well after putting in yet another set of bearings- short story ,

bought a forged ls2-370 boost motor- bearings didn't last the tuning part- pulled the pan and turned the crank 10 and put in new main /rod bearings, well got done tuning and brought it to the track- 2 passes- 9.7's and lost oil pressure again - well maybe I caught it sooner but the thrust bearing and 2/4main bearing are shot- copper everywhere. clearance was set at .0015 , not sure what might be the problem, I see in ls build manuals to hit the crank and "seat" the thrust bearings- I never did that--problem??? said to hit it in the forward direction last- any advice??? has arp main studs- I assume it was line honed- second it in a vette with a th400 conversion- could the driveshaft be driving it forward? the reast of the rod/amin bearing look ok-ie no copper but scarred

 

Normally after tapping the crank to set the thrust bearing you need to check the crank end play with a dial indicator. If you didn't check end play the thrust may have been too tight from the get-go.

There are a lot of things that can bite you in an engine build. If you are set on building the engine yourself, it might be worth the time to find someone that does it on a regular bases to work with you.

Sorry to hear you lost the engine. Great number for your run while it was running. Hope you get her going again soon.

 

I never checked the end play or tapped the crank to align the thrust bearings, why do you need to align the bearings?

 

This is a forged crank that has been turned .010"? Check the journal diameters with an outside micrometer in three locations 120 degrees apart on every main bearing and perform an indicator run out at every main bearing.
This will let you know if the crank is true and if the journals were machined within accetable tolerances. You should also check the bearing clearances, most use plastigage, I recommend using inside and outside micrometers or telescoping gages.
As Eric D said, you must also check you end-play and set it if necessary. How did the connecting rod bearings look when you took it apart?

 

it's a factory crank, the rods looked rough but no copper along with 1/5 main bearings, number 2/4 main bearing are "cupped" , they just fell out of the main caps

 

1a-play,

You might be better off purchasing a short block to build up. The ls2 has a cast crank, not a forged and with the damage it sounds like you have the short block might be the most cost effective means to get back on the track. Just my humble opinion.

 

I would also check the bearing housing alignment with a bore gage.

 

Something isn't straight to cause damage like your talking about.

Have the block line honed and have the crank checked for runout as well.

 

I bet it has something to do with your converter either not seating in the pump fully or ballooning from the power you're making. It takes on a round shape when you make big power and a 1/4" antiballoon plate has not been welded to the mating surface pushing the nub in the middle forward into the crank. Take or send the converter to a very highly qualified converter shop so they can check it for you or call them for the critical measurements so you can check it yourself. Need a very flat surface to measure it. We have a good shop here in Wichita, KS my friends and I deal with a lot and thats how I learned about converter ballooning. (Chance Racing Transmissions. This guy invented the bolt together converter) A friend of mine had a similar problem from his converter till Chance was able rebuild it. I think his was killing tranny pumps also and he was only in the 10's with a 383 till the fix.

 

If the converter is OK, are you running an aluminum block (block distorsion under extreme power), stock crank (deflection under power), good oil pressure through complete run, heavy detonation? You must be in the 800HP range to be in the 9's in the 1/4...
Another thing, make sure you don't have a pilot bearing installed in the back of the crank with an automatic converter.

 

:I do have a pilot bearing installed- what keeps the input shaft aligned if not installed, convertor is a yank and it's a rear mounted th400

 

I am mistaken, I was thinking the converter was on the flywheel of the automatics. Definately sounding more and more like you are overpowering your short block.

 

What does this mean?

 

I have no clue, I don't build or machine LS motors, I can't BS on the forum on this one

I do like post #9

 

Yes, it's balloning al the way from behind the torque tube to the crank, THAT ONE MADE MY HEAD HURT!

 

I still stick with my advice since you said "I assume it was line honed".

When you build an engine the last thing you ever do is "assume" something was done. Normally line honing isn't needed, but that's where I would start as well as checking runout on the crank to make sure it's not bent.

 

Is this an iron block or aluminum block build? If its iron, the crank is bent or twisted and/or the main bearing alignment is off, but if it is aluminum it could be that the block is flexing under this power level. What about the blower belt tension, too much will play havoc on the mains. Was this engine running prior to your possesion of it, sounds like from your original post this is the second car its been in? Very bad sign that it didn't make it through the tuning phase. Another long shot, but could the main caps be out of order? That will end your day in a hurry too. It would be good to know if a pro or amateur built this engine. Sell your bad parts to the obese IPUIG guy with the self portrait to recoup some of your losses so he can tell people he has something that makes power and breaks parts. He'd be the guy who drove a 6cyl Vette if there was such a thing...LOL

 

Blown,

First off I would suggest reading the rules of engagement for this forum. Making derogatory remarks about others here service no useful purpose.

In regards to your post, I understand that you are trying to help someone else, but unless you are supplying the information first hand I would suggest having links to your source of the supplied information. Have you ever played the campfire game where each person passes on a story that another has whispered to them? By the time the story makes it way around just a few folks its meaning has totally changed.

As far as if the engine were iron or aluminum, I'm not sure where you are getting this from, but I would be interested in any links talking about what you described.

 

If the engine in question is pushing the car into the 9's it is making pretty substantial power. It is my understanding that an aluminum LS block will only tolerate approx 800HP before it breaks. If this engine is in the neighborhood it may be suffering from block flex. When we build old school engines shooting for 1000HP+ we use block fill (concrete like substance) to stabilize the cylinders and block to prevent this phenomenon from leading to bearing and or block failure on an iron block. Everything I comment on I have first hand knowledge of or I will state it is only an opinion. I was just getting tired of the personal comments from one member, therefore the cheap shot. The original thread starter is making big power which causes weird problems those who aren't making will likely never see, like the ballooning of the torque converter. I am unfamiliar with the Auto trans setup on the Vette, but assumed the converter was on the flywheel as is the clutch on the 6spd. I currently street drive and race a Supercharged BBC capable of making in excess of 1200HP in race tune (850HP street tune) and have experienced much of what I've stated for potential problems this LS engine may be experiencing. I'm on my 5th blower engine in 15 years due to unique failures and when I can at least get someones gears turning maybe it will help save them time, money, and frustration. Most of my friends run high boost big and small blocks in as fast as low 7 second ET's.

 

Wow. It really sounds like you know little to nothing about the LS platform, or it's variants (other than it's an aluminum block)

A lot has changed in the last 20 years. Still filling the bottom end of a bored BB Chevy for stabilization? Check out the specs on a cast iron LSX block.....good for 2500 HP. Take a look around next time you go to the drag strip........things have changed.

By the way, the transmission is in the rear of a C5.