Advise needed: serious issues with mechanic

[S2central.net]

Sorry if I'm being a bit thick here, but isnt the torque setting more about controlling the loading on the bearing shells than any special consideration for the conrod bolts ?

Hence why Audi says 30Nm to take clearance measurements, then another quarter turn to finish them off.

[GazzaG60]

there is always a risk with engines. usually a risk assessment is taken. time/money against chance of a failure. id expect the shop to have done all the checks but as you will know thats not always the case. there was a thing a few yearsd back where one of if not the biggest subaru engine builder in the states had a few failures on thei hands. it turned out they had the blocks pre-sleeved prior to pistons being measured. that created a few slappers of the non female type.

id have the rods checked by another machnie shop for tolerence to to the documents and go from there. if they are reported as ok then id speak to the builder.

it wont be easy. engine failures are easy for a builder to evade.

[GazzaG60]

did the enginme builder use build lube and was the oil pump lube packed to ensure good oil pressure from the first turn.

[A80Avant]

you dont need any balancing to be done if you are only changing rods. if you had so big weight difference between rods then you would have heavy vibration from the beginning,isnt that right? you would know that something is wrong

[driftin jo]

Is this guy an engine builder or just a “mechanic” I don't thing a general mechanic should build engines.
Engine builders should be have a machinist back ground in my opinion , if he had, he would have
used plastigage and measured every time as it would be in his nature to do this .
The fact that he admits he did not use plastigage and says you don't need to is proof enough for me that he should not put engines together and that said I would not go back to him for more work.

Not sure how you stand legally as it can be hard to prove things , unless you measure the crank journal and bearing and find a large clearance between them as Knight Rider S4 mentioned in post #15, if that was the case then maybe you could prove he was incompetent .

The fact is that when you replace bearings regardless of whether or not you change the rods you should always measure every thing and use plastigage as you don't know If the crank had been reground in the past before you owned the car/engine. If the crank has been ground in the past then it would probably be 0.010” / 0 .25 mm smaller than standard possibly even more.

[Jamo]

you dont need any balancing to be done if you are only changing rods. if you had so big weight difference between rods then you would have heavy vibration from the beginning,isnt that right? you would know that something is wrong

Scat rods are notorious for being unbalanced out the box, you do not want an unbalance set in the engine

[surprise]

Very interesting input "driftin_jo"
Thank you for your help
The thing is that I do not want to pay for a performant engine builder to repair the expensive mess.
I believe that my mechanic should fix it and assume the labor part of it.
But if he does not know how to do it, it is a difficult decision.

[AUDIS2avant]

Did you supply the bearings to the shop also?
It could be that either he messed up the tightning or used the wrong bearings.
Seen before.
As the engine worked fine before, then he could have used the measure on the old bearings for the new ones.
BUT, normal, on a used engine, you ALWAYS measure the thickness on the cranck BEFORE choosing the new bearings.

[surprise]

I just gave him the rods, he supplied all the other hardware. He said he is sure his bearings were fine.

[jade]

Very interesting input "driftin_jo"
Thank you for your help
The thing is that I do not want to pay for a performant engine builder to repair the expensive mess.
I believe that my mechanic should fix it and assume the labor part of it.
But if he does not know how to do it, it is a difficult decision.

Look mate if he can,t do it the first time, what makes you think he will succeed a second time

[A80Avant]

Scat rods are notorious for being unbalanced out the box, you do not want an unbalance set in the engine

Where did you hear that and where is the evidence for it?

checked mine and they were spot on. 034 also claim they are correct and within limits.

[S2central.net]

This is a very bad situation... could be a fault with rods or bearings - or it could just be the excessive torque that squirked the crank. Either way - any decent engine builder would have measured the clearance - before and after the rod swap.

[AndyP]

I just gave him the rods, he supplied all the other hardware. He said he is sure his bearings were fine.

Do you know that your crank is std size or has it already had a re-grind? Did your mechanic check this before ordering the bearings? If not he could have ordered the wrong size.

[GazzaG60]

scats i have always been told are not too bad. suppose it depends on the set. i had mine weight matched anyway. not worth not doing it. the engine feels smoother if its balanced.


the lube i ask about is on the shells. the rods come supplied with arp lube. i use moreso IIRC red lube on other moving parts and in the oil pump.

it may be asimple case of not using lube and the oil if used has run dry creating the start of the end on first start.

[Elio]

.damaged crank bearings...

well....sometime i think we fly to high with the car technic...i have seen in this thread even the miss balancing the rods could damage the crankshaft....let's stay a little beat with the feet in the floor..
somebody wrote.. maybe the problem is in the bolts torque
somebody point the finger to the plastigage procedure missing..but..are we shure that the bearing was the correct measure for the crankshaft journals..?I mean..most of us don't use to plastigage the work before tight the rods..and the engine..especially those who runs at max 7000 rpm are stil running....after that the machine shop can tell what happened exactly..it's enough to bring the damage shaft,the rods,the bearing..