Re: Digest Number 826

[Benson]

Hi All, Thanks Chip and others for solving another mystery. Checked head today and its an early one. Casting no. 22952 BTW the original head has the date cast on it as well (22 May 1939). Will get some nice new shiney plugs tomorrow and try it out weather permitting. Regards. Ron Benson TB Date: Sat, 27 Apr 2002 13:27:31 -0400 (EDT) From: Chip Old fold@bcpl.net> Subject: Re: Digest Number 822 XPAG heads use either 1/2" or 3/4" thread length plugs, depending on age. The heads used on the TB, TC, and early TD use 1/2". The heads used on the late TD, TF, and TF 1500 (XPEG) use 3/4". There is no need to measure, as there are several other indicators. If the head is on the engine, look for a casting number on the top surface of the head, right front corner. If it is "22952", it's an early head. If the number is something else (I forget what) or nonexistant, it's a late head. If the head is off the engine you can tell by looking at the small water passage holes that carry coolant between the block and the head. If they are oblong (some say banana-shaped) it's an early head. If they are round it's a late head. The early head is sometimes referred to as a "banana head" and the late head as a "round head" due to the shape of the water holes. XPAG engine blocks also have either oblong or round water holes, again following the "TB through early TD" and "late TD and TF" pattern. It's okay to use a late head on an early engine or vice versa, as long as you use the appropriate head gasket. If head and block both have oblong water holes, use a gasket with oblong water holes. If head and block both have round holes, use a gasket with round holes. If you use a head of one type on a block of the other type, use a gasket with oblong water holes. -- Chip Old 1948 M.G. TC TC6710 XPAG7430 NEMGTR #2271 Cub Hill, Maryland 1962 Triumph TR4 CT3154LO CT3479E fold@bcpl.net ________________________________________________________________________

[Benson]

Greetings again, Probably a dumb question but I presume you cannot use 3/4" plugs in a early head? Regards, Ron Benson TB

On Sat, 27 Apr 2002, Benson wrote: > I thought all XPAG heads used 1/2" reach plugs, the one that I have > modified is not the original head and I am not sure what it is off. Is > it just a case of measuring? XPAG heads use either 1/2" or 3/4" thread length plugs, depending on age. The heads used on the TB, TC, and early TD use 1/2". The heads used on the late TD, TF, and TF 1500 (XPEG) use 3/4". There is no need to measure, as there are several other indicators. If the head is on the engine, look for a casting number on the top surface of the head, right front corner. If it is "22952", it's an early head. If the number is something else (I forget what) or nonexistant, it's a late head. If the head is off the engine you can tell by looking at the small water passage holes that carry coolant between the block and the head. If they are oblong (some say banana-shaped) it's an early head. If they are round it's a late head. The early head is sometimes referred to as a "banana head" and the late head as a "round head" due to the shape of the water holes. XPAG engine blocks also have either oblong or round water holes, again following the "TB through early TD" and "late TD and TF" pattern. It's okay to use a late head on an early engine or vice versa, as long as you use the appropriate head gasket. If head and block both have oblong water holes, use a gasket with oblong water holes. If head and block both have round holes, use a gasket with round holes. If you use a head of one type on a block of the other type, use a gasket with oblong water holes. -- Chip Old 1948 M.G. TC TC6710 XPAG7430 NEMGTR #2271 Cub Hill, Maryland 1962 Triumph TR4 CT3154LO CT3479E fold@bcpl.net ________________________________________________________________________

[Ray]

A genuine TB head! Best, Ray

----- Original Message ----- From: "Benson" Carole_Ron@benson30.fsnet.co.uk> To: mg-tabc@yahoogroups.com> Sent: Sunday, April 28, 2002 12:12 PM Subject: Re: [mg-tabc] Digest Number 826 > Hi All, > Thanks Chip and others for solving another mystery. Checked head > today and its an early one. Casting no. 22952 BTW the original head has the > date cast on it as well (22 May 1939). Will get some nice new shiney plugs > tomorrow and try it out weather permitting. > > Regards. > Ron Benson TB > > Date: Sat, 27 Apr 2002 13:27:31 -0400 (EDT) > From: Chip Old fold@bcpl.net> > Subject: Re: Digest Number 822 > > > XPAG heads use either 1/2" or 3/4" thread length plugs, depending on age. > The heads used on the TB, TC, and early TD use 1/2". The heads used on > the late TD, TF, and TF 1500 (XPEG) use 3/4". > > There is no need to measure, as there are several other indicators. If > the head is on the engine, look for a casting number on the top surface of > the head, right front corner. If it is "22952", it's an early head. > If the number is something else (I forget what) or nonexistant, it's a > late head. > > If the head is off the engine you can tell by looking at the small water > passage holes that carry coolant between the block and the head. If they > are oblong (some say banana-shaped) it's an early head. If they are round > it's a late head. The early head is sometimes referred to as a "banana > head" and the late head as a "round head" due to the shape of the water > holes. > > XPAG engine blocks also have either oblong or round water holes, again > following the "TB through early TD" and "late TD and TF" pattern. It's > okay to use a late head on an early engine or vice versa, as long as you > use the appropriate head gasket. If head and block both have oblong water > holes, use a gasket with oblong water holes. If head and block both have > round holes, use a gasket with round holes. If you use a head of one type > on a block of the other type, use a gasket with oblong water holes. > > -- > 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/ > >

[Chip Old]

On Sun, 28 Apr 2002, Benson wrote to mg-tabc@yahoogroups.com:

> Probably a dumb question but I presume you cannot use 3/4" plugs in a > early head?

Well, you can, but you'll probably wish you hadn't. The thread is 1/4 inch too long, so that amount will extend into the combustion chamber. The exposed threads are a potential hot spot, so might cause preignition. Once the plugs have been in there a while, carbon will build up on the exposed threads, making the plugs very difficult to remove. If you use extended electrode plugs with 3/4 inch threads, there's a possibility of the pistons colliding with the electrodes at TDC. -- Chip Old 1948 M.G. TC TC6710 XPAG7430 NEMGTR #2271 Cub Hill, Maryland 1962 Triumph TR4 CT3154LO CT3479E fold@bcpl.net

[Donald Wilkinson]

Plugs stick 1/4" into combustion chamber; exposed threads (sharp) get incandescent; pre-ignition/detonation happens, piston heads acquire large holes (gives poor compression), connecting rods appear on the road, etc.etc.etc. Don TC7993

>From: "Benson" Carole_Ron@benson30.fsnet.co.uk> >To: mg-tabc@yahoogroups.com> >Subject: Re: [mg-tabc] Digest Number 826 >Date: Sun, 28 Apr 2002 20:53:16 +0100 > >Greetings again, > Probably a dumb question but I presume you cannot >use 3/4" plugs in a early head? > > Regards, > Ron Benson TB > > >On Sat, 27 Apr 2002, Benson wrote: > > > I thought all XPAG heads used 1/2" reach plugs, the one that I have > > modified is not the original head and I am not sure what it is off. Is > > it just a case of measuring? > >XPAG heads use either 1/2" or 3/4" thread length plugs, depending on age. >The heads used on the TB, TC, and early TD use 1/2". The heads used on >the late TD, TF, and TF 1500 (XPEG) use 3/4". > >There is no need to measure, as there are several other indicators. If >the head is on the engine, look for a casting number on the top surface of >the head, right front corner. If it is "22952", it's an early head. >If the number is something else (I forget what) or nonexistant, it's a >late head. > >If the head is off the engine you can tell by looking at the small water >passage holes that carry coolant between the block and the head. If they >are oblong (some say banana-shaped) it's an early head. If they are round >it's a late head. The early head is sometimes referred to as a "banana >head" and the late head as a "round head" due to the shape of the water >holes. > >XPAG engine blocks also have either oblong or round water holes, again >following the "TB through early TD" and "late TD and TF" pattern. It's >okay to use a late head on an early engine or vice versa, as long as you >use the appropriate head gasket. If head and block both have oblong water >holes, use a gasket with oblong water holes. If head and block both have >round holes, use a gasket with round holes. If you use a head of one type >on a block of the other type, use a gasket with oblong water holes. > >-- >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/ > >

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