Engine build LB7 with LML parts

[MAXX IT OUT]

I believe I have a cracked piston, oil coming out of the exhaust and tons of white smoke. I Replaced the turbo hoping that would fix it, but no. So tomorrow I am going to start to pull the engine. I read about one of Fleece's guy doing a LML short block with LBZ heads and was looking at doing the same thing, but with my block and heads. Question are the LB7 pistons stronger and now much horse can the LML rods stand up to. I would love to do rod, but don't have the money. Also how much diffrent are aftermarket rods from stock? Just different material and bigger oil passages?

 

[Kspen90]

lb7/lly pistons are the most tested and durable stock pistons. Im not sure about the lml rods, last i checked the lbz rods were still the best stock rods but i have been away for a bit. lbz rods are supposed to be good for 700rwhp iirc. Are you sure youve cracked a piston though? I dont really see that happening with just the edge juice unless you had an injector issue that caused it. Have you ran an injector balance rate test? Compression test? I would hate to see you rebuild your motor if you only have a cracked head or blown head gasket although burnt piston is a good possibility if you havent checked the balance rates. Personally, if i were in your position and in need of a rebuild, i would find a complete lly or lbz and do the swap to get rid of the bad injector design. How long have you had the truck?

 

[duramaxsandwich]

with a cracked piston you should have blown your oil fill cap off...

with twin pumps and a charger you're going to need rods at the bare minimum, and eventually pistons someday... dont waste a lot of money in a build with stock parts, just find a stock short block and put your heads and drive your truck until you can afford crower/carillo/etc... rods and do it right. trust me many of us have tried to get by cheap and a few make it but most end up spending more money in the long run.

 

[MAXX IT OUT]

I had the scanner on to clear a misfire code and one other code(can't remember what is was, I can check again) both were on #6. I looked at my injector balance and it was running around 7 with #6 running high until i hit the gas then it fell back with the other ones. I had just bought the truck had it for two days. It smoked like hell if you gave it much with the right foot. I was running it with LBF at 2 and power level at 0. There was no oil in the coolent, or coolent in the oil. At idle after the new turbo when in the truck was running a little ruff like a mild cam and a little haze, but after reeving it up then the white smoke and oil came again. The oil is come out of the drivers side uppipe.

 

[AubleAK]

Id think the balance rates would be much worse on a blown piston. When i dropped a valve my balance rate for the cylinder was 15.xx

 

[ikeG]

The max the ecm can read is 15.xx so if it was a piston, it surely would be reading maximum value.

 

[MAXX IT OUT]

Any suggestion on what is wrong? I am going to do anther rate test, and see how much blow by it has. Did you lose oil when you lost your valve? I would be more then happy if it was just a headgasket, injector cup, or a cracked head that way it will be running faster.

 

[Harbin_22]

Are you sure it is oil and not diesel with soot mixed in it

 

[paint94979]

Do a compression test.

 

[MAXX IT OUT]

It is oil, one of the probes in drivers side up pipe is not in there properly and oil is coming out of there as well as the rest of the exhaust. I just changed the oil, and it has lost around half a quart or more. As for a compression test how is the best way to do that? Can it be done through the OBD port or do I have to do it the old way?

 

[TheBac]

What are your plans for the truck in the future? What are your hoped-for power levels after you get the engine redone?

 

[Kspen90]

Are you sure it is oil and not diesel with soot mixed in it

It is oil, one of the probes in drivers side up pipe is not in there properly and oil is coming out of there as well as the rest of the exhaust. I just changed the oil, and it has lost around half a quart or more. As for a compression test how is the best way to do that? Can it be done through the OBD port or do I have to do it the old way?

http://www.duramaxdiesels.com/forum/showthread.php?t=2091

 

[MAXX IT OUT]

As always I like power, but i don't like fixing it all the time. I was looking for 600-700 HP, I just don't want to drop 7 grand into the engine right now. That was why i was wondering about the LML engine parts, especaly after just buy the truck.

 

[Kspen90]

I had the scanner on to clear a misfire code and one other code(can't remember what is was, I can check again) both were on #6. I looked at my injector balance and it was running around 7 with #6 running high until i hit the gas then it fell back with the other ones. I had just bought the truck had it for two days. It smoked like hell if you gave it much with the right foot. I was running it with LBF at 2 and power level at 0. There was no oil in the coolent, or coolent in the oil. At idle after the new turbo when in the truck was running a little ruff like a mild cam and a little haze, but after reeving it up then the white smoke and oil came again. The oil is come out of the drivers side uppipe.

I hate to say this but it sounds like the previous owner knew there was an issue and that's why he sold it. Sorry for you luck.

 

[MAXX IT OUT]

Yes I agree, but I think i still got a half way good dealt on it. I figured that out after he wouldn't return any calls, Joys of a dealer....Thanks for the link, if the compression checks bad the out she comes. Do you think a cracked head would leak that much oil. Right now my theory is that the oil cooling the bottom of the piston is going right into the combustion chamber, so there much be a big hole, but a cracked head would still read low on a compression test?

 

[MAXX IT OUT]

What are your plans for the truck in the future? What are your hoped-for power levels after you get the engine redone?

The biggest think is to get it running. Head studs are going on, going to cut the piston, main-studs, and key the cam and crank. All I would need is rods then I would be good, the key is good tuning and the edge shouldn't of been on the truck IMO with what it had done.

 

[MAXX IT OUT]

K I when down to my shop to night and ran it again. My snap on scanner read the injector rate as .2 to .4 on 1 to 3 and .4 to .6 on 4 to 8. The truck was running rough at idle and there was no major blow-by, but there also was no oil on the dipstick. The truck has studs and the was no pressure built up in the coolant system. Any other input... I am going to do a compression test tomorrow...

 

[TheBac]

As always I like power, but i don't like fixing it all the time. I was looking for 600-700 HP, I just don't want to drop 7 grand into the engine right now. That was why i was wondering about the LML engine parts, especaly after just buy the truck.

There's the real answer to my question. IMO, save your money and build it right the first time, or leave the truck stock.
As DmaxSandwich said, many of us tried to "cheap out" on our rebuilds, and it just doesnt work in the end, mainly because most of us then push the limits again. You must pay to play in the Duramax diesel game.
You've GOT to do a compression test before you do anything else. Hopefully its just injectors. Good luck to you tomorrow.

 

[MAXX IT OUT]

I just want to know where the oil is coming from...I hope I don't have to do a rebuild, I will do it, but I would rather drive it then to a rebuild. How bad is it to reuse a stud...

 

[bmos37]

The only time my motor had similar type issues is when I lost a turbo, when the turbo went, all the oil drained through the exhaust. Also which snap on scanner do you have? I have the one that is 2nd best not sure but I think it's a versus, anyways I have never been able to get correct balance rates with it.