Cam to use with Webers question

[Jim Maxwell]

Jim Inglese can hopefully advise you on a proper cam for your setup. A stock cam will probably do just fine. I am ignorant of the physics of reversion, but I had to do the same thing when I added Webers to CSX 2401. The hot cam wouldn't work properly, as Jim Inglese advised me, fortunately before I had the engine rebuilt and the Webers added.

[saltshaker]

Webers like a wide lobe seperation CL 114
I ran webers on my 428 with a Comp 282S which had a 110 cl
Motor ran ok but would of run better with a wider CL
Call Oregon Cams they know FE's or ask Brent he also ran webers on a 428
Jon

[Gaz64]

This is about as close as I can find in the Herbert catalogue:

CHH2 240/240 DUR@.050, 640/640, 110LC, 2500-6500 - HERBERT CAMS

280 at 110 would be inlet open 30 BTDC, close 70 ABDC, exhaust open 70 BBDC, close 30 ATDC. Overlap advertised would be 60 degrees.

240 at 110 would be inlet open 10 BTDC, exhaust close 10 ATDC. Overlap at .050 would be 20 degrees.

The issue with picking a cam for Webers is not just the LSA, because 110 would be fine if the cam was only say 210 @ .050.
Once you start getting into above 230 @ .050, the LSA becomes more critical.

[olddog]

Reversion air flow happens at idle (low rpm) with higher valve overlap cams. The intake valve is opening, when the piston is still moving up. At higher rpm and power the exhaust gasses have enough mass and momentum to crate a vacuum and pull air through the intake valve. At idle this does not happen and the piston shoves exhaust gasses out the intake valve. This blows air and fuel backwards through the carburetor. A typical single carburetor manifold has long runners and a plenum that adds up to a lot of volume, compared to Webbers. The volume dampens the affect. The Webbers have very little volume, and the reversion flow causes a haze of fuel to float above the carburetors at an idle.

The reversion flow not only makes tuning the fuel air mixture difficult, that haze of fuel only needs a spark to make for a very bad day.

Let the experts guide you here. Red neck engineering does not mix well with Webbers.