Need more cooling

[trailblazr81]

My 73 K20 has a 383 with 10:1 comp. Aluminum heads and around 425-450HP. I have a re-cored radiator out of a truck with A/C. (I dont have A/C) I am using a hi-flow water pump, hi-flow 160 degree T-stat and a 17" Flex Fan with fan shroud. I am still running too hot. What are my options to cool this thing? Do I have to spend $600 on an aluminum radiator??

 

[HarryH3]

Find a 454 (w a/c) radiator from the same year. It should run ya about $250 new.

 

[4xcrazy]

Get rid of the flex fan, go with a stock fan and a heavy duty clutch,

 

[trailblazr81]

How does the OEM type fan cool that much better??

 

[dyeager535]

There are a few different possibilities:

Stock clutch fan may have more/more effective fan blades.
Stock clutch fan does not stay locked up on the freeway, inhibiting airflow through the radiator.
Stock fan should be set in the fan shroud in the optimum position.
Stock fan will be optimum diameter for the shroud.

Anyways, that's not to say that your fan can't be the same as 3 out of the 4 above, but those are differences that will affect cooling, stock vs. flex fan.

 

[Mad-Dog]

Chill out man...

What is too hot...?

Are you sure the gauge is accurate...?

Does it run hot when stopped at a light...?

Does it run hot on the freeway...?

Is the radiator cap the highest point in the cooling system...?

Do you check the coolant level when the thermostat is open...?

 

[trailblazr81]

Well I know this isnt the best thing to do but I just got the motor in and havent gotten the new Autmeter gauges hooked up. I did some around town driving one day and highway cruisin the other day. Both times it puked most of the coolant out of the radiator. I made sure it was full with T-stat open. The upper hose gets higher than the Radiator cap. I know I shouldnt have done anything without all the gauges hooked up but I couldnt resist cruisin in it. Tuesday I should have gauge hooked up for a more accurate reading.

 

[kyser_soze]

How is your fuel mixture? Are you running too lean is the major question.

 

[Mad-Dog]

Ok.....try and push the hose down and purge any remaining air out the system, then replace the cap with a unit that has a higher pressure rating, don't retard the timing as this will make the engine run hotter......if it pings then ya gotta raise the octane level,
Also try running colder plugs if the ignition system is hot enough.
lemme know how it turns out....

 

[trailblazr81]

Actually I think I'm running rich. Timing is higher than stock tho no noticable pinging. Im running a MSD 6AL with MSD wires and Accell header plugs. Im using a "Rad-Cap" radiater cap. It has the little piece on it that supposed to keep your cooling sytem from corroding.

 

[jarheadk5]

Get a gauge of some sort in there. Hard to judge too hot or cold without some numbers...

What is the pressure rating on the cap? 12psi, 14, 16?

 

[4xcrazy]

Also curious, may be a dumb question, but how many coolant rows are in the rad? i know you said it was one from an AC truck,,,,,

I was also told awhile back, somewhere that for optimum working conditions of the fan, it needs to be positioned in the fan shroud something like 2/3 of the way out or something like that, don't remember the exact measurement, maybe someone on here will know what i'm talkin about.
Basically 1/3 of the blade area tucked inside the shroud, the other 2/3 is outside the shroud????
Personally, i tried the use of a flex fan once, didn't like it, too noisy, could definately feel drag on the motor under acceleration, and just didn't cool like i wanted.
Maybe good for short stints like racing or whatever, but for long-term daily driving,,,i never liked it.

Just my opinion.

 

[trailblazr81]

Well the Flex fan is barely into the stock shroud. Thats with the 2" spacer. Cant find a longer spacer and dont know if I want a long spacer on it. And Im not worried about noise from fan. Cant hear it over the gear drive!! This radiator I have was re-cored a while back (been sitting in garage) I believe I had it done as a 4 row. After work I will have to see what pound cap I have. I'll also hook up the temp gauge, pull a plug or 2...

 

[Mad-Dog]

another possibility is the lower radiator hose is collapsing at cruising speeds and shutting off the flow of coolant, there should be a spring inside the lower hose to prevent this.......
not sure what cap you're talking about, what matters is the psi rating at which the cap vents to atmosphere, if it's too low then then it will vent prematurely and allow the coolant to expand causing a overheat condition...

 

[mrk5]

My 73 K20 has a 383 with 10:1 comp. Aluminum heads and around 425-450HP. I have a re-cored radiator out of a truck with A/C. (I dont have A/C) I am using a hi-flow water pump, hi-flow 160 degree T-stat and a 17" Flex Fan with fan shroud. I am still running too hot. What are my options to cool this thing? Do I have to spend $600 on an aluminum radiator??

A simple answer to your question would be to install a diesel radiator from a 6.2L truck. It is about 6" wider. You'll need to get the fan shroud for the radiator, but other wise it will drop in.

Wider is better than thicker.

But like others have said, you need to make sure that you don't have some other problem with the current cooling system.

 

[Mad-Dog]

What question...... and why do i need a bigger radiator?

 

[mrk5]

What question...... and why do i need a bigger radiator?

Umm, I was refering to the person that actually started the thread. When you hit the post reply button, it automatically replies to the last post.

 

[Mad-Dog]

Ohhhhhhh. i didn't know that.

 

[Wingnutt]

Not to sound like I'm over simplifing the matter, but if everything in the cooling system is working correctly (ie: waterpump, t-stat, overflow can, lower hose not collasping at speed), you are producing more BTUs than you are getting rid of. You need a larger radiator (either in cores, or core size).




Oh yea, I did think of one other possibility. A long time ago, I had a 67 Mustang with a very hot 390 in it that I couldn't drive for more than 30-40 minutes without it overheating. When I say overheating, I mean 260 degrees +. I replaced EVERYTHING in the cooling system EXCEPT the radiator.

The third time I took it in to be rodded out, one 'ol fart in the shop asked me why I kept bringing it in. After I explained what was happening, he showed me something. He cut the core out, then carefully cut the cooling fin away from one of the tubes, then cut the tube, including the solder that had held the fin in place.

Under a high powered maginifing glass the culprate reared it's ugly head. The solider had corroded internally, thus preventing heat transfer from the metal of the radiator to the air. You couldn't tell it be looking at it from the outside, and everytime it had been cleaned, it looked better and cleaner. I put in a new radiator, and waddya know, it ran much cooler (about 190 with a 160 degree t-stat)

You can pick up a new radiator at Auto Zone for about $200. I found that a mid 80's 3/4 or 1 ton with a 454 has the same core size as my '88, but check the books to make sure of your core size before you buy one.

Hope this helps.

 

[trailblazr81]

The radiator is good. Ive used it in another vehicle. I had this motor in another vehicle and it seemed to run OK. Thats why I'm stumped. I took the motor out of my 72 Nova and dropped it in the truck now its running hot. Oh and the rqadiator cap is a 16 pound.