Running on 3 cylinders!

Post by **RogerRust** » Mon Jul 20, 2009 7:16 pm

I have carefully checked the comp both wet and dry.

The front 3 are fine and don't change much when wet.

BUT the back one reads zero both wet or dry!

There is no evidence of crankcase pressurisation and no sign of the head gasket blowing so I am hopeful that its a valve problem. In anycase its head off tomorrow and have a look and see where the problem lies. I'll post some pictures then.

Post by **alanworland** » Mon Jul 20, 2009 10:06 pm

Probably a burnt exhaust valve, with luck the seat should be ok. I had one a while ago but the seat was ok, the valves are supposed to rotate slowly during normal operation but I think lubrication to the stems at the top of the valve chest can be a bit inadequate at times, particularly during hard running.

Post by **autolycus** » Mon Jul 20, 2009 10:08 pm

RogerRust: I'd check the tappets before taking the head off. You'll have to get at them sooner or later if the head does have to come off, and it's a lot easier to adjust them (you only need three hands) than to fit the collets (where you need three hands and eyes on the end of your fingers. Having said which it will probably prove to be a valve with a head like a threepenny bit, to use an age-related analogy.

Alan: no harm at all in keeping it simple, but someone was bound to ask how you could get 160 psi compressions on an 8.something to one engine. So I told them.

bmcecosse: Yes, these things often do cancel out, and anyway I reckon it's difficult to compare different types of engine measured under different conditions with uncalibrated equipment. I'd have thought that heat transfer during a compression test might be from air to cylinder wall, bicbw. Personally, I usually like to do tests on cold engines, so you have a feel what to expect when you test an engine that won't start. Agree about the need for a good battery, and I usually try to turn the engine over the same number of times for each cylinder, especially when I can't operate the starter and watch the gauge at the same time.

Kevin

Post by **RogerRust** » Tue Jul 21, 2009 5:28 pm

The head just won't move, I prescribed plus gas for a couple of days then try and take the studs out and see if that releases the head.

Post by **alex_holden** » Tue Jul 21, 2009 5:56 pm

RogerRust wrote:The head just won't move, I prescribed plus gas for a couple of days then try and take the studs out and see if that releases the head.

Bit of a long shot and I've not tried this myself, but how about turning the engine over with the plugs in? The pressure in the cylinders might just be enough to loosen the gasket.

Post by **RogerRust** » Tue Jul 21, 2009 6:23 pm

alex_holden wrote:Bit of a long shot and I've not tried this myself, but how about turning the engine over with the plugs in? The pressure in the cylinders might just be enough to loosen the gasket.

tried that Alex.

Post by **bmcecosse** » Tue Jul 21, 2009 10:09 pm

Start it up! Just have the nuts undone a turn each. No water in it of course. Worked with one of my Morris 8Es - many moons ago.

Post by **rayofleamington** » Tue Jul 21, 2009 10:25 pm

I've posted the rope trick in the other thread...

Post by **RogerRust** » Thu Jul 23, 2009 5:36 pm

The head has moved enough for the gases to escape sideways out of the block.

It seems that the studs are corroded into the head. I have tried locking two nuts on the studs but they won't budge. At the moment Squiggle is applying plus gas twice a day.

Is anyone else available to have a look? I've come to the end of my knowledge and I'm not prepared to damage the head because I suspect side valve heads are hard to get.

Help.

Post by **bmcecosse** » Thu Jul 23, 2009 5:42 pm

Just need to keep working away at the studs - Plus gas and repeated turning back and forth until they break free one by one. Maybe apply heat to the stud -with some kind of shield to keep the heat directly off the head. Hopefully that will burn off whatever is causing the sticking - and the expansion/contraction may break the bond. Similar problems experienced by many with the Triumph engine (in TR7/Dolomite) where the studs go through the alloy head an an angle - and Plus-Gas and patience seem to be the way forward.
The main trick of course is to NOT snap any of the studs!!