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Johan3500
Johan Van Wyk

(9 posts)

Registered:
03/06/2009 06:17AM

Main British Car:
Plenum tubes: a-gain?
Posted by: Johan3500
Date: April 01, 2011 06:36AM

Thank you to the gents who responded to my query on the shortening of tubes- I did not completely clarify my thinking, so please read and comment again. It seems as if the gap or space between the top of the tube and roof of plenum box is quite small and the shortening will be done only to allow an easier "turn" for the gases to get into the tubes, not more than 10 to 15mm, or 1/2". A bit like cutting the choke tower off a Holley to increase space between body of carb and ceiling of 14"air cleaner.

Thank you,
Johan


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(6470 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: Plenum tubes: a-gain?
Posted by: BlownMGB-V8
Date: April 02, 2011 11:47AM

Your theory seems sound but without a means of testing it is unlikely someone could give you a definitive answer. You could try cutting them down about 1/4" at a time and see what improvement you get.

JB


Moderator
Curtis Jacobson
Portland Oregon
(4577 posts)

Registered:
10/12/2007 02:16AM

Main British Car:
71 MGBGT, Buick 215

authors avatar
Re: Plenum tubes: a-gain?
Posted by: Moderator
Date: April 03, 2011 03:32AM

If I had the means, I'd also test variations of the flare itself: increasing the radius and continuing the arc further around.
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DiDueColpi
Fred Key
West coast - Canada
(1366 posts)

Registered:
05/14/2010 03:06AM

Main British Car:
I really thought that I'd be an action figure by now!

authors avatar
Re: Plenum tubes: a-gain?
Posted by: DiDueColpi
Date: April 03, 2011 05:07AM

I'm in with Curtis.
Testing has shown vast differences in flow over the lip of the stack horn.
A fully radiused edge seems to have a huge advantage.
I have seen a marked improvement in stability on various carbed motors. And while not verified, an improvement in torque #s on fuel injected motors.
From a purely physics standpoint. An engine doesn't really suck in air. It's pushed in.
If you look at an intake system from that perspective everything changes.
Think of the engine as a valve allowing the air to enter rather than a device sucking it in.
Once you truly grasp that idea the power, so to speak, is yours.

Cheers
Fred


roverman
Art Gertz
Winchester, CA.
(3188 posts)

Registered:
04/24/2009 11:02AM

Main British Car:
74' Jensen Healy, 79 Huff. GT 1, 74 MGB Lotus 907,2L

Re: Plenum tubes: a-gain?
Posted by: roverman
Date: April 03, 2011 12:58PM

Johan, Back on March 26th on your other thread, same subject, I suggested looking at what the "specialist" have accomplished. These mod's have all been done and verified. There is no mystery here. Good Luck, roverman.


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