Hi, I am in the throes of setting up my valve timing for the very first time on my 1968 Plus 2 and just looking for a sanity check on my calculations, assumptions, interpretation and next steps. I have read many previous posts and also referenced Miles Wilkins book but still require guidance / validation.
Being new to this, I was largely expecting relatively small adjustments would be required using offset dowels but the results I am getting are on a much more significant. Am I missing a fundamental understanding here?
My Cylinder head has recently been reworked to the following spec:
• Skimmed to Sprint spec
• Sprint Inlet Valves
• Standard Exhaust valves
I have fitted QED Q360 Camshafts, set all valve clearances to spec and initially set valve timing to original baseline (No1 Piston/Crank at TDC, Camshafts both rocking on No.4 cylinder, my original timing marks are all in alignment). So far so good…
QED have provided the following technical details for Camshaft settings:
• Inlet Fully Open: 105 degrees after top dead centre (ATDC)
• Exhaust Fully open: 110 degrees before top dead centre (BTDC)
Using a DTI Gauge and Timing Wheels I have taken the following measurements multiple times (but I will measure again). The DTI has resting on the No.4 cylinder (exhaust first and then inlet). I have also factored in dwell etc…:
• Inlet Open @146 degrees after top dead centre (ATDC)
• Exhaust Open 98 degrees (BTDC)
In summary this would suggest:
• Inlet has 41 degrees variance from recommended specification (Actual 146 vs. Target 105 degrees)
• Exhaust has 12 degrees variance from recommended specification (Actual 146 vs. Target 105 degrees)
As mentioned above, I was largely expecting relatively small adjustments would be made using offset dowels but these numbers are more significant. At a high level could these be directionally accurate or is there something I am doing wrong?
Assuming that the numbers are directionally ok, would I make the major adjustments by moving by 4 teeth and 1 tooth respectively and then remeasuring for the minor adjustments?