Is there a standard size oil cooler to use behind a 916 or 914-6 front grill?

you can use a rx7,or patrick ,,, But PMB has a Nice repo of the factory GT Cooler..

Oil cooler sizing requirement is highly dependent on engine power and usage (notably street vs. track, climate). There are lots of good options out there these days. One suggestion is to make sure the cooler takes at least a dash 12 size fitting (and not just a smaller port with an upsized fitting on it) to keep up with a 911 engine's oil flow requirements.

A used rx7 cooler would fit my budget, anyone know what years are best for our use?

You need to cut open the rx7 cooler and remove the restrictive plumbing on the end as I recall

Options ..yes depends on year of rx7

If you real want to go RX7 cooler buy a new one, they are very inexpensive. I will cost more to send used cooler off to be properly cleaned. 25years ago I used a RX7 cooler on the front of my 911(worked great), I had a shop modify it and weld in the appropriate fittings. Not sure its worth the trouble today with so many proven options.

john

This would go on an other than stock 4 cylinder engine that was driven all year long in the socal low desert. Doing all I can do to get as much air in for cooling and an oil cooler. I had one in the rear but in the summer it was less than effective. So it will go up front where the coolest air is. I’ve seen the aftermarket rx7 coolers, I’ll just save for a while longer.

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go to eBay and search for RX7 cooler - new and they are less than 100.00. Many years ago I did a used one and had my local welder cut the end cap off put a divider 1/2 way to separate into two chambers and weld in to AN12 male fittings 1/2 was used as inlet forcing the oil down making a U turn and heading back out of the second chamber male fitting. Jim