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MG MGA - Stub stacks?

I was meandering around the merchandise offered on the MGOC website and found and ad for "stub stacks". They are described as "small air rams to greatly improve air flow into carb intake when using pancake filters." Can anyone explain whether and how "stub stacks" improve performance? Also, are "pancake filters" another name for stock MGA (Vokes) filters? Just wondering if these stub stacks are a worthwhile improvement. Thanks!

Regards,
M.D.
'57 Coupe
M. D.

"Spose to be." Owner Dave at APTFast, Riverside CA, sold me some telling me it is the cheapest couple horses you can buy. "They eliminate the turbulence caused by air passing from the horizonal plain of the air filter to the vertical plaine of the carb. neck." He has a pretty good reputation. My modified 18V runs strong but I have no baseline for comparison. I run non stock pancake K&Ns but I believe most are designed to fit stock pancake filters
Steve
Steve Meline

Also, consider that the rather thick cast base plates for the HS-4s which came standard on the later MGBs, integrated a "stub stack" into its mouth as air flowed past it and into the carbs.

This was done for the same reason as Dave at APT Fast claims for his units, and would be worth doing for any vintage B-series BMC engine, including those original to the MGA.

I would doubt that the factory would have spent the money to produce those cast back plates and made them standard had they not found them to be worth the money spent and of value to the enthusiast.
Bob Muenchausen

If by "stub stack" you mean what the factory calls a "venturi", they were fitted by the factory to the mga twin cam air filters.
They were fitted to later production MGA Twin Cam engines. The MG factory thought it was worthwhile.
Pictures at:

http://www.angelfire.com/amiga/mga/index.html

Mick
Mick Anderson

I have heard them refered to as velocity stacks. many racing applications use them, even without an air filter. I recieved a pair with a basketcase MGA I recieved, they are aluminum and appear too tall to fit inside stock air filters. I understand they improove the airflow into the carbs and increase power.
Randy
R J Brown

They are also known as Ram Tubes or Ram Pipes.
General rule of thumb is the longer they are the more torque you get.
I use to use Stockings (Don't ask where they came from) as air cleaners.

Moss have them here.
http://www.moss-europe.co.uk/MossUK/ProductList.aspx?SubSubCategoryID=MGB_UMGB-327

Here are your Stub Stacks also.

http://www.moss-europe.co.uk/MossUK/ProductList.aspx?SubSubCategoryID=MGB_UMGB-324

Very colourful I must say.

Cheers <MARK>
Mark Hester

Steve - that confirms my sense that these are an attempt at "outboard" porting of the air intake. Does the improved air flow require a different needle in the SUs?

Randy-I think velocity stacks are much taller than the stub stacks that I am referring to. The stub stacks are designed to work with a air filter.

Thanks all. I may give them a try.

Regards,
M.D.
'57 Coupe
M. D.

M.D.,
Dave recommeded a richer needle in the origionsl SUs due to the incrreased fuel needs from larger displacement (1823 cc +/-), flowed head and 270 Piper cam kit. I run a "rich MGB needle" also sold to me by Dave. I think they are designated N-5s. My shop, Britalia, confirmed a proper fuel mixture in the cumulative result. I couldn't isolate any need from the stub stacks alone but I've read needle changes may be needed when changing air filters. Hopfully somebody can give you better info.
Steve
Steve Meline

I've dyno tested stub stacks and velocity stacks for articles in Grassroots Motorsports and Classic Motorsports magazines and can hopefully shed some light on this.

Several companies make velocity stacks, which replace and eliminate the air filters. Most of the manufacturers are copying other products improperly and therefore produce velocity stacks that look cool but don't work. I have only found one good manufacturer, TWM, that makes proper units that do work. Moss, APT, and TWM sell them in two versions, short and long. The long ones give you about 2HP more at the wheels, but won't clear the brake booster on a late MGB. The short ones will, and give you about 1 HP at the wheels. The TWM units are extruded aluminum with a rolled radius around the bell. Cheaper units (that have no effect or cost HP) are stamped with a sharp edge around the bell.

K&N and APT make stub stacks, which fit inside the stock or aftermarket air filters. I've found that they usually give about 1 HP at the wheels--not great, but every HP counts. Additionally, they will give a smoother A/F graph on the dyno, which translates into smoother running on the street. I highly recommend them for any car.

--Carl
Carl Heideman

Thanks Carl, that's great info. Since my original post, I learned that the intake ports on my new carbs were "radiused". So my mechanic suggested that, instead of stub stacks, I should try to port match my air filter to my radiused intake ports.

Regards,
M.D.
'57 Coupe
M. D.

I remember, right after I bought my K&Ns and stub stacks, I found that HI-Flow in Australia, Hans Peterson(?) sells good looking air filters with built-in stub stacks. Steve
Steve Meline

I remember, right after I bought my K&Ns and stub stacks FROM APT I found that HI-Flow in Australia, Hans Peterson(?) sells good looking air filters with built-in stub stacks. Don't know how they work.
Steve
Steve Meline

This thread was discussed between 01/09/2005 and 09/09/2005

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