Do a "back-flush".

Or better yet... pour-in a can of cooling system flush "goop", drive around for a couple of hours, then back-flush the cooling system and radiator.
DD

Could you describe how a back-flush is done?

They make kits to do this with, you put a tee inline with your heater hose and hook it up to a water hose. Also its best to take the thermostat out when doing this. But you put your cleaner in (if used) and run the engine to get it hot, then start the water up from the water hose (slowly turning it on until top pressure) . This will force the water back up out of the top of the radiator which is pushing all the crude out backwards.


You can also do it by taking the radiator off and just flushing the water through it backwards, but it doesnt seem to do as good this way. Plus you dont get the engine flushed with it.


Jess

I fought this same problem for 2 years, around town i could drive in 100 degree weather on city streets and not have an issue. As soon as I took it on the highway at extended lengths and speeds it would overheat.

I tried every soltion this board, moparts, and the old other slant board could throw at me, including new radiator. the only thing that worked was having the radiator shop take my stick radiator and make a HD 3 row (fat cooling channels). I told them, make as thickas is practical and will fit.

I have never had a problem yet. This cost me $150 in 2003, Los Angeles. So must be cheaper elsewhere.

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My Swinger gets the Highlight Valet Parking spot over the German sports cars on the Sunset Strip. I love my Mopar.

I ran this car for years with no fan....but it was a stock , worn out Super 6.

Running a 16lb cap is suicide with this old junk....I think more than 8 lbs is foolish. I have a 6 blade fan....I hate it for 12 reasons. Fans are not the issue.

I have the T fitting for a back flush already on the car (and everything else I own.....makes for easy cooling system burping)....and will flush it today.

Ted.....I live 5 hours North of Spokane. You are 12 hours West of me.... Las Vegas is East of here.

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Yeah....Im the one who destroyed this rare, vintage automobile.....

inreased comp and high speed requires extra cooling capacity, in my experience. I would try'n fit that rad you say you have, how much is "really big" ?

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Juan Ignacio Caino

Please use e-mail button istead of PM'ing. I do log in sometimes but I'll be answering quicker thru e-mail.

Fans don't make much difference at highway speeds, unless we're talking flex fans that can flatten enough to actualy restrict airflow.

A thermal imager or a carefully used infrared thermometer would reveal blocked radiator tubes.

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"When you find a big kettle of crazy, it's best not to stir it." - Pointy-haired Boss

1964 Valiant V200, 225/Pushbutton 904
BBD, CAI, HEI, LBP, AC, AM/FM/USB, EIEIO

I have ran my slant for quite some time now with no fan what so ever. It is stock also. Extra compression and over bored cylinders can cause extra heat loads on a system (camshafts also).

I have always looked at the slant radiators and wander just how much it was going to take before it was not enough. Mine is new but I know some day it will reach its limits, probably when I put my new engine in.


Fuel mix can cause changes in temp, at high speeds its either you coming to the top of the T-Slot circuit ( running its leanest) or its starting to dipp into the main circuit ( running its richest). A timing change could help either problem out, richer needing less timing, leaner needing more.


Jess

I'm a big fan of cheap easy fixes that work well and I'll share one that worked for me. I had a van with a straight six (ford) that would go all day in town without over-heating but the minute you got up to 60mph the temp gauge started to rise. If you slowed down to 40mph or less it would be cool in two blocks. I removed the radiator and laid flat on the ground with the hose fittings up and the cap on and fully seated. I then mixed muratic acid and water into a 50/50 solution and filled the radiator with it. After about 30 seconds or so I dumped it out and repeated it. I then flushed the radiator for a while to wash the acid out. The over-heating problem was gone. My radiator never leaked either. I'm not sure if muratic acid removes or damages any kind of radiator seal you might be using or if my radiator didnt need any but I never had any problem with the radiator after that.

I saw this problem with the 64 Dart way back when, and a newer/larger radiator is what fixed it. You can get an Alum Chev "universal" rad from Summit for about $180. Afco is the best. I had a 3-row from a '64 V200 wagon that worked for a few years, but was decaying and ran cool except at high speeds. Replaced with a 2" core alum rad - 21"X19" total size, and all was well.

I have an itty bitty alum rad in there now that has worked well, but haven't tested on the road course at high temps yet, only 75F outside and below.

I don't think anything with fans or tstats will do a durn thing. Fresh bottom end, so engine flush shouldn't help, right?

Lou

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Home of Slant6-powered fun machines since 1988

jess, I think that lean requires les stiming and rich requires more timing. More timing creates an artificially lean condition so if it's really lean, it would make this problem worse.

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Juan Ignacio Caino

Please use e-mail button istead of PM'ing. I do log in sometimes but I'll be answering quicker thru e-mail.

Yes, of course he could be lean too. Get yerself a Holley 350 or 500 2bbl for that sucker. Hard to tune a BBD w/o aftermarket strip kit...

Lou

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Home of Slant6-powered fun machines since 1988

as you said, you can't beat a good holley 500 2 barrels. It works better than 4 barrels on a slant. I made a thick aluminum spacer for mounting it sideways on an offy 4 barrel manifold, with divided plenum, worked even better than a 4 barrels.

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Juan Ignacio Caino

Please use e-mail button istead of PM'ing. I do log in sometimes but I'll be answering quicker thru e-mail.

To a piont, less timing will help with detination. But if I am not misstaking a lean mix takes longer to burn also (I could be wrong though).



Jess

if it's patologically lean, my understanding on the matter is just the opposite. That's why it would knock. But if you're talking about the carb on a hot slant six and that related to a timing curve, you're absolutely right. The richer the carb setting the lesser timing it likes, hence the more likely to build up heat. Never added the A/F gage to my bag of tricks for tailoring up the timig curve and the fuel curve, I would have loved to see how my setups were doing....

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Juan Ignacio Caino

Please use e-mail button istead of PM'ing. I do log in sometimes but I'll be answering quicker thru e-mail.