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Hello,
The timing chains on my 190000km alfa 75 twin spark are getting noisy. What I was wondering is: would it be possible to replace both chains (the upper driving the cams and the lower driven by the crankshaft) without opening the engine? In particular, the removal of the oil pan would allow enough access to remove the lower chain? The upper chain tensioner could be replaced as well without removing the engine head?
Thank you for your attention
Regards
Oscar

Usually you only have to tighten the chain.
I do it by letting the car idle and then loosen the screw on the front of the head a couple of turns and then tighten it again.

Hi Mats,
Thanks for the reply. Yes, as you say the usual procedure is to retighten the chain. Another procedure I heard is to loosen the nut of the tensioner, engage the 5th gear and pull the car forward, then tighten the nut again. I have done that, but no big improvement in the noise. I am wondering if the noise comes from the lower chain and also if the upper chain has now a lenght which can not be fully caught up by the tensioner. I would be curious to know if both the chains are replaceable without opening the engine (which actually does not need any overhaul).
Thanks again
Regards
Oscar

You need to pull the front cover to remove the lower chain but that is about it.
That and the valve cover and probably loosen the sump would do it, but that is only a guess from my side as I have never tried that.

Oscar another thing that can happen is the chain tensioner sticks in place and loosening the bolt is not sufficient to increase the tension on the chain.What I have done is remove the valve cover and then with a long screwdriver reach down and "encourage" the tensioner to move towards the chain.

Oscar,

My experience has been that you can remove both timing chains by removing the front cover and the cam cover alone. The sump does not need to be touched.The head does not require removal.

HOWEVER. The problem you strike if you do not remove the sump and the head is the likelyhood of damaging the gaskets between these parts during the front cover removal. So if you are VERY careful and not ham fisted, it can be done. I have done this operation with complete success.

Much easier said than done.

Mats, Murray, MD,
Thank you very much for you replies!!! I am glad to read that the operation is possible without too big issues. I will definitely follow your suggestions and hopefully the engine will get quiet.
Regards
Oscar

MD: How do you get the front cover back on in between two gaskets that is supposed to be compressed when installed?

MD: How do you get the front cover back on in between two gaskets that is supposed to be compressed when installed?

Mats

Actually that's the easier of the two procedures. The harder one is taking the cover off in the first place without damaging the gaskets as they can be seriously stuck on and you could be up for a new head gasket and new sump gasket !

Reinstall.
To answer your question directly, once the tension of the cover fixing bolts is removed from the sump and the head , the original gaskets are just marginally compressed from their previous use enough that it will allow the cover to slide back if you apply a chem seal of your choice and very gingerly slide it back in place with surgery like care . Of course, as you say releasing some tension off the sump fixings will help create more clearance but you do not need to remove it.

I repeat, you got a 50/50 chance of stuffing the gaskets up during removal.

In any case, this job is for timing chain replacement and certainly should not be required to carry out an adjustment only.

when changing timing chains and gears , check very carefully for wear in brass sleeved bushes where upper gear of lower chain rotate .. these 2 bushes are directly feeded from main oil gallery and if they have weared out, lots of hot oil pressure is lost from there even in freshly rebuild engines some old nords have steel bush instead of brass in chain cover and cause premature scoring of gear shaft , in my case i turned gear shaft on lathe to clear scorings and new brass sleeve to match undersize shaft diam.