View Full Version : afb manifold slots

03-02-2007, 09:46 AM
Why are some of the afb manifolds slotted between the bores
and some are not?

03-02-2007, 09:52 AM
Depends on the manufacturer.
The 'balance slots' tend to even out any pulses at idle (high manifold vacuum).
It cost's money to make slots, so some cut that corner figuring a performance intake manifold doesn't spend most of it's time idling.
Removing the center divider hurts idle, too. At WOT and higher rpm, you can get away without one, but the idle to 3k range will suffer.

quote:Originally posted by Kdancy

Why are some of the afb manifolds slotted between the bores
and some are not?


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Mike Van Veghten
03-02-2007, 02:55 PM
The word Jeff uses..."suffer" is a very "relitive" term.
While he is technically correct why the slots are there, only those with the most sensitive butts will recognize any drivability or idle problems.
And how many really care if it idles at 700 rpm or 725rpm?

A "fully" divided manifold will perform better at lower rpm's.
A divider that has been cut down ([u]OR</u> a spacer was added!!!) will give the advantage to the mid-range and upper rpm range.

I'll bet all those who added a spacer to install an Edelbrock carburetor never even realized an idle difference once the tuning was done(!)!