I'm putting together a '63 Lowriser engine to look right on the outside but for performance on the inside. Half inch arm, 12.5 to 1 compression, a lot of cam, medium riser heads. The problem is I have to use the original manifold. I'm re-doing the ports to mach the medium riser heads, but I don't like whats under the carbs. I believe I will cut away some of the walls separating the two planes. Has anyone tried this and with what results? I have to use the original list 2652-1 carbs.

Paul Frost

This was with a Blue Thunder dual plane intake on my 492" stroker 427, making around 640 HP. I cut away the plenum divider in the intake completely, and then grooved a slot with my mill down the center. Then I made a series of plates to fit in the slot, with different amounts of the plenum divided. Here is a picture of the manifold with one of the plates installed, and a couple of others sitting next to it on a manifold:



I ran the engine on the dyno and tried a variety of configurations, including a spacer under the carb. Results are shown in the following graph:




In my case, a 1/2" open spacer plus cutting the plenum divider down by 1" gave the best results.

You could use this as a guideline for what you are doing with your engine, but truthfully I think you would be better off duplicating what I did with the Blue Thunder intake, and then testing various amounts of plenum divider removal on your particular engine. It seems like your choice of cam, the number of cubic inches, compression ratio, heads and exhaust would all play a part in how effective this mod would be, so the ability to test and tune the different combinations on your particular engine would be the most effective way to manage power optimization.

Jay Brown
1968 Shelby GT 500 Convertible, 492" 667 HP FE
1969 R code Mach 1, 490" supercharged FE, 9.35 @ 151.20, 2007 Drag Week Runner Up, Power Adder Big Block
2005 Ford GT, 2006 Drag Week Winner, 12.0 Daily Driver
1969 Ford Galaxie XL, 460 (Ho Hum....)
1964 Ford Galaxie 500, 510" SOHC