To build or not to build?

[Bateman1lml]

Hey guys. Recently snapped the crank in my LML. Going uphill pulling a 15000lb travel trailer (fifth wheel) not beating it at all. 5th locked under 2000rpm.

I can get my hands on an LML out of a tow truck with a cp4 failure and 350,000 Kilometres for $1000.

OR I can get one with 20,000 KM (allegedly) for $5000. If its worth mentioning this motor is out of a military truck.

My question is should I grab the high K motor and put the alternate fire cam in. Pin the crank and hope for the best OR just pay the 5 grand and stab it in the truck and go?

My motor now is studded and deleted so I’ll obviously swap the studs over into whatever I end up getting and put a fresh set of gaskets in it. Any input is appreciated!

 

[Ridin'GMC]

Get the engine with the cp4 failure and rebuild it with Callie's compstar crank, along with the stuff you have on your current engine. You're more than likely to go through a snapped crank again if you take the complete drop in engine.

 

[Chevy1925]

Eh I wouldn’t say you are more likely to loose a crank by going with the high mileage motor. The 20km one could do the same.

I personally would do the 20km one if it really is in good shape and out of the military truck.

 

[2004LB7]

Really depends on how good shape or how well they are cared for. Hard to tell from over here.

You know how the 350 motor died so it wouldn't be much to swap over your fuel system over to it and get it running. What is wrong with the military one that it's being sold?

For used motors keeping the same crank, I'd skip the alternate firing cam.

 

[TheBac]

Use the $1000 engine. Swap all your current parts over. Simplest, least expensive way to go.

 

[Bateman1lml]

Really depends on how good shape or how well they are cared for. Hard to tell from over here.

You know how the 350 motor died so it wouldn't be much to swap over your fuel system over to it and get it running. What is wrong with the military one that it's being sold?

For used motors keeping the same crank, I'd skip the alternate firing cam.

The motor in the military truck hasn’t been heard running. The guy that has it says he has no reason to think it doesn’t. Says come on over if you get it fired up and you’re happy with how it sounds 5 grand takes it.

You think skipping the alt firing cam just because that crank has already taken its beatings and wont make much difference anyway?

 

[Bdsankey]

The motor in the military truck hasn’t been heard running. The guy that has it says he has no reason to think it doesn’t. Says come on over if you get it fired up and you’re happy with how it sounds 5 grand takes it.

You think skipping the alt firing cam just because that crank has already taken its beatings and wont make much difference anyway?

The current crankshaft in either engine has already been work-hardened to the OEM firing order. Changing that firing order now tires to essentially re-work harden the crankshaft to another pattern.

IMO I agree with them, skip the AF cam. Pin it, shim the oil pump, and run it if you're going to put the used motor in as they are. If the military engine truly has 20,000km (12k miles) I would buy that and maybe do a CP3 conversion.

 

[Bateman1lml]

The current crankshaft in either engine has already been work-hardened to the OEM firing order. Changing that firing order now tires to essentially re-work harden the crankshaft to another pattern.

IMO I agree with them, skip the AF cam. Pin it, shim the oil pump, and run it if you're going to put the used motor in as they are. If the military engine truly has 20,000km (12k miles) I would buy that and maybe do a CP3 conversion.

Yeh I think I’m just going to use the tow truck motor. Much cheaper and like said before. Crank could snap in either one.

Looked into shimming the oil pump. I live in a cold climate in the winter and apparently it could blow the o ring out of the oil filter if not plugged in over night? Who knows.

Any thought on using a used LBZ cp3. Theres one for sale near me with 93,000k on it then just buy the conversion kit. Is there a kit that doesn't require tuning if I’m going to do that?

 

[Bdsankey]

Yeh I think I’m just going to use the tow truck motor. Much cheaper and like said before. Crank could snap in either one.

Looked into shimming the oil pump. I live in a cold climate in the winter and apparently it could blow the o ring out of the oil filter if not plugged in over night? Who knows.

I have not had that issue and I live in Upper Peninsula of MI/Northern WI where we see -20°F to -40°F temps in winter. Run a good oil (we run 5W40 in winter months) and you'll be fine. A quality synthetic 15W40 should suffice too, just let it warm up before driving the truck.

Any thought on using a used LBZ cp3. Theres one for sale near me with 93,000k on it then just buy the conversion kit. Is there a kit that doesn't require tuning if I’m going to do that?

Personally I wouldn't buy a used CP3 when you can buy a brand new Bosch/Exergy/S&S for around $1100 no core as I'm not one to gamble on something that takes hours to change. If it was a dual pump application then sure as it takes ~30min to change that pump but the engine mounted pump can be a pain depending on piping etc.

There are "no tune" required conversion kits but you MUST use that specific pump, not a generic Duramax CP3. To my knowledge you cannot buy a "no tune required" CP3 conversion without that pump.

The only kit I've personally had be "tuneless" when advertised is S&S. I have some shop friends who've used another kit but I refuse to do business with that company due to their shady antics.

 

[Bateman1lml]

I have not had that issue and I live in Upper Peninsula of MI/Northern WI where we see -20°F to -40°F temps in winter. Run a good oil (we run 5W40 in winter months) and you'll be fine. A quality synthetic 15W40 should suffice too, just let it warm up before driving the truck.


Personally I wouldn't buy a used CP3 when you can buy a brand new Bosch/Exergy/S&S for around $1100 no core as I'm not one to gamble on something that takes hours to change. If it was a dual pump application then sure as it takes ~30min to change that pump but the engine mounted pump can be a pain depending on piping etc.

There are "no tune" required conversion kits but you MUST use that specific pump, not a generic Duramax CP3. To my knowledge you cannot buy a "no tune required" CP3 conversion without that pump.

The only kit I've personally had be "tuneless" when advertised is S&S. I have some shop friends who've used another kit but I refuse to do business with that company due to their shady antics.

The problem is I'm in Canada so $1100 US is 6.6 Million Canadian Dollars lol. Thanks for that info though I didn’t know that you had to use that specific pump to not have to tune after. Might just throw that exergy metering valve in and hope for the best.

 

[Bdsankey]

The problem is I'm in Canada so $1100 US is 6.6 Million Canadian Dollars lol. Thanks for that info though I didn’t know that you had to use that specific pump to not have to tune after. Might just throw that exergy metering valve in and hope for the best.

I think that's about what, ~$1500CAD?

So a $1799 CP3 conversion kit would (with Sportsman) would put you around $2500CAD...... Ouch on the conversion rate

 

[Bateman1lml]

I think that's about what, ~$1500CAD?

So a $1799 CP3 conversion kit would (with Sportsman) would put you around $2500CAD...... Ouch on the conversion rate

Haha yup. Plus shipping and duties. It’s about 3 grand all said and done. Now you can see why I’m trying to be a cheap ass and but used LBZ pumps and what not.


Sent from my iPhone using Tapatalk

 

[Chevy1925]

The current crankshaft in either engine has already been work-hardened to the OEM firing order. Changing that firing order now tires to essentially re-work harden the crankshaft to another pattern.

IMO I agree with them, skip the AF cam. Pin it, shim the oil pump, and run it if you're going to put the used motor in as they are. If the military engine truly has 20,000km (12k miles) I would buy that and maybe do a CP3 conversion.

According to Jon’s research and findings, it’s not “work hardened” and adding the AF cam would not increase any risk to the crank, it only decreases it. If the crank already is fractured, there is no saving it though.

It’s not like a diff gear that does get work harden and create a pattern and changing that pattern can cause issues, noise or pre-mature wear. It’s like telling someone to NOT balance the rotating assembly on a used crank because it’s been ran that way for years. Balancing it only helps it

I personally don’t see a reason not to if it’s in the budget.

I wouldn’t shim the oil pump. We aren’t looking for more pressure, we need more volume out of the oil pump and that pump already pushes 10% more than prior years. When the oil gets hot and no longer sits against the oil relief valve, shimming it doesn’t do much. Now on a street/race engine that may run cooler thermostats or is typically ran cooler under full load for short spurts, the shimmed valve won’t hurt (till an oil galley plug pops out lol) as you can have higher pressure on your mains and rods but reality, you don’t gain much other than more oil pumped out of the pan into the heads and working the oil more.

 

[Chevy1925]

The reason the tuneless are out there is due to the regulator. If you can source the regulator s&s uses, you can make it work.

Otherwise put a lbz in with lbz regulator and put the time in to tune it.

 

[Bateman1lml]

According to Jon’s research and findings, it’s not “work hardened” and adding the AF cam would not increase any risk to the crank, it only decreases it. If the crank already is fractured, there is no saving it though.

It’s not like a diff gear that does get work harden and create a pattern and changing that pattern can cause issues, noise or pre-mature wear. It’s like telling someone to NOT balance the rotating assembly on a used crank because it’s been ran that way for years. Balancing it only helps it

I personally don’t see a reason not to if it’s in the budget.

I wouldn’t shim the oil pump. We aren’t looking for more pressure, we need more volume out of the oil pump and that pump already pushes 10% more than prior years. When the oil gets hot and no longer sits against the oil relief valve, shimming it doesn’t do much. Now on a street/race engine that may run cooler thermostats or is typically ran cooler under full load for short spurts, the shimmed valve won’t hurt (till an oil galley plug pops out lol) as you can have higher pressure on your mains and rods but reality, you don’t gain much other than more oil pumped out of the pan into the heads and working the oil more.

I kind of thought it was weird the whole “work hardened thing” never heard of that before but hey Im for sure no expert. The way you put it with the diff thing makes sense. The motor I’m likely going to use has 400,000 tow truck KM on it (250,000 Miles)

Its cheap. I think maybe pin the crank. And put a cp3 in it and hope for the best is what I’ll do. Like everyone says. Could last 400,00 more. Could last 40. So F it Im going to give it the old collage try.

 

[Bateman1lml]

The reason the tuneless are out there is due to the regulator. If you can source the regulator s&s uses, you can make it work.

Otherwise put a lbz in with lbz regulator and put the time in to tune it.

Yeh I figured that because of the extra pressure. Ever heard of anyone using a regulator that worked?

Its got a motor opps tune in it currently and our local tuner guy is awful. You ask for a small tune and he Puts 250hp tune in and blows trucks up. Seen it happen multiple times so thats why I would like to avoid that.

 

[Chevy1925]

Yeh I figured that because of the extra pressure. Ever heard of anyone using a regulator that worked?

Its got a motor opps tune in it currently and our local tuner guy is awful. You ask for a small tune and he Puts 250hp tune in and blows trucks up. Seen it happen multiple times so thats why I would like to avoid that.

Nope, never have but I bet it can be done

 

[Bateman1lml]

According to Jon’s research and findings, it’s not “work hardened” and adding the AF cam would not increase any risk to the crank, it only decreases it. If the crank already is fractured, there is no saving it though.

It’s not like a diff gear that does get work harden and create a pattern and changing that pattern can cause issues, noise or pre-mature wear. It’s like telling someone to NOT balance the rotating assembly on a used crank because it’s been ran that way for years. Balancing it only helps it

I personally don’t see a reason not to if it’s in the budget.

I wouldn’t shim the oil pump. We aren’t looking for more pressure, we need more volume out of the oil pump and that pump already pushes 10% more than prior years. When the oil gets hot and no longer sits against the oil relief valve, shimming it doesn’t do much. Now on a street/race engine that may run cooler thermostats or is typically ran cooler under full load for short spurts, the shimmed valve won’t hurt (till an oil galley plug pops out lol) as you can have higher pressure on your mains and rods but reality, you don’t gain much other than more oil pumped out of the pan into the heads and working the oil

 

[Bateman1lml]

What about fluid dampers? Anybody ever have luck with them?

 

[Bdsankey]

According to Jon’s research and findings, it’s not “work hardened” and adding the AF cam would not increase any risk to the crank, it only decreases it. If the crank already is fractured, there is no saving it though.

It’s not like a diff gear that does get work harden and create a pattern and changing that pattern can cause issues, noise or pre-mature wear. It’s like telling someone to NOT balance the rotating assembly on a used crank because it’s been ran that way for years. Balancing it only helps it

I personally don’t see a reason not to if it’s in the budget.

On some of our military applications (C7) we've seen microcracking that showed evidence of long term work hardening when sent to a metallurgy lab (both internal and external labs). I haven't sent any of these cranks out for testing that have snapped but the grain structure shows evidence that it's certainly possible. Good to know that Jon has taken the time to dig into it, saves me time and money haha. Learn something new every day right?

I wouldn’t shim the oil pump. We aren’t looking for more pressure, we need more volume out of the oil pump and that pump already pushes 10% more than prior years. When the oil gets hot and no longer sits against the oil relief valve, shimming it doesn’t do much. Now on a street/race engine that may run cooler thermostats or is typically ran cooler under full load for short spurts, the shimmed valve won’t hurt (till an oil galley plug pops out lol) as you can have higher pressure on your mains and rods but reality, you don’t gain much other than more oil pumped out of the pan into the heads and working the oil more.

This is why all our built motors get threaded plugs. Agreed on the cooler oil temps tho, it won't make a major difference when the oil is hot & thin.

Nope, never have but I bet it can be done

I wonder what reg is being used? Obviously it's a modded reg but to what extent I don't know.

What about fluid dampers? Anybody ever have luck with them?

They're my personal favorite damper. I have no evidence to back up my opinion other than I think they offer the best damping performance as they "self adjust" to what is needed at that RPM/condition. They are the balancer I install on stock or built engines here if given the choice.