Lancia Motor Club Forum
Model Technical and Interest => Appia => Topic started by: Spider2 on 05 November, 2025, 11:16:09 AM
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I was lead to believe that the timing chain tensioner was operated by oil pressure. I am in the process of investigating a rattling chain and am rather hoping it is a tensioner problem as opposed to a stretched chain. With the engine not running I can see that the tensioner is tensioned by a spring loaded piston that one can push down to relieve tension to allow the chain and sprockets to be removed. Is this spring loaded piston the only method of tensioning or does oil pressure increase the tension once the engine is running? The reason I ask is that if the spring is the only method then my chain is very loose.
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I'm guessing it's a similar scenario to other Lancia of the time period in that the engine oil pressure provides the resistance to stop the plunger being able to go back in, once the engine is running.
There have been warnings about things such as not rotating the engine backwards as the tensioner resistance can be overcome to such an extent that the chain can go slack enough to allow the chain to jump teeth! Leaving the car in gear facing up hill was actively discouraged incase it rolled backwards with similarly disastrous outcomes.
There are detailed measurements to enable chain length to be checked to see if stretch has occured, of course having a new one to compare to makes checking the length a doddle, but I'd be inclined to renew it anyway once in this deep unless they are very expnsive.
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Thanks Kevin for the advise. Yes, you are absolutly correct that I should change the chain anyway. I was a bit hesitant because the method of replacing the chain by offering up all 4 sprockets and the chain as a single unit appears cumbersome and the method of timing the cam shafts appears to be complicated. I have read and re-read the manual about a dozen times and I now understand the timing procedure and it seems to be a very nifty way of doing it. The consortium had the crank bolt and gaskets and am just awaiting a chain to arrive from Italy. Hopefully, I will have a quiet(er) engine soon.
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The problem with the timing is the drag of the inlet sprocket as you rotate the still connected exhaust sprocket plus the pressure from the valve springs on the camshafts pushing them out of alignment.
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Yes, I can understand that. The book method is to set No1 inlet/exhaust valve clearances to 1mm with a .03mm feeler between the valve stem and the rocker and rotate the crank untill the inlet valve just begin to open (the .03 feeler grabs), then do the same with the exhaust valve with the cam sprockets loose turn the crank to TDC. If I completely loosen the tappets on 2, 3 and 4 so the cams do not operate the valves then there should be minimal cam drag apart from the no 1 inlet cam as the engine is rotated to do the exhaust valve. I have heard it can be frustrating, some saying you have to compensate for drag by trial end error.
I think the above procedure is correct, please let me know if I have got something wrong. I may experiment a few imes with the old chain still in place to get a bit of practice. Its annoying Lancia did not devise a way of locking the cam shafts.
Wish me luck!
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My new timing chain arrived today and I notice it has a master link. Looking at the old one, that is still fitted, that also has a master link. The parts manual does not show the chain having one so:
1) I guess in 1951 or so the chains did not have master links
2) The chain must have been changed in the past.
3) Fiting the new chain will be a lot, lot easier than the procedure in the manual that involves taking off all 4 sprockets. I will put the crank at TDC for no 1/4 and mark the cam sprockets with meeting horizontal lines so I can check for cam shaft movement. Wedge the tensioner (stretcher) dog down and undo the master link and take off old chain. Thread new chain over sprockets and insert master link. Simple. as the meerkats say..... I hope!
4) Hopefully no need to re-time the engine.
Interestingly, who ever installed the chain the last time inserted the master link securing clip the wrong way around. Stayed in place for decades.
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Sucess! I have finally changed the timing chain and timed the cam shafts. Looking back, i suppose the procedure is not overly complicated but for someone like me who has never done it before it was definately a case of 2 steps forward and 1 step back. (at times I think it was 1 step forward and 2 or 3 steps back). If anyone is contemplating doing the job get in touch and I can give you the does and don'ts, and I did it without the specialist tools the manual recommends. I have not run the engine yet but I think it will be a lot quieter as the chain now is considerably tighter.
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It was time today to test if the engine would run after the new timing chain and my attempts to get the cam timing correct. 1 second squirt of easy start, half choke and she started first push of the key. She ran smoothly and evenly and best of all with no chain rattle. I am so relieved.
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Very satisfying !
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Well done! you can now write a definitive guide for the Appia Consortium...only kidding.
Clarkey
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Jim, I am quite happy to write a semi-definitive guide. When one knows how (and the does and the don'ts) it is quite staright forward. Problem was that when I started I did not know how and the procedure in the manual looked rather daunting.