Thread: One Particular Question on Valve Lash

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Originally Posted by techinspector1

You can do it any of a several different ways, but I wrote this tutorial for the Crankshaft Coalition wiki and this is the way I do it. All who have tried it say it is the most accurate they have ever tried....And after all, we're not after quick and easy necessarily, but we are after accurate....
http://www.crankshaftcoalition.com/w...stment_SBC/BBC

What Vizard is referring to is companion cylinders. Looking at the firing order 1-8-4-3-6-5-7-2, you can see that when #1 is on compression stroke with the piston at top dead center, #6 will be on overlap stroke with the piston at top dead center. When #8 is on compression stroke with the piston at top dead center, #5 will be on overlap stroke with the piston at top dead center. When #4 is on compression stroke with the piston at top dead center, #7 will be on overlap stroke with the piston at top dead center. And when #3 is on compression stroke with the piston at top dead center, # 2 will be on overlap stroke with the piston at top dead center.

There are 720 degrees of crankshaft rotation for a complete 4-cycle burn to take place for any one cylinder, so each companion cylinder is 360 degrees apart from its companion.

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Man, I liked the method of pushing the rod up and down just until you cant. I was taught on the 'move it both ways with your fingers' but like the article said, unless you do this everyday it can be hard to know and have the 'touch feely down pat.' I reckon placing the tape on the balancer is for making sure you are pretty close to that 1/4 turn each time. Just for added accuracy, would I be correct in saying that when I'm coming up on the cylinder that will be firing, and I've done my 1/4 turn, both valves on that cylinder should be closed, right? Thanks,

Originally Posted by Rdobbs1977

Just for added accuracy, would I be correct in saying that when I'm coming up on the cylinder that will be firing, and I've done my 1/4 turn, both valves on that cylinder should be closed, right? Thanks,

Yep, both valves are closed. The last valve to be open was the intake valve and it closed some 130 crankshaft degrees ago, before top dead center. The next valve to open will be the exhaust valve, about 130 degrees of crankshaft rotation after top dead center for a hot street cam (230 @ 0.050").

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