LOW TORQUE LS Engine Build

CarMotorBarge · Post by **CarMotorBarge** » Sat May 11, 2019 8:42 pm

Well I have decided to build a LOW TORQUE LS engine to put on my airboat. As with any engine build, you have to have goals. Here are my goals:

1. Make maximum HSP at 7000 RPMs. This engine will have no low end torque. I expect that a 540 A/C will make more maximum TORQUE than this LS engine.

2. Make at least 400 HSP.

3. Put the engine on a 5 seater barge with a 2.88 gear.

4. Must run on 93 octane.

5. Make substantially more thrust than Slidin Gator's A/C motor. I figured that him and I could meet at Dave Simpson's place and have him do the thrust testing as an independent third party.

6. Have more low end snap than Slidin Gator's BIG TORQUE and SNAPPY A/C motor. Have to figure out how to measure this. Maybe we just line our boats up side by side and race. Could do this in the water and on the hill. Whoever hits the 50 foot mark first wins? I am putting this engine on a 5 seater barge while he has a light riveted hull. Doesn't sound fair, but I am willing to find out.

My plan is to complete this engine build by Christmas and put it on a dyno. I will post all specs on the engine including the cam specs. I will post all part numbers for all engine parts. Don't want anybody excusing me of building a HIGH TORQUE engine.

I will post pictures as the build progresses. Don't want anybody to say that I used different parts.

All testing will be real world testing. No graphs, formulas, torque curves, or book theory. Just real world testing of a LOW TORQUE LS engine on an AIRBOAT.

Now I need to figure out what LS block to use. I think I am going to use a stock LS block to keep the price down. Let me see what I can find.

lorick · Post by **lorick** » Sat May 11, 2019 9:45 pm

Hope it's faster than your moped you been driving around

JB550 · Post by **JB550** » Sun May 12, 2019 9:17 am

You are a mess. LOL

CarMotorBarge · Post by **CarMotorBarge** » Sun May 12, 2019 10:01 am

Here is an update. I think I found a used LS2 block for $500. It is a stock 6.0 aluminum block. Now I need to determine what length stroke I am going to use keeping in mind that max HSP will be at 7000 RPMs.

CarMotorBarge · Post by **CarMotorBarge** » Sun May 12, 2019 10:07 am

JB550 wrote:You are a mess. LOL

I probably am a mess for building a high RPM LOW TORQUE motor for an airboat. Remember it is all about TORQUE.

I am just hoping I don't have to cruise around at 4500 to 5000 RPMs sucking tons of gas.

lorick · Post by **lorick** » Sun May 12, 2019 11:29 am

Just build a higher compression 5:40 or go 720 remember it's all about the tort can you produce 600 foot pounds of torque at 3000 RPM

airduds · Post by **airduds** » Sun May 12, 2019 2:16 pm

It's all about torque at the rpm you want to turn your engine. A water wheel might make 10,000 lbf of torque but if it does it at only 1 rpm it's not going to do a lot of work.

Torque is like peanut butter and rpm is like jelly. You have to have both to make a pbj. You can have a lot of power with a little torque but a lot of rpm... or a lot of torque at a low rpm. Best is a lot of both.

If you pick 3,000 rpm as your reference speed, then yes, torque is king.

Prototype · Post by **Prototype** » Sun May 12, 2019 9:19 pm

JB550 wrote:You are a mess. LOL

But some still see this as a valid post??????????

Fools born every minute including the op!
Boredom and failure welcomes company in every fashion.
Should be a good post of "Bad Build" by the time it's done!

lorick · Post by **lorick** » Mon May 13, 2019 3:12 pm

Chill out there's nothing wrong with a little b s every now and then

Post by **kwanjangnihm** » Mon May 13, 2019 3:37 pm

CarMotorBarge wrote: All testing will be real world testing. No graphs, formulas, torque curves, or book theory. Just real world testing of a LOW TORQUE LS engine on an AIRBOAT

Finally a real airboater's airboater, a harbinger with olive branch extended, the first fully transparent disclosure build, minimizing the CM & AC hatred, bringing balance to the dark-side, all the while reducing torque and dispelling horsepower myths. Sir we salute your endevours!

SWAMPHUNTER45 · Post by **SWAMPHUNTER45** » Mon May 13, 2019 5:20 pm

Kneel at the throne of POWER !

Let me fan you with my 4 "SUPERWIDE" blades as you rest your weary engine.

CarMotorBarge · Post by **CarMotorBarge** » Mon May 13, 2019 6:48 pm

SWAMPHUNTER45 wrote:Kneel at the throne of POWER !

Let me fan you with my 4 "SUPERWIDE" blades as you rest your weary engine.

I think I need an additional goal for this build. Turn 4 S blades pitched at 1 to 1900 prop RPMs.

Swamphunter45, can I borrow you prop for this test?

CarMotorBarge · Post by **CarMotorBarge** » Mon May 13, 2019 6:50 pm

Got another update on the build. I have decided to use a 4 inch stroke. Hopefully I don't throw a rod thru the oil pan when turning 7000 RPMs. Now I need to figure out which pistons and heads.

CarMotorBarge · Post by **CarMotorBarge** » Mon May 13, 2019 6:56 pm

kwanjangnihm wrote:
CarMotorBarge wrote: All testing will be real world testing. No graphs, formulas, torque curves, or book theory. Just real world testing of a LOW TORQUE LS engine on an AIRBOAT
Finally a real airboater's airboater, a harbinger with olive branch extended, the first fully transparent disclosure build, minimizing the CM & AC hatred, bringing balance to the dark-side, all the while reducing torque and dispelling horsepower myths. Sir we salute your endevours!

Kwan,

I am going to need your Jedi knowledge to help me post pictures on this website.

Post by **kwanjangnihm** » Mon May 13, 2019 7:59 pm

CarMotorBarge wrote: I am going to need your Jedi knowledge to help me post pictures on this website

per Southern Airboat rules: I can only post unretouched photos - "not having undergone editing or retouching"

Being an airboater's airboater, we can all rest assured the photos of the low torque LS engine will be genuine from CMB!

CarMotorBarge · Post by **CarMotorBarge** » Mon May 13, 2019 9:25 pm

Here is the LS2 block for the build on the engine stand:

The P/N is 12568952:

The LS2 block is an aluminum 6.0 block:

Main bearing bores have been align honed. Cylinders have been bored to 4.01 inches. The block has been decked and had the initial cleaning. Next step is to do the final clean on the block. Also need to finalize the decision on pistons and heads.

Engine will be 404 cubic inches and will be naturally aspirated. So it isn't a 500+ cubic inch motor or boosted engine capable of making BIG TORQUE.

CarMotorBarge · Post by **CarMotorBarge** » Mon May 13, 2019 9:29 pm

Kwan,

I need some Jedi wisdom to get the pictures to show the full size.

Can't see the entire part number on the LS2 block.

Slidin Gator · Post by **Slidin Gator** » Mon May 13, 2019 9:43 pm

Challenge heard and accepted, Game ON!

We still need to negotiate the terms and the win/lose/draw basis, but I am in. Real busy with work this week, so I will just have to let this all fester until later. I will post my counter challenge later this week and we can all pick sides and start trash talkin (looks like it's already started).

I have a pretty good idea about the goal I am after. But round #1 is gonna be my present 260 HP, 500 ft-Lbf AV motor on a newly rigged hull, the sister ship of my present hull. It will definitely make less thrust than CMB's proposed rig, I lose hands down there. As for snapping the prop, we got some talking to do about what prop, even a crappy ass build like a 400 Hp, 7000 RPM LS is gonna make some torque at the bottom and it don't take much with 2.88 worth of gear to outdo what I got right now. Round #1 is probably gonna be early 2020.

Round #2 is gonna take into 2021, that's when I plan to have my present hull back to cherry. I am all over the map on what the round #2 motor might be, but it will be a torque build for sure, making at least 500 ft-lbs and less than 400 Hp at top RPM (at least for the purposes of the challenge). It will make less steady state thrust than CMB's rig on the test stand, but it will make 90% of max thrust quicker off the line (first 2 seconds). It may or may not use gear. The easy choice would be an IO-720 (which would be a great head to head comparison) or a GSO 480, but we will see, it depends on the terms we settle on.

Just 2 non-negotiable ground rules, I think the SA referees (i.e. everyone else) can agree these are reasonable:
#1, We all trash talk here on SA, that's half (most of) the fun of it. This is all in the spirit of a good time, neither one of us have the time to waste on settling grudges. If this was a grudge, we could just meet up at Possum Bluff and deal with it, lick our wounds and go home vs. spending a whole year on it.
#2, We are gonna spend time over the Barbecue, What's a grudge without a party? I got a freezer full of good stuff to start with. Everyone gets a participation trophy I guess.

Finally, What's a bet without a wager?
I propose a wager of 6 months supply of the winner's preferred whisky. That's gonna be 5 cases of George Dickel #8 for me (probably how we both got into this). If CMB is good with a comparable value in Jack, then game on.

Drink Up Shriners.

Msa4x4 · Post by **Msa4x4** » Tue May 14, 2019 2:31 am

Get you a ls3 block and throw a 4.8 crank in it. Should get you 8k rpm easy

Post by **kwanjangnihm** » Tue May 14, 2019 4:51 am

CarMotorBarge wrote:Kwan,

I need some Jedi wisdom to get the pictures to show the full size. Can't see the entire part number on the LS2 block.

CarMotorBarge · Post by **CarMotorBarge** » Tue May 14, 2019 6:41 am

Thanks Kwan.

CarMotorBarge · Post by **CarMotorBarge** » Tue May 14, 2019 6:43 am

Msa4x4 wrote:Get you a ls3 block and throw a 4.8 crank in it. Should get you 8k rpm easy

I have a 5.3 cast iron block and a stock crank with a 3.622 inch stroke. Was thinking about doing a 5.3 build that spun to 7000 RPMs for an airboat build. Need to build and test the current build first.

CarMotorBarge · Post by **CarMotorBarge** » Tue May 14, 2019 6:49 am

Slidin Gator wrote:Challenge heard and accepted, Game ON!

We still need to negotiate the terms and the win/lose/draw basis, but I am in. Real busy with work this week, so I will just have to let this all fester until later. I will post my counter challenge later this week and we can all pick sides and start trash talkin (looks like it's already started).

I have a pretty good idea about the goal I am after. But round #1 is gonna be my present 260 HP, 500 ft-Lbf AV motor on a newly rigged hull, the sister ship of my present hull. It will definitely make less thrust than CMB's proposed rig, I lose hands down there. As for snapping the prop, we got some talking to do about what prop, even a crappy ass build like a 400 Hp, 7000 RPM LS is gonna make some torque at the bottom and it don't take much with 2.88 worth of gear to outdo what I got right now. Round #1 is probably gonna be early 2020.

Round #2 is gonna take into 2021, that's when I plan to have my present hull back to cherry. I am all over the map on what the round #2 motor might be, but it will be a torque build for sure, making at least 500 ft-lbs and less than 400 Hp at top RPM (at least for the purposes of the challenge). It will make less steady state thrust than CMB's rig on the test stand, but it will make 90% of max thrust quicker off the line (first 2 seconds). It may or may not use gear. The easy choice would be an IO-720 (which would be a great head to head comparison) or a GSO 480, but we will see, it depends on the terms we settle on.

Just 2 non-negotiable ground rules, I think the SA referees (i.e. everyone else) can agree these are reasonable:
#1, We all trash talk here on SA, that's half (most of) the fun of it. This is all in the spirit of a good time, neither one of us have the time to waste on settling grudges. If this was a grudge, we could just meet up at Possum Bluff and deal with it, lick our wounds and go home vs. spending a whole year on it.
#2, We are gonna spend time over the Barbecue, What's a grudge without a party? I got a freezer full of good stuff to start with. Everyone gets a participation trophy I guess.

Finally, What's a bet without a wager?
I propose a wager of 6 months supply of the winner's preferred whisky. That's gonna be 5 cases of George Dickel #8 for me (probably how we both got into this). If CMB is good with a comparable value in Jack, then game on.

Drink Up Shriners.

It is hard to pass up a 6 month supply of free Jack.

As for which prop I will use, it will be either a 4 blade R, 3 blade JX, or 4 blade JX. Need to do a little testing to find out which. I will use the same prop to make max thrust and test the snap. So I will be trying to snap a BIG prop with a LOW TORQUE LS. I won't be using any skinny blades. Those skinny blades won't push a 5 seater car motor barge on the hill.

SWAMPHUNTER45 · Post by **SWAMPHUNTER45** » Tue May 14, 2019 8:29 am

If you want to spin 7000 rpm that is the platform to do it.

Can't wait to see the results

CarMotorBarge · Post by **CarMotorBarge** » Thu May 16, 2019 9:22 pm

Here is the latest on the low torque LS build. Decided to use the following cylinder heads:

https://www.texas-speed.com/p-7650-prec ... heads.aspx

Planning to get the stainless hollow stem intake valves with 0.660 dual springs. The intake runner is 257cc and the valve angle is 13 degrees. Definitely not the best heads for making low end torque, but should do OK for a motor turning 7000 RPMs.