I've installed a larger radiator and had 1x10 inch thermo fan mounted in to the old radiator support. Unfortunately this isn't providing enough air flow so looking at installing another. My question is how much does the front apron flex with the stock radiator support removed? Will I need to weld in additional support along the top of the apron to compensate?

Yes, it would flex too much. Instead of cutting the Radiator Core Support, cut a larger radiator opening in it, larger than the stock hole

Here's one that's been widened about 50%



By the way, the stock A12 fan is more than 12 inches. A 10 inch fan would be too small

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  Stock Radiator Opening.jpg (93.75 KB)


  S13 Radiator Opening.jpg (92.81 KB)

I tucked a fan out front of my larger radiator inside of the radiator support as well. When looking at the engine on the left, also cut out the sheet metal out front to allow more airflow.
You may not need a second fan if you do that.

Hey Ernie, did you put the 2nd fan between the radiator and the grille? Got pic? Your 400hp engine must use a large radiator

A single 12" or 13" fan will cool an A12/A14/A15 engine

My other option is leaving one fan on the front and mounting the second in pull configuration on the rear of the radiator. It's snug but does fit. Just a bit ugly!

No picks at the moment. My car is apart. I have a second 4" fan where the AC opening is. That's the area that I cut out.

Nice, thanks for the pictures as I'm about to do the same