Cam Timing

[mintus]

I wish to put the following to you for any input. especially for the pros and cons of having 7.7 degrees of advancement in my engine timing.....

Thank you in 7 x in advance....ha

Cat Cams specifications:
Valve lift @ TDC
Intake: 2.30 mm Exhaust: 0.90 mm
1./ TDC is confirmed with harmonic balancer on the line T/O
2./ Number one lobes at 7 and 5 o’clock
3./ Measure cylinder 6 intake and exhaust spring height.
4./ Intake @ TDC = 32.5 mm
5./ Exhaust @TDC = 34.5 mm
6./ Rotate engine CW 180 degrees and align with T/O mark.
7./ Measure cylinder 6 intake and exhaust spring height.
8./ Intake @ BTDC = 34.6 mm
9./ Exhaust @ BTDC = 35.0 mm
10./ Equate the difference between Intake and Exhaust spring height @ TDC - @ BTDC
11./ Intake spring heights 32.5 mm -34.6 mm = -2.1 mm
12./ Exhaust spring height 34.5 mm – 35.0 mm = - 0.5 mm
13./ Intake difference from specification: 2.3 mm - 2.1 = 0.2 mm
14./ Exhaust difference from specification: 0.9 mm – 0.5 = 0.4 mm
15./ For each 0.12 mm you have 1.0 degree
16./ Divide Intake 0.2 mm / 0.12 degrees / mm = 1.7 degrees advance
17./ Divide Exhaust 0.4 mm / 0.12 degrees / mm = 3.3 degrees advance
18./ Cat Cam specifications: Lobe separation = (Exhaust: 120 degrees + Intake: 110 degrees) / 2 = 115 degrees
19./ Cat Cam Intake Centerline = 110 degrees
20./ Lobe separation – Centerline = degrees of (-) retardation or (+) advancement. = 5.0 degrees advancement
21./ The total degrees of advancement in the timing of my m30b34 is as follows:
Intake: 1.7 degree
Cat Cam timing: 5.0 degrees
Extra thick Head gasket: 1.0 degree
Total: 7.7 degrees advance

Cheers;

Brian

[marc79euro645]

I don't know how that would compare to mine. I have an adjustable cam sprocket and have advanced mine some to pick up bottom end response, which I really like. The only way to be sure is to clay the piston and check it. Thats a lot of work,but could save the motor,or you could do like me, and just try it , and hope for the best. good luck!