Author Topic: Crossram manifold  (Read 42552 times)

PHAT69AMX

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Re: Crossram manifold
« Reply #105 on: October 07, 2019, 09:53:59 PM »
I am no expert, just doing research, and some things I find, or come across, or see surprise me.
So I ask the community and look forward to the discussion and can only hope to learn more.
No intention to stir things up or dispute...  only discussing...
It is my hope to gather and share some more information about this topic.

Yes, research and direct communication resulted in findings that the plenum floor "wet flow ridges" made out of strips of solder and epoxy as seen in the Prototype version pictured above were done at GM by GM Engineering to equalize "wet flow" distribution, Exhaust Gas Temperatures, and equalize all 8 cylinders on the dyno, so they were found to be needed to accomplish that.

So... the production casting flow ridges are incorrectly oriented, since they are non-symmetrical, when compared to the solder strip / epoxy prototype...  or at least it appears that way to me.  And since the production casting flow ridges are incorrectly oriented compared to those in the prototype then the production version would NOT result in equalized cylinder distribution or at least as it would seem...

I would think the Edelbrock version would be "inferior" since it contains now "wet flow equalized distribution management ridges" ?...  where GM Engineering found that they were needed and incorporated them.

I've yet to find online a picture of a production casting with the wet flow ridges oriented like those solder/epoxy ones shown in the pictured prototype.
« Last Edit: October 07, 2019, 10:49:26 PM by PHAT69AMX »

crossboss

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Re: Crossram manifold
« Reply #106 on: October 07, 2019, 11:38:16 PM »
I am no expert, just doing research, and some things I find, or come across, or see surprise me.
So I ask the community and look forward to the discussion and can only hope to learn more.
No intention to stir things up or dispute...  only discussing...
It is my hope to gather and share some more information about this topic.

Yes, research and direct communication resulted in findings that the plenum floor "wet flow ridges" made out of strips of solder and epoxy as seen in the Prototype version pictured above were done at GM by GM Engineering to equalize "wet flow" distribution, Exhaust Gas Temperatures, and equalize all 8 cylinders on the dyno, so they were found to be needed to accomplish that.

So... the production casting flow ridges are incorrectly oriented, since they are non-symmetrical, when compared to the solder strip / epoxy prototype...  or at least it appears that way to me.  And since the production casting flow ridges are incorrectly oriented compared to those in the prototype then the production version would NOT result in equalized cylinder distribution or at least as it would seem...

I would think the Edelbrock version would be "inferior" since it contains now "wet flow equalized distribution management ridges" ?...  where GM Engineering found that they were needed and incorporated them.

I've yet to find online a picture of a production casting with the wet flow ridges oriented like those solder/epoxy ones shown in the pictured prototype.



Phat-
Like yourself, I am no expert on Chevy's Cross-Ram design. Just like I am no expert on a Chrysler 'Rat-Roaster' Cross-Ram. What worked for me on the Boss 302, was by my own 'learning tricks'. Every intake is different, so as the old saying goes: "What works for me, may not for you". My only assertion would be what DID work for the Chevy racers (like Tom McIntyre's) intake. Obviously, Smokey was keen on making odd ball stuff work, and a genius. That said, Chevy's small block canted valve prototype heads were really not much better in achieving the power they desired, yet Ford did have great success with their Boss 302/351 Cleveland designs. My point is not to say whom had a 'better' design, just what worked better on a given engine combo.
Just another T/A fanatic. A new project in the works.

TangoBravo

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Re: Crossram manifold
« Reply #107 on: October 08, 2019, 12:08:46 AM »
The distribution dams were a try-it and see how it works experiment. (These type of manifold distribution corrections were done well into the 1980's at some speed shops I am aware of. Fuel comes out of suspension and needs to be channeled to try to even cylinder a/f ratios!)The dams were done with epoxy and wire (reportedly) on a set of O-dash numbered experimental developmental manifolds (reported to be 4 or 5 of them) They were being sent back and forth and developed ASAP. There was tremendous pressure to get them done fast and some were raced in the developmental configuration. When they were casting the first early production pieces, an error was made configuring the dams in the molds and the dams were reversed front to rear-an apparent last minute lay-up under duress. And undid what they were trying to do. The error was quickly corrected and the regular production manifolds were cast correctly. Wayne Guinns Crossram guide, Mark Donohues "Unfair Advantage" and Smokey Yunicks wonderful autobiography have some great insights to what was going on.
« Last Edit: October 08, 2019, 12:41:13 AM by TangoBravo »

PHAT69AMX

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Re: Crossram manifold
« Reply #108 on: October 09, 2019, 12:43:40 AM »
TangoBravo and others - might you be able to say if these Distribution Dams in this claimed 1967 casting prototype on the left in this picture from the previously posted 2018 Hemmings For Sale Ad are oriented the "correct" way or are they "reversed" ? 

crossboss

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Re: Crossram manifold
« Reply #109 on: October 09, 2019, 07:11:30 PM »
Boys,
FWIW, and sorry If I go off topic. Here is the Boss 302 'Cross-Boss' lower portion of the cross ram intake. IF you look you can see the 'bumps' I was referring to that are one of the offending problems in the design near the entry of the ports. Removing them and modifying some areas with Devcon made a world of difference. Im sure the Chevy racers did similar 'mods' to correct the flow on their intakes as well.
Just another T/A fanatic. A new project in the works.