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Discussion Starter #1
My 360HP 429 (69 Marauder) overheats (210+degrees) at high speed (75-85 mph) . If I drop to 65 mph the temp. drops to 200 degrees. Also at low speed with the A/C on the temp runs about 200-215. Also there is a terrible spark knock on acceleration when the engine is this hot. I've been fighting this for 2 years. The collant system is clean and correct. I have an original factory stock car, so adding an alluminum radiator etc. would violate the "original" status of the car.

Any help would be appreciated.
 

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The radiator is either plugged, or, it has insufficient capacity - get a rad shop to recore your existing one or buy a thicker core brass radiator.

Overheating on the highway is a classic sign of insufficient cooling capacity. Low speed overheating is generally an airflow issue, but can also be reflective of too low capacity.

You also might consider checking your timing - it may be making it run hot, especially if it's too retarded.

215º shouldnt cause you significant spark knock, unless you have real high compression - I think this is a timing issue compounded by a small radiator. 215 is well within operational limits, but shouldn't be something you constantly run at with an older car. (most modern fuel injection cars dont even turn the fans on until 210º)
 

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Discussion Starter #3
Thanks for the reply..

The radiator is either plugged, or, it has insufficient capacity - get a rad shop to recore your existing one or buy a thicker core brass radiator.
>>>>The radiator has been checked out by rad shop.

Overheating on the highway is a classic sign of insufficient cooling capacity. Low speed overheating is generally an airflow issue, but can also be reflective of too low capacity.
>>>>Everything on the car is factory stock..

You also might consider checking your timing - it may be making it run hot, especially if it's too retarded.
>>>>Timing has checked and rechecked many times..

215º shouldnt cause you significant spark knock, unless you have real high compression - I think this is a timing issue compounded by a small radiator. 215 is well within operational limits, but shouldn't be something you constantly run at with an older car. (most modern fuel injection cars dont even turn the fans on until 210º)

>>>>Compression is 10.5:1, radiator is factory stock, timing not the problem.

>>>>What should be the operational upper limit on a 1969 engine??
 

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Discussion Starter #4
Thanks for the reply..

The radiator is either plugged, or, it has insufficient capacity - get a rad shop to recore your existing one or buy a thicker core brass radiator.
>>>>The radiator has been checked out by rad shop.

Overheating on the highway is a classic sign of insufficient cooling capacity. Low speed overheating is generally an airflow issue, but can also be reflective of too low capacity.
>>>>Everything on the car is factory stock..

You also might consider checking your timing - it may be making it run hot, especially if it's too retarded.
>>>>Timing has checked and rechecked many times..

215º shouldnt cause you significant spark knock, unless you have real high compression - I think this is a timing issue compounded by a small radiator. 215 is well within operational limits, but shouldn't be something you constantly run at with an older car. (most modern fuel injection cars dont even turn the fans on until 210º)

>>>>Compression is 10.5:1, radiator is factory stock, timing not the problem.

>>>>What should be the operational upper limit on a 1969 engine??

 

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Are you running a clutch fan, if so take a look there too.

These have been prone to causing overheating issues at specific speeds and conditions.

The idea here is that at highway speed, you do not need a fan to cool the engine as there is enough air flow through the front of the car to keep it cool.

The issue is the clutch "locks" and the spinning fan creates a "wall" that restricts air flow through the rediator, preventing adequate heat transfer.

Good Luck.
 

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How do you know the cooling system is clean and correct as you say? I have seen engines clogged up sith so much bars leaks that it was amazing they cooled at all.

Have you tried running the car without a thermostat? Not a good daily practice, but it will help in troubleshooting this problem.

Don't be so quick to assume that all of your parts are working right, because if they were you wouldn't be here with an overheating issue.

Greg

_________________
'71 Torino GT - 545 stroker, Edelbrock CJ heads w/ 11.8:1 compression, victor intake with 850 DP, C6 w/TCI streetfighter converter, 4.56 detroit locker, a/c with full interior

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<font size=-1>[ This Message was edited by: GregP on 7/3/06 10:28pm ]</font>
 

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Discussion Starter #7
I've had the car 2 years and the engine and radiator have been flushed twice in that time.

I will check to see if it is a clutch fan.. Would that be standard in 1969??

I will also take out the themostat and see if that changes the symptons.

I didn't think I was assuming, as everything has been checked out at multiple shops. I guess I did assume that these shops did a good job, not unusual I guess...

Some theories coming in from other sources:

1. At high speed the water is fowing through the radiator too fast and is not cooled enough, accounting for the temp. dropping when the speed is backed down to 65.

2. The spark knock is from the heat of carbon build up(hotter then steel) on the heads causing pre-ignition. The engine has only 55K miles on it. Does this make sense??
 

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The high speed water theory is bunk. I have never seen it proven.

The more reasonable assumption, is that it takes less power to go 65 than it does to go 85, and since more power generates more heat, the cooling system's inadequacies are brought to loght at the higer speeds.

The spark knock can have many causes. at 10.5:1, these engines are prone to spark knock on thday's gas. A careful chack of timing can help.

Timing check:

Initial timing, should be 6-8 degrees BTDC.

Mechanical advance limit, should get to about 36 degrees with the vac advance disconnected and at 3500 RPM or so.

Vacuum advance, should pull an additional 10 to 15 degrees when fully actuated, this can be tested by connecting the vac advance hose to a nipple on the intake instead of at the carb.

With the engine running at 215 degrees, the spark knock margin of your 429 will be very narrow.

Greg
 

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Discussion Starter #9
Greg,

Sorry, but i forgot to mention that the engine is factory specked for 99 octane leaded gas. I am running 92 octane plus an octane booster and a lead substitute to protect the valve seats.

I have copied your specs on the timing and will get it checked out. I believe the timing is around 10-11 degrees according to the timing mark. the car ran extremely poorly at 6 degrees.
 

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Don't forget - drag force increases with the square of the velocity - Increasing speed by 33% (60-80) would increase drag force by 77%, or, a doubling of speed would quadruple the drag force - which you have to counter by adding more engine power.

Clutch fan would not be standard in '69 - It will be a fixed blade static fan.

Taking out the thermostat more than likely wont make a difference - except your temp will creep more at idle.

Flushing can remove much of the junk from the cores - or it can compress it into an impassable blob. Since you have the stock top-down radiator, and not a crossflow, solids tend to settle in the tubes and bottom tank, hurting flow.

As for the first theory - that isn't possible - your thermostat keeps the water in the block until it is hot enough to pass to the radiator.

The second - the spark knock is probably from what you said - lower octane gas and no lead. The only way to fix that is to cut back your timing or cut compression with either a bigger cam or different heads/pistons. The first would be easier. Remember, if you're setting it to stock timing specs, you should be running stock grade fuel, which isn't available at the pump. On top of that, you could be running a bit lean, which will never help spark knock and can make you run hot. I'd say this is a real possibility.

10.5:1 is really pushing it with open chamber heads, but it shouldn't be a problem with the correct timing curve, as was suggested. My sister's 302 ran 10.5 compression, and got fairly warm a time or two without detonation. My '67 got up to 250º on the highway when my fanbelt broke, and driveability didn't suffer any and I heard no detonation(for as long as it took to get me to a place to stop) I've also made quite a few drag passes at 200º with no detonation and it has 10:1 compression. (but a biggish cam and closed chamber heads)

I really think you need to rule things out one by one, and start with the ones that won't cost you money


1. Timing is easy to solve, try that first.

2. Check and make sure your thermostat is opening at the right temperature - put a pot of water on the stove with a thermometer and the stat in it and note when (and if) the thermostat opens.

3. Check your fluid levels again (both oil and coolant) and also observe the coolant for any combustion products (indicating a head gasket leak)

4. Check your rad cap. Is it sealing? If it isn't, or if its sealing poorly, you can keep your cooling system from becoming pressurized, leading to steam pockets forming, (and that can lead to detonation easily.) Inspect/have tested/buy new rad cap.

5. Try and richen up the carb some and see if it gets rid of/helps the detonation, without making the exhaust rich

5. Money spending time: Have the radiator checked out at another, reputable shop. Have them pressure test the rad with the cap on it. (if possible) to make sure the sealing flange isn't bent up. Have it flushed again if necessary.

6. If you don't already have one, buy or fabricate a fan shroud - an unshrouded fan is very inefficient, and make sure the fan is within an inch of the radiator (but not too close) buy a spacer as needed.

7. If all else fails, buy a bigger capacity radiator. A 3 or 4-core is pretty much a necessity with an AC system and high summer temps.

Good luck! Just take it step by step and rule things out so you don't have to spend a fortune on it. Keep us posted.


<font size=-1>[ This Message was edited by: thekingofazle on 7/4/06 12:45am ]</font>
 

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When my 429 was over heating in a similar fashion, I found that the plate behind the water pump had rusted out, so the flow of the water pump was decreased as the impeller was just sloshing the cooling fluid around. Just my .02!
 

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I am thinking exhaust sytem too. Only a high speed problem. Most cars overheat at the lower speeds or in traffic if the radiator is the issue. Is traffic giving you overheating? Does not sound like it is.

At highway speeds you don't really need a fan, so does not sound like coolent capacity is a problem.

A big flake of rust in your exhaust system, from sitting too long??? Think about it, low speed, low air volume, high speed, high air volume, with restriction means you are backing up exhaust into your heads, and that will cause knocking too....

Mouse nest in your exhaust?

Timing could do it too, but less likely maybe by 10 - 15 degrees extra heat from being too lean, thats about it....
 

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Discussion Starter #14
Exhaust is 1 year old. Low speed with the A/C on and 90+ degree, 90+ humidity weather will drive it up to about 215 degrees. I have not checked out the water flow from the water pump, thanks for that tip.. The car does not sit. I run anywhere from 30 - 100 miles a week on it .
The car has noy yet overheated. When the temp gets close to 220 I back off on the high speed or cut off the A/C. Does anyone know what the max temp i can safely run up to with this 429 engine??
 

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How many rows is your radiator and has the WP been changed? They actually make a difference WP for AC cars. Is the front of your car high in the air? This lets air flow under the car and not threw the radiator due to air pressures. Radiator shroud? Just how big is your exhaust system? AC condensors can make an engine overheat due to the heat from them and the air flow restriction. How's your seal from the radiator top to the hood? All has to do with air flow.
 

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How many rows is your radiator and has the WP been changed? They actually make a difference WP for AC cars.
>>>>It is a 2 core radiator and is factory stock. The A/C is also factory stock. What is WP??

Is the front of your car high in the air? This lets air flow under the car and not threw the radiator due to air pressures.
>>>>NO, not high.

Radiator shroud?
>>>>Fan shroud yes, factory stock.

Just how big is your exhaust system?
>>>>Factory dual exhaust, redone with 2 1/2 pipe

AC condensors can make an engine overheat due to the heat from them and the air flow restriction. How's your seal from the radiator top to the hood? All has to do with air flow.
>>>>Not sure what you mean by "seal from radiator top to hood"??
>>>>All running gear and accessories are factory stock. There are NO add-ons that might cause a problem.
 

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2 core is a bit shy for an AC car - most of the Factory AC cars got 3-core or better radiators.

The reason I say insufficient radiator capacity is because, at speed, you have max airflow through the radiator - and you're making way more heat than slow speeds. At low speeds, the radiator can keep up because you've got sufficient flow from the fan and low RPM, but if your radiator can't physically cool the engine when its making cruise horsepower, when it has highest airflow, that is a classic sign of a small radiator. At idle you have less airflow, but are also making much less power, and burning less gasoline.

A fan shroud will do nothing but slow down incoming air when you are driving at highway speed. Ideally you would have a fan that moved out of the way of the radiator when you got up to 50MPH or so. If it has to force its way through a shroud and past a fan, it wont help your highway problem.

2-cores just sounds way to small to me, especially with AC.

<font size=-1>[ This Message was edited by: thekingofazle on 7/7/06 3:12am ]</font>
 

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Discussion Starter #18
Again, everything on the car is factory stock, and i know that sure doesn't make it right.

I am trying to keep the car, a show car that I drive, as original as possible, so going to an aluminum raditor is not an option. The only option is one that will make the radiator still look factory stock. Is it possible to re-core a radiator?? i.e. make "my existing radiator" a 3 core internally, yet externally look the same (factory stock).

By the way, everyone has been extremely helpful and I appreciate it. I wasn't aware that this forum was that helpful. I found this forum because a while back my car was featured on this web site and I just took a chance. Thanks, and I do not mean that this is the end of my problem, i would still appreciate any additional help, etc. on this problem. This is just a pause to thank you guys.
 

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Any time I can help is a good time.

I wasn't suggesting an aluminum radiator. You can get a bigger capacity stock radiator, I am 100% sure they exist.

Like you said, you can also have the radiator re-cored. They keep the tanks, and just change out the core. Not sure how much that will run you.

Just a thought, have you tried burping the coolant system? Air pockets can heat up an engine easily.


<font size=-1>[ This Message was edited by: thekingofazle on 7/7/06 5:01am ]</font>
 

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Ok, further research indicates your stock radiator IS a crossflow! I didn't know that. The stock style radiator has two tanks on the side, and the core in between. Does yours look like this?

Here's a direct replacement from 1A Auto:

http://www.1aauto.com/1A/Radiators/Mercury/Marauder/1ARAD00174/282129&ovchn=OTHER&ovcpn=MSN&ovcrn=&ovtac=CMP

If yours doesn't look like that... you may have a smaller capacity radiator that was installed along the line. If you do end up getting another, call them before you order and make sure it is stock looking.
 
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