carb. jetting?

rod · 06-02-2017, 10:30 PM

Holley 4776-600 CFM DP, since the blades are the same size and the venturis are the same size---you should be able the square jet. right?
the only thing I can see,which would be different [SBC-Power Products intake] is that the front manifold runners are shorter than the rear runners.
your thoughts.
Thanks Rod in AZ

Myron Piatek · 06-03-2017, 03:25 PM

4776-3 & newer versions come with 66 primary and 73 secondary jets. You can usually jet square if you eliminate the power valve. But to make sure you compensate correctly, you should measure the power valve channel restriction. Somewhere there is a list or formula showing how much difference in jetting there is based on the size of the 2 holes under the PV. It can vary between carbs.

Distribution can be tricky, but I did find a different need between the shallow side and deep side of an aftermarket dual plane intake I tried once. But different manifolds can have different distribution issues, or compensation built-in.

06-02-2017, 10:30 PM	#1
rod Member Join Date: Dec 2009 Location: Kingman, NW AZ. in the middle of the longest stretch of Route 66 Posts: 313 Likes: 0 Liked 20 Times in 15 Posts	carb. jetting? Holley 4776-600 CFM DP, since the blades are the same size and the venturis are the same size---you should be able the square jet. right? the only thing I can see,which would be different [SBC-Power Products intake] is that the front manifold runners are shorter than the rear runners. your thoughts. Thanks Rod in AZ

06-03-2017, 03:25 PM	#2
Myron Piatek VIP Member Join Date: Nov 2001 Location: Florida Posts: 1,542 Likes: 34 Liked 138 Times in 51 Posts	Re: carb. jetting? 4776-3 & newer versions come with 66 primary and 73 secondary jets. You can usually jet square if you eliminate the power valve. But to make sure you compensate correctly, you should measure the power valve channel restriction. Somewhere there is a list or formula showing how much difference in jetting there is based on the size of the 2 holes under the PV. It can vary between carbs. Distribution can be tricky, but I did find a different need between the shallow side and deep side of an aftermarket dual plane intake I tried once. But different manifolds can have different distribution issues, or compensation built-in. __________________ LOCOMOTION Racing