Aluminum versus iron when buying used LS

[short&wide65]

I've started to look for an LS for my 65 GMC and while I had been leaning towards an iron block Gen IV 6.0 such as the LY6 or L96, I keep seeing running, high-mileage Escalades and Denalis around my area with the 6.2 aluminum L92 for a decent price for the entire vehicle. My initial thought is that I could part it out after taking everything I want.

With either engine, I'm really only interested in the block, crank and heads and the plan is a complete rebuild. So my question is, should I be looking at these? Could the ability to hear them running or performing a compression test help with the decision?

My guess is that the inability to bore the aluminum blocks makes these higher mileage less attractive than a higher mileage iron block. I have no interest in sleeving a block.

I am still weighing the pros and cons of a full rebuild versus a crate engine though.

Thanks!

[mongocanfly]

I've got both iron and aluminum engines...I wouldnt be worried about either one..the LS has proven itself with longevity..but yes , hearing one run is a bonus, as is compression test, run a bore scope in and look at piston and cyl wall.. low mileage engines are hard to find and you pay premium for them

[Ziegelsteinfaust]

The aluminum should have iron liners, and can be bored just fine.

I am not into LS's, but depending on how much hp you want. There's a point where iron is worth the strength again over weight

[Warrens69GMC]

I bought a new 6.0 with a iron block about a year ago. It has aluminum heads and should be able to power my 1978 easily down the road.

[Accelo]

The 6.2 aluminum L92 is an LS3 with DOD. (Displacement on demand)
If you have looked into the price of a used LS3 the L92 is a bargain.
I would snap one up. Having the complete vehicle would solve a lot of problems like radiator, fans, ECM and the transmission. Their are kits available to change over the motors to LS3 specifications (no DOD). Typically, in my area, the aluminum blocks bring a nominal $1000 premium over the cast blocks. Max overbore is limited but cylinder wear isn't typically an issue.
Starting with a factory rating of 403 hp is amazing. With a camshaft and headers you will be closer to 5oohp than 400.
Cheers.

[short&wide65]

Originally Posted by mongocanfly

I've got both iron and aluminum engines...I wouldnt be worried about either one..the LS has proven itself with longevity..but yes , hearing one run is a bonus, as is compression test, run a bore scope in and look at piston and cyl wall.. low mileage engines are hard to find and you pay premium for them

Good advice. Also, I'm looking at high mileage ones because I don't want to pay the premium for a low mileage one that is only going to get a rebuild anyway.

Originally Posted by Ziegelsteinfaust

The aluminum should have iron liners, and can be bored just fine.

Except they can't be bored just fine if there is an issue. The max overbore is .010 over.

Originally Posted by Accelo

The 6.2 aluminum L92 is an LS3 with DOD. (Displacement on demand)
If you have looked into the price of a used LS3 the L92 is a bargain.
I would snap one up. Having the complete vehicle would solve a lot of problems like radiator, fans, ECM and the transmission. Their are kits available to change over the motors to LS3 specifications (no DOD). Typically, in my area, the aluminum blocks bring a nominal $1000 premium over the cast blocks. Max overbore is limited but cylinder wear isn't typically an issue.
Starting with a factory rating of 403 hp is amazing. With a camshaft and headers you will be closer to 5oohp than 400.
Cheers.

Yes, the DOD and VVT will have to go. Good to know about cylinder wear typically not being an issue. Great point about all the accessories but I'm going to be running a Tremec so I have no interest in the transmissions. Actually, for one of the Escalades I was looking at, a blown transmission is why it's so cheap.

[Accelo]

No LS aluminum block will accept a tenth of an inch overbore. Maybe you meant .010?

Aluminum LS1 blocks have very thin, centrifugally cast iron liners. The blocks are actually cast in place around these liners (rather than the normal practice of pressing the liners into the block after it has been cast). On the very earliest LS1 blocks produced in 1997 and 1998, the sleeves may not always be positioned 100 percent perpendicular within the block casting, meaning that the final-bore sizing and honing process left one side of the walls thinner than the official engine design specs called for. Therefore, 19971998 LS1 5.7L aluminum blocks can only be safely honed (not even bored!) just 0.004-inch over the stock bore diameter. Improved liner positioning in 1999-and later 5.7L LS1 blocks and all LS6 blocks permit boring up to 0.010-inch oversize. Either way, you are SOL at wanting to go 0.020-over for a reliable LS1 aluminum block rebuild.

I have personally observed LS blocks with over 100K miles on them and you could still see the hatch marks. With proper servicing they just don't wear much. With low tension rings, better metal and proper air fuel mixtures they just last. Typically they loose a rod bearing before any issues with the bores.

[short&wide65]

Originally Posted by Accelo

No LS aluminum block will accept a tenth of an inch overbore. Maybe you meant .010?

I have personally observed LS blocks with over 100K miles on them and you could still see the hatch marks. With proper servicing they just don't wear much. Low tension rings, better metal and proper air fuel mixtures they just last. Typically they loose a rod bearing before any issues with the bores.

Yes, I had the decimal in the incorrect spot. I did mean .010 over.

Most of the ones I am looking at have 160-200K miles which I'm guessing since they are still running well, have received proper maintenance.

[LS short box]

The only real advantage going alum is the weight saving. I done two 6.2 alum swaps. One awhile back a 2010 6.2 dressed like a LS3/TKO 600 combo and my current project is a 2012 6.2/4L60E combo dressed like a LS3. Neither had DOD but both had VVT which I deleted. I used the a kit from Texas Speed to delete the VVT.
The 2010 L92 chassis dyno tuned was 420 RWHP. Ran great and easy to tune.
A buddy of mine has a 6.0 iron block with L92 heads, LS3 intake and a small to medium cam (225I/230E .600 lift 112c/l. It chassis dyno tuned at 408 RWHP. Runs great and easy to tune.
The gen 4 engines have better rods compared to the gen 3 engines.
If I was going to build another LS from scratch I would start with a gen 3 6.0 iron block. Stroke it to 408 cubes. L92 heads. Medium cam. 3.73 gears. Man I like spending other peoples money!

[Accelo]

Great advice to make hp on the cheap. (If there is such a thing)
With 420hp you had to be making really close to 500-hp on an engine dyno.
Why I love the LS motors.
My LS1 made 354 at the wheels. With a small BTR Stage II truck cam, headers and an LS6 intake. It would appear moving up to an 6.2L from a 5.7L with basically the same mods is a 70hp gain.
I believe the weight saving is typically 60 to 70 lbs.

[LS short box]

The best LS I did HP wise about 6-7 years ago was a re-sleeved LS2. Stroked to 427 cubes. I bought a LS2 bare block from RED (Race Engine Development) in CA. They cut the old sleeves out and put in new Darton sleeves. Then bored to 4.125 IIRC.
Bought a Manley 4.00" stroker kit. LS3 heads and intake. 230I/235E cam. Made just under 500 RWHP. Again super easy to tune. I put it into a 67 Nova. Super fun car to drive. So much fun to say "it's a 427".

[Sovereign]

If you're planning a rebuild, why are you starting with a Gen IV motor? Personally, I see no advantage to paying the premium for Gen IV especially if you start with a 6.0 Gen 3 which will accept Gen IV heads should you want them. But again, it's not like the Gen 3 cathedral heads are bad. My suggestion would be to identify your power goals and work from there. If they're modest, anything below 500hp NA, any LS engine will get you there reliably, except the 4.8. The iron blocks will just do it for less.

Good luck whatever you decide.

[short&wide65]

My initial thought had been to try and get around 600 horsepower NA since I plan to autocross the truck. I'm not trying to be nationally competitive though as I will also be street driving it.

Up here there doesn't seem to be a lot of price difference between the Gen III and Gen IV 6.0 litre engines. I'd also read about the Gen III reluctor wheel failure issue. The cathedral heads aren't bad per se but they aren't as good as the rectangle port heads.

I started thinking 6.2 when I started seeing how cheap I could buy an entire running Escalade or Denali for.

[Accelo]

600hp is a lofty goal.
Go with the 6.2 for the extra displacement. It will give you 12hp to 15hp more everything being equal. Yes, going with the square port heads is the best option for 600 plus horsepower. Heads will have to be ported or replaced to reach 600hp.
Their is no way to do 600hp inexpensively. The camshaft will have to be aggressive you will have $1800 into getting an intake manifold with a throttle body. An you will still need injectors. Might consider a stroker to make the goal somewhat easier. You will need good internals as 600hp will require close to 7000rpm.
Check out this youtube video, might help.
https://www.youtube.com/watch?v=dv2WYRh1oWo&t=574s
Sounds like a blast
Enjoy

[Sovereign]

If 600hp is the goal and you want mildish street manners, you should stoke the engine in my opinion just as Accelo suggested. I would also say starting with either a Gen 3 or 4 will be fine as you'll need aftermarket or factory ported heads regardless. Basically, you need to start with a block that has a 4.0 bore. Everything else will be bought new. The reluctor wheel issue can be corrected if it concerns you.

If you lower your goals to 500hp, life will be cheaper, easier, and more manageable.

Since I don't know you or your car history, do you have any idea what driving a 600hp vehicle is like with no traction aids? If not, I would suggest stepping back to no more than 500hp or, honestly, 400hp until you get used to it. Modern engines along with fantastic modern traction aids give an incredibly false sense of what it's truly like to manage 500 and 600 hp. I can assure you, a stone stock LS3 in a C10 that can handle and brake will be a riot to drive and be easy to live with.

Sounds like it's going to be a fun truck.

[LS short box]

On my Nova with the stroked LS2 you did need to be a bit careful. Light car you light up the tires at 45-50 mph with ease. The other thing is with a big cam you aren't going to have enough vacuum for power brakes. So that means either hydro boost or manual brakes.
My thought would be to build a nice stout short block. Then upgrade heads, intake and other stuff as you move up the HP levels.

[short&wide65]

Thanks all!

Originally Posted by Accelo

600hp is a lofty goal.
Go with the 6.2 for the extra displacement. It will give you 12hp to 15hp more everything being equal. Yes, going with the square port heads is the best option for 600 plus horsepower. Heads will have to be ported or replaced to reach 600hp.
Their is no way to do 600hp inexpensively. The camshaft will have to be aggressive you will have $1800 into getting an intake manifold with a throttle body. An you will still need injectors. Might consider a stroker to make the goal somewhat easier. You will need good internals as 600hp will require close to 7000rpm.
Check out this youtube video, might help.
https://www.youtube.com/watch?v=dv2WYRh1oWo&t=574s
Sounds like a blast
Enjoy

Excellent advice I'm also a fan of Richard Holdener's videos. I love engines that rev and lust after his destroked LS 4.8 crank in a 6.2 block.

Originally Posted by Sovereign

If 600hp is the goal and you want mildish street manners, you should stoke the engine in my opinion just as Accelo suggested. I would also say starting with either a Gen 3 or 4 will be fine as you'll need aftermarket or factory ported heads regardless. Basically, you need to start with a block that has a 4.0 bore. Everything else will be bought new. The reluctor wheel issue can be corrected if it concerns you.

If you lower your goals to 500hp, life will be cheaper, easier, and more manageable.

Since I don't know you or your car history, do you have any idea what driving a 600hp vehicle is like with no traction aids? If not, I would suggest stepping back to no more than 500hp or, honestly, 400hp until you get used to it. Modern engines along with fantastic modern traction aids give an incredibly false sense of what it's truly like to manage 500 and 600 hp. I can assure you, a stone stock LS3 in a C10 that can handle and brake will be a riot to drive and be easy to live with.

Sounds like it's going to be a fun truck.

Also excellent advice. I'm certainly not set on a certain power number as driveabilty and cost are factors.

While I do have 20 years of autocross and track experience everything I have driven with 500-750 horsepower has been newer things with track modes (which are staggeringly good) such as the Mercedes AMG GT, McLaren 570S and C7 Z06.

[Sovereign]

My suggestion is to build the truck with a stock engine. You'll have plenty of bugs to work out and adjustments you'll need to make to the chassis. Get all of that done first. Then, start building up from there. You can easily plan everything in the beginning with the intent to upgrade later on.

Side note: The AMG GTR is my favorite Merc. I want one in Green Hell color. I'll never be able to afford one and most likely won't even get to ride in one, but I do lust after them. Mercedes absolutely nailed it with that car. Seeing and hearing them run around Nurburgring was a treat that I just happened upon when I was in Germany last. God what a car.

[short&wide65]

Originally Posted by Sovereign

My suggestion is to build the truck with a stock engine. You'll have plenty of bugs to work out and adjustments you'll need to make to the chassis. Get all of that done first. Then, start building up from there. You can easily plan everything in the beginning with the intent to upgrade later on.

Side note: The AMG GTR is my favorite Merc. I want one in Green Hell color. I'll never be able to afford one and most likely won't even get to ride in one, but I do lust after them. Mercedes absolutely nailed it with that car. Seeing and hearing them run around Nurburgring was a treat that I just happened upon when I was in Germany last. God what a car.

While it's a good suggestion, I figure a higher mileage engine will need a rebuild anyway.

The truck is also a full ground up build. I'm currently C-notching the frame then getting it ready for paint and a host of No Limit suspension parts. The 12 bolt is also getting rebuilt over the winter too. Since the chassis will be brand new, I figure it should get a brand new engine and transmission as well.

Agree about the AMG GT R and the Green Hell paint. I've only driven the GT S before the R came out and it was pretty incredible.

[Joyridin]

Are you looking for 600 crank HP, or RWHP? 600 crank HP is pretty easy to obtain with an LS3. You can almost do that with headers, cam, rocker arms, and springs. 600 rwhp is something I doubt you will hit without major work.

My LS3 with a BTR stage 4 N/A cam, headers, lifters, springs, and pushrods put 479 rwhp. We estimated a 15% loss due to IRS and a few other things.

[Sovereign]

I'm at 192k on my 06 Tahoe which has the 5.3. I wouldn't hesitate to start with it knowing eventually I would pull it or swap it for bigger and better. I certainly wouldn't be building anything very nice though where pulling the engine after the fact would be scary.

[short&wide65]

Originally Posted by Joyridin

Are you looking for 600 crank HP, or RWHP? 600 crank HP is pretty easy to obtain with an LS3. You can almost do that with headers, cam, rocker arms, and springs. 600 rwhp is something I doubt you will hit without major work.

My LS3 with a BTR stage 4 N/A cam, headers, lifters, springs, and pushrods put 479 rwhp. We estimated a 15% loss due to IRS and a few other things.

600 crank. I know 600 wheel would be expensive.

I guess my next question is what's cheaper, building an engine completely or buying a built LSX crate engine?

[Accelo]

If you use 15% Loss its 510hp at the rear wheels to have 600 at the crank. (manual)
If you use 20% Loss its 480hp at the rear wheels to have 600 at the crank. (automatic)
So Joyridin is very close to 600 Crankshaft HP without ported heads.
Of course this is a square port head on the LS3.
Use Joyridin setup and add ported heads, possibly up the compression a hair and you will be well into the 600hp, crank, range.

[Joyridin]

Originally Posted by short&wide65

600 crank. I know 600 wheel would be expensive.

I guess my next question is what's cheaper, building an engine completely or buying a built LSX crate engine?

I bought the 430 hp LS3 crate engine. Swapped the cam, exhaust manifolds, pushrods, springs and retainers. I also installed CHE bushings in the rocker arms. All that was about $1000 at the time, and the engine was $6500. So for $7500, I had roughly 550-600 crank hp.

I couldn't touch an engine from any reputable builder for that price. I think the 525 hp LS3 was a bit more than what I had in it.

[short&wide65]

Originally Posted by Joyridin

I bought the 430 hp LS3 crate engine. Swapped the cam, exhaust manifolds, pushrods, springs and retainers. I also installed CHE bushings in the rocker arms. All that was about $1000 at the time, and the engine was $6500. So for $7500, I had roughly 550-600 crank hp.

I couldn't touch an engine from any reputable builder for that price. I think the 525 hp LS3 was a bit more than what I had in it.

That's a really good deal. Definitely something to consider.