Looking to sort my engine out this year. Stopped driving the van 6 months ago as the engine started popping and knocking/rattling. Engine starts fine, but rattles/tinkles as the revs are increased. It settles to idle when warm, but still pops but the rattle goes away but runs rough. Today I have found something new which I would like help with. I ran the engine for about 5 minutes until it idled without needing any throttle. I got underneath and found the no 3 and 4 cylinders side rocker cover and heat exchanger very hot and far too hot to touch. The no 1 and 2 rocker and heat exchanger, very cool, just about warm and can be gripped easily. Heat risers on both sides were too hot to touch, maybe on the no 1 and 2 side a bit cooler. No 3 and 4 input manifolds hot, No 1 cold, No 2 warm. Is this uneven heat a clue to my engine problems.
I think you need to start with the basics and gradually work through everything. Check the valve clearances Check the ignition timing and gap the plugs Make sure your choke on the carb works properly and the throttle position is correct Look for any signs of exhaust leaks. If that doesn't get you to at least fairly smooth running then you need to move on to compression checks and leak down tests
Fortunately I am retired so have time to do more tests on the engine. I don't want to give up with it until I've tried to fix it. Re looking for exhaust leaks, I thought it was blowing on the 1 and 2 side but the air flow seems to be from the crankcase hanging down breather pipe. I was checking that when I noticed the cold side and very hot on the 3 and 4 side. Re valve clearances, when I bought it 4 years ago, the 3 and 4 exhaust ones were tight with no clearance and I have checked and adjusted all round regularly since then, but the 1 and 2 closed up again.
^this. Does sound like one side's running hot. Ideally, prob best to pull the engine, whip the heads off & have a good looksee...
From your description the 1 and 2 side is misfiring. I would check the rocker arm nuts are tight as well as the inlet manifold to head joint nuts are done up. Something like a heck of a lot of air leaking on 1/2 side so no combustion and some air leaking across and making the 3/4 side run barely and run hot and lean. My major yellow taxi time was down to a snapped securing clip on the No 2 exhaust valve rocker arm. Sudden loss of power and the backfiring burst the opposite manifold boot so then 3/4 were lean as well. It ran at about 20mph bucking and leaping but I failed to leave the motorway because a slight hill was too much. The loose rocker arm happened more recently and that just caused a progressive loss of power over about 5 miles until it would only run on the level. By the time I stopped the No3/4 cylinder head was cold . About 30 minutes of fault finding and a quick tightening up with a 13mm spanner and I departed just as the haulage company whose driveway I had parked opened for business.
I forgot to mention with the engine idling, the air flow out of the oil filler (cap removed) and the breather hanging down pipe is quite strong. Is this some form of blow by or air leak symptom.
Thanks for the helpful responses. Seems I have a lot to check out to get to the bottom of the problem(s). Just thinking whats best to start with, ?? rocker covers off remove spark plugs set cold valve clearances to spec rocker covers back on remove king ignition lead do compression tests write down the psi squirt some oil in spark plug holes do compression tests write down the psi rocker covers off check out rocker arms and valve springs unbolt rocker arms and remove pull out push rod tubes what next?
I would do the easiest first - whip off plug leads one side at a time - then do compression test - then if no joy take off rocker covers and see what's loose/tight
^this, probably easiest. If you've got contact breakers, just whip the green lead of the coil -ve to kill the ignition.