Greetings all, I hope everyone is enjoying a great racing season. In preparation for my next race, I am performing the routine regimen of care and feeding which includes of course adjusting valves. Adjusting valves is nothing new to me and I have performed this procedure on various makes/models over my 46 years of existence on this fine planet of ours. However these VW’s are something else. As some of you know I’m still relatively new to FV. I maintain 2 Citation Vee’s that have engines from different engine builders. Admittedly, the motor in one car is pretty long in the tooth, while the other appears to have been refreshed (judging by the clean cylinder hone pattern) but then locked away for 11yrs or so but it still runs great.
The weirdness is this: When adjusting the valves, the lash changes as the crankshaft is turned. At first I simply wrote this off as wear on the valve tip (the valve rotating to a “new” spot causing the change in lash) however last night I realized that the lash is changing even before the valve is activated. For example if I set the lash with the piston at TDC on the compression stroke, the lash of both valves is greatly diminished (sometimes to 0) as I turn the the crank and the piston moves downward in the cylinder on the power stroke. Also I have noticed that if I check one valve at a time ie. one valve open, checking the other (being mindful of valve overlap), the lash of the un-opened valve becomes 2-3 thousandths greater than when the other valve is “unloaded” apparently due to some flex in the rocker shaft and/or rocker shaft studs.
It’s funny (not) ‘cause every time I tell myself I’m gonna adjust these valves “real quick” it turns into a 2 hour ordeal…
So first of all, before I go into total detective mode to answer the mystery as to why this is happening (although the rocker shaft phenomena seems pretty clear already), perhaps someone (or everyone) has encountered this already and can enlighten me as to what the heck is going on here? Camshaft bearing clearance, or 8mm head stud spring action are two of my early guesses..
Secondly, the adjustment method in described in Jim Schings book (one valve at time method, one valve open adjust the other) contradicts what is written in the VW factory manual which prescribes a single cylinder approach, adjusting each at TDC according to the firing order. So which method are you all using, and what lash setting are you using? Are you setting it it once and forgetting it, or do you spin the motor and try to dial it in somewhat?
Thanks,
Joe