Compression tests as follows: cold engine, no valve adjustments. tested as is. No.1 cylinder 150psi No.2 cylinder 122 psi No. 3 cylinder 120psi No. 4 cylinder 118 psi repeated them several times. No. 1 spark plug hole has some oil around the threads, all others dry.
The no1 is actually very high, heading into Diesel territory.. the others are good. Do the valves move properly?. could be a cam problem. Or sticking valves. Do the rockers all move equally? And please check the rocker arm is tightened down and that the pushrods are all straight - roll them on a flat table.. you might have one thats bending..
with the higher compression, oily plug and lack of firing on that cylinder, along with the crank case blow by out of the oil filler breather tube, that put together suggested to me that it could be piston ring failure. maybe that metal in the oil was cylinder/ring wear. it was aluminium rather than brass colour. and there's the clicking/rattling type sound when revs are increased, maybe that sound is piston ring. what do you think?
.... and fit some points when it’s back together to exclude all electric type issues to get it running again.
I am enjoying it as always. Its a sunny day here, I have a big mug of Yorkshire tea and playing with my van. Points I like as they work well on the mgb and never been tempted to go electronic. I am thinking at this time that the cold no.1 was due to plug fouling with oil causing no ignition on that plug. Oil on a plug presumably has to be either worn rings and/or worn valve guides.
You're guessing until you take it out and pull the heads off, you've got enough pointers now to know it's inevitable!
Its a learning process for me. I have set valve clearances all round to 6 thou and redid the compressions, same numbers as before. Checked operation of the push rods and valve rockers and springs and all seems fine with nothing visibly broken or loose. When I bought the van 4 years ago, I was told the engine had a partial rebuild, the heads look like new and maybe only new heads were fitted to a worn recon.
Not much wrong with the compression pressures, 150psi is the top end of where it should be, 100 psi is the minimum, max 45 psi difference between cylinders. No 1 may be explained by more oil between the rings but unlikely to be causing your immediate problem.
The immediate problem is misfiring or non firing on no.1 , fuelling is fine, fuel is getting to all cylinders, so its likely to be ignition. When it stops raining cats and dogs. I will check for sparks on 1 and 2 and maybe use a timing gun to check as well. Prefer not to rip out the engine and tear it apart just yet.
The reason I believe 150 PSI to be wierd is that with a 50cc combustion chamber, a bit of deck height say 5cc and a swept volume of 1584/4 cc or 396cc the pressure should go to (396+5+50)/(5+50)*14.7 or 120 psi. More than that and there is some kind of wierd pumping going on or the combustion chamber is full of oil...
I did the compressions again and No 1 is 140 and the others around 122 to 125. I think those readings are ok. Maybe the little bit of oil on no 1 plug and in the cylinder is more to do with non firing on no 1, which I am now investigating. Been looking on TheSamba in the Bay and Beetle sections as there is a lot on there about 1600 engine misfiring and air leaks, which I still feel is the root cause of my engine problems. The oil is new and up to the max mark on the dipstick. Now with new plugs, leads, cap and rotor and charged up battery, hoping to move forward with it and get it to fire properly and retime it.
Lovely sunny day here yesterday, so moving on with the engine. New ignition parts, fully charged battery and new fuel. Started first time and all 4 cylinders firing and both sides very hot. Run it for 20 minutes and it settled down to idle. The old rattle/ticking is still there as expected. On the next dry day I would be looking for air leaks. I checked the exhaust manifolds and exhaust, no sign of leak there.
