open or divided plenum
Thread Starter
Racer
Joined: Aug 2009
Posts: 307
Likes: 1
From: dallas texas
open or divided plenum
When I built my 496 big block, I installed the stock 3885069 intake with the divided plenum and a Holley 850 with vac. sec. My solid cam has the 4,7 swap. I want to keep the dual plane intake for hood clearance and stock look. My question is this: does the 4,7 swap change the airflow characteristics of the stock intake enough to warrant removing the plenum divider as in the L88. The engine runs strong all the way up 7000+ rpm, my interest is in improving the idle characteristics. Thanks for any input. TJS
Team Owner
Joined: Oct 2000
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From: Washington Michigan
Race Director
Joined: Jun 2006
Posts: 17,901
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From: Inverness FL
St. Jude Donor '07
i have never heard of this before so i did a google search.
the last post in this article explains what the 4/7 swap is all about:
http://forums.chevyhiperformance.com...ion/index.html
Bill
the last post in this article explains what the 4/7 swap is all about:
http://forums.chevyhiperformance.com...ion/index.html
Bill
Thread Starter
Racer
Joined: Aug 2009
Posts: 307
Likes: 1
From: dallas texas
Thanks for the post wmf62. After reading through 10 or 12 articles it's obvious that most all the bbc racing engines are being built with the 4/7 swap, with the power gain in the upper rpm range, and slightly smoother low rpm operation. I chose the 4/7 swap cam for those reasons. It definitely has a different sound at idle. The info on dual plane and single plane open plenum intakes is conflicting, with some reports of gains with a dual plane as opposed to a single plane open plenum. I guess i'll stick with my stock intake as the info does not appear to support a change.
