I've got to pull the head on a Nytro. This is a built engine with a head shim. Before I pull the head, I want to have an understanding of where the cam timing is at and whether they degreed one or both of the cams to compensate for the head shim.
The numbers I am getting do not seem to make sense. I am wondering if anyone could help me out with this.
Here is the valve timing for a Nytro:
I have measured true TDC by putting a dial gauge down the spark plug hole and measuring where the piston stops moving from both directions.
I then put the dial indicator on the intake and exhaust shims and measured valve movement. These are the results I got. It is hard to be exact on where the valve initially starts opening or closing, but the 0.040 lift numbers are exact.
Intake open: 79degrees BTDC, 24degrees BTDC @0.040 lift
Intake close: 79degrees BTDC, 139degrees BTDC @0.040 lift
Exhaust open: 102degrees ATDC, 139degrees ATDC @0.040 lift
Exhaust close: 60degrees ATDC, 15degrees ATDC @0.040 lift
Lobe centers:
Intake lobe center
(Iopen+Iclose+180)/2 - Iopen where Iopen is BTDC and Iclose is ABDC
Iopen = 24 BTDC
Iclose = 139 BTDC = 180-139 = 41 ABDC
=(24+41+180)/2 - 24 = 98.5
Exhast Lobe center
(Eopen+Eclose+180)/2 - Eclose where Eopen is BBDC and Eclose is ATDC
Eopen = 139 ATDC = 180-139 = 41BBDC
Eclose = 15
=(41+15+180)/2 - 15 = 103
These don't seem to match any of the numbers I have seen, nor the table above. Can someone explain if these numbers represent properly degreed stock cams?
Thanks.
The numbers I am getting do not seem to make sense. I am wondering if anyone could help me out with this.
Here is the valve timing for a Nytro:
I have measured true TDC by putting a dial gauge down the spark plug hole and measuring where the piston stops moving from both directions.
I then put the dial indicator on the intake and exhaust shims and measured valve movement. These are the results I got. It is hard to be exact on where the valve initially starts opening or closing, but the 0.040 lift numbers are exact.
Intake open: 79degrees BTDC, 24degrees BTDC @0.040 lift
Intake close: 79degrees BTDC, 139degrees BTDC @0.040 lift
Exhaust open: 102degrees ATDC, 139degrees ATDC @0.040 lift
Exhaust close: 60degrees ATDC, 15degrees ATDC @0.040 lift
Lobe centers:
Intake lobe center
(Iopen+Iclose+180)/2 - Iopen where Iopen is BTDC and Iclose is ABDC
Iopen = 24 BTDC
Iclose = 139 BTDC = 180-139 = 41 ABDC
=(24+41+180)/2 - 24 = 98.5
Exhast Lobe center
(Eopen+Eclose+180)/2 - Eclose where Eopen is BBDC and Eclose is ATDC
Eopen = 139 ATDC = 180-139 = 41BBDC
Eclose = 15
=(41+15+180)/2 - 15 = 103
These don't seem to match any of the numbers I have seen, nor the table above. Can someone explain if these numbers represent properly degreed stock cams?
Thanks.
