Question on Cam Gear Marks - UPDATE

[Russ/40]

Originally Posted by Mart

Russ, Please clarify "almost closed".

Mart.

Mart, after further scrutiny of number 6 with 1 at TDC, i think both valves are closed. if any valve is off the seat, I cant really see it. Rocking the crank back and forth opens and closes both valves in opposition.

Brian, I've had the heads off this thing three times. In the past I have never had to do that even once. It would be my very last ditch effort to do it again. Can the cam be degreed without removing the heads?

[bbrocksr]

Originally Posted by Russ/40

Mart, I don't know how else to state it. The exhaust valve on number 6 is barely perceptible to be off the seat, and the intake is closed when number one is at TDC. One thing puzzles me Mart. How is it we are talking about number 6 in this timeing discussion.

Brian, I've had the heads off this thing three times. In the past I have never had to do that even once. It would be my very last ditch effort to do it again. Can the cam be degreed without removing the heads?

When number 1 is at TDC firing, number 6 is at TDC overlap. The easy way to find TDC firing on number one is to put number 6 on TDC overlap.
Overlap is when the intake and exhaust valves are both off their seats at the same time for a few degrees at or near TDC number 6.
number 1 & 6 come to TDC at the same time, one is firing the other is
overlapping.
Intake valve opens 0 degrees BTDC on a stock 59a , so if the intake on number 6 just starts to open at TDC the valve timing is correct.
Bill

[KGS]

Just a shot in the dark here so don't laugh. Is the cam gear a press on? If so, could it have slipped to cause this problem? If it is a bolt on cam gear and possibly slotted, could it have moved?
Ken

[JSeery]

Originally Posted by bbrocksr

Intake valve opens 0 degrees BTDC on a stock 59a , so if the intake on number 6 just starts to open at TDC the valve timing is correct.
Bill

Keep in mind this is not a stock cam, so there is overlap. The intake on number 6 will not be just starting to open in this case. Needs to be in a positions such that the exhaust and intake are the same height above the valve seat.

If the cam spec posted is correct, it would be intake 19 deg BTDC and exhaust 19 deg ATDC. A problem is there is very little valve movement at these positions, that is why cam numbers are given at 20 or 50 degrees, so you can actually detect valve movement.

I have never tried to degree a cam with the head on. I would think you could at least check the exhaust valve if you can get a dial indicator through the sparkplug hole and on the edge of the valve such that it can move without rubbings on anything. If alum head, need to figure out a way to mount the base. Looking for very slight movements during part of the cycle, so everything needs to be very secure.

[bbrocksr]

Originally Posted by JSeery

Keep in mind this is not a stock cam, so there is overlap. The intake on number 6 will not be just starting to open in this case. Needs to be in a positions such that the exhaust and intake are the same height above the valve seat.

If the cam spec posted is correct, it would be intake 19 deg BTDC and exhaust 19 deg ATDC. A problem is there is very little valve movement at these positions, that is why cam numbers are given at 20 or 50 degrees, so you can actually detect valve movement.

I have never tried to degree a cam with the head on. I would think you could at least check the exhaust valve if you can get a dial indicator through the sparkplug hole and on the edge of the valve such that it can move without rubbings on anything. If alum head, need to figure out a way to mount the base. Looking for very slight movements during part of the cycle, so everything needs to be very secure.

There is overlap on a stock cam as well, the point is if the overlap occurs at TDC the valve timing is right .