Running Hot

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bahoward

bahoward

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I have a 66 Valiant (amarican dart), 400 with stock heads,M1 single plane intake, 2 1/4" with 4" collectors fender well headers, 4" flowmasters, .528-284 mech cam, MSD 7al2 ignition. Had a wilder 383 before but too much for the street. My problem is that once it gets hot it won't cool down. I have tried running an electric water pump with electric fans, belt driven water pump and a 7 blade stock fan. No shroud on the rad as the fan is only 1" from the rad. Tried usig a thermostat and also a restricter disc. Went from the stock 3 row rad to a 26" 3 row rad out of a charger. Tried more timing and less timing, changed carbs, changed temp gauges. Found a frost plug in the block and removed. The egine uses a motor plate to mount the front, has a hood scoop on it as well. Could the two things together cause the air flow through the rad to stop or slow down while the car is in motion? I gave up on it last year and drove it around with the temp gauge reading 230, put a 20 pound rad cap so it won't boil over. I have run out of ideas except replacing the engine. Does anybody have an idea? I GIVE UP

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It doesn't matter that the fan is only an inch from the radiator--get a shroud on it. You're only pulling air through the radiator where the fan is, nothing off to the sides, above or below the fan. A shroud will funnel the air out the back of the shroud, pulling air through the entire core.

Get the biggest 7-blade fan you can as well. And I don't mean to be insulting when I type this--make sure your fan is on the right direction. I've seen it happen.

Seal the bottom of the hood to the core support with a rubber gasket of some type (many cars used a simple rubber flap) and make sure the shroud is sealed to the core support so the fan isn't pulling air from the perimeter of the shroud.

What are you running for coolant? I highly recommend Water Wetter.

My daily driver is a SBC-powered '62 Suburban, and I drive it in all traffic without problems. 4-row copper-core radiator, 7-blade clutch fan, 50/50 antifreeze mix (though I'm going to re-evaluate that), and a 160-degree thermostat in the summer, 180-degree in the winter. I don't have the shroud on it yet. The fan sits back from the radiator an honest 8 inches, and at idle that 7-blade, 17.5-inch fan will suck a piece of notebook paper tight to the radiator. I expect that once I get the shroud in place, it will suck small birds out of the air.

What t-stat are you running? The t-stat opens at a given temp to regulate the water temp. I like to run the 160-degree in the summer, because it lets the coolant circulate at a much cooler temp... when I get stuck in traffic, it gives me an extra 20-degree head start on keeping things under control.
I also drill a small 1/16-inch hole in the flange of the t-stat, so any air in the block will bleed out when I fill the radiator.

Check your system for trapped air. Check and make sure the used radiator you have isn't plugged. If a couple tubes are plugged, you're losing cooling in a large area.

Be sure your hoses aren't crimped or collapsing.

Also, check and make sure there isn't sediment in the bottom of the block's water jackets. I've seen engines where the jacket plugs were pulled out, and nothing came out--the sludge had to be moved with an ice pick before the block would drain.

Also, a switch to an aluminum radiator would be a big help--aluminum transfers heat much better than a copper core rad: in a copper rad, the tubes are copper, and the fins are copper, but they are connected by a lead soldier joint, and lead is a horrible conductor of heat.

Finally, if you're running an auto trans, get an auxiliary trans cooler, or you might think about running an oil cooler.

-Brad
 
this may or may not help you but my 340 always ran hot (with a new build) i took the cover off and checked the chain it had so much slack in it that when i moved the dist. in either way it was still off..and you want know it because when you st the timing you will bring it up to 2000 and the slack will not be there. so if i was you i would remove the dist. cap put a shocket on the crank bolt and turn the motor and look at the dist very good. then stop turn it the other way and see if it moves when you move it..if not thats your problem...hope this helps cause i was going in from 1 thing to the next money here money there.hope this helps you out.....i replaced 2 or 3 sets of head gaskets before i found the problem:read2:


oh yea when i was running the car before i found the problem it would run 190/200/210 sometime,now 180 and i did put a alum. radi. in but after i found the problem....
 
Thanks for reply, don't have room for a shrould, use 50/50 water antifreeze with water wetter, have 7 blade fan and is correct, tried different t stats and a resticter disc, no trapped air, hoses ok, there was some crap in the block but removed a couple of frost plugs and washed it out, the only thing have not done is seal the bottom of the rad cradle and an aluminum rad is my next step. Hate to spend the money and still have the same problem. Have enough parts to bulid another engine and try that first. Thanks for input and will find out in the spring.
 
The part that gets me is I have a 68 newport custom with a stock 383 2 bbl. This car has 93.000 original miles. Ican drive it on the highway at 80 mph all day and it won't over heat. It can be driven in bumper to bumper traffic in the heat and it won't overheat. It never has left a coolant puddle under it. It also has a smaller rad the the valiant and it has no shroud. Something to think about.
 
just ran across this thread,
If I may, a couple of questions?

1) stock bore ?
2) valve lash specs ?
3) you removed an old freeze plug left
inside the block from a previous repair?
4) do you know the history of the 400 engine ?
5) are you running stock pulleys ?
 
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