Cylinder 5 Missfire and Balance Rate 15 Bad Injector??

[Chevy1925]

cyl 5 for sure should have had the piston kiss the crank. no broke bits or cracks from it? mine broke a piece off.

the actual difference has never been proven. its been said about 5-10% improvement over LBZ/LMM but ive seen both make the same power with no issue.

 

[04LB7yz]

theres a very small "smear" of aluminum on the edge of the piston. It is not near as bad as IKEG's photo. I can get pictures later. I think I am going to pick up the used set of LBZ rods and balance the assembly.

Is it worth deliping my pistons? Should I be concerned with the higher 17.5:1 compression ratio with my LLY pistons? I can get a new set of loaded MAHLE pistons for $800 but I believe these are factory replacement pistons that would still be at that 17.5:1?

 

[Bdsankey]

theres a very small "smear" of aluminum on the edge of the piston. It is not near as bad as IKEG's photo. I can get pictures later. I think I am going to pick up the used set of LBZ rods and balance the assembly.

Is it worth deliping my pistons? Should I be concerned with the higher 17.5:1 compression ratio with my LLY pistons? I can get a new set of loaded MAHLE pistons for $800 but I believe these are factory replacement pistons that would still be at that 17.5:1?

The mahle factory replacement piston will be the same compression ratio as factory. You would have to machine them or step up to the motorsport piston to drop compression ratio.

 

[04LB7yz]

Are the factory LLY pistons MAHLE? If I was to replace the one piston that hit the crank, would the MAHLE factory replacement be the answer?

 

[Chevy1925]

theres a very small "smear" of aluminum on the edge of the piston. It is not near as bad as IKEG's photo. I can get pictures later. I think I am going to pick up the used set of LBZ rods and balance the assembly.

Is it worth deliping my pistons? Should I be concerned with the higher 17.5:1 compression ratio with my LLY pistons? I can get a new set of loaded MAHLE pistons for $800 but I believe these are factory replacement pistons that would still be at that 17.5:1?

yes, very much worth delipping.

something you need to consider is piston to wall clearance. If you stick with the pistons you have and have the block honed, your piston to wall clearance will probably be in the .004-5 range (thats typically where ive seen them). you open this up and you will burn more oil than normal as well as might get some rattling or tapping noises when cold from piston slap.

new pistons will shrink that up about .001-2ish (closer to 1 be my guess) but cast is better off around .0015-.002 as they dont really grow with heat like forged.

if you are going to buy new pistons, i would say to have the block bored .020 or .040 over and get your clearances back. a bore and hone vs just a hone is not much more.

Are the factory LLY pistons MAHLE? If I was to replace the one piston that hit the crank, would the MAHLE factory replacement be the answer?

i know 06-10 are, i dont know if 01-05 are.

 

[TheBac]

I would not use a set of stock rods in the rebuild, no matter the model. Spend the money once, or spend more money later to rebuild it again...

 

[04LB7yz]

I do understand that putting a quality set of aftermarket rods is the correct thing to do.. but I really have no desire to put 5-7k into a truck with 220k that may be worth 12k. It had a good run and is on the downward slope. All of the work is being done myself and while I value my time, it is not the end of the world. Machine time is basically free as my father runs a high performance engine machine shop. He has done a few of these before but specializes in gas engines. All I am trying to do is be as informed as possible in order to make the best decision I can on getting this thing back up and running. I do not plan to add anymore power to it. The plan is to put it back together and use it to tow my tows around the country. With the occasional hurt feeling pulls here and there. The feedback on this site has been incredibly helpful to me over the years and appreciate everything you guys do for the industry and myself! :hug:

 

[Chevy1925]

if you go LBZ, just make sure you de-torque that tune a little more. at the rate you bent cyl 5, you can do the same to LBZ or LML rods.