Weber accel pump cam / Air cleaners yet again / Ansa resonators

More esoteric Weber and airbox airflow stuff

While wondering why I've always had the rather large blue puff when rapidly opening the throttle, I talked to Steve at Pierce Manifolds. Apparantly the 40 DCNF-12s have a huge gorilla accel pump cam length of 10.3mm when compared to the rest of Weberdom where the max is usually 3.5 mm or so. That would explain the dump in my A/F to < 10 on tip-in as well. Steve's looking for the original Ferrari specs on the pump cam. My bleed-back and pump jet are already about the same. Anybody have that spec or can measure?

Also have a sl chunky rich area in the mid range, so will be going from F-24s to F-36 emulsion tubes.

Despite intensive psychotherapy, I'm still obsessed with my 20hp+ loss on the dyno due to the airbox and K&N when compared to open air horns. Even with the cool air factor, my last stand is going to be to try larger seperate filters for the Webers, which Steve thinks will make a big difference. It's already been shown by another thread that the overpressure due to ram is negligible. He said to point the cool air duct toward the carbs to minimize the ambient heat. As far as surface area, the stock fiter is about 11.5 X 14 X 1.5, yielding an approximate filter area of 76.5 square inches. Each of the 4 separate air cleaners is 4.5 X 7 X 2.5, yielding an individual surface area of about 55 sq. inches, or a total of about 220 square inches. I do realize there are flow differences due to aggregate steady verses pulsed separate vacuum, but it's worth a shot at about $100 for the four filters, even if I recover half of the lost hp. If this works, the numbers may be applicable to my 308 carb buds. It will certainly make servicing easier in any event.
Any personal experiences, qualitative or preferably quantitative , happily solicited.

And on a final note, installed quad Ansa resonated tips on the end of the Dynomax muffler and the tone smoothed out immensely - very nice at cruise and whompin' when you open the throttle.
best
rt

 

Exactly right - this is the rub that I've been struggling with.
Even calculating resulting loss from a 40+ degree increase in ambient air temp, the increased flow should more than overcome - certainly wouldn't be losing 20 hp in any event. Will be blowing the air from the scoop at the new filters as well. At speed, I do not think the temps are going to be that different as the engine bay is so wide open to below (this is a Mondial) since the removal of the FI and the new exhaust is more open.

In addition, I think there is some reversion wave pressure thing going on, but can't be sure, and I may be all wet.

Will install this weekend and dyno thereafter. All opinions welcome.
best
rt

 

10mm of lift acting on the lever arm of the accel pump.

Similar to your idea, I was thinking of a shroud like the original 4 cam Carreras.

best
rt

 

I installed the 'Ferrari' accel pump cams today recommended by Pierce to fix my blue smoke on throttle application and momentary very rich mixture (A/F<10) at tip in. The 'Ferrari' cams only go up a third of the way as the stock DCNF-12s (3mm vs about 10) that I used in the retro-fit to the 3.2.

Well, not even close.
Took off the carbs and put the 'Ferrari' accell cams in and guess what - it still blew blue on throttle application from idle but now went totally dead coming through about 3000 rpm starving for fuel.
Soooooooo...back off come the carbs again (taking 1/3 the time of the first change)and the old cams go back on and we are back to where we started.

I did install the separate air boxes replacing the stock 308 airbox. and while I do not yet know if it helps, it does look great and makes it 100% easier to get around and work on. I'll send a photo to anyone that wants to see what they look like. It is rather impressive - and did I mention the sound?

See - I even report what doesn't work!

Tomorrow will install a Holley Red fuel pump and regulator and rear 11 mm wheel spacers from Hill engineering.
Waiting on the F36 emulsion tubes.
Have decided to go to 50 idles from 55.
Will install temp wideband A/F in car to watch as I drive next weekend as well.

Have a set of chrome wire meshed 2.5" 40DCNF velocity stacks, as new from Superformance, if anyone is interested. Best for track use.

more later
rt