Hello,
I'm trying to figure out how much CFM I need to pull through a big block Chrysler Summit 4-core radiator (
radiator link) to keep a street/strip 440 cool. Is there a formula to use (ex: engine HP to BTUs)? I read a good rule of thumb is to have fan(s) that can pull 2500cfm for an 8-cylinder (
how to choose an electric fan). I was looking at this shroud and fan combo from summit racing (
kit link). However, it advertises only 1500cfm, which may not get the job done. I am trying to help my dad; it is his car.
The car is a 1967 Plymouth Satellite with a street/strip 440, Indy EZ440 heads, .530/.232@050, 10.8 comp, 22 degrees initial/37 total timing (we are in Colorado and he uses race gas), auto, 4.10s, flowkooler pump, 160 thermostat, factory fan shroud with a flex-a-lite fan (no viscous clutch installed; but he has one that could be used). It is an original big block car, so it has the larger radiator core support opening. The trans cooling lines are going into an external cooler and then into the radiator. I am not sure why the guy who built the car went that route; but I may try to bypass the trans oil lines going into the radiator. That might help. I also need to check that the radiator cap fits the radiator neck correctly and the pulley sizes. The car overheats (230+) in traffic, but runs around 190 or so cruising down the road. I believe the issue is airflow.
Questions/comments/concerns/thoughts?
Thank you in advance.
Another data point: 1972 Dart, low-deck 451, .652/272@.050, 10.3 comp, 27 initial/36 total, 4-speed, 3.91, Flowkooler pump, 180 Milodon hi-flow thermostat, Champion 3-row 26" aluminum radiator, Ford Contour electric fans with Autocoolguy PWM controller.
Idles at 182 all day in 90+ degree weather. It does heat a bit on the highway (65 mph is 3300 rpm) and after 15 minutes it levels out at 198. Slowly comes back down once off the highway. This is probably due to the Contour fan shroud blocking airflow when the fans should not be needed at highway speed, but I can certainly live with temps at or below 200. Especially since it stays cool in stop & go (or just stopped)
Something to watch out for, besides the electrical upgrades which have already been mentioned: more small cores (4) is not better. All that metal interferes with the airflow and the multiple small tubes don't have as much heat transfer capability as fewer large tubes... IMHO the best radiator to use is a two-row with 1.25" or even 1.5" tubes if there is room between the core and the engine.
Chevy HHR fan is supposed to work well but I'm not sure it'd be big enough either. Also a Lincoln (Mark VII?) fan is a good one. But the Contour dual fan is cheap and readily available.
The additional trans cooler probably helps a bit, but I would not use it instead of the radiator cooler. It'd have to be pretty big depending on the converter...
