All Big Six Clifford Plenum Divider

Relates to all big sixes


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others -- Still would like an answer to post #36 above.

Apples & Aardvarks.
All the formulas are geared around WOT acceleration, and have little to do with what you're theorizing.
IMO, on your intake, the plenum/runner line is more vague. And practically irrelevant.
A bent 8 isn't an inline 6, and each case is different anyway.
Some manifolds, on certain combos, like a split plenum. Unless it's a common combo, there's a lot of trial & error. Mostly error.

Stronger mixture signal seems the goal, and the ways to get it are several.
Splitting the intake, more thoroughly.
Reducing plenum volume, as FTF and I have mentioned.


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Firepower354 -- I get where your coming from and I really feel like I am over thinking this whole plenum thing. As I have the setup currently I am sure I have improved the mixture signal somewhat.

1st -- Like I said before I will try the intake with the adapters like they are with my Holley 2300 350cfm / 62 jets / 6.5 PV.

2nd -- I will leave intake alone & install 59 jets & maybe 57.

3rd -- When I get the jetting ware I want it I will build a 1/2" thick aluminum adapter with studs to replace the Clifford 4V & 4x2 adapters and retry my 2300 with best jets.

4th -- I will replace my 2300 with a fresh rebuilt Autolite 2100 1.08 venturi with 57/55 or 54 jets & 6.5 PV, get the best jets.

Will get new AFR numbers at idle & 40-60 mph cruising.

Like you said "trial & error" the old school way, I can handle that.


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Well as much as I would like to finish my Clifford Plenum Divider tests it is not going to happen. Medical issues are stopping work on the project. I will be listing the manifold for sale on this site in the next week or so. If interested PM me and I will try to answer any questions you might have. Thanks Tom


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Frank, thanks for the good word. The grass is still under my feet, things could be a lot worse, just some changes in types of projects I can take on.


Active member
Sorry to hear of your troubles old racer. I, for one, would have liked to see it completed.

A week ago, I would have been buggin' you about that manifold. Maybe then I would have picked up where you left off, and see what kind of results could be attained. I ended up going in a whole 'nuther direction though.

Keep after it the best you can. Like you said, the grass is still under your feet!


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ML-- Sorry that you could not do it, I would sure like to see someone test it out that has some 300 background. I get through the days knowing that lots of others have medical issues that are much worse. Thanks for the good word.


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Looking for someone to buy my Clifford 300 4x2 plenum divided intake that will take a Autolite 2100/2150 or a Holley 2300 2bbl.
PM me if interested, can send pictures & answer questions.


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Listed this manifold in the "Big Block 240/300 For Sale" section today 10/26/2021.

The Clifford intake is unchanged. This intake will run a 4bbl carb by removing the the current 4x2 plenum adapter and running the included Clifford 4V adapter that bolts onto the intake. Pictures are in the ad.
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