I'm fitting a single fast road cam to my 70's Mazda and checked the cam timing using a disc on the crank.

I get full lift at 100 degrees when in fact it should be at 108 degrees so I need to get an offset key for the cam to put it right.

The question is should it have a 4 degree offset,as the cam moves at half the rate of the crank, or the 8 degrees shown on the timing disc?
The more I think about the more confused I get!

Thanks in advance

I'd go for 4.

can you not just remove the key and just lock it in postion with the bolt ? or fit a vernier pully?

my zetec has no keys at all

Remove the or dowl from the can set and lock the crank at 100 deg ,then lock the cam at full lift, but the chain on and this will give you the correct position of the sprocket relative to the can you can then mark them both.

The safest way would be to fit a vernier

Thanks for the reply's

Unfortunately this is a pretty obscure motor (only 5 or 6 cars in the UK) so there are no verniers available and also for that reason I don't trust to rely on bolt tension only as a replacement head/valve gear would have to come from Australia should anything come loose.

I'll have to go with a woodruff key

can you set the timming up then drill your own dowell to lock it .i did this with a red top in a grasstrack car