I had a similar problem with a 79 Power Wagon after warming up its 360 a bit. I ditched the 2 row and went with a 4 core. The problem instantly vanished, even when towing a 4000 lb boat.

Russ

Where can I get a 4 core. RockAuto has a new 2 core Proliance radiator for 150

Summit brand aluminum would be worth looking into. They are made by Northern

Interesting developments:

I swapped on a used 600 cfm #1850 holley, in place of the carter afb. Idle quality immediately improved. I went from 12 inches and shaky to 15 inches and much steadier. Ran the engine until it got fully heated up at idle. Set the timing at 15 btdc.

Measured the temps on the thermostat housing - 215F, and then measured the temp at the return outlet on the bottom of the radiator - 195F !!! The radiator isn't doing the job at idle.

When I had checked temps before, I had the engine running at 2000 rpm, I had 220 at the top of the radiator and 160 or so at the bottom, but thinking back this was measured off the tank, not the return outlet, I'll bet it was a similar temp. (meaning 195F or something). I'll check that tomorrow evening to verify.

Oil temp measured off the filter is 205F

Tailpipe exh temp is 105F both sides

Header temps measured very close to the heads on the tubes range from 450 at the front (due to fan cooling probably) to around 550 at the middle two, and 500F at the rear pipe, similar temps both sides. Ive been told these temps are normal ?

So, what this is telling me is that:

#1 my carter is junk, I need to use this holley or other newer carb

#2 Either my radiator is not up to the task - or water flow at idle is not adequate. I doubt this - since the coolant flows like crazy inside the radiator near the cap anyway at idle.

#3 I think I need another radiator to make this go away. I'm guessing a two row 1.25" or 1.5" tube Aluminum radiator with a shroud will be the ticket.

If anyone has thoughts or comments about what I've found and my conclusions, please - by all means make them.

I wont be doing much about buying anything for a week or so, so please fire away.

Year One sells direct replacement radiators that are 3 row cores for 350 bucks. Rock Auto sells
direct 2 row cores for 150 bucks. The 2 row was stock for 340's. It worked ok when they were new, why is everyone so caught up on aluminum and 4 core etc? New cars run at 210 all the time. I'm gonna try to get mine rodded out and go from there. If I
lived in arizona I might look at better cooling I guess.

I rebuilt a 318 so long ago I don't remember all the details but I do remember that I had to bore it to what the shop said was the max for that engine, .060. It was out of a 62 New Yorker and I had it in a 56 Dodge half ton. (Only mopar pick-up I ever new of with push button automatic ) Anyway, I set the timing to book specs and it ran fine temp-wise. But were the A engines beefier than the later LA's? Would that explain my lack of cooling issues?

Verified the radiator inlet and outlet temps. at 2000 rpm. inlet is at 220, outlet at 195 F.

So, its one of two issues. Either the flow thru the radiator is too fast, not allowing the radiator to do its job, or the radiator cant keep up with the cooling needs of the engine.

I have no idea how to tell which is the case other than try putting restictors in the thermostat housing, that way I can tell if its a residence problem in the radiator (= too much flow) or its the radiator cooling capacity.

I'm gonna call the radiator shop again tomorrow and talk with them some more.

I do not think the cylinder walls have ANYTHING to do with this issue.

Did your plugs look ok? Have you checked to see if your fan clutch is working? What type of fan clutch? Is your water pump pully slipping? Also try running at 50-60mph without the fan. Do you have any trash at all in the cooling system? I have a 440 that was a fresh build and ran at 230 on the highway. I finally think I got it fixed with a 4core radiator, 440 source water pump, and the idler pully was slipping. Try all these other things before you buy a radiator.

Just a thought but were the intake gaskets open on both ends for the cyl hd coolant passages? Any pressure issues? Blow back to the overflow etc? Lastly the too thin blocks I have delt with did not perform the way they should. (poor ring seal and minor piston and ring scuffing at least)I noticed you stated it ran fine .(to paraphrase)That might lead to the conclusion that the block is ok.Doesn't rule out a badly core shifted piece but it becomes more unikely.

My recent 318 stroker build was used with a 1970 318 block. It was bored .030 over and with the stock 2 core radiator it ran pretty hot at initial fire up... 220 then up to 230
after about 10 minutes and I shut it off. Driving down the road it would run a constant 210-220. I bought a summit aluminum radiator and now it runs no hotter than 180 in the florida heat. I do run the 8 vane water pump as well.
I would doubt that your cylinder walls are thin. Some 318 blocks have very thick walls that can easily be bored out to stock 340 size. Get a minimum of a 3 core rad or aluminum and I bet your cooling issues will be gone... TBF

GTX the plugs look good, no fouling, a little tan starting to show up (new engine still breaking in). the clutch is new and is a thermal type, its pulling lots of air. the belt is new and Im sure its not slipping. It has one belt, fan, alt, crank. (manual steering), no AC.

Mike S nothing odd about the intake gaskets, stock felpro pieces. I can also read the temps on the outlets from the heads using the infrared thermometer - they are reading the same temp as the rest of the water passages in the pump - thermostat etc. Leading me to believe its okay. No blow back issues, or anything, the block was hot tanked and then inspected by me before I installed the freeze plugs, its clean clean.

TBF - thanks for the input, the block is a 68 casting which might or might not be something special in terms of wall thickness. Im pretty sure that isn't the problem. Espcially after finding these temp issues. From what you said its the radiator. What are the specs on your radiator, surface area, maker, tube size ? I'd really appreciate the specs. if you can get them.

I have a 3 row in my charger and it never runs hot. I don`t even have a shroud.

I have a friend with a one row aluminum that doesnt ever run hot and he doesnt even have a fan.

I used a summit radiator made by Northern.. It is 27" wide and fits pretty good in my J-body Cordoba. Even with a stock fan with NO shroud it cools Waaaay better than the stock 2 core with shroud....... Here is the rad.....

http://store.summitracing.com/partdetail...mp;autoview=sku

TBF

So I found a source in california that has a oem fit
A body aluminum radiator (22") for 200 bucks. No
altering and bolts right in. PM me if you want contact info.

Sounds like you made the diagnosis before running the test.

I do it all the time, don't feel bad.

R.

I had th same problem with a .030 over 318 using my stock radiator Switched to a new replacement 440 radiator and the problem vanished could idle for long periods, stop n go traffic with AC on, how sweet it is.
Let me put it another way
RADIATOR RADIATOR RADIATOR RADIATOR RADIATOR

(So, its one of two issues. Either the flow thru the radiator is too fast, not allowing the radiator to do its job).

This part is a myth. If the fluid is passing too fast thru the radiator to cool it, then it wouldn't be able to pick up the heat in the engine in the first place and have to cool it. Why do people believe the "flowing too fast" thing???? If you burn you finger bad, do you just want a couple drops of water to cool it or a garden hose. I know what I would do!!