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Discussion Starter · #1 ·
Took the new Dart out this afternoon. Drove about 40 minutes on the freeway to the Pavillions in Scottsdale, AZ. Temp gauge got up to 210 by the time I got there. Guess it's time to address the cooling issues. outside temp when I left was 90 degrees. Been windy the last two days and today I had a slight headwind. Drove the car no faster than 60 MPH.

1968 Dart GTS
Carter 625 w/the metering rods stepped up two sizes
Electronic ignition
Timing at 36-38 total degrees
Motor is .040 over
Stock two core Rad (2898033)
Stock fixed fan
Stock Fan Shroud
440 Source water pump
3.91s (but will soon update with 3.55s
Stock Big Block A body pullys
Running 50/50 coolant

Open to constructive suggestions

Premium Member
3,920 Posts
You say you have the 440 Source WP, but do you also have their housing? There has been a known problem with the 440 Source WP housing.

Also, what is the condition of the radiator? I had an Omni years ago that only had 30-something thousand original miles (I had only put about 1,000 miles on it at that time). Started overheating on the highway (over a certain speed), climbing hills, and sitting at a light. Took that radiator out and was there when the shop pulled the tanks off. Out of about 50 tubes, 8 were still flowing.

Also, in my experience big block Chryslers are difficult to keep cool. Everything MUST be working properly. My experience with small blocks is just the opposite. There needs to be a real problem before they run hot (doesn't mean I won't run big blocks...).

21 Posts
Once 440 Source discovered that casting error many years ago (12 or so years) they fixed it pronto. I bought mine 4 years ago and it is cast and machined perfectly. The factory setup for 340 A/C abody's and all of the b/rb and HEMI abody's used a shrouded 3 row core radiator @ 16psi. They used 5-7 blade clutch drive fans in various years, and ultimately decided the asymmetrical 5 blade worked best which is why I am using it on the 470 pictured below. The direct drive low pitch fans like you are currently using were abandoned by 1969 on high heat demand applications so the fixed blade direct drive fans were found only on the little engines and low performance 383 cars without A/C.
The fan drive in my photo is the Jaguar type, and it results in a half inch radiator clearance. The shroud and radiator are original to the car 340 parts. I had to change the top tank nipple location to suit the BB and A/C.
This engine is 11.3:1 aluminum head 470ci A/C Automatic, cam is 246*@ 0.050 lift. 192* thermostat, 3.55 rear on 9x29" tires. Probably 525hp. On a 90-95* day the coolant doesn't rise above 200 on the highway with A/C on hi. It will rise to 220 at a long traffic light but cools down as soon as the engine hits 2000 RPM. The 16 psi radiator cap holds so there's no boil overs until after shutdown. The catchcan gets maybe a cup or two at most, and that gets sucked back in as it cools.
You should locate an OEM or replica 3 core vertical brass radiator and shroud because your existing 2 core was specified for light duty applications like non-A/C 273-318-and 383 2bbl applications. The 3 core has at least 25 % greater capacity. If you have an electric pusher fan in front of the radiator I'd advise you remove it as it seriously blocks airflow. Are both the front and rear hood seals in place? The front one (radiator support to hood) is very important in preventing the fan from blowing hot engine room air over the top of the radiator where it is sucked through the core instead of cooler air coming from the grille. Lots of those seals don't get reinstalled because they are stiff, or dirty, or warped, or the clips are broken. Put it back on there is a required cooling system part. The rear one at the cowl is there to keep hot engine air out of the cowl vent for the sake of cabin comfort. The whole idea is to force all the air coming through the grille to go through the radiator, over and around the engine, then down and past the transmission. If the air can find some other escape route is easier then you get overheated wiring harnesses, burned out valve cover gaskets, failed ignition coils, blistered paint on the inner fenders, embrittlement of underhood plastic parts etc.

3 Posts
I thought I would let you in on what I did:


'68 Dart post sedan. 383 that I pulled from another car. .060"-over w/a Comp XE275H. 727 with a big trans cooler mounted to the front--but NOT ON the core. Additional trans lines bent to the front cooler, and bottom tank NOT USED to cool the trans.

The radiator is for a late-'80's B250 van! I got it off eBay for around $80!! It's a 1 1/4" SINGLE row, and it works great!

This is my fan of choice:

Another eBay find for less-than $100. Dorman-replacement fan asm. for a modern Challenger/Charger! These fans do a GREAT job! They fit with 1/4" between them & the bolts that secure the water pump hub!

I ordered factory replacement harness that plugs into the fan connectors, and wired them to a control box of my making that puts each fan on it's own relay & circuit breaker. One thermal switch turns them both on at apx. 185*.

This radiator is big, and sits against the bottom arch of the core support with rubber padding, and sticks up above the top arch, but the cap clears the underside of the hood. I only used weatherstrip around the plastic shroud that sits against the core & that's it. The side brackets needed to be trimmed to fit & clear the frame rails, and certain protrusions on the surface of the core support. The battery tray needed a notch cut out of the front corner. I did not cut the core support opening bigger--it's stock.

All I have is my factory gauge to judge, but in a heavy-use scenario on a 100* day in LA traffic, the temp may get a little elevated, but still at normal positions on my temp gauge! When cruising around, the temp reading is BELOW that first 1/3 of the gauge where normal temp typically hovers! I did this last December & have had great luck ALL THROUGH this summer so far! Nasty LA traffic jams in the summer don't concern me, and I drive my car ANYWHERE with peace-of-mind!

Your car seems to be performing typically with all stock stuff (radiator & fan setup) but with a warmed-up motor. Certainly not horrible, but let us know if you improved your situation.
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