LS-style project

Here is a backburner project, this will no doubt fade in and fade out for a good while.

Have procured a 5.3L LM4 from an '04 trailblazer with low 100kish miles, and will prepare it over the next off few seasons for eventually marine use.

Its not in my basement for teardown yet, but will get there

Upon studying the layout, it seems the simplest cooling system, would be to run it with coolant for the block and boat heater. Run continuous raw water through the tranny cooler conventionally, then the heat exchanger and to the exhaust manifolds and out.
Already procured a mercruiser 4" heat exchanger on CL that was just too easy to get for 60 bucks. A poly pressure tank at the junkyard should be 20 bucks.

engine mount adapter plates are about 35 bucks. A bellhousing will be conventional SBC.
a used flywheel can be centered and drilled for a damper. A flywheel spacer and bolt kit puts it at the expected depth.

Hard decisions would be go closed loop efi and burn the ecm and play around with the efi.. Or go microquirt which is super simpler, but batch fueled and fired. Microsquirt does not support drive by wire (DBW) however a different intake/TB could be gleeped at the boneyard to make it DBC. (cable)
Though, retaining DBW has exiting hobbying possibilities for ZO-style PID speed control

Holley/msd make a conventional intake and programmable spark controller system, respectively for a conventional route that keeps the individual coils and uses the existing crank trigger. Carb, thats easy.

Fuel supply - needs to be solved. But marine rated parts exist.

exhaust Manifold options will be around for a good long time now.
10 years ago they were elusive.
no doubt will be the largest outlay.

the front sump from the LM4 seems advantageous for marine installation angle,


So an easy 290+hp all-aluminum engine at 425 pounds for 500 clams. thats just a bit over buck a pound people!
Consider reserving yours for your projects before they are melted into bearcans.

6L and 6.2L engines are not a whole lot more, considering what you are getting.

Plans are to tear into it over the winter and firstly measure clearances and inspect.
stock Cam is a bit lacking in duration but would work very well.   Stage one BTR truck cam would wake it up 330-340 hp and remain strong off-idle.
Valvespring upgrade is likely, as they are soft. Factory LS6 springs are cheap and permit more lift over .500.
Research says fresh factory lifter trays are cheap insurance, because if the roller walks sideways, it will eat the cam.
Fresh Timing chain, meh.
And trunion bushing upgrade, Seems the stock needle bearings can blow out. Bronze bushings are cheap insurance and make the stock rockers very robust for sustained high rpms.

Could be fun.

Here it is cleaned up.

Cool project! I’d KISS it and maybe start with carb and ignition controller... the marinization and other bits seem tricky enough for starters. We will be running a $70 carter marine lpp on a (carb) vortec longblock this year- I would expect fuel delivery to be an easy thing to resolve.

Would the simplest cooling not be to just straight rwc the thing? Believe that’s the standard set up from pcm these days. Got a line on how the rwp would play in either case? Thinking physical mounting more than anything.

Wish I could dig up that fb post where someone had put a 5.3 in a S&S. It looked to use an adapter plate and ford exhaust manifolds (interceptor logs iirc!). Apparently LS and Windsor geometry isn’t far off. I believe an international member here is running the opposite set up on their Ford.

Edit: found the pics:

Yeah Tim, stages has merit

carburation so easy almost like cheating. the efi, not intimidated either. I even found an older MSD ignition controller for carburation on CL locally for 225 this week, but i would hold out for the newer model
I could put my good 600 on this, and get a qf650 for the supreme...huh...

indeed the simplicity of raw cooling has serious merit,i long considered it also. But then thinking, what if the liner/block interfaces had accelerated corrosion, that would be a bummer.
Conversely, with AF my heater core would last longer and winterization gets simpler. Dissimilar metals and yet unverified water pump metalurgy become less an issue.

Pictures are cool!
manifolds adapt plates, that is an economical solution

huh, i also planned on putting the RWP where the PS pump goes. looks like he made an A-dapter kit with a plate of 1/4". Doesn't have to adjust, the tensioner take care of it.
I have a shearwood on the bench to play with, and looking at that PS location is planned early in the project.

heh, funny, gopro mount on the spark arrestor!

It doesn’t look like the rwp benefits from the tensioner in the set up above, that would definitely be slicker.

I’d like to study up on the current LS (marine) cooling plumbing a bit, I’m sure there’s something to be learned there.

What surfaces are you worried about galvanic?

TRBenj wrote: It doesn’t look like the rwp benefits from the tensioner in the set up above, that would definitely be slicker. I’d like to study up on the current LS (marine) cooling plumbing a bit, I’m sure there’s something to be learned there. What surfaces are you worried about galvanic?

Oh look at that, a separate belt!. Why. Yeah i don't get that, the serp goes right there for the PS pump. and rotation wont matter.

Also looks he deleted the thermostat and stuff and running it like an old H/M

Yeah, please look also.
What i got from the conventional water diagram is that the heater core loop is instrumental to the cerc loop, and should be preserved not blocked. thats what i got from it. I'm thinking treat an expansion tank and H/E like a radiator, done

regarding corrosion...circ pump impeller and backing plate. but most critically, the wet iron liners in the AL block. must seal somehow. LM7 is Gen3 Iron block, this is LM4 Al block. but thats why its 420 pounds or so.

Anecdotal searching is suggesting the alum blocks have closed cooli g STD and optional on the iron block models,

Tim, the 5.3 PCM is rated at 355 hp, the 6.2 is rated at 450 hp and is also the engine in all Nautique 3 event boats. I’m pretty sure both are heat exchanger boats. There is a 5.3 on ski-it-again.com. I know the seller and he is a straight up guy, worked for Correct Craft for 30 years.

Skip is the honest and upright gentlemen I’ve ever met. He won’t sell you a piece of garbage. He’s also a great skier.

DVskier wrote: Skip is the honest and upright gentlemen I’ve ever met. He won’t sell you a piece of garbage. He’s also a great skier.

he’s been more of a help to us with ZO issues than ZO has been. I’ve learned a lot talking once with Skip for about an hour on the phone. Good solid guy is what i gathered.