Ok guys, i am new here so forgive me for any oversights....

I am wondering if anyone has built something like that below before, if not, then do you think it would be possible....otherwise, suggestions? Are the part avaliable? etc...

1. We would be aiming for lightweight....LS2 stock alum. block? or Warhawk when it's ready.
2. Run on race gas or methanol....prefer race gas.
3. Power: 700-800 hp at the crank.
4. Run all summer, not on the street, but say a marine racing application....run for 30-1hour at a time but not at peak rpm.
5. Heads: thinking warhawk 12 deg. when avalible....anyone have anything else that flows 350+cfm?
6. Carberated...yea, yea, i know that takes a lot of the fun out of it...but it's the rules for what we are looking to do.
7. Comp. ratio....13-16:1, 16:1 possible and still get the durability?
8. Any crank and rod recommendations? Steel rods/crank.
9. Size: 390-418 cu in.
10. No blower or N2O.
11. Any guess on rpm range? i was thinking i need to keep it under 8500 rpm.
12. 1.75 to 1 7/8" headers....to 3.5" outlet.

I know i have already scared off a few builders by saying we would like to build them ourselves, but being a mechanical type, i just can see paying the premium, hell for what i could save, i could buy my own dyno and probably will anyway.

Anyway, I haven't seen many combos like this here. I would consider this an all out race engine that needs good durability for an entire season....the course would be like an oval, so you have the rpms peaking twice per lap.

Thanks for any ideas/suggestions/comments.

 

Def gonna need a huge solid roller and at least the 418 CI if not more. I know the ls7 427 block has made 550 rwhp with a cam swap which would be over 600 hp to the crank, so it should be doable, especially with 13:1-16:1 compression. d say you need bigger headers though, maybe even 2" primaries. Just my opinion though, sounds like one hell of a plan for a buildup though!

 

If your were really dreaming, you would have a C5R block.

 

if we are dreaming. A C5R block, a set of ported ls7 heads (390 cfm/ intake) and a nasty came.......you can make 600+rwhp which would give you your 700 flywheel........how much over that depends on how deep your pockets are.


-some others to think about....sheet metal intake, as stated above maybe 2" primaries would get you there easier.....just do the math and figure out which size is the best for what you're trying to do.

 

yes its possible... im assuming the app is for a raceboat?

you have plenty of cooling with the water, so you can run a higher compression.. and if you can run racegas too then its really high.. i donno the limit, i mostly work on pumpgas street cars.

basics id go with would be something along the lines of a warhawk block, max stroke you can get and stay in the Ci limit.... with some ported warhawk LS7 style heads.. a matching carb style intake.. maybe sheetmetal dual carb tunnelram... yea, 800crank hp wouldnt be a problem... i mean, you cant just slap together a motor like that, but its completely possible to even exceed that number...

 

LG hit over 620rwhp with an LS7 cam and mild exhaust port work. I say buy an LS7 long block and get the GMPP intake when it comes out, port the heads and a custom ground cam will net you 700rwhp easy with hydraulic roller. Now throw in more comp, race gas and solid roller and see 750+.

 

correct me if i'm wong, but I thought you want to run marine motors at the rpm point where there is max torque? That would change some of your choices.

 

really you want it at the point of max power... if thats peak torque or peak hp, that depends on the RPM of the motor...

however, id agree that most boats are not at WOT all the time, and are usually held at sustained part throttle.. if it wasnt a all out race boat, id probly go with a hyd roller and not spin it past 7k.. if that.... id also stay EFI, and go with the talldeck warhawk for extra cubes...

 

Boats need torque. More cubes will get you there. If money is no object then the Warhawk is the way to go.

 

There is a limit on what we could spend.....that's why we are looking at the LS2 based engines. We are looking for low cost and good durability.....no $5000+ set of CNC heads or $30K for an complete engine. Maybe i shouldn't have titled the thread "dream engine".

Assume that it's in a car of some type.

It will spend most of it's life above 5000rpm.

Also, can't run FI it's against the rules. A 850 or 900cfm carb would be on top.

We are thinking of switch from the SBC(23 deg heads) we have now 650+hp(7500rpm max) to the LS style engine, so we are looking for combinations that won't break the bank and will make 750-800hp for 500-1000 miles at 7500-8000rpm...not that it will run there all the time or all at once. After 500-1000miles we will freshen the engine.

I have seen the recent post on the GM LS7 heads, sounds very good.

We would need to keep the displacement below 418 cu in., go too big and we have way to much low end grunt....not that it's a bad thing, just something that is not in our design goals.

Race gas and Methanol(or ethanol) are the fuel choice, just don't think we can get there on 94 octane and 418 cu in. Race gas is prefered as the consumption of methanol is amost 2x that of gas. Change in weight over a run is a problem.

I am assuming we need good rod/crank/pistons for the bottom end....but:
1. will the stock rocker arms take high spring pressures and 8000rpm on a repetitive basis?
2. Assuming we would need a total of .700 lift or abouts.
3. Wet sump or dry sump?
4. 14:1 CR is kind of a norm. How high can we go? are we limited just by cooling capacity? Octane helps, but only gets you so far. Also, assume we are not combustion chamber engineers.

Thanks for the input guys. Maybe we will get a good base here and actually build it later on.

 

You might ask Chris Straub (Cstraub) on here. He has a lot of experience in marine applications.

 

well on that note.... something based upon the LS7 style heads with the matching carb intake port matched to it...
1. i would be using a solid roller anyway, and since you need a adjustible valvetrain, you should be looking at shaft mount rockers..
2. i doubt it would be over that.
3. how much money do you have?
4. donno.

i would try to wait for the L92 block when it becomes availible... only because the bigger bore is going to help a good bit, and open up more head options... its expected to be as cheap as the LS2..

 

LS2 402 - callies crank and rods and diamond pistons (or spend a little more and get a complete Lunati Kit).
ETP 245 or 260 11 degree LS1 heads
Edelbrock's LS1 Carb Manifold with a 1 in or taller spacer (port match to the heads)
Cam + Valvetrain Not sure... Never built a boat motor.
Dry Sump or Wet Sump??? Even though the water looks calm most of the time you bounce like crazy so Dry Sump may be a good choice to keep the oil from foaming in the motor.... yeah I know drop the crack pipe.
Biggest thing is going to be get'n a manifold that will flow with the ETP heads.

 

Can you run a prop at 8.5K rpm without cavitating it?

Boats don't need torque, they need HP, same as a car. HP is the ammount of work being done. 400 ft lbs of torque @ 3000 rpm dosnt do you nearly as much good as 350 ft lbs @ 6000 rpm. Depending on what rpm its at, you prop for it accordingly. Most consumer boats are propped and cammed for max HP down around 4700 rpm. You want to keep the rpm down because it may spend all day spinning at WOT.

 

Assume that it's in a car of some type....not boat.

 

ok.
what type? street strip? quick drag race? baja rally? 24hours of daytona or just 500 around an oval?

 

He said in the first post that it was going to be an oval-like track. I think the type of boat racing he is doing is more like car racing with turns and acceleration versus a "cruiser" type boat. Bring the Noise has some good ideas.

 

i can sum it in one word: Katech