The 1947 - Present Chevrolet & GMC Truck Message Board Network - View Single Post - How can I turn the crank and cam so the timing marks line up right?

**jocko** · 07-14-2018, 05:48 PM

as op mentioned, it's been rotated 180 (with the chain on after setting it up dot-to-dot to set valve timing) so he can now drop the distributor in and set approx initial ignition timing. 4-stroke engine, 1 and 6 are TDC twice in one revolution of the cam - picture shows TDC for 1 and 6, just prior to #1 power stroke, i.e. ignition.

as for finding TDC with a dial indicator, isn't too awful necessary - can be done with a dial indicator or just a cam degree wheel/piston stop combo. GM didn't do it when this rolled down the line, no need for you to either, unless you're goin racin. If you were running high compression pistons/high lift cam combo, you may want to go thru the whole enchilada and find true TDC and verify cam specs with the degree wheel - and check for valve to piston clearance. Just not necessary w/stock stuff though.

07-14-2018, 05:48 PM	#18
jocko Senior Member Join Date: Oct 2009 Location: Godley, TX Posts: 17,934	Re: How can I turn the crank and cam so the timing marks line up right? as op mentioned, it's been rotated 180 (with the chain on after setting it up dot-to-dot to set valve timing) so he can now drop the distributor in and set approx initial ignition timing. 4-stroke engine, 1 and 6 are TDC twice in one revolution of the cam - picture shows TDC for 1 and 6, just prior to #1 power stroke, i.e. ignition. as for finding TDC with a dial indicator, isn't too awful necessary - can be done with a dial indicator or just a cam degree wheel/piston stop combo. GM didn't do it when this rolled down the line, no need for you to either, unless you're goin racin. If you were running high compression pistons/high lift cam combo, you may want to go thru the whole enchilada and find true TDC and verify cam specs with the degree wheel - and check for valve to piston clearance. Just not necessary w/stock stuff though. Last edited by jocko; 07-14-2018 at 05:53 PM.