Rod bearing failure again......

[Kjun]

So....engine was knocking. Towed it home and did a leakdown test to check the top end and it came out perfect (about 10% leakdown on all cylinders). I cut open the oil filter and sure enough......... it looked like a metal snow-globe. Since my stock pistons, rings and heads are working great, what's the cheepest and best way to ensure I don't have another case of rod bearing failure? My tune is good, so it's not that.

Couple of questions.....
Anyone think I should use new K1 rods next time, and just grind my stock crank? It was untouched. Do K1's have press fit pins for use with stock pistons? What are the best bearings to use? Will the rotating assembly need to be balanced with K1's? I shut it down right away, so I might be able to get away 10/10 or 10/0 under. Any suggestions?

Thanks, R.

 

[KevinB]

Did you measure the crank and rod bearing clearances? Correct torque on the rod bolts, what kind of bolts did you use?

 

[turbo nasty]

What he said....What was the clearances?

 

[Kjun]

I know I'm going to get a lot of heat for this, but I'm a Chevy builder, so I used the old standby "Plastigauge"...............the spec came out within Buick tollerance though. Arp rod bolts torqued to spec..........I think around 70 ft/lbs. Fire away.....this is the third time I've spun a rod, so I could use a good thrashing.

 

[KevinB]

So, you probably did not check the big ends for roundness. Did you have them resized after the last rod knock? What about the crank?

 

[bison]

I know I'm going to get a lot of heat for this, but I'm a Chevy builder, so I used the old standby "Plastigauge"...............the spec came out within Buick tollerance though. Arp rod bolts torqued to spec..........I think around 70 ft/lbs. Fire away.....this is the third time I've spun a rod, so I could use a good thrashing.

You think 70 ft lbs with a stock rod?

 

[DR BOOST]

i thought it was around 40 for rods

 

[turbofabricator]

Sounds like you need to have all the parts machined by a competent machinist. Using plastigauge is fine. Modify the timing cover and get the oil pressure right. Do NOT re-use the factory oil cooler, as there is not way to completely remove debris from it. I would suggest using new K1 rods and a new steel crank, but the stock crank is ok IF machined correctly. While you are at it, you might as well buy a complete rotating assembly and do it right. What mods have you done to the timing cover? What was oil pressure on start-up? Make SURE the engine is well cleaned after a bearing failure. Check your turbo bearings now, too. Usually that much bearing material will take out the turbo thrust. Have the turbo drain tube cleaned out, too. All the ridges inside will collect bearing material. kinda like a sluice box for a gold miner.

 

[bison]

Post pictures of you bearings as they sit in the caps and registers they were run in

 

[gnbeginer]

I have a set of speed pro stock replacement pistons (std bore) i'll sell ya cheap if ya need or want em. I am not gonna use them.

 

[Kjun]

Nick at Arizona GN is going to build me a shortblock. Wiseco .020 over Forged pistons, K1 rods, stock crank, new cover and HV pump.......... This time I'm going to allow an expert to step in.

But thanks for the offer....

Cheers, R.

 

[turbofabricator]

Nick WHO???? Oh that young guy in Arizona that use to build wagon wheels for the Pony Express. What does he know about a modern Buick V6 engine?

Nick's a good guy. Glad to see you went with a knowlegable builder. That will save you a TON of headaches.

 

[DR BOOST]

problem solved /thread