I don't know if the fat will give me a speed difference but it has to help with how the boat sits. At least on mine. If I can do this at a reasonable cost I think its a win win, any TQ concerns should be able to be fixed by the SC.

I just need to see if it would be better to build myself or not. I don't like the side mounting of Hardin's heat exchanger though, seems to mess up what could be a tight package.

Of course we have the guys that say strap a bracket on with some OB power,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,

I boat in salt so closed is nice no matter what. Crazy how much weight effects your speed, on mine I doubt there is 1 mph difference loaded full gas or light on gas. Temp on the other hand makes a lot of difference. Cast vers AL,,,, that all will come down to cost.

Big thing here is 90-91 non ethanol is all that we have on the water so I have to be able to run that. A lot of times we go farther then a tank will get me there and back, plus if we run to Bimini not sure I could get 93 there.

As for needing a SC,,,,,,,,,,,,,,,,,,,, well maybe not but hell we all like more! LOL.

Great thread, can't wait to see the results of this build.

Very cool, I built a 408 very close for my sons no prep car few years ago, had 11-1 weisco, pistons, K1 rods, eagle crank, but I used the GMPP CNC ported LS3 heads(very resonable) victor JR intake, had patrick from prosystems do a carb and used a daytona box to light it off. We put it in a non cut up 87 mustang fox body with a glide. It ran 6.50 all day thru a exhaust system @ 3200+lbs.on pump gas. I used a cam speced by Brian Tooley and never touched the carb. These things make great power hands down, he has stepped up and now running my old 3rd gen camaro turbo LS. Keep us posted on your build, sounds like you have a handle on it...I'm looking for a jetboat now to do a 6.0 in that I have laying around !

Its great seeing others interested in the LS idea and are not turning their noses up as most do saying "it won't make the torque" On that note I have a BRAND NEW set of CMI headers that i just received a week ago and decided to route the exhaust a different direction so im having them make me another set. Again these are brand new! Just paid $5800 for them... Make me a REASONABLE offer and someone take these off my hands as i dont need two sets.


https://cimg7.ibsrv.net/gimg/www.off...48412251a8.jpg
https://cimg4.ibsrv.net/gimg/www.off...f015cf0d21.png

Are those SS?

Yes, and no need for a $$$$ front drive setup, no water pump, p/s, etc needed, just a alt mount..simple, thinking about twin turbo deal, as can get most of those parts for the cost of the marine exhaust.

yes these are stainless. I had cmi do them in black as i liked the way that the new 860 headers looked in black.. I dont believe cmi will build anything in mild steel...

This will be my 4th season running a 408ci LS in my Checkmate and I love it. The sound is amazing and what surprised me the most was how much the handling of the boat improved over the big block, especially in rough water. To me, this is how the boat should have come from the factory. I'm still playing with my set up prop wise, but so far I have seen a best of 75.9mph. That's only turning 5700rpms. I have a few props to play with this year to try to get those revs up. I will say this, after 3 years I'm getting bored, so the next thing is going to be some kind of boost.

One thing I haven't heard anyone mention on here yet, especially with your cam choices, is reversion. The LS is a water sucking M.F.er!!!! I fought it for months with mine. I'm running lightning headers and started out with just extended collectors. That sucked so much water that it milkshaked the oil in less than 5 minutes of idle time, on the hose. So then I had the headers made dry to the tip. The water came into the exhaust stream in the last 1/4" of the tailpipe and it still sucked it in like crazy. I ended up having to make the exhaust completely dry (still jacketed, just no water in the exhaust stream). While it sounds awesome, the noise can get annoying (98dB at idle in the cockpit) through long no wake zones. So when you guys do your initial fire ups, keep a close eye on the tips.

Here is my cam card. While it is pretty aggressive, I have known quite a few others who have had issues with a less aggressive cam.

https://cimg2.ibsrv.net/gimg/www.off...5be6ca62ac.jpg

I built a set of clamp on mufflers for mine using GGB mufflers. I used the 3 ring sport mufflers and it made a heckuva difference. I can post videos of the differences later when I'm not at work (government computer). I always use the mufflers when I have my 6 year old twin girls on the boat with me, but pull them when it's just the wife and I.

Are you using a cam design program? Or some predictive modeling? Does seem with the cam Corey has that long tube headers would be nice, as for reversion. Down here we just run dry headers, screw the noise and there are no laws. I think ICDPLE uses some type of muffler on his dry pipe blower motor that worked good. I THINK,,,,,

One thing to keep in mind is the oil to the head is the only means to cool the valve springs...big issue on BB's not sure on the LS setups, none of the ones we run or have we did anything to the oiling other than a ported H/P oil pump..Rob

What is "billet barbell for back of block. "?

yep...goes in from the back and directs oil into the oil filter...if it wasn't there then unfiltered oil would go straight up to the bearings. The stock plastic ones have a thicker shaft that's more "restrictive" and they fit kinds loose in the bore...these are made to be tighter so less likely of any unfiltered oil getting by.

Looked through but who's blocks are you using and why cast iron?

So GM blocks and heads not aftermarket? Question, for me I will want closed cooling as I boat in salt. Of course it adds weight, would you still do a cast block or go Aluminum? Its funny because the 6.2SC motor GM offers is aluminum.

What would you do cast or AL?

looking like a nice build.job well done.

Why less HP with the EFI?