Chevy Corvette Forum banner

1 - 1 of 1 Posts

9,816 Posts
Discussion Starter #1 (Edited)
I have never had a Holley choke that worked very good as it was always a bit too rich or a bit too lean. So I drilled two 1/4" holes through the choke's butterfly to see if they'll help. The Rochester QuadraJets use a "choke pull off" to meter the correct amount of fast idle air but the Holley's don't have an accurate method to meter the air so I'm hoping the two 1/4" holes will do the job.

UPDATE: I just had the opportunity to start my 454" on a 25 degree morning and it instantly started and fast idled so it looks like the two 1/4" holes made a big difference..

SECOND UPDATE: I found the two 1/4" holes made a huge difference on a cold start but it still chugged some black smoke. So when I am able I'm going to increase the diameter of the holes to 5/16" to give it more air.

THIRD UPDATE: The two 5/16" holes needed to be a bit larger as it was still chugging some black smoke on a cold start up. So I enlarged them to 3/8" and I'll see what they produce. A 454" is a big engine and big engines need a lot more idle air than smaller engines.

FOURTH UPDATE: The 3/8" holes did the trick as it now starts instantly and fast idles without chugging any black smoke. The carburetor on my TO-30 Ferguson tractor has a choke butterfly with a spring loaded air valve that opens when exposed to engine vacuum; a crude choke "pull off".


1 - 1 of 1 Posts