LB7: Cracked piston?

[djms]

Hey guys I think I got a cracked piston or something along that line. I got lots of blow by at the filler cap and my number six shows a balance rate of
+15. This happened about 2-300 miles after gm replaced my injectors, but anyway I dont have the money to have someone else fix it. I am wanting to start tearing it apart after Christmas. Is this a real tough job and any tips? How long do you think it will take to tear the engine out. And where can I get a piston and rings and whatever gaskets that I need? Can I go used on the piston to save money? Thanks James

 

[TrentNell]

Usually when a piston cracks it scores the block , which means alot more than replacing just 1 piston , hopefully the block is fine . It takes about 3-5 hours to pull the motor , i would atleast pull it and pull the heads and look inside to see what the damage is and go from there on whats needed .

 

[dmaxfireman]

you may have a poorly seated injector or cup as well

 

[dmaxfireman]

i had a copper washer fail and i could hear it leaking compression because my injectors are on the outside of the valve covers yours are under the valve covers (hence possibly why you have pressure pushing out the fill cap)

 

[WolfLMM]

very uncommon to crack a LB7 piston.

 

[djms]

Is there anyway to know for
sure before I pull the motor??

 

[Gmclbz]

If it is an injector issue then the dealer that installed them should fix it...

 

[Bako_Dmax]

With only 300 miles on the injectors from the dealer I would take it back to them and have them fix it.

 

[JD4440]

Most definitely take it back to them first man.

 

[djms]

The stealer said they done their job and they would have to charge me for any other labor. The truck runs it sounds terrible has white smoke out the pipe and cant hardly pull itself.

 

[rgullett83]

could do a compression check

 

[knagel]

I would atleast have them diagnose the problem. It may come down to them installing a faulty injector that caused your problem or it could be an install error on their part. The diagnosis may end up being cheap in the long run. If you are satisfied with the diagnosis and it is a cracked piston and nothing was caused by them, then atleast you know where you are headed and what you need to do.

 

[djms]

Thanks for all the replies. I will try the dealer again. Thanks James

 

[S Phinney]

If they check it for you ask the tech for a complete reading on all cylinders for cylinder pressures. If the piston is cracked they should be very little to no cylinder pressure on that cylinder. If it is an injector issue it should be at least 150 psi area on the cylinder pressure.

 

[Turbo Buick 6]

If you can get ahold of a good borescope pull the glowplug and take a looksy.

 

[djms]

Well I brought the truck to the dealer last week and they said it was an injector and that they would fix it. I was so Relieved!! Then today which is a week later the dealer calls bad news put the injector in. Same thing they said no compression cylinder 6. So I am on my way to town to get the truck and start tearing the motor out.

 

[fast03]

that sucks. the bad injector could cause a hole in a piston.

 

[RKTMech]

That still sounds fishy as hell, the tech should have seen where he installed something wrong when he opened it up, and if he didnt find anything wrong you should have got a call before he put everything back together because at that point the ball would have been back in your court. That sucks, keep us posted what you find.

 

[Huntinducks82]

I would really question the work of the dealer on this one. Lb7 rarly crack pistons. I beleive it is a mistake on there part and that they should at least try a work somthing out with you to fix your truck. Good luck.

 

[djms]

I am thinking about swapping in another motor and then selling off parts from my engine. What do you think my injectors would be worth? They have less than 500 miles. I am wondering if I would be able to recoup any money with selling parts.