droppping the distrib back in correctly after a cam swap



droppping the distrib back in correctly after a cam swap

Postby grumpyvette » September 16th, 2008, 10:08 pm

THE cam gear rotates exactly once for each two times the crank rotates,the cam gear lines up at the 12 oclock crank and 6 oclock cam gear orientation when the #6 cylinders on the compression stroke, rotate the engine one complete revolution and the cranks again at 12 oclock but the cam gears index mark is now at 12 oclock, 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 distrib back in, the distrib won,t fully seat unless the oil pump drive shaft seats up into the distib gear, as you remove the distrib 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 youll learn to gauge the amount the rotor rotates as it seats into the cam gear.

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The CLOYES true roller style is vastly superior to the factory link belt design

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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 TIMEING MARKS YOU MUST ROTATE THE CRANK 360 DEGRESS 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 oclock 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
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http://boxwrench.net/specs/chevy_sb.htm
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look here


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drop the distrib in with the rotor pointing at the #1 cylinder, and YEAH! it physically possiable 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 thats 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 dirrection untill 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 dirrect alignment between the distrib and the number 1 cylinder on the engine, remember the distributor and cam gears are heilical 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 thats done re-install the distrib 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
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
grumpyvette

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