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MG TD TF 1500 - Burnt valves Pt2

She runs,dry run no coolant. I will fit the hoses and fill tomorrow. To make life easy I left the thermostat housing off the cylinder head. as the 2 small hoses are a pain to fit. I will refit it replacing the 2 bottom bolts with Allen cap screws
as you cannot get a spanner in easily. The screws are old gudgeon pin clamp bolts I had hanging around.
Can't find anything wrong with the carbs. Will be going for a rolling road tune up in a couple of weeks.The bloke that does it is ace.
Next job is sort garage,it looks like a bomb hit it. I only have !8" either side of the car and tools are everywhere.
Ray TF 2884
Ray Lee

Nice job--So basically it was just all stuck together, carboned up ---?
It's really weird what happens when they sit for a bit, my elan will stick a valve in the guide if i leave it for a month or so, they're the original untouched valves in the original untouched head that's done 100,000 miles and this has only happened over the last couple of years when the cars had a bit less use ---weird
William Revit

On the first piston the rings were gungey but free,probably from being jiggled past the crank.
after that I pushed them out the top of the bore (enough to remove rings) and they were stuck. Hard to tell if gunge is from trying to get compression.
Going to have a rest for a couple of day to get rid of aches and pains.
Ray TF 2884
Ray Lee

Another little question Ray. With the head, when you pulled that apart you mentioned massive carbon buildup. Were the backs of the inlet valves carboned up badly as well or mostly the chamber and exhausts.
William Revit

Mostly exhaust and piston tops. A little in head mainly where inlet valve is close to the wall of the head.
Hardened seats with the biggest valve that will fit (can't remember size as done many years/miles ago).
Ray TF 2884
Ray Lee

Hmm--I'd been thinking it 'might' have been a valve stem seal/guide issue but if so the back of the inlet valve would have been really coked up.
It's hard to imagine what would have caused such a buildup of crud. Fuel is a lot better than years ago when pulling the head off for a decoke was common. I can't really see fuel being the cause. It would have to be way out of tune to do it, but because you obviously know your car you would have known if it was way out of tune. Too cold heat range spark plugs would cause a buildup maybe but that would be more over a long term---really strange that it was going good when you sheded it then it just stuck together--
It'll be interesting to hear what your engine tuner guy says when you go.
William Revit

I have a horrible suspicion that when I topped up to go on the New Years day run that the fuel was contaminated with diesel. It does not look or smell right. My car is used regularly so never has old fuel in it.
Going to start from scratch tomorrow and set up the carbs.
The only good thing to come out of this is I know my reserve fuel is good for 90 miles.
Ray TF 2884
Ray Lee

interesting- probably not diesel, you would have seen the smoke, although if it was just a low percentage mixture it mightn't have noticed.
We have an issue here where one of the servo's (not yet identified) mixes their dead E85 in with regular petrol to get rid of it--causes all sorts of starting and running issues ---E85 has a limited tank life because of it's high alcohol content.
Our test for that fuel is to spill a bit on a hard surface--good fuel evaporates away quite quickly, this blended stuff just sits there for ages. Also this mixed fuel takes on a slight milky look, but you wouldn't get that with a diesel mix - maybe
Not sure what would happen with a diesel blend but at a guess it'd take longer than normal straight petrol to evaporate away.
Sounds like you might be onto something though, it's good to find the cause of problems.
Cheers
willy
William Revit

that looks like it.
wrong smell and colour,milky trace and slick feel between fingers.
All dumped now and full of fresh.
Just got to run the rings in then rolling road on the 22nd
Ray TF 2884
Ray Lee

Run in and performing well. Still fine tuning fuel and ignition,running a bit rich on front carb.
Only bad thing,a friend reversed into my front wing/running board. As my car is a user not show it will have to wait till winter. I hate not being on the road.
Back to happy MotorinG
Ray TF 2884
Ray Lee

The woe never ends.
I have had a mysterious occasional misfire since the rebuild. It has now turned into a more regular occurrence. I thought I had cured it with my spare
dizzy and coil,no such luck.
I now suspect it is a valve hanging up as it is too abrupt for fuelling.
Ray TF2884
Ray Lee

This thread was discussed between 05/03/2025 and 24/04/2025

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