Camshaft puzzle

[Horse]

As some will realize from my previous post, I have been busy changing the timing chain tensioner and chain on my 4A. The sprockets were in excellent condition with no evidence of any wear.

 

In so doing, I met with a puzzle. Advice from others and in the official workshop manual is to set the tappets of valves 7 and 8 to 40 thou. so one can confirm the correct position of the camshaft should it be moved inadvertently. This I did, only to find the with the crank at TDC I could not get a feeler in between the rockers and valve stem. I had to increase the tappet clearance to over 50 thou to be able to confirm the valves 7 and 8 were in the "rocking" position. Not only that, but the correct positioning of the camshaft was critical and left no margin at all; it had to be absolutely spot on to get the same clearance on each valve. Incidentally, the quality of the tensioner, which came from a reputable source, was not a patch on the one that had broken in any respect (except that it was still whole!). I am not optimistic that it will not fail again.

 

I have had the car 9 years (in which I have done about 16,000 miles) and have been unable to contact the previous owner, who had the car rebuilt in 1992 and which has done less than 20,000 miles since then. Do you think I have a non standard camshaft fitted and if so, what, if anything, is the implication? The engine does not idle happily below 950-1000 rpm, but the cause of that may be something completely different.

 

I shall be grateful for any views members may have.