with 5/16" added to top of runner same 1.4 x 1.1 main runner and 1.6 x 1.22 entrance flowed 213cfm. flowed 166cfm with stock head.with head that flows 250cfm it flowed 200cfm. probably 3 passes of weld on top of runner would do it. flow started going down when more was added to top of runner. this is so much easier than what I did while learning.
the .2" taper is part of the design. show as #1. # 2 shows the 5/16" added
larger main runner still needs the taper too be efficiency.
best case, would be to taper the entire runner. not an option for stock intake.
been doing research on intake runner design. making the entrance bigger than the main runner is common. mini ram, crossarms, import intake porters do it.

 

found an interesting article. blades under TB's are for fuel distribution and mixing. also this top plate isn't the same as. wonder what car it's from
Improvement or Impairment? To Modify G.M.’s New Fuel Injection You Have To Get With The Program

 

I did get test port to flow 248cfm. 1.185 x 1.6 MCSA

enjoyed all this learning and looking forward to purchasing renegade 2.0 manifold

 

From the published date of the article, Oct, ‘81, I’d have to say it was probably a pic of a test prototype CFI lid from GM.

 

Hello
all good morning……
it’s been a while but I’m getting another CFI third gen….. ( 1982 Trans Am LU5…. ) and I want to tweak it a bit….. it’s not a race car…. Just a weekend cruiser and maybe 🤔 a car show or two…. And a burn out here and there……. I used to mess with this stuff but that was years ago and I think I forgot some details lol🤪….. I’m 54 now…… I want to clean out the inside of the intake…. but I don’t want to weld anything…. Which intake is better….? And why…? I think there are two or three different versions of the CFI intake manifold….. I want to eliminate ALL the emissions crap 💩…… but I want to keep the ancient computer happy so that CEL stays off ….. unless it has to tell me something else….. lol 😝…….. I also want to….. oh my god…. I’m so sorry I just got carried away……. Oops…..😬 I’ll stop here and wait…..
Thanks

 

gasket match, round sharp edges at entrance and clean entire length of runner. remove bumps. doesn't take very long.
superL98 does a great job illustrating porting.