LakeBoat4

Glad to have someone talk real LS issues!
I couldn't agree more with CG, Power potential, efficiency, etc. This post started by saying that this LS was going in a totally NEW boat build, not a repower. All of the figuring, measuring, weighing is critical to have a boat be balanced correctly. We are figuring if a SCX is Correct or an SCX4. It is down to less than the 2 inch difference for X Dimension and engine height.

When it comes to SC 'ed the head flow and number of valves become less critical. I would like to see a 4 valve head on an LS but when the boost is 20psi or more it is about pressurized flow, not as free flow in NA engines.
The use of the LS/LT based engine has been around as in Ilmor and the others for some time. It has not been that long ago the "7 Marine" program was discontinued by Volvo for environmental reasons. Supercharged LS based with ZF trans, outboards.

Mercury made the 1990 4-Valve ZR-1 engine for the Corvette. Think it was a predecessor to the 860-1750hp I/O's they produce today. This brings up the point that these Mecury's are 4-valve engines and a LS can make a lot more with twin turbos and 2-Valves. For an LS endurance engine there would have to be extensive testing to see if it could go the 100 hours before rebuild as the Mercury's. That is after rebuilding the #6 or 8 drives at least twice.

Precision

Here is an interesting comparison.

The RED lines are a Sterling 1300 race engine with a PSI blower with 598 CI, 11.5:1 CR 13lbs of boost and running on C16 with a solid roller cam and a 25hr life span.

The BLACK lines is one of my 366 CI LS Twin Turbo engines with 8.3:1 with 19LBS of boost, running 89 octane with a hydraulic roller and a 300 hr valve train life ( I'm already at 220hrs).

Tartilla

Lakeboat, I don't think there's been many serious LS performance threads on here. MGdoors was making a set of NAs up for his Cat, but I don't remember seeing much at all.

GM may be making a new SBC with 4 valve heads. Seems they've been changing direction the past few years with Covid and floundering with the EV direction etc. Maybe some traction on the 4 valve on the near future.

Darin Morgan has some good info on SC head flows etc. He makes the point that SC engines don't need bigger intake ports per say, as the pressurized intake acts very similar to the NA port, just denser air. But I would say the head flow is just as important NA/SC. Yes you can "blow it through", but that creates more boost than required.

LS floeW and better BSAC/HP is likely from the better port/valve angle, and the better valvetrain coming from the larger base circle.

I really want the LS to make the Marine Perf stress test. I see BBC data and info on here just as important. We need real world examples of benefits/pros/cons on what makes the best engine for diff setups. The best way to do that is overlay good LS data on the Marine Perf powerhouse...the BBC.

ICDEDPPL

iTrader: (1)

So riddle me this , Teague is $120k for his engines. but the LS is $60k . Why in the world would anyone buy Teague (or any other big name) if the LS is so great and so cheap??
Where`s all the big boats with LS engines running around? I`ve never seen one.
LS engines have been around 27 years , if so great why hasn`t it replaced the BBC ?
Ilmor has an LS but they are putting them in the correct application, light runabouts.
Why won`t they make a 1000+hp engine for actual 'offshore'boats? . They certainly have the means.
LS9 is 436hp . Why didn`t GM use an LS engine when they needed to make 650hp in the ZO6? Why switch to an LT1?

1350hp on 91 octane that would last about a weekend in my heavy tank if I was lucky .
. Heavy straight bottom boats like mine, Apaches and whatnot eat engine for breakfast. Load makes all the difference in longevity.
Don`t get me wrong LS is a great engine I`ve modded them in the last in my cars and they are great to work on .
I`m sure it`s great for egg beaters, open bows and ski boats but the LS will never replace the BBC in anything high hp and high load .

my .02

ICDEDPPL

iTrader: (1)

So to summarize Sterling built a 1300HP engine.
It ran on C16
It had a 25hr life span
Lots of cubes.

The OP is running an LS at 1/3 of the cost and 50 more HP and doing it all on 91 octane.
I thought Sterling was a pretty high end builder. Guess they doing it all wrong.

Precision

I never said Sterling was doing anything wrong. Its more about the efficiency of the cylinder head and no parasitic loss.

And those Sterlings were $65K for the pair from Dave. I have way more than that in my LS engines. I’m simply sharing performance data I have measured. I’m not saying one is better than other.

The PSI engines are cooler IMO. They were so obnoxious they knocked the lights down in the dyno. They looked cool, sounded cool, and screamed power boat.

hogie roll

This can not be true

cheech

The Lotus designed, Mercury manufactured LT5.

The 4 valve LS has already been done. By none other than Mercury Racing! Around 2016-ish as an automotive crate engine. Unaware if they still produce them.
They offered the LS7 based SB4, had 4 valves per cylinder and DOHC, utilized a dummy cam in the block.
Here
Here
And Here; PDF Brochure

hogie roll

He ended up with superchargers. All the talk about crushing big blocks NA didn’t turn out.

ICDEDPPL

iTrader: (1)

Correct me if I`m wrong but at the end of the day an engine is a pump, you can make a more efficient pump but the basic principle is the same. Expansion of air and fuel is what creates the force to move that piston down.
It`s cylinder pressure that makes power. The more cylinder pressure the more chances of detonation and pre ignition . Generally a smaller displacement engine needs to operate at higher cylinder pressures to produce the same power as a larger displacement engine since it needs to extract more energy from each combustion event to compensate for its smaller size. Larger displacement engines will have higher tq (important in boats) at lower rpms and they do not need to make as much cylinder pressure to make the same power and the octane requirements are lower .
There is no replacement for displacement, thats not a slogan that`s just physics.
You better have some high octane to make 1350hp in an endurance engine especially if it`s a small block.
The LS is not some magic engine that defies physics.