I set my 73 stock 400 4 barrel at 15 initial, and 35 total. It never ran so smoothly, and real nice acceleration. While on a nice short cruise on the highway, I ran the A/C. Temp went to the high range. I did the heater trick, and man, was it hot air!!. Coolant is new and full. Clutch and viscus fan are all in good-working condition. Stock 28 inch radiator. It's a Cali car, so I can't imagine this is all kosher. What are your thought? Thanks. Need it worked out for the Nats. By the way, outside temp was only 75. Thanks

some people say advancing the timing will help the cooling. i've been playing with this "idea" for the last couple of weeks going from mild to aggressive timing curves. i haven't found there to be any noticeable difference.

timing is fine. need a better radiator.

Totally agree..I need a 4 core 28" asap. Something that looks stock. Maybe at the Nats??

Are you running a shroud on the radiator?

Try hooking up and making sure that the vaume advance works for part throttle cruising I did that recently on my pump gas 1969 383 4 speed GTS Dart, it seems like it is running cooler now at part throttle cruise than before without it hooked up

Cab, roger on that!! Stumpy, yes on the factory shroud. I think the radiator might have gotten changed out in the last 43 years. It only has a 28 2 row. There is a lot of room for more rows, so the fan is inside the shroud a little deeper.

i'd try flushing the system before i blew a bunch of bucks on a radiator. i spent about $650 on a new radiator, 4 row u.s. radiator. 23 of the tubes were blocked off, 30 were 50% blocked, and the top tank split open at the seam; maybe a 1000 miles on it. oh, and $650 doesn't count the other junk i had to buy to make the thing fit. real bargain! work with what you have first.

Stock 73 400 on today's gas, with stock jetting and carburetor?

If so your lean as heck and that where the heat is coming from.

I bet you whether I'm right or wrong that riching up the main jet helps a bunch with power and drivability.

"Correct" meaning enough but not too much timing increases engine efficiency and reduces heat. Sure sounds like you were in the right ballpark with timing. Lean can make things hot as mentioned.

Usually hot at speed means inadequate radiator or radiator plugged. Could be other things but with a 2 core radiator of unknown? age and history, I'd consider a better more effective radiator. The Mancini "Muscle Car" 26" radiator with two very deep AL cores has worked well for me on a warm '70 Challenger. The 4 core Champion has worked well on a stockish brand F PU.

Stock 73 400 on today's gas, with stock jetting and carburetor?

If so your lean as heck and that where the heat is coming from.

I bet you whether I'm right or wrong that richening up the main jet helps a bunch wer and drivability.


I bet you might be correct. It's got an Edelbrock 750 on it. I wish I could get some A/F..lol.. Wonder if I should chassis dyno it..lol I'll need to check the plugs while driving to the Nats. I'll pull off on a rest stop.

shoot a temp laser gun
on the radiator
to find hot spots/ blocked tubes

(far) easier yet, block the metering rods up & take it back out for a repeat. You'll have your answer in an hour

Retard the timing 2 degrees and see what happens. It will take you 5 minutes.

If you do need a radiator talk to Glen Ray. A little spendy but it will look factory, fit, no modifications etc and your car will run cool. I am sold on them after trying to solve a couple cooling issues.

What jets are in that stock 750? I may have a few eddy jets/rods if you want to try them. If you put a bung in your exhaust somewhere, I can bring my LM-2 wideband and we can get some readings at cruise to see where you're at

If you don't have a bung, stop by on Thursday. We can weld one in here at the house. Only takes about 15 minutes. I have a few in the shop

Sparky
Check your timing chain stretch, you may need to give it more advance as it is running "late" in cam timing. As long as it does not ping don't worry about the total. You may be in need of a new chain and gear set...If anything the car may be running rich in the cruise mode-did you look at a plug or 2?

Radiators are about 249.00 on rock auto. You do not need to get stupid about buying a rad as for these cars the stock rads work fine when they are not plugged.

My technical support conclusion is the radiator.

Are you suggesting that cam being retarded 2° will cause it to over heat? Or that the igniting timing will be off 2°.

Of course the ignition time has nothing to do with cam timing. If the timing light says 15°, it is 15° no matter what the timing chain is doing. And the cam being retarded 2° will not measurably effect heating/cooling.