Riverracer

I marine endurance jet boat race and am very impressed with the power coming out of the new LS series engines. I've given more specific details in my introductory for more general background info. I currently run in a class with few rules,
- Max 6.0 Litres
- no power adders - NO2, forced air induction.

I am very curious about how the LS series engines will compare in regards to power, price and durability. It appears that it is fairly easy to produce about 500 lb/ft of torque and 550 hp with an LS 2, but how hard is it to bump it up to at least 650 hp @6000 rpm and have it live. As with all endurance racing, power is great, but durability is KING! We usually have about 50% attrition during our races.

Below is info on a typical engine in my class;

- cost $40,000 +/- USD
- 366 ci/6.0 +/- litre traditional chev engine design
- 13-1 compression ran on c12 or c14 VP race fuel
- 4-5 stage dry sump
- twin carb with custom sheet metal intake
- shaft Jesel rockers
- Solid roller cam, .700 lift, 255 duration. LSA of 108
- dual valve springs, 275 closed, 675 open
- billet, fully counter balanced endurance crank
- .937 extreme duty rollers
- short stroke, big bore, 3.30 stroke, 4.125 bore +/-
- MSD ignition
- most heads used flow about 390 cfm @ .700 on the intake
- engines are designed to produce the most torque possible @ 6000 rpm +/-. (Our jet pumps loose efficiency after 6500 rpm and gear reduction drives don't work in this application.) Typical engine power is at least 650 hp (570 lb/ft +/- of torque) @ 6000 rpm and about 700 hp @ 6500 rpm.
- engines are ran WOT at/around max torque rpm for up to 45 minutes at a time. Torque is what makes a jet boat fast. Bottom and mid range power is not important in a jet boat, engines are built as if they were going to be used in a dyno (the jet drive in a jet boat works under the same basic principals as a water brake dyno) competition with a max rpm of 6500 rpm and who ever produces the most torque/hp in the 5800-6500 rpm WINS!

So, how will an LS engine compare for power, durability and cost.

I have tried to supply as much info as possible. There is much more info in my "Introduction". If there are any unanswered questions, please ask.

Thanks in advance to all of you for your help.

Adrenaline_Z

It seems from your description that this engine is running wide open throttle
most of the time, and a very short useable power band of about 700 RPM.

The LS motors are very good breather's up top. I don't think you'll have too
much trouble making peak power between 6000-6500 RPM.

Since you don't need/use much RPM below 5800 and have a small RPM window,
you can tune the cam to produce a fairly flat, or inclining torque curve over
700 RPM.

What is your current compression ratio? What are your current cam specs?

How about info on your heads such as valve sizes, runner volume, modifications?

Riverracer

Adrenaline - Please see more info I included about my application in the "Introduction" section of this forum. It is fairly indepth and lengthy so I didn't think the administrator would want me to copy it over, perhaps I should have. You should find the info you mention there. Thanks.

Adrenaline_Z

That's a very impressive intro.

The motor you have spec'd above is fairly stout on cam specs and compression.

Getting an additional 150 HP out of any more Naturally Aspirated is going to
be a big challenge, especially with a displacement limitation.

I'm going to send you a Private Message with a link to a site which can offer
better advice for the calibre of engine you require.

gun5l1ng3r

Is there a sight that goes more in-depth for technical articles than LS1Tech?
I would love to know if such a site exists.

96 Comp T/A

iTrader: (8)

Couple of questions
1. Is weight of primary concern, i.e. would you gain anything by making the engine lighter by allowing a better performing boat because of weight placement/ distribution. Or are you already below minimum weight and have to ballast anyway?

2. How do you address impeller speed as you increase horsepower? What I mean is that say you have an impeller spec that can hold a given engine in that 600-6500 range when the motor makes 650 HP. Now you start making 700 HP.That same impeller is going to end up spinning faster. Can you change the impeller spec to provide more bite to increase thrust and put a larger load on the engine?

3. What about gear reduction device doesn't work? Does it provide non-optimal engine placement? Are they unreliable? Torque is torque, HP is irrelevant it is simply a math equation. A higher shaft speed may produce less torque in a higher RPM range but you will get the torque multiplication from the reducer (minus the parasitic drag). If the net torque is higher I fail to see the problem.

4. While I think you could be competitive with an LS series engine, you would probably be better off with something SB2 based. There will be a lot of that stuff surplussed here this year thanks to the R07 engine. You can readily obtain strong cast iron blocks with big bores, there are plenty of parts available. If your goal was to come up with a cheaper mousetrap than it may end up being false economy. The difference in the cost of the componentry would be negligible (for what you require quality wise).
5. Where can I come and watch? I have always wanted a jet boat and they don't seem to be as popular as you would think over here on the west coast of Florida. <--Nevermind, I went and looked at your intro. Video looks like it's hella cool.

Mighty Whitey

is there a limitation to valve angle for these engines you use? meaning, are you limited to the SBC's 23* valve angle? or can you use something more exotic like an 18, or 15* valve-angle head?

if you're limited to 23* then you better count out the LS-series of engines, all of which are 15* or less..

if not, go all-out LS1!

airflowdevelop

is the compression and lift limited? Normally in these deals it is not.

the LS platform is not the right choice....if you are doing what I think you are doing.

Shoot me a PM with the actual class and rule info, and I may be able to help...as long as time is not an issue.

Dennis

Big-DEN

Thoughts...

I know you've all seen these new 500,510,520/450-460rwtq 5.7L street machines.

Really no downside to them. Some of the TQ curves are better than the 410rwhp/390rwtq b1/t1 day wonders at every single RPM point over 2000RPM.

Look at the TQ curve. This guy was saying TQ and where it occurs is really important.

On the dyno's that I mentioned, you know it sits at 400rwtq for a while and then climbs up to 450rwtq and hangs there for a while before dropping down.

I've always said that "double hump" was due to either the airspeed being at the critical point or the intake runner harmonics coming into play.

In any case, this guy is saying it would be better for that "hump" to 450rwtq to come in around 5500RPM and hang around to 6500RPM.

What cross section of intake runner, runner length would be needed? What exhaust header piping length and cross section would be necessary to crutch best at 5500-6500 RPM on a 6.0L motor?

These are some of the questions.

700HP@6500RPM is great for 6.0L, its very low RPM point.

The numbers the fellow speaks is 650HP@6000RPM which is 525ft-lb@6000RPM and 700HP@6500RPM which is 565ft-lb@6500RPM

Converted to RWHP using 12% drivetrain loss is 572rwhp@6000RPM 462rwtq@6000RPM
And 616RWHP@6500RPM and 497RWTQ@6500RPM

Just for reference.

These numbers are very good for a street 7.0L by the way neverthe less a 6.0L.

Just throwing bits out there.

Riverracer

96 Comp T/A - To Answer your questions;
1. Weight is very important, and as a rule you want as much of the weight back as far as possible and we have already done this.

2. We can change impellers to match the engine power to our desired rpm.

3. Gear drives are impracticle for a couple of reasons. First they add weight and then the engine has to be moved forward a significant amount to make room for the drive. This has been tried by a few racers and it becomes more of a detriment than an advantage.

4. SB2.2 engines are an option. A couple of racers have tried them and they have been competitive. The only problem is that most of these 2nd hand heads are sold by either 2nd or 3rd parties and you never know their "REAL" history and we can't take the risk that we're getting repaired or worn out heads. To buy new SB2.2 heads are extremely expensive and I believe there are better heads for our application like the new Gen 2 symmetrical port head GM is coming out with or the Little Chief, again very expensive. I have thoroughly investigated these options and want to look at other options. This is why I'm here to look at the LS engines.

Might Whitey - We can use whatever head we want. Most of us are already using heads between 12 and 15 degrees.

Dennis - I have posted the rules in the "Introduction" section of this forum. Compression is not limited. However, long periods of WOT at peak torque tends to build extreme heat and increasing compression much higher than 13-1 is playing with dynamite. Some have tried and all have failed.

Big-Den - Double check your torque #'s. The formula is tq = (hpX5252)/rpm. The numbers should be- 650 hp = 569 lb/ft @ 6000 rpm, 700 hp = 565 lb/ft @ 6500 rpm. And, yes it these power numbers are tough to achieve.

Thanks to everyone for your responses. Please keep them coming!

Big-DEN

TQ - sure is. 568.6* @ 6000 RPM, I was using "calculator" and plugged in 6500 instead of 6000 for the RPM.

slow67

iTrader: (2)

I would check out the engines from Katech ---------> a sponsor here, they build a few different size engines with the LS7 heads (very similar in flow to the SB2.2) and cost much less. I'm sure they can get you exactly what you need.

96 Comp T/A

iTrader: (8)

Well,
Here are my thoughts on the matter. For cylinder you really only have one stock block casting to go with and that is the truck 6.0 block. I wouldn't even really consider it except that you started to mention cost being somewhat of a concern in your last post. In reality, the bores are probably too small and the cylinder walls are too thin to be a best case scenario. Go with some 1/2 head studs and those hella expensive gas ring cometic gaskets. In reality you should look towards a warhawk, C5R or LSX. MY persoanl pick for generating horsepower would be the LSX for dimensional stability. I have no practical experience with any of the last 3. The LSX would probably need to be lightened up and all would require some prep work (deburring, oiling system mods) in addition to the bevy of machinework needed for a competion engine of the level you require.
Next on the agenda are heads. I would skip all the stock castings. Why? well the stock castings are lightweight. I doubt seriously that you will be able to get valve seats and guides to stay put after running WFO for 45 minutes. Talk to the ET guys about some of their small port canted valve stuff or even their regular C5R/LS7 castings. Not much of a cost savings when you factor that in.

Rotating assembly will be pretty standard across whatever platform you choose. Either a high end forging or a mega dollar billet crank, with complimentary rods and pistons. No real cost savings to speak of there.


So, while I applaud your efforts, I think in the end it would be false economy. If I was doing it, I would look at an aftermarket ford 8.2 or 8.7 block or an 8.5" chevy block. With some appropriate cylinder heads from the Nascar family of engines. (maybe 18 degree chevy stuff?) That way you are not reinventing the wheel when it comes to pistons, cranks, and to a lesser extent, connecting rods.

I am also just throwing this out there, but have you ever thought about a destroked big block? I have never really messed too much with big block stuff, but if you could take an inch off the deck of a big block and come up with a trick rotating assembly with right sized rod journals that would be the *****. The only snag I could see with that is the deck would be non-existant and I am not sure how the structure of the head bolt holes would look. maybe look at some aftermarket blocks and see what can be done. When there is money there is always a way.
Good luck, this stuff sounds mega fun!!

pist0lpete

iTrader: (3)

If you are still considering an SB2 setup heres a 380 cfm + brand new topend for sale for a good price. http://www.pro-touring.com/forum/showthread.php?t=25584

knightec

Riverracer - I couldnt see your valve sizes?.......what intake and exhaust sizes are you using?.......certainly a very interesting motor spec

without wanting to throw a cat among the pigeons.......if your after low down torque.......have you considered increasing the stroke and reducing the bore slightly?........something like a 4 inch bore?........

I dare say the LS community are now going to kick the crap out of me again for saying that. .....see my post about converting an LS7 to 96.9mm bore to create a long stroke 6.0 Litre.......a more extreeme version of what I'm reccomending to you :-)

96 Comp T/A

iTrader: (8)

An increase in stroke doesn't generate a torque increase by itself , an increase in displacement does. You do get a few other minor benefits by decreasing bore size but they can easily be overcome by proper parts selection.

Adrenaline_Z

Although, I don't agree with most of the tuning ideas I believe he's talking
about moving the torque peak lower in the band using a longer stroke.


Riverracer seems to need torque peak in the upper RPM as his useable window
is very small between 5800-6500 RPM. I don't think he wants to go with a
small bore / long stroke combination for that reason.

Cheatin' Chad

iTrader: (3)

Jumping in to address this comment:
Having a longer stroke DOES NOT in and of itself mean you will make more torque than with a shorter stroke. I have seen dyno charts provided by David Vizard and Ken Duttwiler (in magazines) show that a longer stroke does not always produce more torque down low.

Riverracer

Knightec, I think my valves are 2.2 and 1.58, but not positive as I bought the motor 2nd hand off of another racer. We usually go with a big bore short stroke combo, similar to the Nascar motors. My engine is 4.135 X 3.35. As far as torque goes, we don't care about bottom and mid range, ALL we want is MAX torque in our operating range of about 5800-6500 rpm +/-. So our torque curve can be fairly steep up to our usable range and then we like to see it as flat as possible within this range.

96 Comp T/A - The big block idea wouldn't work for us as it would add too much weight, and light weight is very important in this class, 2 of my motors are all aluminium. The big block wouldn't be able to put out enough extra power to compensate for the extra weight. My all aluminium Brodix SBC is about 150 lbs lighter than my all aluminium Donovan BBC.

96 Comp T/A

iTrader: (8)

Well, I am not sure what your budget is but if you have a complete aluminum big block and small block sitting around I would venture to say that this isn't a shoestring operation. Have you looked in to compacted graphite iron blocks and some cnc lightening? The new GM blocks for cup are all CGI (which by itself is about 20% lighter and 5x as strong) and all are lightened up by a fair amount. I think I heard somewhere in the neighborhood of 35-40 lbs. Check out http://www.lsmeng.com for some pictures and details. If weight ends up becoming the next best thing to a horsepower increase, there are plenty of ways to accomplish that. to start with you can replace those hefty sheet metal intakes (who said aluminum intakes had to be light) with polymer or carbon fiber equivalants, CF valve covers, lightweight exhaust, new style high pressure hoses instead of stainless braided, the list goes on and on. Hell I saw a company "printing" an intake manifold with polymer stereo lithography at the PRI show. If you can draw it in cad you can have it nowadays. Also what do you guys do for cooling? do you use the jet pump to pump water through the engine and then spit it overboard after it has gone through the engine, or do you have a closed cooling system? have you tried any cooling system tricks (reverse flow, or external cooling passages) in order to be abe able to tolerate higher compression? This stuff interests the hell out of me, too bad I would have to fly 4000 + miles to see it.