SB Air Gap mods

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raymond

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Hi, anyone have any thoughts or info on SB Air Gap plenum mods similar to the LD 340 mods from decades past, I've seen vids where there have been improvements on the dyno after cutting the divider down on a SB Chev AG, just wondering if anyone has given theirs a bit of a cut and if so is there anything to be gained. Thanks
 
My son gave this intake a bit of a cut yesterday. Still has a bunch more blending to do. On a dual plane a cutting the divider equalizes the pull through the carburetor and balances the charge. Old school trick and is how LD340's came.

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I agree. Airgap is fine as is. I switched to Victor 340 intake and don't miss airgap to be honest. This intake rips from low end to top. Even though it's rated for like 3000 starting rpm range it does fine down even lower.
 
I had the center divider milled down 1/2" on my Airgap did it make a difference maybe maybe not but my stock stroke 360 went 11.70's with it!!!
 
FWIW../

LD-340 did not come with a milled center divider.

But I did the mod and liked it. It’s a mod designed for a big cam and to “Legally Cheat” when the rules said “You must run a dual plane intake.”

“A big cam” back in the day was .600 lift and greater which always came with big duration @050 numbers.
AKA - A RACE CAM.
 
If you have the hood clearance you can try an open spacer to see if there is any improvement and avoid cutting the divider.
 
The open spacer was gonna be my suggestion too. Un-doable if you don't like it, and you won't have to pull the intake off the engine to try it.
Engine masters spacer test: open on a two plane, four hole on a single plane.
 
You need to give some thought to the desired outcome......before cutting.
Generally when you cut down the divider on a dual plane manifold, it adds a little top end but softens the low end.
If the engine is in a heavy car with tall gearing, it might hurt overall performance. And vice versa.
 
If you have the hood clearance you can try an open spacer to see if there is any improvement and avoid cutting the divider.
That's the problem. very close to the hood now, thanks for your response.
 
You need to give some thought to the desired outcome......before cutting.
Generally when you cut down the divider on a dual plane manifold, it adds a little top end but softens the low end.
If the engine is in a heavy car with tall gearing, it might hurt overall performance. And vice versa.
Thanks for the response, it has a butchered up LD340 on it now with pretty much the complete divider missing out of it, right down to the plenum floor and even removed under the roof towards the front, although it seems to run half OK I don't see the total fuel distribution being great.
 
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