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Old 05-25-2007, 09:34 AM
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496 overheating

Hello, The car is a 1972 Ventura. I originally had a be cool radiator with two one inch tubes, the radiator is 26X19" and the core is 22X19. I had a 2700 cfm electric fan with a shroud on it and the motor would creep to ~230-240 and I would shut it off. The weird thing is that if I let the car sit at an idle, and dont drive it, it never gets over 200. As soon as I start driving it, it slowly starts creeping up. We figured that the radiator must be clogged as it was an old radiator so we bought a new triple pass FSR crossflow radiator. We are still using the same fan and shroud and it runs a little cooler, but still gets to 220-230. I am wondering if a mechanical flex fan with a shroud would have a good chance of solving the problem. I think the electric fan and shroud may be causing more airlfow restriction than anything and that the mechanical fan would help. Below is the fan and shroud I am thinking about as well as the fan and shroud I currently have. Does anyone have any experience with a mechanical fan and shroud like the one I am looking at?

This is the exact fan and shroud I currently have.
http://cgi.ebay.com/ebaymotors/64-67...mZ150125394870

This is the flex fan I am considering
http://www.jegs.com/webapp/wcs/store...44431_-1_10115

This is the shroud I am considering, I may run two, one right side up on top and the other one upside down on the bottom.
http://www.jegs.com/webapp/wcs/store...56129_-1_11483

If it matters, I have a march pulley kit with a long water pump

Thank you
Adam

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Old 05-25-2007, 09:41 AM
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I wouldn`t use a flex fan for no reason. Reason being, too noisy, and if it decides to come apart it takes stuff with it, biggest reason is it eats horsepower. What kind of water pump are you using? what are you using for coolant? Do you have a overflow connected? are you certain it`s not running too lean? is the timing set to spec?
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Old 05-25-2007, 10:12 AM
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The water pump is a mechanical high volume. Coolant is a 50/50 mix with water and the prestone green coolant. Overflow is connected and it spits some out if it gets to ~230 it has a 20 lb cap. The motor is running rich as of now, and we richend the mixure screws which did no good. Timing is a whole different story. We made the mistake of buying a cheap pro comp HEI and for some reason with 8 degrees initial, we can only get around 28 total with the mechanical advance. The vacuum advance does not work with the cam and carb that I am using, it is too erratic. I am switching to an MSD pro billet/6AL/blaster 2 to solve that problem.

Thank you
Adam
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Old 05-25-2007, 12:43 PM
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It seems like you should be running alot more than 8 degrees initial, and certainly more than 28 total, I`d think that`s alot of the issue there, No vacuum advance can make it run hot. I recall when I was coming back from a 140 mile trip going down the interstate the car felt like it lost power, and the temp gauge creeped up to 220 from 195, I right away thought the vacuum advance went out, I got off the exit ramp, the car would barely Idle and I knew right away it went south, I checked it when I arrived home and sure enough it was ruptured. By the way, what temp thermostat are you using? Another reason I don`t recommend a mechanical fan is since it will pull less air at idle than the electric does due to low idle speed, at highway speed you shouldn`t need the fan at all. I think you already found the problem in the ignition.
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Old 05-25-2007, 12:49 PM
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Quote:
Originally Posted by firestone
Hello, The car is a 1972 Ventura. I originally had a be cool radiator with two one inch tubes, the radiator is 26X19" and the core is 22X19. I had a 2700 cfm electric fan with a shroud on it and the motor would creep to ~230-240 and I would shut it off. The weird thing is that if I let the car sit at an idle, and dont drive it, it never gets over 200. As soon as I start driving it, it slowly starts creeping up. We figured that the radiator must be clogged as it was an old radiator so we bought a new triple pass FSR crossflow radiator. We are still using the same fan and shroud and it runs a little cooler, but still gets to 220-230. I am wondering if a mechanical flex fan with a shroud would have a good chance of solving the problem. I think the electric fan and shroud may be causing more airlfow restriction than anything and that the mechanical fan would help. Below is the fan and shroud I am thinking about as well as the fan and shroud I currently have. Does anyone have any experience with a mechanical fan and shroud like the one I am looking at?

This is the exact fan and shroud I currently have.
http://cgi.ebay.com/ebaymotors/64-67...mZ150125394870

This is the flex fan I am considering
http://www.jegs.com/webapp/wcs/store...44431_-1_10115

This is the shroud I am considering, I may run two, one right side up on top and the other one upside down on the bottom.
http://www.jegs.com/webapp/wcs/store...56129_-1_11483

If it matters, I have a march pulley kit with a long water pump

Thank you
Adam
I'll start with the question of where do you live? Weather has a lot to do with cooling. Hot, humid weather is the worst add some altitude and it's more so. Hot and dry is next on the difficult list, and cool to cold better.

Lots of things affect operating temperature, however, your description certainly sounds like not enough coolant circulation as speed goes up. This is rather typical of underdrive pulleys. You said you have March pulleys, are they under drive? Is this a serpentine or V-belt setup, there is a difference in water pump rotation between them.

A 26x19 inch radiator seems small to hang 496 inches on whether a 2 tube aluminum of a 3 tube brass design.

Is there air conditioning ahead of the radiator?

An improperly timed engine puts a lot of heat into the cooling system, the distributor set up needs to get fixed. Similar for the mixture, although rich mixtures can be used to cool the inside of the cylinder, they do really bad things to the engine by burning late and wiping too much oil off the cylinder walls, which increases friction, heat, and wear.

Universal fan shrouds are mostly ineffective and in my experience not worth the bother.

Going to an engine driven fan might help as I'm not keen on your electric fan's layout, if what you have linked is what it looks like. That configuration will interfere with and obstruct high road speed air flow thru the radiator. Your electric fan would be better as a dual set up if the one you site as an example is what you have. This and the potential use of underdrive pulleys is high on my list of "Root Causes". The fan is really there to pull air for stop and go traffic, where essentially you state you have no problem. It doesn't take much road speed to supply sufficient air flow over the core. The fan just gets in the way as road speed goes up and the one you have has a shroud that appears to obstruct flow over about a third, perhaps more, of the core; and restricts outlet of that air to the diameter of the hole in the fan shroud, minus fan blade swept area if it can keep up to the ram effect into the radiator.

I don't have anything particularly against flex fans but you have to keep an eye on them. The rivets securing the blades fail from the constant vibration and the blades come off with messy results. If you use one, you've got to stay on top of rivet condition which means carefully inspecting the fan at least everytime you change oil. As it ages you should step that up to weekly. You must look at both sides of the rivets and gently prod at them just to make sure you don't have the two ends of a broken rivet looking good but holding nothing together.

Other tricks too cool an engine if you can't get enough radiator on it are to install an engine oil cooler. Use one with a thermostatically contolled fan as this is efective at idle, when there's no airflow over the core and get a thermostatically controlled bypass valve so oil isn't routed thru the cooler when the engine is cold, this warms the motor up a lot faster. If you're running an automatic the same hardware for cooling engine oil is also good for cooling the tranny oil and takes that job off the radiator. These two things will take 20 to 30 degrees off the coolant temp.

Lastly is the thermostat itself, you need to make sure it is both installed correctly and it functions. A thermostat installed backwards will be forced toward the closed position by coolant flow. The faster you drive the more the closure force. A thermostat stuck partially open may flow enough coolant at low speed but not allow enough flow as speeds rise. Another is the lower hose, sometimes when they become soft, the pump's suction causes them to collapse cutting off the intake flow to the pump.

Bogie
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Old 05-25-2007, 02:22 PM
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If your 496 has a radical rough idle racey cam, you need to run a lot lot of initial timng at idle or it will overheat.
Try locking out the distributor and set the timing to 38deg at idle.
BBC's like 38deg. BBC's with big cam timing like the distributor locked out for full advance at idle. Get an dial advance timing light or a timing tape for your balancer. 38degrees total advance for a BBC on premimum gas.

The only fan/ Shroud combo that has a chance to keep your BBC cool is the Factory GM HD 7 blade Big Block 396-427-454 air conditioning clutch fan and the factory 1970 396 NOVA fan Shroud. You can buy reproduction parts from Year One.
http://www.yearone.com/
It's more important to keep the motor cool than the small amount of power lost thru stock drive ratio fan pulleys. A overheated motor doesn;t make much power
or last long.

Last edited by F-BIRD'88; 05-25-2007 at 02:30 PM.
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Old 05-25-2007, 02:28 PM
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Are you using the bypass hose? You know that little hose that goes between the water pump and the intake manifold? I would use it and make sure it is the right size (3/4 inch hose)

I use a 19x31, 2 core alum on my 454 with stock size pulleys. It would run a little warm with march pulleys. I had to go back to the stock setup in the summer months. Stock bbc uses OD in the water pump and fan belt, march pulleys don't.

2700 cfm is not enough for a 496. That is good for only a 250hp engine. I recommend using the stock 19 inch fan and fan clutch along with a tight fitting shroud. I made my own shroud but I'm sure you could find one at a junk yard. Make sure to get the fan clucth with the same size hub as the water pump. If the put a 5/8 clutch on a 1/2 hub it will fly off at high rpm. Don't ask me how I know about that.
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Old 05-26-2007, 04:06 PM
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overheating 496

You could also try going to an overdrive water pump pulley. Evans coolin has these. Also check out Derale mech. fans or Vintage air. I have have the same problem as you. Living in Texas with 100 deg. summers.
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Old 05-26-2007, 05:39 PM
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I tend to agree with F-BIRD'88 and the timing issue... But would also like to know about the bypass hose from intake to water pump if its installed as asked before...? Timing and a BBC and keeping cool are real issues... Late timing will for sure tend to make one run warm or hot... I too tried a base of around 8-12 degrees of timing with a pretty radical cam and it wanted to overheat... Bumped it up to 18-20 degrees and guess what even down here in southeast TX it ran nice and stable never over 210 even after light to light blast with 90 degree plus weather...
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Old 05-29-2007, 03:52 PM
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Thanks for the replys, It does have the by pass. The waterpump pulley is over driven. The crank is 7" and the water pump is 5". We (My dad, our mechanic and I) are actually thinking that the coolant may be moving to quickly through the radiator. I also think the shroud could be causing an airflow problem. We have a couple of 12" pusher fans laying around so we are going to give two pushers along with the 16" puller with no shoud a chance and see if that helps at all. I had a $60 pro comp HEI that was giving me issues with getting the timing where I want it so I am currently also having a pro billet/blaster 2/6AL installed. Has anyone used the additives that reduce the surface tension of the water in an attempt to increase heat transfer, like purple ice from royal pruple? Thanks for the replys.

Adam

Last edited by firestone; 05-29-2007 at 04:03 PM.
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Old 05-29-2007, 04:09 PM
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Stock pulleys are even more OD than that. The stock pulleys are stepped, crank has a real big water pump pulley and smaller ac/power steering pulley's, and the water pump also has a stepped pulley and is driven off the smaller pulley. I think it is like 7.75 crank x 4.5 water pump.

The march pulleys are the same size (no steps). They don't drive the water pump and fan as fast as the stock pulley setup does.

I did the math a few years ago on the difference between the stock pulley system and the march street pulleys and came up with a 10 to 15% difference (forgot the exact number). But I have it in my log book at home and will let you know tomorrow.

The fan should fit tight in the shroud (1/2 to 3/4 inch clearance on the sides and blades 1/2 way out) and the shroud should fit tight to the radiator.
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Old 05-29-2007, 04:21 PM
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I have used Red Line Water Wetter in two applications. For street applications it has less effect. They even tell you that on the bottle! The reason is you have to still use antifreeze as opposed to just the water wetter and water.
I used the combo of water and 15% glycol and then the whole bottle of wetter. The best I can tell is I lost 5-ish degrees. Nothing to write home about.
Same results from a 350 and 307. 307 has stock internals and the 350 was 10.5:1 big cam. Lost About 5 degrees on both.
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Old 06-06-2007, 10:30 AM
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Did a plug check and found antifreeze in the number 8 cylinder. Had the head pulled and the gasket looks OK. The head is off getting checked for cracks. The block was checked before the motor went together so I would think it is OK. The machine shop guy said that there is a chance that the valve guide is leaking. I'll keep you updated.

Thanks,
Adam
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Old 06-07-2007, 11:31 AM
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Coolant inside the engine isn't a good sign for sure. A blown gasket would be the simpler problem. As it is this is probably the result of a crack from overheating. Never head of coolant getting in from a stem guide. Cracks in the head are usually between the valves, from the valve seat to the sparkplug, or in the exhaust port, occasionally in the intake port. Or some combination of all of these.

You just can't discount the block, you've cooked this motor pretty good and anything is fair game.

Cast iron doesn't like to be heated unevenly nor a lot, it leads to cracks in the darnedest places.

An engine that heats as it's being driven is a good sign of several problems which could be individual or a combination of events. These are;

1) Insufficient coolant flow
A) The radiator is plugged and cannot meet the demands of the pump, this will show a pressure increase on the return side as coolant stacks up in the return tank.

B) The pump delivers insufficient flow, this can be a high RPM racing pump that doesn't push enough coolant under 6000 RPM. Or at the opposite scale any pump running underdrive pulleys that cause insufficient flow for the speeds being driven. My comment to this is there's way too much BS out there concerning power to be gained by turning the pump more slowly. While there's small gains to be had for sure, on the street they'll come at the expense of overheating the engine, which usually leads to cracked castings. The engine gets hotter and hotter the longer/harder you drive it, with temps falling at slower speeds.

2) Insufficient radiator area
A) This is simply a radiator that is too small. This can be a lack of overall size, or an inadequate number of tubes and or fins. Either way the radiator cannot loose BTUs equal to the rate they are being delivered. Similar to coolant flow problems, the coolant will just keep getting hotter the harder and longer you drive the engine. Temps will tend to fall back toward normal at slow speeds or idle.

3) The inverse problem of heating at idle or at low speeds in traffic but cooling off when you get moving is usually the result of insufficient air flow through the radiator's core.

Reguarding Water Wetter:

I've never had any measurable decrease in operating temperature with this stuff in either street or competition engines. I have, however, lost the occasional hose to clamping failures with this stuff. All of these I suspect are do to water wetters being essentially non-foaming detergents that reduce surface tension or the water, thus, allowing coolant to seep past what otherwise appear to be tight connections. Once the interface between the rubber hose and metal fitting has become thusly lubricated the hose finds it easy to blow off as flow and pressure increases. Now you can tighten hose clamps till it becomes a strength test, but certain nipples such as those on the radiator are pretty thin material and can be distorted or broken by unlimited strength tests of one's ability to torque clamping screws. Plus I find the failure rate of pump seals goes way up probably for similar reasons of the wetted coolant being better able to soak into things similar to the cause of the hose failures. But in any event, your symptoms are not something that water wetters can solve.

Bogie

Last edited by oldbogie; 06-07-2007 at 11:43 AM.
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Old 07-11-2007, 04:26 PM
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The problem is solved. First, all of the exhaust valve guides were leaking, the #8 cylinder was the worst. They were bronze. We were told that on big block heads, for some reason this tends to happen with bronze guides. We replaced the guides with steel ones. Block, heads, and head gaskets were checked and were OK. The motor was put back together and it cooled much better, but still had a little trouble. We took the electric fan off and bought a non flex mechanical fan. We had a custom shroud built and it completely solved the problem. It just sits at 185 when the car is moving. If you stay in one spot idling for a long time it will creep up, but if it is driven for 1/2 a block it drops back to 185. I think a larger radiator would solve that but I am happy with how it does now. Thanks for all the help.

Adam
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