THE cam gear rotates exactly once for each two times the crank rotates,the cam gear lines up at the 12 o'clock crank and 6 o'clock cam gear orientation when the #6 cylinders on the compression stroke, rotate the engine one complete revolution and the cranks again at 12 o'clock but the cam gears index mark is now at 12 o'clock, indicating the #1 cylinders at the compression stroke, you use the 12/6 index to install cams simply because its easier to align correctly ,visually, but you need to rotate the engine to the 12/12 orientation before dropping the distributor back in, the distributor won,t fully seat unless the oil pump drive shaft seats up into the distributor gear, as you remove the distributor the helical gear interface tends to turn the pump drive shaft slightly, you can use a long flat tip screw driver to turn that back to the correct location and with a bit of practice you'll learn to gauge the amount the rotor rotates as it seats into the cam gear.
watch video
http://www.youtube.com/watch?v=UYGU7mTw ... r_embedded
The CLOYES true roller style is vastly superior to the factory link belt design
viewtopic.php?f=70&t=1015&p=1864&hilit=+tabs#p1864
viewtopic.php?f=70&t=9921&p=38008#p38008
how come its 180 degs out of phase?
I get this question all the time, well here’s something I see lots of guys don’t understand, ONCE YOUVE INSTALLED A CAM WITH THE TIMING MARKS YOU MUST ROTATE THE CRANK 360 DEGREES BEFORE DROPPING IN THE DISTRIBUTOR, while its true that if the, timing marks are positioned so the crank is at 12 o,clock and the cam gear is at 6 o,clock that the cam lobes will be in the position that fires #6 cylinder that HAS NO EFFECT AT ALL (on finding TDC,) for aligning the degree wheel with TDC,or THE timing tab pointer, for degreeing in the cam, the piston passes thru TDC TWICE in every firing cycle once on the firing/power stroke and once on the exhaust stroke, the cam rotates at exactly 1/2 the speed of the crank so to make it easy to line up the marks they install it with the marks at the closest point 6/12 for easy indexing, rotate the engine 360 degrees to the #1 TDC power stroke and the crank gear will still be at 12 o'clock 12/12 but the cam will be at 12 o,clock also, rotate another 360 degrees and your back where you started. its simply easier to index the cam at the point where the index marks align closely. look at how the cam lobes themselves open the valves when the cam is just installed the #1 cylinder valves are slightly open and the #6 are closed per "Lunati" ‘’YES YOU ARE RIGHT - WHEN CRANK IS AT TWELVE AND CAM IS AT SIX THEN #6 CYL IS FIRING AFTER YOU LINE UP YOUR MARKS AND INSTALL GEAR THEN ROTATE YOUR CRANK ONE REVOLUTION AND THEN DROP THE DIST. IN - AT THAT POINT
be sure to verify the oil pump drive shaft won,t binds and has proper clearance
http://boxwrench.net/specs/chevy_sb.htm
look here
drop the distributor in with the rotor pointing at the #1 cylinder, and YEAH! it physically possible to get the distributors rotor to point at any place you want it too by changing the oil pump drive shaft alignment with a large flat blade screw driver while the distributors out of the engine and that's easily changed, but to do it correctly,you want the rotor to point at the #1 cylinder on the compression stroke, so pull the #1 plug, get a large ratchet/socket on the damper and put your finger over the open plug hole and slowly rotate the engine by hand in its normal rotational direction until you see pressure build under your finger as the rotor approaches #1 cylinder location on the distributor base which you should have marked as its supposed to be in direct alignment between the distributor and the number 1 cylinder on the engine, remember the distributor and cam gears are helical and the rotor turns as it seats so compensate slightly. and the rotor should be just coming into alignment as pressure builds under your finger, once that's done re-install the distributor cap and plug and use a timing light to set the timing, you normally want about 6-12 degrees BTDC at idle and watch it advance to about 37 degrees as the rpms build to about 3000rpm
finding TDC
http://forum.grumpysperformance.com/viewtopic.php?f=70&t=967
http://forum.grumpysperformance.com/viewtopic.php?f=52&t=966
step one, pull the #1 plug and place the tip of your finger over the plug hole and rotate the engine until you feel COMPRESSION build as the number one cylinder, piston starts its compression stroke as the mark on the damper gets close to the timing tab, then remove your finger and continue turning the engine until the timing line on the damper aligns with the timing tab (0) TDC
once that's done the engine should no rotate any more until the distributor is seated correctly.
once that's lined up you drop the distributor into the engine so the rotor on the distributor points at the #1 cylinder when it seats and you install and lightly tighten the clamp and connect the wires, connect the timing light and set the timing at about 6-8 degrees BTDC at idle as a start point., if the distributor won,t fully seat the oil pump drive shaft needs to be turned a few degrees with a long large flat blade screw driver and re-try seating it while, it might take several tries until it lines up, it will seat into the distributor base gear once the oil pump drive aligns with the oil pump slot in the distributor gear base
http://forum.grumpysperformance.com/viewtopic.php?f=50&t=54
http://forum.grumpysperformance.com/viewtopic.php?f=44&t=464
http://forum.grumpysperformance.com/viewtopic.php?f=70&t=1411
watch video
http://www.youtube.com/watch?v=UYGU7mTw ... r_embedded
The CLOYES true roller style is vastly superior to the factory link belt design
viewtopic.php?f=70&t=1015&p=1864&hilit=+tabs#p1864
viewtopic.php?f=70&t=9921&p=38008#p38008
how come its 180 degs out of phase?
I get this question all the time, well here’s something I see lots of guys don’t understand, ONCE YOUVE INSTALLED A CAM WITH THE TIMING MARKS YOU MUST ROTATE THE CRANK 360 DEGREES BEFORE DROPPING IN THE DISTRIBUTOR, while its true that if the, timing marks are positioned so the crank is at 12 o,clock and the cam gear is at 6 o,clock that the cam lobes will be in the position that fires #6 cylinder that HAS NO EFFECT AT ALL (on finding TDC,) for aligning the degree wheel with TDC,or THE timing tab pointer, for degreeing in the cam, the piston passes thru TDC TWICE in every firing cycle once on the firing/power stroke and once on the exhaust stroke, the cam rotates at exactly 1/2 the speed of the crank so to make it easy to line up the marks they install it with the marks at the closest point 6/12 for easy indexing, rotate the engine 360 degrees to the #1 TDC power stroke and the crank gear will still be at 12 o'clock 12/12 but the cam will be at 12 o,clock also, rotate another 360 degrees and your back where you started. its simply easier to index the cam at the point where the index marks align closely. look at how the cam lobes themselves open the valves when the cam is just installed the #1 cylinder valves are slightly open and the #6 are closed per "Lunati" ‘’YES YOU ARE RIGHT - WHEN CRANK IS AT TWELVE AND CAM IS AT SIX THEN #6 CYL IS FIRING AFTER YOU LINE UP YOUR MARKS AND INSTALL GEAR THEN ROTATE YOUR CRANK ONE REVOLUTION AND THEN DROP THE DIST. IN - AT THAT POINT
be sure to verify the oil pump drive shaft won,t binds and has proper clearance
http://boxwrench.net/specs/chevy_sb.htm
look here
drop the distributor in with the rotor pointing at the #1 cylinder, and YEAH! it physically possible to get the distributors rotor to point at any place you want it too by changing the oil pump drive shaft alignment with a large flat blade screw driver while the distributors out of the engine and that's easily changed, but to do it correctly,you want the rotor to point at the #1 cylinder on the compression stroke, so pull the #1 plug, get a large ratchet/socket on the damper and put your finger over the open plug hole and slowly rotate the engine by hand in its normal rotational direction until you see pressure build under your finger as the rotor approaches #1 cylinder location on the distributor base which you should have marked as its supposed to be in direct alignment between the distributor and the number 1 cylinder on the engine, remember the distributor and cam gears are helical and the rotor turns as it seats so compensate slightly. and the rotor should be just coming into alignment as pressure builds under your finger, once that's done re-install the distributor cap and plug and use a timing light to set the timing, you normally want about 6-12 degrees BTDC at idle and watch it advance to about 37 degrees as the rpms build to about 3000rpm
finding TDC
http://forum.grumpysperformance.com/viewtopic.php?f=70&t=967
http://forum.grumpysperformance.com/viewtopic.php?f=52&t=966
step one, pull the #1 plug and place the tip of your finger over the plug hole and rotate the engine until you feel COMPRESSION build as the number one cylinder, piston starts its compression stroke as the mark on the damper gets close to the timing tab, then remove your finger and continue turning the engine until the timing line on the damper aligns with the timing tab (0) TDC
once that's done the engine should no rotate any more until the distributor is seated correctly.
once that's lined up you drop the distributor into the engine so the rotor on the distributor points at the #1 cylinder when it seats and you install and lightly tighten the clamp and connect the wires, connect the timing light and set the timing at about 6-8 degrees BTDC at idle as a start point., if the distributor won,t fully seat the oil pump drive shaft needs to be turned a few degrees with a long large flat blade screw driver and re-try seating it while, it might take several tries until it lines up, it will seat into the distributor base gear once the oil pump drive aligns with the oil pump slot in the distributor gear base
http://forum.grumpysperformance.com/viewtopic.php?f=50&t=54
http://forum.grumpysperformance.com/viewtopic.php?f=44&t=464
http://forum.grumpysperformance.com/viewtopic.php?f=70&t=1411