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I was talking to a jet boater and he was telling me to run my infeed water lines into the block drains on the bottom of the block! Has anyone tried this? He said there were some advantages to running this setup! 1 block is always drained of water. 2 Cooling oil first. 3 Always fully load block with water. What do yall think!:)Unsure
 

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I know a few people who have done it that way,
Don't know the exhaust you are using but cooling block first is a good thing. What temp does the motor run at now???? I run the water thru my logs first to warm and then thru the motor and out, motor runs at 160 to 190 which is perfect.
 

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Rollin With Fink
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Heres my experiance and only mine. Did it that way on a gen 5 motor, ran cool at wot and a little below. At cruise and idle it got way to hot and I could not control it. If you go away for the weekend to try it, bring your old hoses;)
 

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Cooling

GM spent alot of time on R&D to come up with there cooling system. Stick with the standard way of plumbing and you can't go wrong.
 

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Greg, Goes with what I have said for years. Auto mototive builders have spent hours testing to make a motor last. Ideal temps and proper running temp of motor.It would be to hard to tell all the guys running at 120 to 140 all day long the big three are wrong, Tempeture in the motor makes motors last and build power.My 2 cents. M
 

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...a jet boater...was telling me to run my infeed water lines into the block drains on the bottom of the block! Has anyone tried this? He said there were some advantages to running this setup!
Automotive passenger car engines use a closed cooling system where heated water is always entering the engine. As a result, the water temperature throughout the cylinder block is reasonably uniform.

But most high performance jet boats force lake-cold water right smack into the front two cylinders of the engine block. Depending on how optimally you've managed to maintain the operating temp of your engine, it is not too uncommon, upon disassembly, to see accelerated wear in the front to cylinders because they don't have the chance to get to full operating temperture as do the rear six cylinders in the block.

One way that some people have tried to "even out" this operating temperature differential is by plumbing the water inlet at the middle of the block, specifically the block cooling system drain holes.

I'd say that if you are going to attempt this, then do not try it with the tiny NPT-threaded drain back holes that are currently in place for draining the block. They should be enlarged and retapped to a larger thread size so that the newly installed fitting has enough ID to allow water to flow.

Will this even out the temperature differential? I don't know, as I've never researched it. But bear in mind that your V8 engine's head gaskets have holes in them allow the water to pass from the block to the cylinder heads, and these holes get larger as the you inspect the head gasket from the front of engine to the rear. In other words, the gaskets are engineered so that as water enters from the normal locaton (waterpump holes), it will be influenced to flow toward the rear of the block rather than just turn straight up to pass right through the head at the front and then out the intake manifold/thermostat housing (thereby causing the rear of the engine to have stagnant water and run hot). The cooling system is desinged so that water flows front-to-rear. Of course, this does not help the "overcooling" situation at the front two cylinders, but the other question is: how is this system affected when you plumb at the middle fo the block? Think about it...hmmmmmmmmmm.

LO
 

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I drive a 93 1 ton dually with stock tbi 454,at 80,000 miles the thermostat hung up so I removed it.I was told after removing it that the motor was designed to operate at 180 - 200.I never put it back in,(happy the motor was not on the threshold of over heating living in the hot ass gulf region). It stays at 110-130 unless I'm in traffic or towing.I have 258,000 miles with no trouble,no smoke,no blow by that i can see.It makes me wonder about the correct temp a motor will survive the longest at.
 

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I drive a 93 1 ton dually with stock tbi 454,at 80,000 miles the thermostat hung up so I removed it.I was told after removing it that the motor was designed to operate at 180 - 200.I never put it back in,(happy the motor was not on the threshold of over heating living in the hot ass gulf region). It stays at 110-130 unless I'm in traffic or towing.I have 258,000 miles with no trouble,no smoke,no blow by that i can see.It makes me wonder about the correct temp a motor will survive the longest at.
It will survive longer at 200* F than it will at 130* F. Probably make a little more power, too. The internal combustion engine is a "heat" engine and for a number of reasons works better with a certain amount of internal heat.

LO
 

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It will survive longer at 200* F than it will at 130* F. Probably make a little more power, too. The internal combustion engine is a "heat" engine and for a number of reasons works better with a certain amount of internal heat.

LO
What would be the correct temp to keep a jet boat motor at to extract the most power and longevity,with out a thermostat I don't remember seeing over 135-140.
 

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How about backwards

I'm not tryin to thread jack. But while the subject is brought up. What about running it bass-akwards?? heads down??
 

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jetboataholic
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I'm not tryin to thread jack. But while the subject is brought up. What about running it bass-akwards?? heads down??
No thread jack there. It is based off the original question. Good question, might help solve the cold front cylinders thing, but I'm not a mechanic or someone who knows a lot about engines. So, I don't know?
 

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Wide ,Old school V -drive boats were sometimes plumbed that way and it probably worked for them (seen a few) these "basically automotive" motors were designed to have coolant/water flow '"up" from the water pump inlet area thru the block and heads and out the out intake "T-stat" hsg Kreg Ive seen a few plumbed backa$$wards that always ran hot just my Heat rises ! 02 Tom
 

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jetboataholic
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Wide ,Old school V -drive boats were sometimes plumbed that way and it probably worked for them (seen a few) these "basically automotive" motors were designed to have coolant/water flow '"up" from the water pump inlet area thru the block and heads and out the out intake "T-stat" hsg Kreg Ive seen a few plumbed backa$$wards that always ran hot just my Heat rises ! 02 Tom
Good point! Forgot to think about how heat rises!:)sphss
 

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What would be the correct temp to keep a jet boat motor at to extract the most power and longevity,with out a thermostat I don't remember seeing over 135-140.
My boat is plumbed in the standard fashion with OT headers and when I am wide open accross the lake it runs at 160*. After such a pass, if I enter 5 mph zone the temp goes up to around 190* (since the flow of water through the engine slows with jet pump speed), but then the water temp slightly drops off after peaking and while I'm idling around.

I know, I'm pushing it...but the engine runs good there. :D In my particular case my gate valve is only 1/4-turn to 5/8-turn open, and let me tell you that water temp adjustment becomes VERY sensitive to gate valve postion when it is almost closed. BE CAREFUL and don't cook your engine if you try this. Take time and experiment.

LO
 

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I'm not tryin to thread jack. But while the subject is brought up. What about running it bass-akwards?? heads down??
I believe that the first passenger car vehicle with reverse-flow cooling was the chevy corvette...around the turn of the century. But remember that this is a closed cooling system with warm water being fed directly to the cylinder heads. Remember that our boats use cold lake water and I don't think that, with the volume of cold water that our jet pumps send to the cooling system, reverse flow is a good idea...sending this cold water straight to the HOT cylinder heads. For example, what is likely to happen if you pop the hood of your running car and spray water from your garden hose directly onto your engine's exhaust manifolds? C-R-A-C-K!

Since the cylinder heads are the component(s) that are subjected to/carry the greatest amount of heat (compared to the cylinder block), it has been suggested that the cylinder block also serves to preheat the water before hitting the f-in' hot cylinder heads...sort of a water manifold that "pre-heats" the water before sending it to the heads.

Food for thought,

LO
 

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I believe that the first passenger car vehicle with reverse-flow cooling was the chevy corvette...around the turn of the century.
LO
Yes, and GM thought they could safely increase compression by about .5.
Car engines are also worried about mileage and emissions
So ask yourself what is the point of changing the cooling system?
I run cold myself, but I have nothing against somebody running warmer or use a thermostat. You could build a whole heat exchanger for closed cooling, but what's the point?;)
 

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It will survive longer at 200* F than it will at 130* F. Probably make a little more power, too. The internal combustion engine is a "heat" engine and for a number of reasons works better with a certain amount of internal heat.

LO
How about this, as you are running logs, wet logs first then motor. Thats how I have it and If you remember I asked first about exhaust you were using
 
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