Thread: 12 O'clock and 12 O'clock

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At dot to dot on the timing set, I know number 1 is on TDC and my timing plate needs to reflect TDC at this point. However, am I correct in stating this: When both of my dots are at 12 O'clock and I drop distributor in, that distributor should be pointed at number 1 when I drop it in, correct? At 12 and 12, number 1 is set to fire, correct? It's been two years since we built an engine and now that we're working on this 355 (and soon a 383), I feel the need to refresh or confirm my memory. Thanks!

I think yours should look more like this.

I appreciate that 34_40. I know in this picture, my TDC on timing plate and balancer should be in alignment. My question is in that picture, #6 would be on the compression stroke, right? If I were to rotate crank one more time so both dots are at 12, that would put #1 on compression so that when I drop distr in, it will be pointing at #1, correct? Thanks,

Originally Posted by Rdobbs1977

I appreciate that 34_40. I know in this picture, my TDC on timing plate and balancer should be in alignment. My question is in that picture, #6 would be on the compression stroke, right? If I were to rotate crank one more time so both dots are at 12, that would put #1 on compression so that when I drop distr in, it will be pointing at #1, correct? Thanks,

Correct. When you put the motor together and align the crank sprocket at noon and the cam sprocket at 6PM, the number 1 piston is at top dead center, but it is on the overlap, not ignition stroke. #6 will be at TDC also, because it is the companion cylinder to #1 and will be on the compression stroke and ready to fire. If you turn the crank one turn, 360 degrees, and put both sprockets at noon, #1 will be at TDC on compression and #6 will be at TDC on overlap. I've often wondered why the Chevy engineers did it that way. I do know that it is prone to error to try and align the cam sprocket at noon and the crank sprocket at noon. It's much simpler to align the cam at 6 and crank at noon and then turn the crank one turn to get the motor ready to drop the distributor in and begin with #1. Put the rotor at 5:30, run #1 and then run the rest of the wires clockwise around the cap.

somewhere back when v8s with cam/oilpump driven dist-----used 2 identical length lifters(back then called tappets) in the overlap cylinder(gm/mopar #6) with a straight edge across them would indicate split overlap------this was in a historic period of time before dual pattern camshafts----so this is where the cam crank was set up in the days before degree wheels and dial indicators