Mike:
Few comments about your filter thoughts.
1. The area of the filter media would be very restrictive and not near enough for a heathy engine.
Yes, I wondered about that. I had randomly looked at the filter for 1990s Camaros, figuring that it would give a good indication of what was deemed reasonable by OEMs. The Camaro filter is 6 5/8 x 6 5/8 inches, so I hoped that the two openings in the GT40 hatch would approximate that amount of square inchage. However, I failed to recognize that the Camaro uses *two* of those filters. No chance of getting that much air in through the GT40 upper inlets. :shrug:
2. The real problem is sealing between the deck and the bulkhead in front of the engine. Most of the air for the engine would actually be coming up from in front of the engine. This is compounded with a Mark I because of the integral engine cover with rear deck. On a Mark II you can cut the removable panel to fit a filter base like on my car but not so easy with a Mark I and I know that a Mark I is what you will have.
I failed to recognize that the U-shaped cover that is part of the Mk 1 hatch did not extend all the way forward. My recollection was that when shut, that the leading edge of that cover basically touched the firewall. If it doesn't, is there any reason WHY it doesn't?
Actually, now that I think about it, I know why--it doesn't need to. The back and sides of the U-shaped channel should seal against the top of the cold air box.
I hadn't considered the gap between the front of the cold air box (turkey tray) and the firewall however.
But in looking at a photo of a typical GT40 engine bay:
you can see that the gap is quite small. Just a small strip of foam between the leading edge of the cold air box, and the firewall, should seal it just fine. If an open-cell foam was used, it could even act as a sort of air filter and allow air to pass through while stopping debris.
So there you have it. The cold air box is now sealed on all four sides. :thumbsup:
3. If it is the exposed trumpets that you want just have Jack Houpe build you a clear filter like on my car. The cover is also made and gasketed to seal around the base of the filter to prevent hot engine air into the air box. I don't have a picture with the rear deck closed but you hardly notice the filter media. You can even make the media out of the blue stuff. All I did for the media was buy a stock K&N filter with the right height and cut it. It actually took two filters. Plenty of free area in the filters and you can still see the velocity stacks.
Extremely clever, exceptionally well-made, unquestionably effective. But it's oh, hmm, what's the word....?
Well, it's certainly not very 'authentic'-looking. My whole ambition is to come up with a pragmatic solution to the filtration problem without compromising 1960s aesthetics too much.
4. Another problem with sealing between the motor and rear deck air box is the movement of the motor relative to the rear deck due to flexible motor mounts. This is not a problem on my car because the motor has solid motor mounts.
I would think that if a seal of sufficient height/width/squishability was used on the three sides of the underside of the hatch, that it would 'give' enough to maintain a seal even with the minimal engine movement that takes place. I have a poor-man's cold air box on my 427 Cobra, formed by a simple flat sheet of stainless steel that acts like an air filter base and sits flat on top of the Holley carburetor. It's got closed-cell foam on all four sides, which seals against the underside of the hood; fresh air is introduced solely through the hood scoop. A rectangular K&N filter surrounds the carburetor opening and is covered with a flat stainless steel lid.
Anyway, that's where I got the idea of sealing the GT40 hatch underside against the lip of the cold air box, with a similar type of rubber or foam--like drag racers and roundy-round racers do, with their cold air boxes.
Attached is a picture that Ron McCall took at Road America of my motor that shows the filter assembly that Jack Houpe made for me.
I like the open stack look too but there WILL be positive filters on my motor.
Here is a little warning for those that might test drive their chassis without the rear deck installed and with open stacks. The rear tires love to through little rocks up in the air and toward the front of the car. Wasn't me but it could have been.
Ah yes, that technique would negate all of the advantages of the sealed airbox...:laugh: