Your new camshaft can be the latest, trick profile in the world, but it will not run correctly if it is not phased properly. Cam phasing is usually checked by the procedure known as "degreeing the cam". This month's Tech Topic will describe a simple method for checking one cam lobe's relationship to the crankshaft using the stock timing marks. This will help assure that your cam is "degreed " right !
You will need an assistant, a 15/16" socket, 3"-extension, and breaker bar. You should use a dial indicator with an adjustable magnetic base, however, it is possible to use a dial caliper. You will be measuring the maximum lift position of the #8 exhaust valve.1 Remove the passenger side rocker cover and all the spark plugs.
2. Set up the dial indicator with the base on the flat surface at the rear (firewall side) of the passenger side head. Position the adjustable base and dial indicator so that it reads the lift of the #8 exhaust valve at the retainer. The actual amount of lift is unimportant to this procedure.3. Rotate the engine with the socket & wrench on the harmonic balancer bolt until #8 exhaust is fully open. If you have hydraulic tappets, rotate the engine to just before full #8 exhaust open and wait several minutes for the tappet to "bleed down". Stop rotating the engine just when exhaust is fully open. There will be some dwell at full lift, so the exact position may be a little tricky to determine. Repeating the procedure several times will allow you to zero in.
4. After you have determined full lift, stop exactly there and note the relationship of the timing marks and TDC line on the harmonic balancer. The phasing of the exhaust can be determined from this listing:
Timing Mark Exhaust Lobe Phasing TDC 90 Before TDC 2 92 4 94 6 96 8 98 10 100 12 102 14 104 16 106 18 108 20 110 22 112 24 114 26 116 28 118 30 120
To extend the timing marks on the stock timing cover, mark another line 1" circumferentially clockwise from the TDC mark. This new line is 17 BTDC, so just add 17 to whatever mark it lines up with. Example: the new line is across from the 14 mark on the timing cover, therefore the actual timing is 17 + 14= 31, which corresponds to 121 BTDC exhaust lobe phasing.
5. For your information, here is the exhaust lobe phasing specification for the popular Pontiac and H-0 camshafts.
Camshaft Exhaust Lobe Phasing
HC-01 068HL 116 BTDC HC-02 744HL 120 HC-03 041HL 118 HC-55 (9779068) 119 HC-56 (9785744) 118 HC-57 (9794041) 115
6. To calculate the exhaust lobe phasing -given only the valve timing events, use this formula: (opening minus closing plus 180)/2.