Just got all the parts in for my 1995 LT1 then I'm going to put in my 1980 Kona jet boat I know about the reverse cooling system for the LT1 and how it all plums together in the car what is the best way to plum it from the jet drive cooling system

Plumb it to the water neck first instead of to the block.  Pretty simple swap.  The cooling system was designed to run in reverse so I'd leave it that way. 

However, unless you're swapping to an old school dizzy or putting cool on plug I would think twice about running an LT1 in a boat. 

The opti was pretty much junk on a street car where it saw minimal moisture, a jet is going to be hell on it.

The cool thing is, you can machine the intake and modify it to accept a dizzy off of a 99-00 Chevy van and then run updated OBII with a newer ECU and you get a decent top mount dizzy with FI control.

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Plumb it to the water neck first instead of to the block.  Pretty simple swap.  The cooling system was designed to run in reverse so I'd leave it that way. 

So, how do you keep the heads cool, without forming steam pockets?

Dan'l

After thinking about it for a second, an LT1 would be a little difficult to plumb in a boat without some sort of adaptor.  Since the water neck is part of the pump you'd have to have a plate made up that would feed into the block on the top, then out on the bottom.  Basically two fittings on each WP attachment point instead of one.



http://garage.grumpysperformance.com/index.php?threads/lt1-vs-lt4-corvette-engine-parts-differences-useful-links.13141/

You could plumb it like i did my ls

Make the front motor plate the inlets and outlets for water

If you aren't doing a rail kit and plates then just make a plate with pipe fittings. Same theory


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X2

Filling the block first, and exit out the top. Minimal chance of steam pockets in the heads.

Exhaust choice would determine the plumbing route of the water hoses from the pump. (Headers, logs and snails, Merc center risers, etc)

Dan'l

An LT1 is designed to cool the heads first.  I would think that plumbing to the block first would be bad for cooling.  The heads are designed to work this way and don't look like normal SBC heads with regards to cooling passages, steam pockets wouldn't be an issue like they are on a standard 350.  They're more like a 400 for cooling than they are a 350.

And lt1 also has a closed cooling system in a car.

A jet boat engine, just sitting in the water is mostly dry / empty.

When water enters the top, it will seek the path of least resistance, and out the back, leaving the majority of the block and heads uncooled/dry.

If you restrict the water on the exit, you will over pressure the block and heads, pushing out a head gasket or even the core plugs.

When an Lt1 is in a boat, car rules no longer apply.

With a whole lake full of water, reverse flow cooling or not, it WILL stay cool. Exit temp should be 120° or so with headers.

Dan'l

If you plumbed it from the top, the block and heads would not 'fill' the entire cooling area. It would simply exit out the water pump ports.

Also, some of the theory on a reverse flow cooling system is to cool the heads with the coolest water from the radiator, to the hottest part of the engine, rather than cooling the block first then the heads, sbc style.

What's normal for an Lt1? 195° ? 210° ?
A good, I mean really good radiator drops the temp by 50°. Most are less.
So 195° coolant drops to 145° at best. The engine WILL add 50°, and the cycle continues.

So lake water, at 70°, on a single pass thru the engine, should gain 50°, and run at 120° or so with headers, and 140° or so with logs and snails.

Just my $0.02

Physics and thermo-conductivity played a part, too.

Dan'l

You guys plumb it however you want, it's not my boat.  But if I was doing it, I'd run it the way GM designed it.

http://www.enginebuildermag.com/1999/09/rebuilding-the-chevrolet-lt1-engine-2/

EXTERNAL COOLANT LINES

There is an extra hole that goes into the water jacket on both ends of the heads. These should be plugged when they’re in the front, but left open when they’re on the back. There’ s an external coolant transfer line that connects the holes on the back side to a reservoir that vents the air and steam vapors that would be trapped in the head and cause hot spots.