Radiator Overheat.

New Griffin Radiator, new water pump, new serpentine belt set up, front and rear fans which together push 3,000 CF, 165 degree thermostat. Checked radiator flow in driveway with cap off. Appears good flow. Temp gauge at 215 degrees after 20-25 minutes, fans running and boiled over when car shut off as expected. Where to start?
I may have overlooked the obvious! I was consulting with friend about the problem and he raised a question about the shroud since he has seen my car and questioned why I am not using shroud! I had no answer. He is running a 440 in his 65 SF with the same size radiator that I have without any problems and a engine temperatures of 180-190; he is also here in Phoenix.

I am running a 16", 2,400 cfm, electric fan, no mechanical fan, and a 15" pusher fan, 1,400 cfm and since one since in front of the other, not sure what the total cfm would be. Using simple math, however, the area covered by the 16" and 15" fans is 201" square inches vs a radiator core size of 21" x 18" or 378 sq. inches. Bottom line is that the 16" covers 52%, 201 sq. inches, of the area of the radiator core, 378 sq. inches, which means that at an idle, 48% of the core has no air flow and that is when the temperature begins to increase, quickly!

My first task to solving my heating problem is to install a radiator shroud to cover 100% of the radiator core and hopefully this will solve my problem!
With the outer fan lower air flow and directly in front of your other fan, could it actually be blocking/ restricting air flow? The airflow is likely not additive. Also if you do a shroud the diameter when inline with the fan should have minimal clearance for the best airflow coverage. Without the shroud you may be better offsetting the two fans for better coverage of the radiator. If only everyone had an anemometer in their toolbox it would be easier to diagnose these things (and learn in the process). I don’t have one either (yet).
But at $16 on Amazon I may try one. It will definitely show your dead spots.
In my post 15 I was wondering about the pull and push fans too. If I were you I would ditch the pusher and use that 16" puller with a shroud and you should be golden.
I have a 22" radiator in my 65 with a thermo clutch fan and my 383 runs right around 190 even when the temps get up to close to 100 degrees. I also have a window screen in front of the radiator to keep the bugs at bay. I do notice the temp gauge runs a bit higher because of that but not enough to concern me.
I'm running the exact shroud MEANT for my radiator now, which I found this spring. They help SOMEWHAT, but again, a cheap pusher gives better cooling help when in stop and start traffic in Sunny AZ. I've VERIFIED THIS REPEATEDLY FOR 6 OF THE 7 YEARS I'VE RUN THIS 383 I'm still using.

When revving the engine a bit, a mech shroud with a fan can help pull a bit more air through the radiator. I got this one as part of an unbelievably good find, another 2524984 radiator. I plan to better seal the shroud to the radiator this week using some high temp aluminum tape. Ma Par mounts it well, but it could be better sealed, and will be.

A good electric fan helps more. I see a nice one used as a puller above. If you go for an electric puller, you MUST SHROUD to get dollar value, but as a pusher, an electric supplements whatever is behind the radiator. I might go all electric with cooling next year, or more likely won't, but if I decide to, that's the only scenario I foresee with an electric puller setup for me. I likely will use two for that also, one 16 inch and one 10 inch or smaller as a supplement. This will require yet more alternator current of course, but a good Meziere pump might be worthwhile, in town.

If you plan to drive mostly in town, I say upgrade your electric pusher now, get a shroud for whatever puller you use, and a good pump. I sometimes see temperatures as high as 205 F when I do plenty stop and start in sunny traffic even now. My setup held the line at 210 pretty nicely last summer. We'll see how it does now with the Edelbrock 1405 and the 915 heads. I expect to need to twiddle this setup a little, but major revision shouldn't be needful. I might advance the timing until I hear the telltale clatter of detonation, then pull it back a few degrees from such.