LMM Stock Bottom End Limits

[PACougar]

My buddy's getting a 08 LMM and starting in the winter we'll begin "modifying it". I'd like to know what you guys think a reasonable limit for a DD and a reasonable limit for the track would be? I'm not interested in what I should do to achieve the power, just in your experiences with LMM's what can they take without digging into the bottom end. Thanks for all of your help!

 

[arneson]

Fronts whatever i have neen involved with, and talkin with people in tuning its more keepin the tq under 12-1250ftlbs. But many have 6-650hp, not sayin its goin to last a long time at that level. Its kinda like anything, some hold it for along time, others break at close to stock. Good Tuning helps a ton tho.

 

[Bonestock]

Fronts whatever i have neen involved with, and talkin with people in tuning its more keepin the tq under 12-1250ftlbs. But many have 6-650hp, not sayin its goin to last a long time at that level. Its kinda like anything, some hold it for along time, others break at close to stock. Good Tuning helps a ton tho.

I would agree with 650 being a number of reason. It will not last forever @ this level but has proven to many including myself that it will will last a while. A couple of dmax's in my area have lasted for 40,000 miles @ this level & still going strong.I really think the torque below 1200 plays a huge roll in this.

 

[DuramaxPowered]

600RWHP is about all the more I'd push it you wanna do it with any reasonable amount of reliability.

 

[hondarider552]

With the known issues the LBZ/LMM's have with pistons, personally I wouldnt push it over 500rwhp and it will live just fine.

 

[Harbin_22]

Tuning and keeping EGT's and drive down are key in my opinion. Mine has handled a lot of abuse over the last couple years and the last couple months at 700+

 

[PACougar]

Thanks guys, I'm thinking I'll set it up for 550 on the street and maybe 650-700 only at the track. As far as egt's go what appears to be the safe range for these LMM pistons, both as a peak and as a constant?

 

[Bonestock]

The highest I have hit has been 1400 for short period of time. I have plenty of air just need more fuel but I am chicken!

 

[arneson]

I know what i mean by being chicken. I also need fuel. Lol

 

[Harbin_22]

I buried a 1600 gauge a time or two sled pulling but now I don't like it going past 1400.

 

[Dirtymaxx03]

600rwhp and 1200 ft lbs is about all you wanna push any dmax. After that its a toss up if your lbz/lmm is gonna have pistons for long or if your lb7/lly rods are gonna bend.

And i bury a 1600* gauge all the time

 

[JustinD]

Rich Stanley made 637 with a Cheetah, CP3 X2 and 65% over sticks on a stock motor. Tony tuned it, ran beautiful.

 

[coker6303]

I don't think the HP level is as much of a factor on LMM/LBZ pistons cracking, the heat is the biggest culprit.

It would be better to push 650hp at 1400deg than 500 at 1600+deg.

There are quite a few 700hp LBZ/LMM motors. The stock rods seem to hold pretty good. The pistons are like duck duck goose...you either have one that fails pretty quick or last a long time.

 

[JoshH]

I cracked a piston in my truck when it was stock with twins. EGTs never got over 1350 after I put the twins on, and they had been on for over 10k miles when it cracked. I don't think EGTs are the problem.

 

[coker6303]

Think it's just a crap shoot all together on the pistons?

 

[Bonestock]

I don't think the HP level is as much of a factor on LMM/LBZ pistons cracking, the heat is the biggest culprit.

It would be better to push 650hp at 1400deg than 500 at 1600+deg.

There are quite a few 700hp LBZ/LMM motors. The stock rods seem to hold pretty good. The pistons are like duck duck goose...you either have one that fails pretty quick or last a long time.

Now I have all the confidence in the world! Here come the dual c's! Lol!:thumb:

 

[Chevy1925]

IMOP, heat, cylinder pressure, timing, pulse width, and strength of the piston all play a big part if you have a motor that will hold together at high HP. Guy once told me "if you have a lbz/lmm, run it at 600hp and enjoy it, if you have LB7/LLY run it at 500hp and enjoy it". Obviously, you need a tune built to help the reliablitly side of that HP you want but it dont garentee anything.

If you push it over what most run, you better subconciously tell yourself you will be building a motor or pullin the old one for another. You start flurting with high HP and all bets are off.

 

[trailler2004]

Guys...i read all this thread...am i crazy for doin 71.5 mm turbo...60 over exergys...dual pumps..manifolds and up pipes..vavle springs on my stock lmm bottom end and hoping it will survive 6-8 months til i can afford to build another shortblock??

 

[PACougar]

Yes, you are crazy!

 

[Lbzmax90]

Guys...i read all this thread...am i crazy for doin 71.5 mm turbo...60 over exergys...dual pumps..manifolds and up pipes..vavle springs on my stock lmm bottom end and hoping it will survive 6-8 months til i can afford to build

How hard do you beat on it??