LML Marine swap

kidturbo

Piston Tester
Jul 21, 2010
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Somewhere On The Ohio
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You try using just the silicone clear coating of prop speed yet? I use it without the etching primer on outboards to avoid anti fouling paint, works great and is clear so its hard to even tell its there...

That's kinda what I was thinking for lowers. Cerakote makes a high gloss clear that ya bake on I found. https://www.clearcoating.com/products/H-300/
Know that's a popular coating with guns these days.. These lowers were originally "hard anodized" but have scratches in them now and need some love.

Thanks Hawk, I'll take a look at those two. Doing the boxes up from raw alum again so need a good primer to fill some pits. I also thought of going to LOTO but just got back from St Louis last week. So going to the SBI race in OH instead and hit some guys up for parts..

I figured you'd have plenty of room up front with the plug in 6's. Cause I'm having to move all my mounts fwd and set exchangers to the sides without. Am shopping for exchangers right now if haven't sourced those yet let me know.
 

Hawk 40

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Oct 30, 2014
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They look like little toys in there
Way more room than I thought, still a lot of work to do
 

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Hawk 40

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Anybody know how the engine cooling requirements for a duramax compare to a BBC ? I assume the duramax needs more but how much more?
 

THEFERMANATOR

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Feb 16, 2009
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Should be directly related to the amount of hp you're pushing. It's the load that creates heat. You also have to step up x amount in cooling sinxe you will probably also have an aftercooler of some sort to cool before the heat exchanger.
 

Hawk 40

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I was thinking a heat exchanger adequate for a 700-800hp big block would be plenty for a 500 hp duramax.
I have high volume 3 stage sea water pumps so the intercoolers will have separate dedicated water and not warm water coming from the heat exchanger.
 

RPM Motorsports

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May 13, 2008
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Anybody know how the engine cooling requirements for a duramax compare to a BBC ? I assume the duramax needs more but how much more?

Guessing it's directly related to the load. We race with no fans and little radiators (mine was 6"x2"x17"). One of my last "street" events, we hot lapped five passes in about one hour, never even got hot. I didn't even have enough time to change the ice in the AW/IC, so I drained it and ran it dry. The ic water was boiling after the 2nd pass, so it was useless anyhow! Rick has been daily driving his Chevelle (550hp LB7) in traffic for years with no fan, and a stock style Chevelle radiator. He's made trips up through the mountains with traffic as well without issue.
 
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THEFERMANATOR

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If you're running direct sea water to it, I would say a hear exchanger meant for a 600-700 hp big block would do the job just fine. I was always told to add 20% for the difference between diesel and gas btu's just to be safe. Running direct sea water to it instead of going through the aftercooler 1st will make a big difference in the amount of heat exchanger ability required.
 

WolfLMM

Making Chips
Nov 21, 2006
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Actually it needs less. Cooling capacity than a BBC of equal power. However with the know high oil temps of these motors, I would size your exchanger like a typical marine BBC of equal horsepower.
 

WolfLMM

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Example, take a lb7 radiator and install it in an 8.1L truck. Watch the 8.1 overheat.
 

THEFERMANATOR

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Example, take a lb7 radiator and install it in an 8.1L truck. Watch the 8.1 overheat.

The 8.1l radiator isn't much bigger than an lb7's(lb7 is 1235 cu in, and 8.1l is 1424 cu in), but the lbz dwarfs them both(1782 cu in). If you do a hp vs radiator size breakdown, the diesel uses more cooling capacity than the 8.1l by about 10%(lb7 is 300hp, lly 310, lbz 360, and 8.1l is 330). Another example, the 454 and 6.5l used the exact same cores, necer heard of 454's with wide spread overheating, was comm9n place with the much lower power output 6.5l diesel.
 

WolfLMM

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Lbz has 60 more hp also.


You have 2 engines of equal hp, one Diesel one gas. We all know the Diesel is running more effiecsntly (using less fuel) so from a thermodynamics stand point it is required that the more effiecent engine run cooler. It has to. The Diesel cycle is adiabatic, meaning heat is contained. The Otto cycle, not so much.
 

THEFERMANATOR

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Lbz has 60 more hp also.


You have 2 engines of equal hp, one Diesel one gas. We all know the Diesel is running more effiecsntly (using less fuel) so from a thermodynamics stand point it is required that the more effiecent engine run cooler. It has to. The Diesel cycle is adiabatic, meaning heat is contained. The Otto cycle, not so much.

The diesel uses less fuel because diesel has more btu's per gallon than gas, thus the greater efficiency. And an lbz has 30 more hp than an 8.1l. You can look at it anyway you want, but take the figures I gave, and the lb7 has more cu in of radiator core per hp than the 8.1l does. And I used the optional hd radiator for the 8.1l for it's core size. There was 2 listings on ra for the 8.1l, and one was ALOT smaller than the lb7.
 

WolfLMM

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The diesel cycle converts chemical energy to mechanical with less fuel. It has to run cooler this is physics. Petrol engines use 20-30% more fuel per combustion event than diesel of equal output, so btu per unit reasoning is a wash! In this case the energy per unit is irrelevant, one uses more fuel to make up for having less energy density.

I'm not spinning it any way. The 8.1l WILL overheat with an lb7 radiator. I've seen it first hand. The gas guys would love to use our intercooler because it works with there trucks with no mods, other than requiring the smaller diesel radiator. The gasser will over heat idling and most def under full power.

In the end, I do agree he needs a larger cooler simply for the safety factor (marine use). No argument there. Not here to argue just pointing out something interesting.

Wolf
 

Hawk 40

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Looks like the production engines like the 5.9 and 8.3 Cummins use heat exchangers with about the same dimensions as the BBC's, maybe a little bigger but not much.
 

Hawk 40

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Catching up on some boat rigging while engine plumbing stuff all gets here.
Got the engines/trans/drive plates in a couple months ago and mocking up exhaust tailpipes, intercoolers, heat exchangers now.
 

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