L5P Weakest Links

[kidturbo]

Had a customer hit me up recently about possibly marinizing an L5P. Looking for a solid 750hp setup for use in a lightweight pleasure craft.

After considering the cost of bullet proofing a LBZ/LMM to hold 800hp for 1000hrs, I had to consider that maybe it's time to finally test waters with the latest design. Plenty of note worthy upgrades like the oiling system, that takes many of the old failures points into account. We are considering starting with a new crate motor to get all the latest options.

So question is, what does everyone feel is the weakest hard parts to consider. What's been the piston failure rate would be my first concern..

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[1FastBrick]

The 2024 changes look interesting. I can't wait to see them getting turned up.

 

[2004LB7]

With the engine itself I've only heard of the turbo (Borg Warner) having a higher failure rate then the Garrett ones. Also the injector pigtails are supposedly having similar issues to the LLY's and can be replaced with the LBZ for better reliability. No idea on the limits of the internals.

How do you plan on powering it? LBZ ECM?

 

[kidturbo]

With the engine itself I've only heard of the turbo (Borg Warner) having a higher failure rate then the Garrett ones. Also the injector pigtails are supposedly having similar issues to tha LLY's and can be replaced with the LBZ for better reliability. No idea on the limits of the internals.

How do you plan on powering it? LBZ ECM?

Good to know on the turbos. The one thing we will likely change anyways due to power levels.

As for control, the latest aftermarket advances makes tuning easier and cheaper than going wirh the old plan best I can see.

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[Chevy1925]

Pistons are weak.

Fish out in cali makes updates injector connectors, highly recommend but won’t matter if you are going to Bosch or something for ecm control

You can spool up large turbos FAR sooner than n the rpm range than you can earlier years due to head flow. Case in point, a s472 will spool to 15+ psi at 1500rpm and starts building boost at 1200rpm.

That will make getting on the chargers easier but changes your rpm operating range too. May need to do a custom cam to push the power band up much higher

 

[JoshH]

The three things I've seen give the most problem on the mechanical side is pistons, main bearings, and lifters.

 

[TheBac]

What is it with GM and failing roller lifters?

Not good on failing mains, either.

 

[Bdsankey]

What is it with GM and failing roller lifters?

Not good on failing mains, either.

They took one part that hardly ever failed because it was so overbuilt and they made it a problem, gotta love it!

 

[Chevy1925]

What is it with GM and failing roller lifters?

Not good on failing mains, either.

Could be like the new dodges and have hydraulic lifters that are failing everywhere

 

[kidturbo]

That's certainly some new issues to consider then. I once ruined a set of LMM lifters by leaving them in a bucket out in the rain.. GM somehow topped this internally by screwing with the main galleys? Or did they change the lifters completely?

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[JoshH]

That's certainly some new issues to consider then. I once ruined a set of LMM lifters by leaving them in a bucket out in the rain.. GM somehow topped this internally by screwing with the main galleys? Or did they change the lifters completely?

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Lifters are a completely new design. They're similar to LS lifters that use a plastic tray to align the roller with the cam but still a solid roller.

The nice thing is the block still has all the features in place if you want to machine them for the old style lifters.

 

[TheBac]

Was just going to say that they are similar to LS lifters, which have problems with needle bearings and galling.

 

[kidturbo]

Ok, so two of the three biggest issues are easily fixable. Which leaves the main bearings. What's everyone's findings been pointing to there?

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[JoshH]

I wouldn't say pistons are an easy fix since there aren't really any off the shelf options available. GM changed the wrist pin diameter and compression height on the piston meaning you can't use a 01-16 piston, and as far as I've been able to find, the only option is a custom made forged piston. We ordered a set from Ross last year, and it took them a solid 6 months to get them to us.

 

[kidturbo]

Got ya. The forged piston approach for marine use never got much traction. The only one I was involved with lasted mere minutes, and produced a 100% failure rate. The monotherm approach lacked any interest due to no real world need.

Is anyone exploring backwards compatibility with a rod piston combo yet?

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[Chevy1925]

I wouldn't say pistons are an easy fix since there aren't really any off the shelf options available. GM changed the wrist pin diameter and compression height on the piston meaning you can't use a 01-16 piston, and as far as I've been able to find, the only option is a custom made forged piston. We ordered a set from Ross last year, and it took them a solid 6 months to get them to us.

How much we talkin for height and wrist pin? Something that can be machined?

 

[JoshH]

Got ya. The forged piston approach for marine use never got much traction. The only one I was involved with lasted mere minutes, and produced a 100% failure rate. The monotherm approach lacked any interest due to no real world need.

Is anyone exploring backwards compatibility with a rod piston combo yet?

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We talked to a few companies about building a hybrid rod that would allow an L5P block and crank to be used in conjunction with 01-16 pistons, but we didn't have any luck finding anyone interested in building them for us.

How much we talkin for height and wrist pin? Something that can be machined?

Piston compression height and block deck height were both raised by 4.3mm, and wrist pin diameter went up to 36mm from 34.5mm.

 

[Dozerboy]

There's a local shop here that said they were going with a delipped LB7 piston in his L5P. I didn't even think about them not fitting when he mentioned it. I have to ask him if they found someone to make them or what.

Pistons is the only issue he has had. IIRC he's gone through 3 sets now and is running 100overs and a S476.

 

[Chevy1925]

We talked to a few companies about building a hybrid rod that would allow an L5P block and crank to be used in conjunction with 01-16 pistons, but we didn't have any luck finding anyone interested in building them for us.

Piston compression height and block deck height were both raised by 4.3mm, and wrist pin diameter went up to 36mm from 34.5mm.

Ah hell. Could probably bore the wrist pin bore out but raised piston height is an issue.

 

[Bdsankey]

We talked to a few companies about building a hybrid rod that would allow an L5P block and crank to be used in conjunction with 01-16 pistons, but we didn't have any luck finding anyone interested in building them for us.

Piston compression height and block deck height were both raised by 4.3mm, and wrist pin diameter went up to 36mm from 34.5mm.

I'm surprised Wagler didn't jump on board for that.

I wonder if D&J would do it? I know they made the very limited runs for Dustin Mintern where he copied the CP hybrid setup but used D&J rods, D&J FSR pistons, total seal rings, and trend pins.