I thinking about swapping my intake manifold from the rpm performer to an Air gap on my 408 sbc. Wondering if its even worth the effort... buddy of mine has a air gap just laying around and said i can use if I want. Little about he motor...

408 sbc
profiler aluminum 195 heads
262 cam
750 edelbrock
rpm performer w/ 1" spacer
9.3:1 cr
GLM manifolds and hardin stainless risers

What do you guys think? worth the effort? I plan on changing the cam this winter to the xm270 if that makes any difference and hope for some stainless marine exhaust for Christmas...

I doubt you will see any change at all.
I have ran 3 different intakes on my engines and have seen no change what so ever. Weiand Stealth, Modified Wieand Stealth and a Dart single plane.
I actually am running 1 Stealth and 1 Dart right now and the engines run identical. I have my throttles and throttle blades sync'd so they open at the exact same rates and my RPMS are identical.

I guess I'll just hold off until I do the cam and exhaust change over the winter... Do the GLM exhaust manifolds a performance manifold at all? Few guys I know say they are nothing special and are probably hurting my performance big time.... I really only 46ci from being a big block...

My Challenger runs low 80s gps with a 383 and the aluminum tuned runner GLMs with Hardin stainless risers. I do have 20" extensions welded on the risers making them dry to the tips to prevent reversion. I would save the money on the exhaust and upgrade to a healthy hydraulic roller cam setup from Bob Mardera. Your gains will be far greater with that setup vs a slightly larger flat tappet cam and better exhaust. A member here dyno'd years ago with the GLM vs Stainless Marine on a 383 and the SM made 7 more hp.

I run a port matched rpm airgap on mine. I used to run a performer rpm with the center divider machined down to mimic the air gap design with great results. There is a slight advantage to the air gap.

Youtube rpm air gap vs performer rpm. There is a good dyno video showing comparisons.

Dyno #'s look good...won't see anything on the GPS I bet...

yes it makes a differance on power..if you dont have a lifter valley baffle in their now it will make a big differance because the hot oil is warming up your intake's fuel charge which also cuts down your uper rpm..do it!

Picked up an rpm air gap today for 150.00, not a bad deal. Also picked up an Quick Fuel 850 double pumper. Going to install them this week and see what comes of it.

It's all a package deal. The intake wont do it with out the carb, the carb wont do it with the cam and the cam needs the right heads and so on and so on but every little bit helps.

If that 850 has stock jetting I say you pick up 2~3 GPS stretched out....let us know.

Are the vacuum secondaries even opening up with that Edlbrock carb ? You need to be pulling a lot of cfm's to get them open with a 750 Edl. Mechanical secondary Holley is the way to go .