Factory 911, 914/6, 916 air boxes, How many different designs? Options

[horizontally-opposed]

Went to the dyno to do a first dial-in on the carbs and made 169.9 hp at the rear wheels with no air filters. Was pretty jazzed, and then the dyno operator said "Now watch when we put the air box back on...it'll be even nicer."

We lost 20 hp.

It was the end of the day, and I still need to finalize exhaust before we really dial the thing in, but we pulled the snorkel and air filter to do one more run. We gained 12 hp back, so 162 hp at the wheels. This from a 2.2 six with E pistons, a bit of compression, Solex cams, a bit of head work, headers, a single-tip Leistritz muffler (now a two-tip Dansk sport muffler), and Webers.

My question: How many variations of the factory air box were there between 1965 and 1973? Carbs, MFI, T, E, S, etc? I know there were metal ones and plastic ones (my air box is plastic), but I'm wondering if anyone knows a link that explains the variations, or can provide Cliff Notes from which to start my research? I'd love to keep a factory air box on the car, as I like the noise reduction, but would like to get some of that power back. Engine also feels hesitant past 6000 rpm.

I know, I know—rain hats. I'd prefer not to go that way. Thoughts?

[horizontally-opposed]

Posted a request for same info over on the Early 911S board, and one guy has weighed in. There have to be more people with more info on this. After all, induction is a pretty important part of the equation—and there are a lot of us with carbs on flat sixes.

http://www.early911sregistry.org/forums/sh...es-from-1965-73

Fwiw, the factory air box sounds GREAT when paired with a Dansk sport muffler (I chose the 57mm two-out version sold by Patrick Motorsports). One ex-962 (and current) 3.0 RSR racer looked over in shock and remarked at how good the car sounded, then emailed the next day to say it was the best sounding 914-6—and flat six, period—he'd heard in a very long time. It's also quiet enough that you can still have a conversation at speed. Wind noise is more bothersome than the engine...which sounds wonderful and appropriately loud.

For me, it's the ideal setup. Would just love to figure out how to ensure I'm not losing 20 hp due to the air box, which all research suggests I shouldn't be.

Anyone?