Carburetors

[Victoria Vernon]

Hi out there, I read some time ago, can't remember the source, about shaping the throttle shaft, where it passes thro the venturi. The writer stated that this was the equivelent of increasing a 11/4"carb to 1 1/2". Haven't tried it myself. Clem TC 7218 -----Original Message----- From: Chip Old [mailto:fold@bcpl.net] Sent: 25 July 2002 06:17 To: MG-TABC Subject: Re: [mg-tabc] Carburetors On Thu, 25 Jul 2002, Gene Gillam wrote to mg-tabc@yahoogroups.com:

> Excuse me if this is a dumb question, but will the 1 1/2" carburetors > from an MGA or MGB bolt up to the manifold for the XPAG? If not, does > anyone know if there's much adaptation to get them to fit?

The 1 1/2 inch carbs from a TF or MGA will bolt right up, but if I remember correctly the MGB carbs have a different bolt pattern. You'll need to either enlarge the manifiold bores to match the larger throat size, or else switch to a TF manifold. The linkage is different, so if you want the throttle, choke and slow running controls to work as they do on a TC, you'll have to substitute levers etc from your TC carbs. The standard TC air cleaner setup won't work, so you'll need TF filters or aftermarket pancake filters. However on an otherwise stock XPAG larger carbs are a waste of time and may actually make "around town" performance worse. To take advantage of the larger carbs you need larger TF-size valves and higher compression ratio at the very least, and preferably also larger displacement, a modified camshaft, and an extractor exhaust. By the way, if you come across a set of 1 1/2 inch carbs from a TD Mk II, leave them to the folks with Mk II's. They are 1 1/2 inch SUs, but of a different design. The TD Mk II is the only MG model to use them originally, as far as I know. -- Chip Old 1948 M.G. TC TC6710 XPAG7430 NEMGTR #2271 Cub Hill, Maryland 1962 Triumph TR4 CT3154LO CT3479E fold@bcpl.net Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/

[Donald Wilkinson]

Air flow can certainly be increased with this technique, though likely not to the extent of an entire upsize. See Des Hammill's book-"How To Build & Power Tune SU Carburettors" which goes into this extensively. Don TC 7993

>From: "Victoria Vernon" vernons@ibex.co.za> >To: "Chip Old" fold@bcpl.net>, "MG-TABC" mg-tabc@yahoogroups.com> >Subject: RE: [mg-tabc] Carburetors >Date: Sun, 28 Jul 2002 17:47:51 +0200 > >Hi out there, >I read some time ago, can't remember the source, about shaping the throttle >shaft, where it passes thro the venturi. The writer stated that this was >the >equivelent of increasing a 11/4"carb to 1 1/2". Haven't tried it myself. >Clem >TC 7218 > >-----Original Message----- >From: Chip Old [mailto:fold@bcpl.net] >Sent: 25 July 2002 06:17 >To: MG-TABC >Subject: Re: [mg-tabc] Carburetors > > >On Thu, 25 Jul 2002, Gene Gillam wrote to mg-tabc@yahoogroups.com: > > > Excuse me if this is a dumb question, but will the 1 1/2" carburetors > > from an MGA or MGB bolt up to the manifold for the XPAG? If not, does > > anyone know if there's much adaptation to get them to fit? > >The 1 1/2 inch carbs from a TF or MGA will bolt right up, but if I >remember correctly the MGB carbs have a different bolt pattern. You'll >need to either enlarge the manifiold bores to match the larger throat >size, or else switch to a TF manifold. The linkage is different, so if >you want the throttle, choke and slow running controls to work as they do >on a TC, you'll have to substitute levers etc from your TC carbs. The >standard TC air cleaner setup won't work, so you'll need TF filters or >aftermarket pancake filters. > >However on an otherwise stock XPAG larger carbs are a waste of time and >may actually make "around town" performance worse. To take advantage of >the larger carbs you need larger TF-size valves and higher compression >ratio at the very least, and preferably also larger displacement, a >modified camshaft, and an extractor exhaust. > >By the way, if you come across a set of 1 1/2 inch carbs from a TD Mk II, >leave them to the folks with Mk II's. They are 1 1/2 inch SUs, but of a >different design. The TD Mk II is the only MG model to use them >originally, as far as I know. > >-- >Chip Old 1948 M.G. TC TC6710 XPAG7430 NEMGTR #2271 >Cub Hill, Maryland 1962 Triumph TR4 CT3154LO CT3479E >fold@bcpl.net > > > > >Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/ > > > > > > >Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/ > >

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