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454 Overheating Problem

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simplysigns

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OK I have check all the threads on overheating and I am going nutts!! So bare with me.

Here is what I have....
Engine....1972 Chevy 454 (came out of a 2wd 3/4 ton truck). Has been rebuilt but nothing crazy. 30 over, Mild cam, heads back to stock, After market aluminum intake, Holly 670 avenger carb, Headers. This engine is 98% new. I have put every hour on it (I installed a hour gauge).

Cooling system.... After market High flow water pump, 3 core Aluminum radiator, 160 degree T-stat, Dual 15" electric fans with a shroud.

Now here is what goes on. Going down the road I have no problems. Gauge stays around 160-180 degrees. It only gets hot on trails and at idle (after 10 or 15 minutes). If I get back on the road. It cools back down. So this tells me it is air flow. Right?

Here is what I have done. Went through 2 T-stats (1 180 degree & 1 160 degree, both do the same). Went through 2 Radiator caps (both good, same). All new hoses (no kinks). Coolent is flowing fine. And there is nothing blocking the grill in front. Everthing is clean. The fans are pulling air through the radiator like crazy. But not enough! WHY????

I did read a post about the timing may be off. Causes overheating. Is this something I should look into? It runs great. I have a small hesitation if I hammer it from stop position. But after that, it runs like a bat out of hell.

Any input is always welcome. So please feel free. At this point I am up for anything!!
 
i like to keep all the electrical stuff simple.. have you ever thought of the fans going out on you, then what do you do,.. id say have it as an aux not primary.. will the stocker pull more than electric? hmmmm lets think about it... it came stock so probly...good luck.
also check timing.. i got two 496 strokers in my rigs and they are cut 60 over so you got some problem there for sure... one truck has the stock fan,.. the other has a flex fan due to clearance issues.. ford aerostars, volvos are thin fans.. also stay away from those zipp tie type of mounting in time those zipp tie mounts will ruin your radiator from all the jumping bouncing etc...
 
What kind of fans are you running?

Personally not a big fan of the "cool" thermostats, 195* works fine, if it doesn't, your cooling system is not up to par. It may help in some extreme examples, but the fact is, whatever your thermostat rating, your engine should run at that temp.
 
I am running the stock fan off my 454 c10 on the 79 k30 and it cools great. I am running a 160 but going to propane at some point.
 
If your vacuum advance is hooked up to ported vacuum I would try using full manifold vacuum. Then retune your idle RPM and ratio screws (for max vacuum) with the new timing (RPM will increase). that can help reduce idle temperature.
 
simplysigns said:
OK I have check all the threads on overheating and I am going nutts!! So bare with me.

Here is what I have....
Engine....1972 Chevy 454 (came out of a 2wd 3/4 ton truck). Has been rebuilt but nothing crazy. 30 over, Mild cam, heads back to stock, After market aluminum intake, Holly 670 avenger carb, Headers. This engine is 98% new. I have put every hour on it (I installed a hour gauge).

Cooling system.... After market High flow water pump, 3 core Aluminum radiator, 160 degree T-stat, Dual 15" electric fans with a shroud.

Now here is what goes on. Going down the road I have no problems. Gauge stays around 160-180 degrees. It only gets hot on trails and at idle (after 10 or 15 minutes). If I get back on the road. It cools back down. So this tells me it is air flow. Right?

Here is what I have done. Went through 2 T-stats (1 180 degree & 1 160 degree, both do the same). Went through 2 Radiator caps (both good, same). All new hoses (no kinks). Coolent is flowing fine. And there is nothing blocking the grill in front. Everthing is clean. The fans are pulling air through the radiator like crazy. But not enough! WHY????

I did read a post about the timing may be off. Causes overheating. Is this something I should look into? It runs great. I have a small hesitation if I hammer it from stop position. But after that, it runs like a bat out of hell.

Any input is always welcome. So please feel free. At this point I am up for anything!!
Click to expand...

I have the same problem with my 496 in my K20. Since it cools down on the road it has to be and airflow problem. I am gonna end up putting a factory style fan and shroud in mine. Also unless you have a shroud over your electrics they are pulling on a small percentage of the radiator leaving a bunch of hot spots that are hard to overcome.
 
simplysigns said:
Will stock fan pull more then my dual electics? And I do not have room for both type of fans.
Click to expand...

Depends on the dual electrics. If they are good ones they will pull more at idle than a mechanical fan but less at higher RPM, which is the opposite of your problem. If they are whimpy electrics they won't pull much anytime. Dual 15" should be good I would think, as long as they are shrouded well. I would look at your vacuum advance like mentioned above, if that's not it then you need more water flow or a better radiator.
 
It appears the concensus is not enough airflow at idle and low speeds. I used 2 Perma cool 17" fans ( offset one mounted at upper left one mounted at the lower right behind the radiator ). They are controlled by an adjustable temperature switch (from NAPA )with the sensor tube located in the upper radiator hose ( to duel fan relays ). The temp switch is set to turn on at 205 and off at 185. When they come on I can see the temp guage indicator lower - quickly.
The bottom line is a big block needs a lot of fan capacity to remove excess heat. The specs on these 17" fans claim 3500 cfm each. You have a big investment in that engine, make sure the fans are up to the job. Good luck.
 
As you mention too small electric fans seem to be a common problem. The Windstar fan swap is so popular because it works. No one knows what they are rated at, but if 7000CFM cools your setup, you have to figure the stock clutch fan and the windstars are somewhere around that.
 
Go back to stock. We have the same issue with the 6.2 diesel, put dual electric fans on it and it will over heat just putting around. Put the stock fan and shroud and you have to really beat on it to get the temps up.
 
And you need to use one of these when t'stat is removed to slow the flow and give radiator time to cool
JEGS Water Restrictors



javascript:open_window('ProductDisp...0002&productId=756441&langId=-1&showValue=3')
Product images may differ from actual product appearance.


Allows you to control the rate of heat absorption from the engine block and heat dissipation from the radiator in Race Only Applications. Used by professional engine builders to obtain optimal temperature control and maximum power. Kit contains 3 anodized discs with an I.D. of 5/8'', 3/4'' and 1''. Color coded for easy identification. Fits most AMC, Ford & GM V6, V8 engines with a 2-1/8'' O.D. thermostat.
 
Those are used to keep pressure in the block developed by the water pump without the restriction of the thermostat. Their description is wrong.

Since water will boil off of the cylinder walls under lesser pressure, removal of the t-stat may induce overheating.
 
If that is the case every manufacturer of the restrictors has the wrong description. In either case they restrict or slow the flow between the block and the radiators. All of the racers and boggers in this area use them to lower temp.
 
I guess I will try to change to a stock fan & shroud this weeknd. I just cant see why two 16" fans pulling 2250 CFMs each will not cool my engine. You would think a stock fan would pull less at idle speed.

So does anyone know how many CFMs a stock fan pulls??
 
I realise that an aluminum radiator is more efficient in removing engine heat than an equal sized factory radiator, however a 454 requires a 4 core radiator. Is your aluminum radiator equal to a 4 core (4 rows of cooling fins ) radiator. If it isn't than that is your problem ( idle and low speed overheating ).
Here is another suggestion, try running mid grade gas and bump the timing up a few degrees. What we call mid grade gas was the octane of regular back in the early 70's. Try it for several tankfuls and see if your overheating goes away. Maybe retarding the timing to run on todays regular gas ( to prevent pinging ) is causing the overheating. When you rebuilt the engine you should have used dished pistons to reduce the compression to run on todays low octane regular gas.
 
simplysigns said:
I just cant see why two 16" fans pulling 2250 CFMs each will not cool my engine.
Click to expand...

Because the manufacturer of those electric fans is full of sh_t.

It's one thing to measure CFM of a fan without a radiator in front of it (which is how most manufacturers do it)....it's quite another to measure the CFM in the actual environment with a restrictive radiator core in the way.

One of the giveaways is the maximum current draw of the fan....if the number is low (15 - 20A), it can't possibly pull a high volume of air under load. I just picked up a dual-electric fan setup from Ron Davis Racing for my own build and the current draw is 80A for the fans!! :yikes:

You should give them a call and listen to what they have to say. They've done a lot of testing of electric fans from all manufacturers out there and you'd be surprised at how poorly some of them work. After all of their development work, the brand they like is SPAL... not surprisingly, they are expensive but they will move the air and with a proper shroud, I'm willing to bet they solve your cooling problems. :deal:


:usaflag:
 
dyeager535 said:
Those are used to keep pressure in the block developed by the water pump without the restriction of the thermostat. Their description is wrong.

Since water will boil off of the cylinder walls under lesser pressure, removal of the t-stat may induce overheating.
Click to expand...

Huh?
 
I think his point is that water boils at 212 degrees and will be a vapor (steam) in the engine block without a radiator cap to increase system pressure.

With a 15Lb cap, the boiling point increases to 260 degrees so the coolant circulating in the block stays in liquid form until a much higher temperature.


:usaflag:


Edit: Hmmm..... I was reading "thermostat" but was thinking "radiator cap". Not sure how to explain the pressure issue with a t-stat though I can certainly appreciate that without restriction the coolant will be moving way too fast to cool properly in the radiator.
 
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