Valve Timing - some Dumb Questions

[rgh0]

I assume you are measuring opening at TDC ? or are you measuring MOP using a degree wheel and checking an equal lift either side to get the MOP point? if you have a 3 degree difference between No1 and No 4 inlet opening and assuming the rotation and chain tension is the same each is measure then it could be one of 3 factors.

1. Different valve clearances - a small difference can make a difference in lift at TDC between two lobes, but it would not affect the timing using the MOP method on two different lobes.

2. Cam bearing wear allowing the cam to move excessively - again would only really affect the opening at TDC method

2. A poorly ground cam with the lobes not properly aligned. - unlikely but not impossible, cam grinders do make mistakes.

cheers
Rohan

[Tomtecno]

Thanks very much for the advice. I’ve been working on it this morning and I’ve managed to get some figures so just need to order up some dowels tomorrow.

As I said, I wasn’t sure about the cylinder1/cylinder4 thing since I had seen so many different approaches but when I think about it logically it makes perfect sense.

Thanks again for your help.