The biggest improvement to air flow to the engine, is to enlarge the air box cover in the area of the rear carb. Hours of dyno work when I was racing cars equipped with Weber style carbs, showed a ratio of distance between the end of the air horn/trumpet/velocity stack and the outer edge of the air box. We found the minimum distance to be one and one half times the diameter of the air horn/throttle plate. So, with a 40mm carb, 60mm is the bare minimum. Seems to work with SU type carbs as well. In standard form, the air box cover for the twin cam is much too close to the outer end of the air horn, and even gets closer as it gets to the
rear end. The front carbs distance is much better. What’s need is to make a new mold that affords an equal distance for both carbs. Keep in mind, that one cover does does not fit all, as there are several different types of covers.
Hi Prezoom,
Didn’t Tony Tompson make a bigger airboxcover where the backend is as wide as the front?
Martijn
I do not know, never contacted Tony Thompson. A one time mold was made from my existing front cover, that increased the rear clearance on my Elan. On my Plus2 Zetec, an early back plate was obtained, but had to be modified as the Weber intake manifold for the Zetec has a different spacing for the carbs than the twincam. Another one time mold was made for that setup. I purchased a totally fiber glass, front and back, from Famous Frank on this list, that is enlarged, that I will be using on the TC going in my Elva Coupe. I hope it fits that application without mods.
There is a guy on eBay, ‘davenmandy0’, who sells full width airboxes. I bought one a couple of years ago - if I recall it was about £90. I think he makes batches, then offers them for sale on eBay.
You could try contacting him.
Hi,
I found an email address on this forum relating to him. I emailed him 2 days ago but unfortunately no reply yet.
Anyway I ordered the advised items for correctly mounting the carbs so happy with the tips.
Martijn
Please check your messages,
Dave
I fitted one of Martijn’s full-width airboxes on my S4 about five years ago. An excellent product, with finish way better than the original.
Skypilot, did you mean “Dave’s” and not “Martijn’s”
Dave
Oops. Sorry. Yes, Dave’s
Deep air box fitted in 2016. Bought from howsam2@hotmail.com