Hotjava66

Hello everyone, new member so please bear with me while I learn the ins and outs of another forum.

Looking for some input on components for a scratch build I have been researching for some time and am about to move forward with. Will be working with a builder and machinist but my experience is with old school BBC and SBC so trying to get up to speed on LS stuff and educate myself proir to the build. Basically looking for opinions from the guys on here who are already running the stuff or better yet have broken it lol.

The goal of the build first and foremost is to have an engine that will live at extended high RPM and load use, with the power levels I am looking for. Going to be an iron block, aluminum head, carbureted, hydraulic roller engine. Thinking 4.185 bore x 4.00 stroke as of now, 6500 RPM target could stretch to 7000 if needed, looking to make 650-700HP NA, pump gas. Will build bottom end to handle forced induction down the road so build for 900-1000HP. Looking to use good components but nothing exotic or extravagant.

Block wise I am pretty much thinking Dart LS Next for the extra sleeve length and less hungry oiling system. Don't see a lot of other options in iron other than the lsx piece.

Crank, rods and Pistons I am still researching and would like some advice. Are the overseas forgings such as Compstar or K1 ok at this level or would you go to the mid level US stuff? I like to go US made when possible not sure how much $ is involved to do so yet. Pistons seem to be pretty close price wise between Wiseco, Diamond, JE etc any one better for the $?

Another question would be compression ratio, with a good aluminum head what is a safe number for extended RPM operation at 91-92 octane?

Heads, I am looking at either some worked on LS3 heads or going up to AFR 245's or Dart Pro 1's. Any thoughts there or thoughts on cathedral port vs square? I hear cathedrals carry more torque down low and if so would be an advantage.

Valvetrain, upgraded GM rockers or aftermarket? Have not heard much good on the aftermarket stuff. Springs etc will be speced to match cam.

Intake will probably be a super Vic or Vic jr, will talk with Pro Systems on carb.

I know this is kind of low tech but it's already wordy so apologies, please feel free to expand on anything and advice or input is much appreciated.

lil john

Callies crank..cost more but *BOOST APPROVED*..all other questions you have the answers.. the Aftermarket heads have more beef for Boost. I would generally think a AFR or the TFS heads would work out better. But your on the right track, there all the same (Engines) you just have to get with a good team. If your were to make 650-670 with around 9.1 comp and add 14 lbs. of boost = 1000+ hp
With a Hydraulic Roller and stock rocker arms. USE the STOCK CAST IRON EXHAUST MANIFOLDS. Sounds simple but will make for a helluva combination.

lil john

Oh yeah 4.185 Bore with Boost is not a good combination 4.125 works out better. Stronger cylinders and meat for future rebuilds.

gnx7

iTrader: (28)

I have an EFi 5.3 in my waterski boat and run Marine Power cast exhaust manifolds (water jackets and a riser) on stock truck intake/inj/rail etc and z06 cam with a tune for 91 octane. It moves along great but when fully loaded it could use a little more. In hindsight I wish I went 6.0 liter for more torque.

If you plan to go forced induction I would go EFi from the start. A stock iron 6.0 block and a forged crank will go a long way 1000hp+ with just about any cylinder head and boost plus stock intake.

Is the engine bay enclosed or open?

Look into a $600 take off LSA (Cadillac CTSv) blower all over eBay and do a built bottom end for that. With your unlimited cold water source the intake/intercooler would never heat soak. 700Rwtq at 2000rpm would make for a wicked boat.

Hotjava66

Thanks for the reply. Not really planning on boosting in the near future, only looking at down the road so really not a huge concern now. More concerned about making the power I want NA within the RPM range I need. What CR is safe NA with pump gas? 11.3-11.4 I see some places but would like to confirm. As for bore size I had 2 reasons, one to unshroud the valves as much as possible and second to gain cubic inches, need as many cubes as possible for torque and don't want to stroke past 4.00 due to low compression height and exaggerated piston rock at BDC. With the dart block piston should be fully in bore at BDC and they say max bore is 4.22 so there is some meat there yet even at 4.185. If I do boost down the road it would be low boost 4-6 lbs max. Feel free to correct me if wrong. Oh and I willbe running headers 2 inch primaries, can move water dumps back depending on cam choice.

Hotjava66

Looked into going the 6.0 route but since I want to stay NA for the time being I can't get the cubic inches I am going to need. Really need to pull some serious torque from 3500-6500 to make this work. Engine compartment is enclosed and there will be two of these monsters in there.....

v8pwr

iTrader: (19)

What type of engine is the boat set up for? I would do a solid roller BBC. This has been gone over quite a bit. The marine environment can be very harsh and kill an engine. I would prefer the BBC because it will make the power for less money, weigh a little more, and live for years. The solid roller should be a mild to moderate cam and will give up nothing. Hydraulic rollers fail on the water.
If you have to have an ls go to the LSX block. I see the Dart as another step in the wrong direction. A 434 can make 700fwhp. A solid roller should be a must as it gives the most control. They also will last longer in that environment. Cathedral ports are more responsive in a car but a boat doesn't load the engine like a car does.

Hotjava66

Please elaborate on why you think the LSX Block is better than the Dart piece, I am curious. As for going BBC I have them now, just want to do something different, plus they are a bit heavy for the boat and I need more room to work in the engine compartment. I am aware of the differences in marine use vs street, have been in boats for many years, plus I am in freshwater not ocean so bit of difference there. Very few of the big name marine builders I know of are using solid rollers anymore with the new hydraulic roller tech and profiles. Not trying to be contrary, just what I have been seeing. Have friends with 800 plus HP blower motors that have switched from solid to hydraulic roller setups in the last few years with much better results.

v8pwr

iTrader: (19)

I know that people are switching from old marine solid roller cams to modern hydraulics and seeing nice gains. Newer technology can be rewarding. The good hydraulic stuff costs more than some quality solids. I think the Dart is a nicely made block but why would we turn the ls block back into a standard sbc? Most of the high strength blocks in a myriad of applications are a Y block design. A majority of the good larger heads can make 700 on a 434 and live a long time it just might have too much compression for FI down the road.

Jontall

The aluminum Dart LS Next block is very expensive so I'd save a few bucks and get the RHS aluminum block. It will be ~100+ pounds lighter than any iron block.

Tuskyz28

66, if I was you I'll hunt down a LS2 block or a aluminum 5.3 block and then send it off to Racing engine development in California. A Darton dry sleeve would fit this build just right.

How much is this boat going to weigh ?

Cylinder heads...... you mentioned torque. You'll have that anyway you go on heads with a 4 inch stroker crank. For max torque down low the cathedral head is king. The LS3 rectangle port doesn't really start breathing and getting the job done to 4500 rpm or so but then again the CAM has to be on point no matter which head you choose. With a big bore build you have all kind of head choices. No one here mention using a LS7 head which in my opinion is the best bang for the buck. I personally like the LS7 head over the LS3 head as far as factory head goes. It's plenty of head porters that can get those bad boys flowing over 400 cfm!!

GSAWYERS

Another option is a sleeved LS7 block from R.E.D. or ERL, Callies Dragonslayer crank, Carrillo, Oliver or Dyers rods, JE asymmetrical pistons. Properly assembled with a quality dry sump setup should take plenty of high rpm abuse and have strength to spare. For the heads you could go with worked LS7's or any one of the higher end aftermarket offerings(Mast, All-Pro, Frankenstein, etc...) For the cam, I'd talk to some of the experts, they can steer you in the right direction. Something along these lines with 43x-44x ci's should provide plenty of relable power with room for fi in the future. You could also go tall-deck LSX and build a long rod version ....
Good luck

Unreal

I agree with the tried and true BBC comment. I don't see any of these high RPM big power LS motors living at that level for extended RPM in a boat. Now if you wanted a nice NA ~550-650hp motor, that could be doable.

Also 11+ compression isn't going to like boost later, so either build it for NA power, or build it for boost. Cam choices, etc are going to be vastly different.

Hotjava66

Thanks for replies, I guess I should have elaborated a bit on current goals. Looking to stay N/A, just thought if for a few bucks more I could have a crank and rods that could take a small amount of boost sometime down the road it would be worthwhile. What I really need to do is make 600+ foot lbs of torque in a flat torque curve to make it worthwhile. Not going to run extreme rpm want to stay hydraulic roller so 7000 MAX prefer 6500-6800. Thinking now maybe I should go with a little taller deck and do 451 or 454 cubes but not sure if it's worth the cost. These are also going to be iron block engines, local water is hard on aluminum and they are a bit cost prohibitive. Like the dart blocks also for the longer cylinder bores and better piston support, want some longevity and no oil drinker. If I were to do forced induction it would be at next rebuild and would only do 5-7 lbs boost and look for 800hp or so.

allblowdup

If what your looking for is 600 ft lbs and a running rpm around 6500 max go for the GM lsx crate motor and drop in some better lower comp pistons. Mine made 720@6400 stock with a holley tunnel ram 670 with a single carb. My buddies made 674 with a fast 102 on it. I would not take a BBC over an LS ever, especially when sustained rpm come into the picture. BBC valve train is all way to heavey for rpm and one is forced to buy expesine valvetrain components. The stock ls stuck lives forever at 6500.

Tuskyz28

Call R.E.D and do a aluminum 5.3 block with darton dry sleeves. That block alone can hold up to 1500 horsepower. Also the bore can be taken up to 4.185. Put you in a 4.125 crank which those sleeves can take and you'll have a 454ci monster. With that much stroke you'll you'll have a great torque curve...... especially combined with a big cathedral head/cam to match. Stay away from hi rise intakes they hurt that flat torque curve you want to achieve.