<VV> 140 timing (with 280 isky cam) and 4 primary carb tuning advice wanted

[Ray Rodriguez III]

Hey folks,

     I finally got my fresh set of carbs all synced up and working beautifully (still a few questions on that), but I still had the bucking/oscillating problem at mid speeds with steady throttle when no load on the engine... stepping down or letting up makes it go away.  This occurs on level roads or slight downhill when throttle is held just to maintain speed and you are half coasting....   mostly at 45 mph and below.

     Disconnecting and plugging the vacuum line for the vacuum advance makes the problem go away...  I'm trying to decide why....  my first guess is maybe I have too much total ignition advance when the vacuum is connected.  Where should I be setting my timing?  I have it set at about 17deg which I got out of one of my books as the 140 spec, but that is a lot and I also have the 280 ISKY cam to think about...    should I be running less advance than specified due to the 280 cam?  




     For those still reading...  about my carbs....   I have 4 primaries... currently running them like stock secondaries.. idle screws all the way in, and linkage set so they dont come in till heavy throttle...   can anyone give me opinions backed up by logic/facts on:

A)  reasons I might want to use the secondary idle circuits...  opening the mixture screws and setting them up (balancing with the vacuum guage I would assume?)  What affect this would have on performance etc....   I have only a very vague understanding of carbs.. I dont know why two extra idle circuits would improve performance...  wouldnt it only affect the engine at idle anyway?

B)  opinions on setting all four carbs to open at once instead of secondaries coming in late.....  Dont worry about fuel mileage as I will test that myself (obviously will get less), but how will this affect performance exactly, and do you have any advice on setting up 66' linkage this way?  (as far as linkage.. if I set the throttles to begin opening simultaneously the secondaries will reach WOT before the primaries correct?  Is this ok?  Seems to me it would be fine but wanted to check).

Thanks for your help!  The car is running beautifully now (except for the flywheel rattle... dammit, that's next on the list).


Ray Rodriguez III
CORSA member
66' Corsa 140/4 hot rodded coupe