MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG TD TF 1500 - Warped Block Face

Regular readers may have noted I am having horrendous problems with the running of the TF's engine. I have had serious backfiring and spitting through the exhaust. After hours of tinkering I eventually lifted the head and found a slight bow in the surface. This was machined flat using a state of the art fly cutting machine and refitted with a new gasket. The problem appeared to be slightly better but soon returned. Since then I have replaced every part of the ignition system with the best quality components and have totally rebuilt the carbs. Compressions are all exactly 120 psi and the static timing is TDC, set with an expensive dial in strobe. I can stop the back firing and spitting by running a very rich mixture but the engine runs rough and will not tick over. I feel that if I pull the leads to plugs 2/3 it doesn't have the same effect as 1/4. I have even moved the distributor rotor round so the leads are in different places on the cap and the middle two still don't appear to be firing as well as the end cylinders. The problem is the engine will only tick over at 1500 revs so it is difficult to tell if pulling the leads has any effect. There was certainly a black mark on the old gasket between 2/3 and I now wonder if the block is also warped. Has anyone experienced this before? Would this not be reflected in the compressions? Would running very rich counter and blow through? I must admit I am starting to dislike the TF and am depressed when I open the garage door. To illustrate the point there was a superb model of a TF in a recent collectables auction in Glasgow and I didn't even make a bid!

Jan T
J Targosz

How old is the gas you have in your tank?
M Grogan

Could you take and post a picture that shows the distributor cap and plug wires in place (ie the side of the engine)? George
George Butz

Take a look at your intake manifold. There is supposed to be a plug in the center with a small hole in the center. This plug is located by a locating bolt from the outside. I had one that came loose and it's impossible to balance anything until plug is relocated and locked in the mid position.This is a balancing device.
Sandy
st

Jan. I don't think the symptoms fit the possibility of the block being misshapen, and besides that the compression test is not indicating an issue there. It sounds more like a carburation problem to me, like an air leak. However, its impossible to know the full story from brief messages on the forum. I guess we've all been there with issues that seemed impossible to fix, but a solution comes sooner or later so don't lose heart! Is there not a local MG group (MGCar Club or MG Octagon) where you can get some hands-on support and assistance?
Dave H
Dave Hill

The spitting issue suggest to me that ignited fuel is getting into the inlet side, then that suggests sticking valves. Similarly for the backfire suggests leaks from the valves of fuel/air mix is leaking.

Did you check the valves for easy movement when assembling the head. Other than that the cause could be the push rods.
Ian Bowers

Is it at all possible that the valve timing is off?
Kevin McLemore

Hi and thanks to all especially George

Photo of plugs etc attached.

I think the car is trying to tell me something since the previously dry rear crank seal is now dropping oil. I propose to remove the engine and inspect everything and fit an Edney rear seal conversion.

I will post what I find

Cheers

Jan


J Targosz

Was it ever running right? I agree with Kevin indicates valve timing. Or is it possible its timed on #4 and not #1 ? I've never seen an TD or TF run timed 180 degrees out.

Did the backfiring start after a rebuild?
ECS Stanfield

Jan, please tell me about your spark plug wires. Are you running a pertronix II ignition module? One that doesn't use the ring of magnets. What are the NGK components that are connected between your plugs and the plug wires? Bud
Bud Krueger

All looks fine in the picture. Does not sound like headgasket leak to me. Have you checked for intake leak by spraying carb cleaner (carefully) at manifold to head and carb to manifold areas- there should be no RPM change? Tried more new plugs? Is the new dizzy rotor red or black in color? If all of the above are OK, try loosening the dizzy and just rotating around to see if different timing will cure. George
George Butz

The compression test indicates the head and block are happy back together again. I have a block that was .005" low between cylinders 2 nd 3, but that only caused periodic head gasket failures which showed up clearly with compression tests.

"The problem is the engine will only tick over at 1500 revs " which could be a vacuum leak causing very lean running. Try a vacuum gauge, if you can, to see what going on from idle on up.... I doubt you'll see a normal vacuum from the sounds of it. Like George said above, sparingly spray carb cleaner or pass a propane torch (unlit of course) throughout the intake area snooping around for a vacuum leak.
JRN JIM

I spent weeks on similar symptoms! It got so I hated going in the garage as well. I was surfing the new 2017 Fiat 124 Sypder! My wife said you gotta sell the TD first. It was tempting. Turned out it was only a simple 1/4" twist of the dizzy and all is now well! Didn't even need a timing light. Go figure...
efh Haskell

Edf
A twist of 1/4",,
Clock wise or counterclockwise ??
Steve
Steve Wincze

I would suggest you get someone else to strip down and redo the plugs and timing and dizzy position,check cap and rotor etc. while you watch.

Sometimes we all become blind to the thing that is wrong because we are looking to closely.

It is just like getting your wife to look for the butter in the fridge that you swear is not there...

The mind plays tricks and fills in the blanks with what it expects to be there...


Dave
D Moore

Hi Jan,
going back to your original post.
Are the bobweight pins in the hole nearest to the slot and the rotor in the outer ones ?.
Ray TF 2884
Ray Lee raybar2(at) tiscalidotcodotuk

Gents,

A year or two back I wrote an entry called "Stupid is as Stupid does". At the time I spent three or four days with an engine that spit back and would not rev much above 1500RPM. After days of trouble shooting I finally noted the arrow on the rotor indicating the direction of rotation. I had the firing order set up backward. Old guys are slow to catch on. I know!

Best regards,

Jim Haskins 1953 TD
J M Haskins

This thread was discussed between 14/08/2016 and 19/08/2016

MG TD TF 1500 index

This thread is from the archive. The Live MG TD TF 1500 BBS is active now.