Seeing as I have the engine out to do various things I decided to measure the valve lift I am getting and to check the rocker geometry. This engine has done 3 tarmac rallies since being rebuilt and has run faultlessly. I have just relied on the engine builder doing the right thing up till now.
Measuring the lift with the gauge resting on top of the spring retainer;
Cylinder Inlet Lift Exhaust Lift 1 11.42 12.04 2 11.54 12.09 3 11.78 12.15 4 11.65 11.85
The Kent Cams website shows that for a GTS4 cam I should have 13.69mm inlet and 13.36 exhaust. I am missing out on 2mm inlet lift! Q: I am led to believe that stated cam figures are often not achieved so do mine look ok? Me thinks they are a little low. Q: Is there likely to be power lost here? I cannot visually ID any wear in the cam or rockers.
Next I looked at the rocker position. I made up some gauges as per the Des Hammill book but cannot use them as the cam lobe is wider than the rocker meaning I cannot get the gauge to sit in a useful position. Re-reading Hammill book it seems I have to remove the camshaft thrust plate and move to cam backwards 5mm. It also seems to suggest that checking geometry is done with only 1 rocker in place at a time. My head is currently complete and I didn't really want to take it apart unless I ID an issue. Q: Can I do these checks with it complete? Q: Can I remove the thrust plate with it complete? This is a learning exercise for me but the water is getting deep!!
Q: As a check of my understanding, the rocker adjusting post ONLY changes the cam to rocker clearance at zero lift (what is than value?)? Q: To change the rocker position (if it is wrong) I have to use lash caps on the valve stem? Q: Are lash caps available in various thicknesses off the shelf? Q: Does the rocker geometry effect lift?
Kent Cams rockers and valve keepers. Crow Cams dual valve springs. GTS4 cam. Group 1 stainless steel valves.
Sorry for all the questions...........
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