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Discussion Starter #1
I have a 1964 1/2 coupe restomod that has an overheating issue that has me stumped.
Background info:
- Block year is unknown. I haven't taken off the starter to check.
- Heads are believed to be '70's era (5/8" plugs).
- Holly 4-barrel carb.
- Cylinder compression is 177-180 throughout the motor.
- Standard water pump (C80E-D casting).
- 185 degree thermostat. Installed correctly - I promise!
- C4 automatic transmission (later model based on shift pattern).
- 9" rear end, 3.00 gears.
- 2-row aluminum radiator (1" tubes). Leak-down test conducted and passed with flying colors.
- Derale elctric fan (16926) pulling 2200 CFM.
- Classic Auto Air a/c under the hood, 1965 Ford in the cabin. Runs great.

Issue:
The car gets to about 180-190 at idle and while driving around town. Won't get above 195 even sitting in traffic for long periods of time. When driving for over 5 minutes at over 2500 RPM, the temp climbs to 210 and over (that's when I slow down and let the temp drop). Fan on or off doesn't seem to matter at highway speeds - it still gets hot. One weird thing I noticed is that the UPPER hose was seen to collapse at 2600 RPM, so I inserted a spring. There was already a spring on the bottom hose. The heating issue continued.
I was told I was pumping almost too much water at idle, and not nearly enough at higher revs which may be due to the impeller slipping on the shaft(?) - replacing the water pump with a new (not rebuilt) unit this weekend just in case.
The only other reason for overheating I can think of is a block/head mismatch that is causing some sort of restriction in the water flow. That's going to be checked this weekend.

I'm out of ideas. Has anyone else see this problem before? Any solutions?

Thanks,
Dave
 

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I had a small headgasket leak that caused that condition exactly

go to your local autozone and rent one of these guys

OEM/Block Tester (27145) | Block Tester | AutoZone.com

run it down the highway so it overheats a little, and then see if you have combustion gases in the cooling system.

mine only showed positive if i had driven it enough to make it overheat. damn thing drove me nuts!
 

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(Hi all. New to forum. Have 4 classic Mustangs and seen lots of problems!)

dahens1,

I had a similar problem once with a 70 Mach I w/351W engine. Problem turned out to be a worn and stretched timing chain. Longer and faster I went at highway speeds, the hotter it got.

Quick way to check the timing chain...pull the fuel pump and stick your finger or a dowel into the hole to push on the timing chain. If it deflects more than an inch or so, it is definitely stretched. If so, it causes a retarded cam timing which will, in turn, cause the engine to run hot with increased RPM.

This may be a long shot, but it's worth checking out.

Hope this helps,
Ron
 

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Discussion Starter #4
302 Overheating Problem...

(Hi all. New to forum. Have 4 classic Mustangs and seen lots of problems!)

dahens1,

I had a similar problem once with a 70 Mach I w/351W engine. Problem turned out to be a worn and stretched timing chain. Longer and faster I went at highway speeds, the hotter it got.

Quick way to check the timing chain...pull the fuel pump and stick your finger or a dowel into the hole to push on the timing chain. If it deflects more than an inch or so, it is definitely stretched. If so, it causes a retarded cam timing which will, in turn, cause the engine to run hot with increased RPM.

This may be a long shot, but it's worth checking out.

Hope this helps,
Ron

Thanks Ron! I'm at the point that a long shot is about the best shot I have! Leak-down and combustion chamber gas tests were both negative, so I'm 99% convinced it isn't a head gasket (maybe I'm just in denial). I'll let you know what I find out.
Dave
 

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did you do the combustion gas test after the car had actually over heated?

I let mine idle up to temp and did the test and it came up negative twice. then i drove it. made it overheat, and the test came back solid positive.

the car barely even used any coolant.
 

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dahens1,
I just got done going through this same issue. I was going crazy because I had this engine out and into the machine shop twice and I was still having this wonderful over heating experience. Then I read an interesting thread that suggested that their could be a pin hole leak between the water jacket and cylinder. I had tried everything else(twice) so I said "what the hell" and bought Blue Devil Head Gasket Sealer, and I'll be damned, it worked. I was beginning to think I was some kind of retard that could not install a head gasket. I am not one for liquid mechanics but I replaced the head gaskets 3 times so what did I have to lose? Another thing I ran across was a thread describing the front coolant hole locations on 302 and 289 heads / blocks, They are not in the same place.
Paul
 

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Discussion Starter #7
More info on 302 overheating issue

Finally got the block number: C80E-6015-A, which tells me it's a 1968 block built in Cleveland. Date code (8K22) equates to November 22, 1968.
The heads, with the small tapered plugs, have to be 1975 or later.

As I understand it, the coolant holes in this head will NOT line up with the block.

This (to me at least) would explain why the upper hose was collapsing and the engine would be fine at under 2000 RPM, but gradually (and continually) climb when running above 2100 RPM.
This also explains why, when watching the radiator flow with the cap off, one could see an increase in flow between idle and 1500, but there wasn't any difference between 1500 and 2200 (I didn't go above 2200 - too chicken).

So, does anyone need a set of late '70's 302 heads?
 

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Discussion Starter #8
Problem Solved - and Older might be Better!

Seems the aluminum radiator was actually flowing TOO much water through too quickly - it never got a chance to lose any heat. I went back to a 3-row brass/copper and the thing won't get above 175 unless you really push it. Dumb mistake on my part.
 
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