How likely is a Timing Chain to skip?

[Angle Grinder]

I've read that a Flavia timing chain can skip with incredible ease if a car ever rolls backwards whilst in gear.

As it happens, I inadvertently left the car in 4th gear and didn't realise this when I gently rolled the car (very slowly) a few inches this morning. I'm now feeling a bit paranoid.

My car did have a timing chain tensioner modification done to "provide a positive stop" (according to the invoice from Richard Thorne), so I'm wondering just how violent does the reverse force on the chain need to be to cause a jump?

[brian]

I have heard this "story" (?) before but in the 40 yrs I have been in and around Flavias and 2000s I have never actually heard of a case first hand. It is always "it might/could/possibly". I am sure in all my 2000 days I did roll back in gear at some point(s) but timing was not a problem I met - lots of others!
I think I would be happy with what the guys who did the timing chain said.
However I do understand your anxiety and it would not be a big job just to check the timing - so no definitive answer!!

[stanley sweet]

My brother-in-law did his apprenticeship with Rob Walker when they were Lancia dealers in the Fulvia era and did a bit of work on mine years later. He said they were great cars but warned me never to be lazy and stop it rolling backwards by lifting the clutch as it could make the chains slip a tooth.  He worked on all sorts of exotic engines and really knew his stuff so I have never done this. I don't know how likely it is in reality but would rather just avoid the the risk anyway.

[chriswgawne]

Somewhat embarrassingly at the time, I had exactly this happen to a friend of mines Fulvia 1600HF in the early 80's that I was working on.
We were giving his car an oil change, a new set of points and plugs etc and I pushed the car backwards in gear to check the points gap.
Nothing untoward happened but when time cane to start the car, firstly it didn't start easily then when it was running it was evident that one or more pistons were touching the valves! A quick shutdown and repositioning the timing chain sorted it out without any damage but the timing chain itself was quite stretched and was changed shortly after as was the tensioner which was badly worn.
Since then, on any car I always only pull the car forward to check the points gap.
Chris

[Angle Grinder]

So started her up and all was fine. Phew!

[Brian Long]

I owned an 815 Flavia sedan back in the late '60s which had done about 200,000 miles. Its timing chain slipped when it misfired on starting-up because it was extremely worn.
By my reckoning, the shoulder on the chain tensioner should 'bottom' against the crankcase, when there is no oil pressure, and still constrain the chain if the latter is not too worn. Admittedly, I haven't tested this theory on a dismantled engine as yet.
Nevertheless, I have fitted a threaded-rod and locknut stop on all of the five Flavias that I have owned over the last forty years.
A simple modification for some peace of mind!
Brian

[bobhenry999]

Brian,

Like you I have owned Flavia/2000`s for a number of years (35 years and counting !) but have never had this problem myself. How would one go about doing the threaded rod and lock nut stop modification the you have suggested ?

Regards,

Bob

[Kevinlincs]

Really interesting thread, never occurred to me before that it could happen but logical when you think about it if the tensioner doesn't have any means of stopping full retraction which would cause a slack enough chain for it to skip...

[Brian Long]

The modification is quite simple.
Remove the brass hexagon plug on the block which contains the tensioner spring. Drill and tap a thread into the plug e.g. 1/4".
Cut a piece of threaded rod long enough to reach down to the inside of the tensioner plus enough to protrude through the hex and to allow a locknut to be fitted on the outside. Hacksaw a screwdriver slot across the end of the rod.
Reinstall the plug and run the rod down until it bottoms on the tensioner. Back it off a turn or two and lock in place.
Cheers.
Brian

[Kevinlincs]

The modification is quite simple.
Remove the brass hexagon plug on the block which contains the tensioner spring. Drill and tap a thread into the plug e.g. 1/4".
Cut a piece of threaded rod long enough to reach down to the inside of the tensioner plus enough to protrude through the hex and to allow a locknut to be fitted on the outside. Hacksaw a screwdriver slot across the end of the rod.
Reinstall the plug and run the rod down until it bottoms on the tensioner. Back it off a turn or two and lock in place.
Cheers.
Brian

A modification I'll be sure to do when the time comes, thanks for the info.