I got my original 4-core radiator fixed (they said it was better than the "new" one I bought), and am going back to the original.
I think as bobc455 says, going with the stock mechanical (1/2" from shroud and 1/2 in the shroud, may allow me to use the Zirgo ZFB16S, too.
Or I could go back to the flex-fan from Summit--with thicker pitched fins. The electric puller will not fir with the 2"spacer.
No one can give me an answer (even TA)about the cooling demands of a mostly stock'73 Riv GS.
One thing I've noticed is my new 12-SI 94-amp alternator case is burning hot after a drive. I have my fan wired either to be completely on or off. I'm looking for a thermostatic control. Even my new 75 amp relay is warm to to the touch. Zirgo said that fan may use 25 amps continuously. my wiring is sufficient. 4 gauge from alt "+"post to the battery. 1o gauge fused at 30 amps to a tyco 75 amp relay, 5' of 10 gauge ground and power wires, 16 gauge switch to ground that activates the relay.
IF I add electric pushers--only 2 10" may fit because there's a structural element that divides the condenser.
And my alternator isn't going to take much more of this. I'm planning for a sstealth audiphile stereo with 60-amp rated high-current amp. Rarely does it take that much, but they do have needs for instantaneous high-current capability. My new ignition system is fused at 15 amps (it still works great, but the old-style jacob's Ultra coil seems to get somewhat hot on the heatsinks )
I'm going up to an alternator with more current at lower rpms.
any more suggestions for the cooling part?
I'd love one of those 1" 2 rows, which are better at dissipating heat, but if I can return the new proliance one, and put in the original 4-core one(that was tested up to 20psi), maybe use the stoc fan/clutch--which worked when I put it a sink of hot water. (I still wishe there some that locked up more quickly.