big mistake....

[Figoulu]

Hello all

I was happy to get my engine overhauled and before putting it back in the car I checked various elements, from which the valve clearance.
Suprisingly almost none was correct, and I checked twice so happy to have made the chekings as the engine was outside

I put everything back inside the car, put oil, check again all the wires and connections and tried to start the engine.
Half a second later the engine was stuck as if the battery was dead.
I understood quickly that some pistons met some valve...

I figured out that as my head has been machined, the thickness of it is different so as the valve clearance. Actually I understand now that the original clearances were correct...

Now what to do ?
I sent an endoscopic camera. Nothing bad so far from what I could see. The engine only turned 1/2 a second.
I want to remove the head and see what to cure.

Probably I will need to cut the timing chain to be able to remove the head, unless I can remove the camshaft gear as well as the belt tensioner to let it go
Once this will be solve what shall I fear as damage ?
I assume only the head as to be checked, what about the block and the rest of it

I'm really stupid... but that's the costly way to learn

[Peter]

Engine is build-in  again: then I would set de clearance correct and see how the engine performs.
Alternative is, what also will happen when the engine does not perform nicely, is again a complete overhaul, as the crankshaft could be (minimally) bended, the crankshaft bearing can be “oval”, valves bended,  etc…..
I know, a horror scenario. Sorry for this.

[Cees Klumper]

I would not expect the skim of the head would be so much that setting the valve clearances to original specifications would cause the valves to hit the pistons. The machine shop would have had to remove a lot of material.

 What I would do:

- try turning the engine by hand after removing all spark plugs
- double and triple check the engine timing: valves vs pistons vs ignition
- if engine spins freely by hand then use the starter to spin the engine briefly
- try starting it again, if the engine spins freely

Could it be that there is 'something' obstructing the free movement of the engine, such as a wrench, the timing chain, a loose bolt somewhere?

[Figoulu]

I would not expect the skim of the head would be so much that setting the valve clearances to original specifications would cause the valves to hit the pistons. The machine shop would have had to remove a lot of material.

 What I would do:

- try turning the engine by hand after removing all spark plugs
- double and triple check the engine timing: valves vs pistons vs ignition
- if engine spins freely by hand then use the starter to spin the engine briefly
- try starting it again, if the engine spins freely

Could it be that there is 'something' obstructing the free movement of the engine, such as a wrench, the timing chain, a loose bolt somewhere?

Impossible to turn the engine even with the spark plug removed... in one way and in the other way
I have no idea if something else could have blocked the engine... yes could be a nut, but nothing like a tool, I don't believe that

I guess the only way to see more is to remove the head, but there might be a way to loosen the head and remove the timing chain other than to cut it. With removing the camshaft gear ??

I forgot to mention that the endoscopic camera shows the very slight print of a valve... But I agree with you, how could the machine had potentially removed so much "meat"... so that the valve met the pistons

Before doing all this I had checked the timing and everything was well synchronised...

[yves]

What about à timing chain opened ? And blocked ?

[MikeSimon]

I would guess that the cam chain was not installed properly and a valve protrudes into the cylinder when the piston is at TDC and caused the interference. The head comes off from the engine with the engine installed. It is a hassle, but not a problem.

[Figoulu]

I would guess that the cam chain was not installed properly and a valve protrudes into the cylinder when the piston is at TDC and caused the interference. The head comes off from the engine with the engine installed. It is a hassle, but not a problem.

Thanks
How about the chain ? How would you remove it ? Shall I remove the camshaft gear ?

As far as I remember the timing was ok. I checked it when doing my valve clearance

[waltklatt]

Bummer to hear that.  I would take cam cover off and look at the valves to make sure all of them are still in place(not dropped).
Then do like others said, remove plugs and try to turn by hand.
If nothing, mark location of camshaft to chain sprocket wheel and make sure you don't loose timing marks.
If the camshaft is in wrong position(180 degrees) off from crank, then the timing is all off.
Reset by turning the crank and camshaft independently till you line them up properly.
You said you spun the motor briefly, then you should be ok with unbent valves and uncompromised pistons.
I don't know how much you spun the motor before locking up.
Go ahead and cut the chain and remove head.  New chain and head gasket is in order.
Have head and valves fixed(pressure test).

Bought a 1970 280SE with the timing turned 180 degrees off and the valves were trashed.
Got a new motor and installed it, with no problems.
That was many years ago.

Walter
1967 220SL diesel
1969 280SE
2003 Beetle TDI
2005 Honda Element

[DaveB]

I wouldn’t think it’s necessarily pistons hitting valves Figoulu. I believe the engine would likely still turn one way or the other in that case. Could the starter have got jammed somehow? Maybe take it off and have  look. If you didn’t hear anything disastrous hopefully the engine internals are ok.

[Benz Dr.]

No need to cut the chain. Remove the chain tensioner which should take some of the tightness out of the chain.

You have a valve hitting a piston which indicates incorrect valve timing. Even one tooth advanced will make valves hit pistons. Two teeth advanced and the engine will lock up solid.

No need to remove the head if you can retime your camshaft.

[Figoulu]

Thanks for your advice.
I will do it asap
For the Time being I need to stay away from that car…

[stickandrudderman]

Check again your valve clearances. If they have increased since you set them then that is an indicator of bent valves due to incorrect camshaft timing.
If they are bent then you'll need to remove the cylinder head and renew the bent valves.

[Figoulu]

Check again your valve clearances. If they have increased since you set them then that is an indicator of bent valves due to incorrect camshaft timing.
If they are bent then you'll need to remove the cylinder head and renew the bent valves.

Thanks a lot for the advise !
My pro went back to me and ask me to send it back to him

[Peter]

We are of course very interested in what the diagnosis is, please keep us informed.

[Figoulu]

Thanks to all for your messages including pm
At the end of the day the engine will be sent back to the pro.
When removing it from the car I will try to investigate something by just removing the rocker arm cover just to see if something obvious appears

I will post the end of the story when I know more.

For those who know the answer, do we expect the engine block/ piston / rods to be damaged or only head and valves?

[DaveB]

At the end of the day the engine will be sent back to the pro.

That seems the best thing to do, especially if you had not altered anything after receiving the engine from them. Good luck.

[RAY]

Regarding the machine shop removing a lot of material may not necessarily the case. It may just be that the head had already been skimmed once or twice before ?

[ja17]

Remove all spark plugs. Remove all the rocker arms that can be removed with the head still on the car. Next increase the clearances of the valves on the remaining rocker arms on the car until they can be removed or the engine can be turned again. Proceed until all rocker arms are removed. Next turn the engine and check the valve timing marks. Correct if needed. Next, install each rocker arm one at a time and set the valve clearance to specs.
Continue until finished, one at a time until finished or until problem occurs.