So... Here's what I've gone through:

2 water pumps
2 rad caps
New hoses all around
2 thermostats
Hosed away from heater core to make sure it wasn't plugged. No difference.
Reverse flushed with and without the thermostat
Removed and replaced freeze plugs and went through the block with a coat hanger and screwdriver. It was pretty clean, frankly.
Run water and water wetter.
Ran with water and coolant.
Had radiator cleaned professionally twice.

Still getting to the high end of the temp band when I hit speeds above 65 for about five minutes. Temp is middle ground below that speed, but upon slowing down, does take time to re-cool.

Running electric fans. Kind of at my wit's end here. I bought HEI and am going to install it once it comes in the mail, but I really don't understand what is going on here. My block was clean as a whistle to start with.

This has been a war, and I'm still losing

Have you changed the head gasket?

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☼

FYI
Saturday I went to the track (75-80 Dragway) with our slant/2 barrel intake/hooker headers. it was 1 second faster then all stock. I knew something was wrong. it ran warmer then normal. next day i strated it up and let it warm up. then i took a can of starting fluid ( fire extingisher by my side) sprayed around the carb/intake in short blasts and the idle went up.
I fixed 2 air leaks

cooler running much better

2 much retard makes them run warm @ high speed too.

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slant six's RULE!
http://www.usajon.com

Two thoughts:

1) If using a stock temp gauge, it may not be giving you useable feedback, and it's not running hot at all. Try an aftermarket gauge, or point an IR thermometer at things in the engine bay while "hot" and see what the actual temps are.

2) Radiator is plugged, corroded, or otherwise not flowing/cooling properly.

Lou

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Home of Slant6-powered fun machines since 1988

Sure sounds like a radiator that is not shedding the heat.

Another vote for a faulty radiator. If the solder junctions corrode between the tubes and the fins, the heat won't be transferred effectively or efficiently off the coolant and onto the air.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

You may laugh at this question, but anyway: Have you checked that your electric fans run in the correct direction, ensuring that they are not actually working hard to prevent air from entering the radiator? That could very well be because of incorrect rotational direction of the fans, things are normal as long as the fans don't run.

Olaf.

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Aspenized

Agree on the radiator....
Also sounds like your running too lean...... ...intake leaks or carb base gasket leaks or too lean of a jet. Did you ever check the jet size?

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Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

I want it to be the rad as much as the next guy. But the guy who did the cleaning actually took it apart. He said that 3 tubes were clogged (of 60), but otherwise everything looked fine in there.

How about a new temp sending unit. Your old one might be bad.

If you are sure the radiator is OK, the it might be time to get the water jacket in the block and head acid cleaned or "hot tanked."

This (#1) makes sense; the gauge might be inaccurate.

Again: it doesn't matter how clean it is if the tube-to-fin solder junctions are no longer able to transfer heat effectively.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

I'm pretty sure if the junctions were messed up, the rad guy would have told me. I mean, I basically asked him if there was anything he could do, and he said, the rad is in excellent shape.

*shrug*

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一期一会
Too many people who were born on third base actually believe they've hit a triple.