This test is by no means a replacement for a degree wheel, but can be a quick visual during the initial diagnosis.īeing off a tooth will also affect compression test numbers. If the exhaust valve closes before TDC the cam is way advanced, if the intake valve doesn't start to open until after TDC the cam is way retarded. Unless you have odd cam timing or a major split in duration and lift, the 2 valves should be pretty close in the amount they are open at TDC. THEN I believed it.Ī quick little visual test is to pull the driver's valve cover and watch #1 valves as you approach TDC on overlap. Finally slapped on an old chain set I had laying around and suddenly everything came back in line with the cam card specs. I still rechecked everything about a bezillion times.
Fortunately, degreeing a cam is something I started doing on my motors very early in my hotrodding career and I caught the error before it became a problem. I had a timing chain set years back with the dot on the top gear off by 1 tooth. Yes, this is pretty rare stuff to be wrong, but it does happen. Doesn't mean the dowel pin hole is in the right place on the timing gear (should be just slightly past the 3:00 position- about 3:15- when you're dot-to-dot) or that the cam is ground properly to spec. Piston at true TDC and the balancer's timing mark lined up with TDC on the timing tab are fairly conculsive observations, however.
Although I will point out that having both lifters all the way down on the heel of the cam doesn't mean much, since they spend about 70% of their time there. Given the multiple checks you did when installing it, I doubt being off by a tooth is your problem. It'll run pretty crappy if you are off by one tooth in either direction.
Do the division and that's about 16 crankshaft degrees per tooth. A typical double roller timing chain set for a small block Chevy has 44 teeth on the cam gear and they cover 720* of crankshaft rotation (two rotations of the crank).
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