Morris Minor Owners Club

First off, engine is all standard 1098 with points, original carb and original head. "Refreshed" by myself and my father about 5,000 km ago with new rings (std), crank bearings (.010 or .020 I believe), journal bearings (.010), new oil pump, new valve guides, timing chain and pretty much that was it, the rest was just cleaned and reassembled, and so far after a bit of teething issues the engine had been working absolutely great up until last night.

Engine seems just a little bit down on torque but revs good, and the sound is a bit different than usual. Also I'm getting loud bangs when engine braking which I didn't get before so my theories are either:

1. Distributor moved and the timing is off.

2. Valves need adjustment. (but why so soon?)

I'll appreciate further ideas on what could be happening, and I'll update after checking up on the car if I can figure out what's going on.

Do the easy ones first but a compression test would be a good idea. Could be your head gasket is failing - most probably between cylinders 2 & 3. Go and listen to your exhaust on tick over. Has the note changed?

Hopefully it will be something that is cured easily but I'll throw that idea into the pot. And let's face it, if the worse comes to the worse a new head gasket on a Minor is not exactly a big job.

Good luck

Could be something a simple as an air in-leak, first thing to check are the vac line and ensure the carb is secure.

Air leak/blowing at the exhaust manifold? Gaskets rarely fail between 2 nd 3 - there is a large space between the cylinders there - but doesn't sound like gasket problem anyway. Did you retorque the head after the first heat cycle? Reset the valve gaps anyway - and check simple stuff like points gap and carb piston moving ok.

bmcecosse wrote:Gaskets rarely fail between 2 nd 3 .

Thank you Roy. Quite correct. That should have been 3 and 4

Or indeed 1 and 2 but I find that less often.

Anyway we trust it is something simple.

Andy

Finally an update. Got to work on the car Friday afternoon, the exhaust clamp had come a bit loose so I tightened that first then checked, in this order:

1. Head torque - All nuts were fine, the wrench clicked right away except the last one with the bar which moved perhaps 1/8 of a turn before clicking so probably fine.

2. Valve gaps - Really thought I'd find a problem here, from running the original head on unleaded and a heavy foot but all gaps were ok.

3. Points gap - Was spot on at .015.

4. Distributor timing - Was getting lazy by this time but I tried moving it to see if it had come loose and couldn't, so I'm guessing it was where I'd set it to previously.

Went for a drive afterwards and the car was running fine, could it have been just the loose exhaust? Did I clean the points when measuring the gap? Haven't really done anything but apparently it's running fine now.

Will take the suggestions and check the carb piston, I've had problems with that before, and for leaks in the manifold. Engine is a bit dirty on that side suggesting an exhaust leak but probably just from the loose clamp.

Just throwing other ideas in the air, the day it wasn't running well the weather was a bit colder but I did wait for the car to get warm so I don't think that's likely the cause. Also, I filled up the tank since so maybe some moisture in the fuel?

Of course it was the loose exhaust!

I suffered from the same issue last year, the sound of the engine had changed and it just didn't seem right. I fitted some wire as advised in the tech tips section, http://www.mmoc.org.uk/index.php?page=336
now running grand again. I think the problem was caused by the amount of speed humps and the general condition of the roads, every time you go over one or a pot hole the exhaust must swing around a lot.

Engine sounding a bit strange I can see being caused from the loose exhaust clamp but wouldn't have thought the explosions when engine braking could come from that, those I associated more with bad timing or valves.

Might try the copper wire since my exhaust clamp seems to be always coming loose even though I've tightened it a bit more than I'm comfortable with, I've read it's quite easy to crack the manifold and I really wouldn't want to do that.

The air getting in at the loose flange can cause 'popping/ back firing' noises. Have they stopped now??

They stopped so I'm glad it was just that. It does sound cool sometimes though

Thought I was having spark + open valve at the same time so was looking into that; have a pretty short exhaust pipe so probably not much back pressure there but still, problem was cured so now I know where to look first for the next time.

You can always fit an exhaust steady bracket.
Regards
Declan[frame][/frame][frame][/frame]

get a decent exhaust clamp esm do a cast one much better qualiaty than the pressed steel ones