Engine Swap

[HondaBoi]

Hey everyone

All my work has been an exercise of absolute futility, sad to say its time to give up on the 5.3l LH6 in my 06 trailblazer EXT LT (its eating itself and refusing to run right.
Ive been trying to fix the motor but shes pretty screwed m8.
I want to put the cheapest LS based truck motor I can find off facebook market place, does anyone know what i would run into if i did that?

 

[TollKeeper]

Welcome to the Forums!

Your going to have to provide a bit more info. You have a LH6, which came in 2 variants.

Please provide your VIN, and Year.

What are your symptoms of present?

The LH6 is known to have a AFM/DOD issue, which I just went thru on my LH6 in my Saab. 350ish bucks later, and shes running great!

 

[HondaBoi]

I'll post the vin tomorrow, Its a 2006, EXT.

Its freshly put together. I put a ton load of work into it (bought truck with blown head gasket ran fine for being super thrashed)

I cleaned the whole DOD manifold and added a new gasket and lifters. Its ran like hot dog since i first turned the key after reassembly, had a compression issue but it was fixed with shorter push rods on one side. I was already at my limit trying to get the P0300 to go away, but now it cant run longer than 80 seconds before the oil sending filter gets clogged with metal bits.

I'm at my wits end with this thing, and im gonna need it come winter time

 

[TollKeeper]

If it's a 2006, you have a stop gap LH6, 24x. Same as my Saab.

So you need to find a LS that is 24x, cathedral ports. A AFM DOD engine is going to be a direct swap. A non AFM DOD engine will work, but you will have to send the PCM TCM out to get programmed for that no longer being in the system.

A L33 is going to be your best candidate. Aluminum block, non DOD AFM, just need a PCM TCM program

Now if you don't mind being a little lower on power, you could always find a LR4, which is a 4.8 LS. It's a direct swap, but would still need the PCM TCM programmed.

Yes you can go with a 6.0 LS. But you will end up blowing your transmission or your differential as it's not designed for that power.

You can not use any engine that is a 58x. Don't try.

This is a reference sheet from Summit Racing about the LS engine breakdown.

https://www.onallcylinders.com/wp-content/uploads/2018/04/05/LS-LT-Reference-Guide-Summit-Racing.pdf

 

[Mooseman]

If you are unable to find an LH6 aluminum block, an iron block from the same 24x cathedral port type will also work with DOD deleted from the tune. It's a direct swap except that the front end may drop a little due to the extra weight (150 lbs apprx). May be able to use a different set of springs or spring spacers to bring it back up.

 

[HondaBoi]

Thanks guys, I'm gonna tear my LH6 down first but yall have def made picking a possible replacement much less daunting

 

[northcreek]

shes pretty screwed m8.

 

[HondaBoi]

There's no way this thing will be drive-able without at least pulling the motor

 

[TollKeeper]

When you get ready to put it back together... Do yourself a favor and replace the oil pan side seal on the front differential.

Also, dont look for a LS V8 out of a FWD LS4 Vin code -C- car. Although the heads appear to be the same, the block is different.

Vin code refers to the sheet above, and the 8th digit of the VIN.
Bear in mind you can find LH6 engines, but its the same VIN code for both the 58x and 24x engine. And as stated above, you can only use the 24x

 

[HondaBoi]

When you get ready to put it back together... Do yourself a favor and replace the oil pan side seal on the front differential.

Also, dont look for a LS V8 out of a FWD LS4 Vin code -C- car. Although the heads appear to be the same, the block is different.

Vin code refers to the sheet above, and the 8th digit of the VIN.
Bear in mind you can find LH6 engines, but its the same VIN code for both the 58x and 24x engine. And as stated above, you can only use the 24x

This is some of the best help I have received, thank you.

Really is a sad situation, I was excited about this LH6, and now this whole thing is probably the biggest L of my entire car building. I really wanted the afm dod too, despite how shoehorned it is. I cant even really plan my next move out till i know what is creating the shavings.

I got a vacation coming up and i wont be able to pull the motor till October.

 

[Mike534x]

To be honest, the AFM/DoD isn't all its cracked up to be. When I had my 05 Ext, at best I got about 2-3 MPG more then I do with my Envoy (AFM/DoD disabled via tune). Its also a contributor to these burning so much oil, with the TB I was going through a quart every 800 miles. Its a good system on paper, but practicality wise its just a headache when something does go wrong.

If you end up going with an iron block from the GMT-800 platform, swapping the front springs for a set of Moog 81114's would help a bit with the "droop". They're the stiffest spring, and usually result in a 1-1.5" lift (between the I6 and LH6) so it could compensate for the difference before deciding on spacers if you go that route.

 

[HondaBoi]

To be honest, the AFM/DoD isn't all its cracked up to be. When I had my 05 Ext, at best I got about 2-3 MPG more then I do with my Envoy (AFM/DoD disabled via tune). Its also a contributor to these burning so much oil, with the TB I was going through a quart every 800 miles. Its a good system on paper, but practicality wise its just a headache when something does go wrong.

If you end up going with an iron block from the GMT-800 platform, swapping the front springs for a set of Moog 81114's would help a bit with the "droop". They're the stiffest spring, and usually result in a 1-1.5" lift (between the I6 and LH6) so it could compensate for the difference before deciding on spacers if you go that route.

Yeah, givin all the issues I had with these lifters (one showed up broken and then it took them 3 weeks to get me the right replacement) . There's a good chance that system is causing my problem too. I think even if I go the route of keeping this LH6, DOD AFM is probably going bye bye regardless, the only way it isnt is if i find a cheap AFM DOD engine which I doubt.
I think ill treat myself to a nice choppy truck cam in for my troubles at this point. esp if i gotta send the computer off. Screw it, as long as i can still tow stuff, its cam time, and If I go iron block Ill put my nitrous kit on it and just be way more of a hot rod setup than i anticipated, but if i have to say good bye to fuel saving, may as well really enjoy my first V8

 

[TollKeeper]

The LM4 I have in my Envoy has been a great engine, and she just keeps trucking along. 211k on it as of today. Still gets nearly 17mpg too. Has the economy gears in it, GU6/3.42 which helps. The LH6 with the AFM/DOD tuned out (still in the engine) gets nearly 16 MPG. The drop in fuel mileage is from the different gears, GT4/3.73. although I'm still confused with it. The Saab is nearly 1200ish pounds lighter...

 

[Mooseman]

AFM/DOD is a crock. Even GM's own literature said it saved up to 5%. So on 17 MPG, you'd get maybe an extra 0,85 MPG! And with the extra oil burning and parts failures, those savings are non-existent or even a deficit. When I had it in my Saab, I saw no difference with it working or not. And they must have learned after the lawsuits because they don't have it anymore except for the turbo 2.7L I4.

Go forth and enjoy a DOD/AFM free life.

 

[Mike534x]

AFM/DOD is a crock. Even GM's own literature said it saved up to 5%. So on 17 MPG, you'd get maybe an extra 0,85 MPG! And with the extra oil burning and parts failures, those savings are non-existent or even a deficit. When I had it in my Saab, I saw no difference with it working or not. And they must have learned after the lawsuits because they don't have it anymore except for the turbo 2.7L I4.

Go forth and enjoy a DOD/AFM free life.

Sadly its just the Silverado line up that doesn't have it included, hopefully this makes it way over to the Yukon/Tahoe/Suburban and the rest. Off the top of my head, the 3.6 still has it standard for the Blazer/Acadia. We're already sent about 8 trucks at my work (22 Tahoe/Yukon between 25-55k for dropped lifters in the last 3 months).

@TollKeeper 16 MPG??? Is that on the Highway or City? I'm lucky to get 12-13 city, but I can get a steady 19-21 HW.

 

[TollKeeper]

@TollKeeper 16 MPG??? Is that on the Highway or City? I'm lucky to get 12-13 city, but I can get a steady 19-21 HW.

16MPG is a mix of highway and city. But the speeds I drive on the highway are far worse for fuel mileage. Speed limit here is 75, and I can count on my one hand how many times I have been anywhere near that speed for an extended amount of time that wasnt traffic forced.

The 17 I get on my Envoy is a lot more speed limit, and the Envoy is also the daddy wagon.