RootesRacer
Donation Time
OK at the risk of teaching to suck eggs, let me explain myself a little with the cam timing. First you need to determine if in fact the cam / chain relationship is in order with the crank, having done that you can be prove / disprove that the timing pulley marks are correct / incorrect.
So we are focusing on the fact that the cam to crank timing is correct, after that we can be safe in the knowledge that the timing marks are correct.
As a means to prove this, check the valve opening or closing times with the known data of the cam, ie inlet opens x degrees BTDC, exhaust opens y degrees BBDC etc.
A simple way of doing this is to insert a feeler guage, say two to three thou, at the appropiate rocker arm as you move the crank in DOR, when the rocker nips the feeler you know that this valve is about to be opened, now look at the degree marks on the pulley and establish if they are correct or not. If the numbers are right you have reassured that the timing marks are correct.
Longwinded but I hope of some assistance.
Even when the cam is supposedly ground without lobe center offset, often manufacturing tolerances and errors result in the cam be advanced or retarded according to design specs.
Very often we have to install offset keys on the cam to make the cams crankshaft timing accurate according to specs.
That said, if you use an uncorrected cam to verify the crank timing, any error in lobe offset gets multiplied by 2 for the crank.
BTW, I installed a 3 degree offset key in an alpine once.