So I removed the thermostat and unhooked the lower radiator hose. I turned the garden hose on and shoved it in the thermostat housing. The water ran right through the block without backing up at all so the block is fine. I just put the thermostat housing back on without the thermostat and I will run it tomorrow since it's too late to bother the neighbors tonight.

When coolant is flowing, shouldn't I be seeing the coolant in the radiator move/flow?

I'm baffled. As was brought up, Perhaps either the advance on the distributor is way off or the carb jets are too small but I'm pretty sure it's got the 72 jets, which should be adequate. I've tried initial timing of 10 degree and 15 degrees and neither seems to make a difference. Any more suggestions?

If you pull the heads check the 3 cooling slots in the top of the head gaskets....they are like .188 wide on late gaskets, .455 on early stuff. Dirt in block, head gasket issue, blocked water passages could be your problem since you have no flow. Thin slots will not let dirt thru. Google bigblock mopar head gasket cooling slot. I have been making them .250 on everything I do with no issue, right or wrong.

I have had a similar problem on my Power Wagon 440 so will have to pull the heads

I removed the thermostat and topped coolant. I could see some movement/flow in the radiator as I idled, but it wasn't fast movement. I also adjusted the timing. After reading some timing threads pertaining to the 509 cam in a 440, i capped the vacuum line from the carb so no vacuum advance. I set initial timing to about 20 deg BTDC. It's 77 degrees Fahrenheit this evening and about 1400' elevation. As I drove temp steadily but came up to about 190-200 as I drove at 55-65 mph for about 5 miles. As I came back into town I decided to slow to 30-35mph and drive about 4 or 5 blocks into town. The temp climbed to 210 pretty quick so I turned around and headed back to my house about 5 blocks away. Temps reached 230 before I could pull in my drive and shut down. I text a buddy to vent my frustration and he said "are you sure your gauge is accurate"?. I grabbed a towel and mashed it over the cap while I slowly lifted the radiator cap lever. The lever came up without spraying a drop of coolant. I slooooooowly twisted the cap and then slowly lifted the cap. I expected some spray but nothing. The coolant was only about 3/4" below the cap and it was letting off a few wisps of steam/vapor but I expected it to be boiling. Also, the radiator cap I removed was a cheap piece of junk that says 14-16psi on it. With it being that hot, it should have some serious pressure. So, I'm starting to think it is my gauge possibly. Thoughts?

$20 harbor freight inferred gun would be an investment applied toward all your cars.

Yes, find a way to check your gauge.

Grab a radiator cap off another one of your other cars you think is good. Or two...

I haven’t made it to harbor freight yet for the infrared temp tester, but I think I ruled the gauge out. I had a stack of clusters that I needed to test anyway so I ran it up to temp and started swapping out clusters. 3 separate temp gauges showed it was running hot.

At this point I believe that head gaskets are impeding flow and/or I have sediment in the block. It is flowing coolant but not enough. I’ve been through the whole system unless someone has another idea. If I’m going to do head gaskets I may as well pull the engine, remove the freeze plugs, clean out the block, and install in one of my 68 Chargers.

Rule of thumb, hot running at speed means radiator. Hot slow means airflow.

It sounds like you are hot running slow. Not enough airflow.

I think that car wants a radiator shroud. Most do.

Also, check pulley sizes... is there an aftermarket "underdrive" pulley installed?

What diameter are stock crank and water pump pulleys?

It runs hot all the time.It overheats at idle and it overheats while cruising; at 60mph with 3.54 gears, the temps climb to 200 (even on a 77 degree evening). Then as I slow down to about 40 they climb to 210. As I slow down to turn into my development (20-25mph) they continue climbing to 220-230.

I'm thinking partly plugged radiator since it is all the time (slow speeds/highway speeds).

The stock crank pulley is usually 7" to 7 1/4". Fan pulleys vary depending on setup... mostly "with" or "without" AC. The "with AC" setup has a smaller fan pulley that overdrives the fan and water pump for better cooling. Bouchillon covers pulleys well (link attached).

Back to the "rule of thumb". You are running 200 on the highway. Warmer than your stat temperature assuming your gauge is accurate but not really overheating. 220 or 230 is getting a little warm.

I think your system could be minimally OK with addition of a shroud to help low speed cooling. The fan without shroud moves air but not so much through the radiator. These cars need a shroud for low speed cooling performance. This is a first step.

If there is question, verify the gauge. I like to use a low cost mechanical gauge from the parts store installed temporarily to measure coolant temp directly. Sometimes you can tell by how your current gauge acts from cold start. Start cold and drive moderately on the highway and watch it. Does temp rise gradually for a while, then level off for a while then start climbing again? If it levels off around your stat temperature (180) then climbs after that suggests gauge is close and stat is working.

It would not hurt to research pulley ratios. At least some overdrive of fan and water pump helps cooling.

And finally, you may need more radiator. FWIW I run a 26" "muscle car" aluminum radiator from Mancini with their matching shroud on a warm 496. This is a high capacity downflow radiator. Cooling is excellent (with AC). It stays right at 180 stat temperature rolling - even racing - and a little warmer with extended stop.

www.bouchillonperformance.com

You still have not answered my question. What year is the block? If it is a late model motor home block, it will have the extra cooling holes along the bottom row of head bolts. If you don’t have the matching holes in the 452 heads, it will get hot just like you describe. I’ve had it happen twice on two MH blocks. Water will not circulate properly. I bought all my buddies Mopar stuff the other day because he’s done restoring cars. He gave me his MH block that cause him all the Problems years ago. I have it at the shop. I’ll get a picture and post it for you.

Sorry-I missed that question. Its a 1970 HP block

Before I touched it I would be putting a thermometer in the water in the radiator.

I pulled the heads this morning and the saw a couple things. 7 of 8 pistons were kissed by valves at one time or another.....but anyway, the cooling slots seemed suspect. They look way too small. I started a separate thread about what the slots should look like but I wanted to update this thread with some new info.
1. The pistons are .060 over
2. The heads are 906 heads so they are the heads that came on a 1970 HP block.

For a couple reasons, I've convinced myself that it had to be the head gaskets.
1. I've been through all the normal stuff
2. The upper radiator hose barely has any coolant flow through it; my survivor 69 Charger with completely untouched original 383 has MUCH more pressure/flow in the upper radiator hose.

We're definitely on to something there. I've wondered about the slit head gaskets too but iirc people have said they are OK for the most part. But we certainly have a restricted flow for some reason that has to be what is causing this. can you post a larger pic that shows all the holes from front to rear? (to try & get an idea if the total/overall restriction is somewhere other than the gaskets). I have a good cooling mod read for you on circle track chat, a subset from moparchat (VERY informative) that relates directly to this but one thing at a time.

So you just want pictures that show the whole mating surface on the block? With or without the headgaskets on the block?

On one side can you take a pic of the deck with the head gasket setting in the valley close to it (to compare holes) and a pic of the head with the gasket next to it (to compare holes) so we can figure out if the restriction is there or somewhere else (you get the jist of what I am trying to say). I ain't a layout photographer but this might easily let us see what is going on with only (2) pics. Wouldn't hurt to just look at the other side (that deck/head/gasket) without pics & see if the holes are the same as the other side & if so, if the photographed side is good or bad then the other side has to be good or bad.

Here's a question for you. Do you have a six or eight blade water pump impeller?

I recently talked to Bob at Glen-ray about this. He said your pulley ratio determines the number of water pump blades you need. I should have wrote down the measurements but didn't. Anyway, I'd measure your pulleys and find out what type of water pump you have and then call Bob -> (715) 842-3352

Bob knows Mopar cooling systems and will be able to offer some advice.

Also, as I recall, small block radiators have a smaller lower inlet which would probably be the crux of the matter. You likely need a big block radiator.

Years ago we tried running a freshly cored 26" small block A/C radiator with a mildly built 383. It would run on the warm side. It's that lower inlet that makes a difference I guess.

Thanks! Will do!