Aluminum Intake Manifold 3885069 "L72"

[Ken K.]

Viewing the photos below, what 3885069 intake is correct for a stock 1966 427/425hp "L72" car?
(I'm looking at the carburetor plenum holes.) What are the differences between numbers 1, 2, and 3? Did someone modify number 1 and 2? (And for what reason.) Thanks

[David D.]

Re: Number Three is Correct. *NM*

[Mike M.]

Re: Aluminum Intake Manifold 3885069 "L72"

agree witrh dave. # 1 and 2 have been modified, a common practice years ago. mike

[William C.]

Re: Aluminum Intake Manifold 3885069 "L72"

As to why, opening the plenum area provided improved high rpm performance at the expense of low speed tractability. Great for racers, not so great for drivers.

[Mark #28455]

need to stagger jet the carb for #1

The L88 intakes were open like the #1 you pictured. To get even mixture distribution, they required tabs attached to two of the carb booster ventiri's and staggered carb jetting. For numbers, look up the Holley 3418, 4054 or 4296 carbs in the service books, the jetting is identical. By the way, the stock Holley jetting is usually about 2 sizes too rich on the primary and 4 sizes too rich on the secondary as noted in the Chevy Power manuals in the mid 1970's.