Another Caddy cooling question

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AirPat
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Another Caddy cooling question

Post by AirPat » Thu Jun 18, 2009 5:00 pm

I finally got my motor put back together after my first rebuild and to my suprise it fired up on the first crank. ( i was nervous as hell) The oil PSI is at about 60 but I can't seem to get the bugs out of the cooling system. I searched it but still have a couple of questions about the cooling system. I just ordered a burp tank and a overfill tank from classic but would like to see some good pics of how you guys plumbed yours. How far from the prop does the radiator need to be? What type of aluminum radiator should I buy? When I bought my boat it had a hose coming out of the back of one of the heads. Is that needed? I will post some pics later. Right now the radiator is located under the motor. I am getting closer and closer to finally getting to run this boat in the water. After I solve this problem it should be go time. Thanks for the help.

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Re: Another Caddy cooling question

Post by Ruagatr » Thu Jun 18, 2009 5:21 pm

Airpat--Cadillacs are famous for needing to be "burped". I always found that the best way was to pull the top hose off--assuming an "ordinary cooling system" and stick the garden hose into the hose that leads to the radiator and let it fill from the bottom up until it runs out for several minutes. Then yank the hose out, pop the upper hose onto the thermostat housing, and run the engine and check for temp increase. Run the radiator within 24 inches of the propeller and preferably within 15 inches. I run mine about 8 inches from the propeller. The old heater outlet bung which used to stick out of the head may be plugged. Once she is burped, it will cool just fine.
In the woods, when you throw a belt and she overheats, let it cool WAAAY down, fill the system from the overflow tank, fire the engine for 30 secondds and then reopen and refill it. That works too.

Regards, Charles

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JUNIOR480
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Re: Another Caddy cooling question

Post by JUNIOR480 » Thu Jun 18, 2009 6:09 pm

i think before this post goes any further.......(we need to ask james)!!!!!!! :mrgreen:
HAULIN A$$ SINCE 78......

T-REX
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Re: Another Caddy cooling question

Post by T-REX » Thu Jun 18, 2009 8:59 pm

:bounce: cant wait !!!!!!!!!!

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Re: Another Caddy cooling question

Post by T-REX » Thu Jun 18, 2009 9:02 pm

james thanxs ne neadz a carbaretior. prolly a holey. :roll:

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John C
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Re: Another Caddy cooling question

Post by John C » Thu Jun 18, 2009 9:51 pm

Airpat, make sure you get an aluminum radiator for a BBC. you can get one from diamondback or classic. They are about $400 at Diamondback. I think classic is a little more. That big radiator is the one you need on your caddy. I had trouble running hot with a smaller radiator. going to the big radiator and a burp tank solved all my problems. Motor has been running cool with no problems for years.

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Re: Another Caddy cooling question

Post by John C » Thu Jun 18, 2009 10:01 pm

Airpat I just noticed your out in TX. You can get one shipped to you or you can call one of the airboat manufacturers out there. Just make sure its the radiator they use when they rig out a boat with a Big block on it. I think they measure 31x24

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Re: Another Caddy cooling question

Post by AirPat » Tue Jun 23, 2009 9:17 am

Has anyone used a be cool radiator? What is the difference between the 400.00 radiator at Diamondback and the 200.00 I can find on the web or Summit. I saw someone mention a 99 f350 radiator for a V10 for 125.00 thats aluminum and has 3 rows. Will that work? I want to protect my motor so i want a good product I just want to make sure I am getting my money's worth. If the 400.00 radiator is what I need then I don't have a problem with that. Thanks again for the suggestions.

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CactusJack
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Re: Another Caddy cooling question

Post by CactusJack » Tue Jun 23, 2009 10:48 am

AirPat, the radiator needs to be as close to the prop as you can get it (without the prop EVER being able to hit it) and, just IMO, as high up under the engine as you can get it. My experience, so far, is not with airboats (yet) but with Subaru (& Rotax & Hirth engines) on Gyrocopters, but suffer from the same problems.

Radiators are designed to be level with the motor (like when in a car/truck) or above it (thermal flow/heat rises).... a radiator below the waterline [of the engine] is not as efficient because of heat wanting to rise (naturally) The reason airboats have big radiators, is because down there, they are less efficient. For example, on an average turbo gyro, to keep it cool we used a big (very efficient) 6 cylinder type, 2 row crossflow radiator (below the engine) and a burp tank & overflow tank above the engine. If I mounted a radiator above the engine, I used an RZ500 motorbike radiator and a reservoir tank, about 1/3rd the size of the big one below, and had about the same, if not better cooling, carrying prolly a gallon+, less coolant. With a below mounted radiator, the engines cooling depends ENTIRELY on the water pump (thermal flow wont help a cracker, in fact the opposite) If the system leaks, the belt breaks or the pump s@!ts itself, you fry your heads :roll: When you switch off an engine with a below radiator, the heat from the radiator rises so the engine stays warm/hot until the radiator has cooled then the motor can cool. With the radiator above, when you switch off, the natural thermal flow keeps the cooling system going and keeps cooling as normal, even with the motor off.

So the little radiator was at least as good cooling, the weight saving was significant.... only thing was the radiator looked 'out of place' up there :oops: but if you like efficiency over looks, it isn't a problem. The cheaper radiator mounted higher would be my choice.... or the 'most efficient' radiator mounted below with a burp tank above the engine a close second choice.

The hoses from the back of the heads allows the pocket of hot water maybe not flowing so well in the back of the heads, a path to leave and join the circulation of the rest of the coolant, thus 'evening out' the head temperatures, not so much providing 'more cooling'. I would use them if I were you.... they should go to the burp tank or into the top hose of the radiator (to go in for cooling) They also allow air trapped in the back of the heads to escape, so a good idea IMO.

Remember, if you go radiator above the engine, it doesn't have to be as big nor upright, it can be layed over (even flat/horizontal) as long as it is getting some airflow. You can find out if it is getting airflow by sticking some 'blue tack/chewing gum on and around the radiator (both sides) with wool (yup, from mum's knitting) :lol: stuck to the gum..... run the engine and see what the wool does. If it is getting airflow, the wool on top/in front will be stuck onto the radiator, not moving & the wool on the back will be sticking out from the radiator. :wink:

I am in no way knocking folks who use below radiators.... they have worked for years and will work still work, no probs, they just have to be set up right.... the radiator fits so nicely down there, and looks good too..... almost the perfect spot for it, just not quite as efficient, but done right, works great :wink:
I was told I was wrong, once (not sure I believe it though)
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Airboat experience so far, limited to having bolted a gyrocopter to a flat bottom punt.... but THAT.... is about to change, bigtime :-)

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JAMES
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Re: Another Caddy cooling question

Post by JAMES » Tue Jun 23, 2009 12:22 pm

air pat seems your getting some good advice some from guys that no what their talking about some from guys that dont even have water pumpers and some that dont even own an airboat
between all this you can get it right good luck !!!!!!!! :D
https://m.facebook.com/321ccc/?ref=bookmarks Wp383 268 rotator 3 bld WT/EX 14.4 perdator

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Re: Another Caddy cooling question

Post by Joe » Tue Jun 23, 2009 2:08 pm

You just need a trim tab on top of the cage so you can trim the airflow to the radiator :D :lol: :lol:
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Deano
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Re: Another Caddy cooling question

Post by Deano » Tue Jun 23, 2009 10:00 pm

Cactus Jack,

It may or may not be relevent to the discussion at hand (probably the later), but the smart a$$ in me had to point out that while heat does rise in many instances, this is not aways a given. This is generally true where all other parameters are the same (and frequently they are not).

A better presumption than "heat always rises" would be that "heat will always move from where there is more heat to where there is less heat".

For example, look at your cooler (that hopefully still has ice and cold beer in it) and consider what is the purpose of the conductive insulation that makes up the bulk of it. Does it contain the cold inside, or does it prevent heat intrusion from the outside? Anyone versed more than a little in Thermodynamics will tell you it is the later. You can't contain cold. You prevent heat intrusion. When the ice melts it's not because the cold escaped, it's because the heat intruded the space. (Of course these statements are only good on this side of absolute zero, but if it is less than minus 273 degrees centigrade we don't need ice to keep our beer cold :lol: ) If heat always rose, our coolers would only be insulated on the bottom.

I ain't picking on ya Jack, just used to use a lot of Thermodynamics in my prior line of work. Never thought that I missed it, but now I kinda gotta wonder. :?:

A agree with most all of the points you made, however I don't think that the radiator should be
CactusJack wrote: . . .as high up under the engine as you can get it.
I haven't had cooling issues so haven't tried this every way there is to do it, but it seems to me that any given radiator will cool more the more air you move over it. The higher you put the radiator up under the engine, the closer it is to the center of the prop. The closer it is to the center of the prop, the less air is moving over it. While I would keep the bottom of the radiator from being below the top of the transom, I would put it as far from the center of the prop as possible without going that far. Do you know something that I am overlooking, or did you possibly overlook the difference in airflow over the radiator.

Deano
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but it is not the path to knowledge; it has no place in the endeavor of science."
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CactusJack
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Re: Another Caddy cooling question

Post by CactusJack » Thu Jun 25, 2009 6:37 am

Deano, The point about heat rising, is after the engine is switched off. During engine operation, the waterpump and airflow do an excellent job of circulating the coolant and keeping the whole shootin' match cool, no matter where the radiator is in relation to the water level of the engine. My point is, from my experience with gyros (similar power plant and cooling system) and MY findings were that a radiator can be smaller if mounted above the engines waterline.... however, I still use radiators below, because it works fine, has been done for ever.... & will continue to be done.... no need to change (don't fix what aint broken) :wink:

When you swithch off the engine, the coolant circulation stops (unless you have an electric water pump & you leave it on, perhaps with a turbo type timer) So, the coolant stops..... the heat in the system will rise, the radiator will cool from any relative airflow, and the block (& contents) will cool over time.... no probs.

If the radiator were mounted above the engine, with the engine stopped, the cooling system will continue to work, even tho the pump is not circulating the coolant, the radiator will keep radiating its heat with help from any airflow, the coolant will keep bringing the heat from the block below, as opposed to a radiator below, the radiator will pass off its heat, the engine will cool down slowly by radiating its heat (but the engine isn't as good a radiator as a radiator) :lol:

James, every time I offer advice/input, I qualify myself that my airboat experience to date is basically nil*, although, other things I have had alot of dealing with (such as gyros) are 'similar' and my experiences could be of value to someone else. I never claim to 'know it all', I just pass on what I know from past experiences if it is relevant to a question asked. So, please, anyone, never think I am bucketing what you do, I am not guilty.... I am just offering the fruits of my past experiences.... sometimes they are more relevant than others.... & sometimes hearing input from someone 'outside the square' can inspire people to think of other ways of doing things..... they dont have to 'do it any different' but an open mind never killed anyone :lol:

* My airboat experience so far, was I put a complete turbo EA81 gyrocopter, less the top section of its mast (a friend/customer tipped it over whilst learning to taxi & damaged the mast & blades) on a 12' Stessyl V front, flat bottom punt. We enjoyed about 3 months of making an @ss of ourselves in the local waterways, until he sold off the engine/RD/prop which, sadly, ended our fun :cry:
I was told I was wrong, once (not sure I believe it though)
If you can't blind 'em with brilliance, baffle 'em with BS
Airboat experience so far, limited to having bolted a gyrocopter to a flat bottom punt.... but THAT.... is about to change, bigtime :-)

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Wild Bill
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Re: Another Caddy cooling question

Post by Wild Bill » Thu Jun 25, 2009 8:56 pm

Yeah this probably shouldn't work but it seems to so I won't bother changing it till I need to.

Image

I followed Waterthunders opinion on this one from rad placement to burp tank plumbing. could be the cooler temps up here but if it gets hotter up here and in turn so does the engine I'll just add some sheet aluminum to the engine stand legs. Runs 160 idleing around or running up the river. Can't really say I have done much dry, just cruising 2500/4500 rpm. High volume thermostat with a bunch of holes drilled around it, Had to try something different! :wink: RHS rad from e-bay
Oh! and under the front of the engine I added a shroud to direct the air to the rad. you can feel good flow with your hand while idleing!

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CactusJack
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Re: Another Caddy cooling question

Post by CactusJack » Fri Jun 26, 2009 7:27 am

Wild Bill, I know I keep saying it, but I keep seeing your pics..... that is 'one heck of a nice boat' and a dang nice trailer to boot (concidering it was just an afterthought) :wink:

G'd onya mate, hope you are giving it heaps :wink:
I was told I was wrong, once (not sure I believe it though)
If you can't blind 'em with brilliance, baffle 'em with BS
Airboat experience so far, limited to having bolted a gyrocopter to a flat bottom punt.... but THAT.... is about to change, bigtime :-)

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Re: Another Caddy cooling question

Post by Joe » Fri Jun 26, 2009 9:01 am

Hey wildbill,i just noticed in this pic that your air breather is slightly pointed back toward the prop. this could be some of your carb problem.I know if i run mine with no aircleaner at a high rpm the prop will actually suck the gas up out of the carb :shock: I could only imagine it`s creating a negative vaccum in that breather box you have on there. Try turning it toward the front next time your out and see if it helps
Compromise is for those that cant get it done!!

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Wild Bill
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Re: Another Caddy cooling question

Post by Wild Bill » Fri Jun 26, 2009 9:52 am

Thanks Joe! I'll give it a try! Mounted it that way because of bug sucking but filters arn't that expensive :lol: I went with a Mallory 4309 pressure regulator and I think if I have time today I'm going to bolt on the 850 and try it. Preventive Mtc. on the road fleet and gotta take my dad to the doc. A guy is considering trading me his 750, he has the holly upgrade mainbody on his so I would end up with the better deal so I hope so!
Thanks Joe! Some pretty good teachers on here! 8) Bill

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CactusJack
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Re: Another Caddy cooling question

Post by CactusJack » Fri Jun 26, 2009 10:21 am

Good catch Joe, well spotted....I missed that one..... obvious once you been told tho :lol:

Real good point, I reckon..... not much pressure in there, eh?
I was told I was wrong, once (not sure I believe it though)
If you can't blind 'em with brilliance, baffle 'em with BS
Airboat experience so far, limited to having bolted a gyrocopter to a flat bottom punt.... but THAT.... is about to change, bigtime :-)

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