Well yeah a 16" is better, but:
1.) '71-73 cars have no room between the rad and water pump for a fan. ( I can barely snake a belt between the rad and pulley bolts). This means that a pusher fan is the only option.
2.) The 16" fan I have that could be reconfigured as a pusher was too big to fit on the front of the radiator. It hit the core support
and hood latch support.
3.) The nice and thin 16" SPAL fan I have can only be used as a puller.
4.) I already had the 12" and it does fit.
I may end up modifying or ditching the hood latch parts depending on what happens with the hood in order to clear the intake. If I have to use hood pins, then a 16" fan is the obvious choice.
Does this look like fun?
Well, it's NOT. Those spikes and dips on the battery voltage (bottom graph in white) were causing a lot of problems, especially the low voltage dips. This noise is likely coming from the low-z injector circuit and is compounded by having to use PWM current limiting
because they're low-z. When people said the MegaSquirt v3.0 board was sensitive to noise, I thought they meant external sources like RFI from non-resistor spark plugs. Well, it's actually internal noise from flawed design.
There are some ways to fix it with jumpers and trace-cutting, but I elected to:
(1.) install a filter capacitor on the injector flyback circuitry. This brought the voltage swings down to a tolerable level, but they still spiked between 11 and 15v. I knew it could be better, so I
(2.) put
another filter cap on the bootloader header. Finally, rock-solid voltage readings.
Now that noise is no longer an issue, acceleration enrichment is proving to be a tougher nut to crack even without venturing into the realm of
Enhanced
Acceleration
Enrichment (EAE).