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T-Series Stuck exhaust valve on 54 MGTF

classiccarguy

Freshman Member
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Hi all, I have a 54 MGTF that has a stuck open exhaust valve on cylinder 3. The car has been sitting for several years. From looking at the top of the head and valves it looks like possibly someone had just done a valve job before it sat up. Any ideas how to free up the valve without removing the head? Yesterday I sprayed PB Blaster. Thanks!
 

David_DuBois

Jedi Warrior
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It is possible that by removing the rocker assembly, you can spray the PB Blaster around the valve stem and the valve guide (a better penetrate would be Kroil or a 50/50 mixture of acetone/automatic transmission fluid) and then gently tapping on the top of the valve stem with a piece of wood between the top of the stem and the hammer. If this frees the valve stem, then work more penetrate between the valve stem and the guide and work the valve up and down to get things completely loosened and working freely. When putting the rocker assembly back in place be sure that you torque the bolts properly. The smaller (8mm) bolt should not be torqued more than 19 ftlb. You can find a complete set of torque specs in the chart, Torque Values for TD and TF Fasteners in the Other Tech Articles section of my Homepage at: https://homepages.donobi.net/sufuelpumps/ E-mail me at SUfuelpumps@donobi.net for more information.
Cheers,
 
OP
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classiccarguy

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I took your advice and kept spraying PB Blaster (could not find Kroil locally). I pried up gently with a screwdriver and the valve popped up. However I still have 0 compression in that cylinder. Being an exhaust valve, I figure it is burnt. Do now I need a new head gasket. Is there any where yo buy one, but Moss? About $70. seems pricey for that. As always, any help is really appreciated. Thanks as always, George
 

PAUL161

Great Pumpkin
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George, First try something, if the valve is now loose, with the rocker arm off, take a brass hammer and tap the valve stem hard enough to drive it down at least a quarter of an inch, but not enough to pop the keepers. Keep doing this for a couple minutes making the valve slap in the seat. It is a possibility that a gob of carbon is causing a bypass. If this brings up the compression a bit, the valve might not be bad. It will be rare if it seals completely. Bad news is, yes the head should come off! Is your engine a XPAG or an XPEG?
Contact Little British Car Co for a head gasket, as they are a Moss distributor and give a 10% discount on the same part that Moss charges full price for. Jeff is a nice guy and very prompt on replying. PJ

Moss-$69.95
LBC-$59.46

Email LBCarCo@LBCarCo.com

Web site https://www.LBCarCo.com
 
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Does the cylinder head have bronze guides, the reason I ask, is machine shops commonly botch this, a bronze guide requires about .003" clearance which is more than than cast iron guide, due to the expansion rate of bronze. Failure to put the correct clearance on the guide to valve stem on a bronze guide can cause seizing of the exhaust valves.
 

PAUL161

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Remember, some heads have round holes and some oblong. I think, but not sure, the late heads have round holes. PJ
 

Brinkerhoff

Jedi Knight
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Man I love the optimism ! If ever the term " mission creep" ( cadged from University Motors) fit a particular car it was the T series MG ! I'm not seeing how you'll just get by with only buying a new head gasket to fix this engine but I'm on your side . I'd wait until I had the head off and got a good look inside . I always find more money to spend once there. You'll be into hoses and gaskets and other sticky , pricey things soon. Make one parts order so the UPS costs don't eat you up.
 

MGTF1250Dave

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Aloha,

If the other suggestions do not prove successful, perhaps Hal has identified the problem as a sticky valve guide. I have had a recurring problem on my XPAG engine with a burnt exhaust valve on #4 cylinder (twice since head was rebuilt in 2004). Inspection by another machine shop found that the new bronze valve guide was not reamed to sufficient clearance causing the valve to stick. Hopefully a little reaming and a new valve will solve that problem.

If you are unsure of the originality or history of your XPAG engine you may not have the head that left the factory with the block. Here is some info from Neil Cairns book, Engines for MG's, Their Story After 1935:

The 'casting number' is not the 'part number' normally. It is the number of the wooden 'pattern' used to make the casting. The same 'pattern' may well be used for different applications decided upon by the way it is machined. This way a cylinder block may start as identical items but end up as a 1250cc MG TB engine or a Marine version of the Brockhouse 'Morris' boat engine; or a MG YB engine or the Wolseley 4/44 version. They will be differentiated by their 'part numbers' stamped into the machined metal or on a riveted tag. That on the cylinder block appears just behind the dynamo, the one on the head is on the top face.

Casting Numbers.
Model/Item...............................................................................Casting Number
路 Early Morris/Wolseley Ten 1140cc 'X' cylinder block, oval,...................... 22500
路 Later post war 1140cc cylinder block, oval water holes,.......................... 24144
路 Very early 1250cc block with no timing chain tensioner,..........................24001
路 Early M.G. 1250cc 'X' block, octagon cast in, oval water holes,.................24142 & 24146
路 Later post war 1250cc M.G. block, octagon cast in, oval holes,.................24445
路 4/44, later TD, & TF block, no octagon, round water holes,......................168421
路 Early 1140cc cylinder-head, no centre oil drain, oval water holes,.............22812
路 Later post war 1140cc head, same as early 'T' type, oval holes................22952
路 Later TD, & Y oval hole cylinder head, short reach plug,..........................22952
路 4/44, TD & TF head, round water holes, long reach plugs,.......................168422
路 Late 4/44 head, round water holes,.....................................................168425

My engine had a later TD head that uses short reach plugs. This head has oval holes not round holes like original TF head with round holes and long reach plugs. This can lead to confusion as to which Head gasket to use. Again from Neil Cairns book:

THE ROUND HOLE HEAD GASKET CAN ONLY BE USED IF BOTH HEAD AND BLOCK HAVE ROUND HOLES.
Any other combination, use the oval holed gasket.
 
OP
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classiccarguy

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WOW! I am really impressed by the kmowledge, down to small details, you have on this forum. I have worked on MGs over the years, but never a T series. This is a totally different car, it seems. And yes I am an optimist. I thank each of you for the advice and I will heed it and when I find out the situation I will let all of you know. Again many heartfelt thanks. George
 

PAUL161

Great Pumpkin
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Had that happen on my 55 TF with a newly rebuilt head. Cured the problem by shooting PB Blaster down the stems and by putting Marvel Mystery oil in the fuel as a top lube. It works! PJ
 
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