So this is another question about my Skoda Estelle engine rebuild project. Now it cranked and started, after a session of neither of those. To fix that problem I released the head bolts and retorqued them, and I also recalibrated the valves. It now can start but I hear loud clanking sounds, and I can't tell if it comes from the top or the bottom. It sounds like a piston hitting something. In one of the tries, after a few seconds, it kinda seized but it cranked again. If I take the rocker arma off, and the commanding rods, and the spark plugs, the engine cranks without making the sounds. Also, I don't see a bent rod. I didn't touch the timing, camshaft, chain, etc :)
(Adding answers to @CcDd questions)
you sure the timing is aligned?
Well, I didn't touched anything regarding the timing, didn't even took the distributor off, nor removed the damper or took the timing chain out...
Was it banging before it seized?
Yes, it was doing the clank thing...since it could start, it is doing that
is it a bang that leaves through the exhaust port like a backfire?
No back fire, the clanking sound is inside the engine
when it had no spark plugs and you rotated it there was no weird sounds at all?
No sounds at all, without sparks and without the valves gear, i.e, naked head with only the valves and springs installed
Try starting it on 3 cylinders with 1 spark plug out then stop it replace the plug and go to the next cylinder. don't run it for long at all just long enough to hear the noise. see if one cylinder is louder than the rest or if the noise stops or changes when one is not firing.
Ok sir. I also was thinking on doing 3 cylinders at a time, for the "dead" one, remove its valve rods, so it reminds with valves closed and of course, no spark plug. That will tell us if there is a valve hitting the piston, or if the rods/followers are the problem?
Exhaust valves might be taller or shorter than intake but exhaust should be all the same and intake should be all the same. you don't have any that are too low allowing the pushrods to have too much play? one of those could be banging. Not sure how much play they should have for your engine.
The valves are almost all equal in height, only the 2 I changed seemed to be slightly taller. I will check. Should I grind off the tip of those taller than the rest?
I am assuming you are starting the engine outside of the car on a stand or something or is it in the car? if it is in the car you could pull it with another car with no spark plugs and listen but I would be simply connect the clutch at the right speed listen then push the clutch back in so you don't spin it much.
If you hear a bang without fuel such as towing the car or pulling a spark plug then the issue is mechanical where something is hitting something. It may have something to do with compression but this is less likely
The engine is in the car. I'm being assisted by another person who cranks it, then I can see things in the engine. I can't tow it, but perhaps I can jack it one side, put 4th gear and have someone spin the wheel, it will spin the engine without the starter noise and I would be able to pin point the issue?
if you do not hear a bang without fuel you may have some pre or post detonation going on.
If I crank the engine without fuel, and without spark plugs installed, I can't hear the noise...
One other thing to try is retard the spark as far as it will go while keeping the engine running. This may also stop the banging which would means its detonation. it will not make predetonation go away.
I tried that, but I was more scared than happy because the noise :( so I didn't tried for real
Was there any strange or severe vibrations coming from the engine? or was it pretty smooth? if so what were the vibrations like?
The engine was vibrating, I felt it when I was the one cranking, each banging could be felt in the body. It was really upset.
and did the exhaust sound normal or was there a strange lope or pop or anything?
No unusual noises in exhaust
and yes with compression the starter will go slower.
lastly you are getting oil pressure to all conrod bearings? nothing got plugged up while being worked on?
No that I know. I used your suggestion and super oiled everything when mounting the things back. I can't tell about oil pressure because the car doesn't have the gauge...