

To this day I am shocked at the machine shops who profess to be "performance machine shops" that are everything but...
-Jeb

devilfish

damn! I never heard of that Good point