Tuneup,
First I wanted to adjust the valves and took a drive to get it warmed up for that.
The method i use was shown to me a long time ago and is simple enough to remember, no need to look it up every time.
Keep in mind that a 4 cycle engine with an even number of cylinders will have one piston up on the exhaust stroke when another cylinder/piston is also up but at compression. This is handy because the piston nearing TDC exhaust will be closing the exhaust valve and with just a little more rotation of the crank to TDC will open the intake valve.
It is real easy to watch for an exhaust valve closing and right after an intake valve opens. When this happens another cylinder is at TDC (or nearly so) of the compression stroke where both valves are very much closed and those lifters are well seated on the base circle of the cam, perfect place to adjust those two valves.
Simple/short version of the method is just figuring out which 2 cylinders move together, both at the top at the same time.
Write down the firing order (often cast on the intake manifold) in two columns, half on the left and then start the second column on the right.
firing order for a Stovebolt is 153624:
1 6
5 2
3 4
So when the valves/rocker arms just wiggle one after the other on cylinder #6 I can adjust cylinder #1. Rotate the engine a little more and valves will do their thing on #2 and I adjust #5. This can all be done within 2 rotations of the crankshaft.
PICTURE I know by memory (from watching the engine turn over without head on) that the front and rear cylinders do the same thing, and the two center cylinders also do the same, which leaves # 2 and #5 doing their thing together, knowing that saves making the little chart.
The GMC service manual is vague on the valve lash. It suggest 0.012" intake and 0.020" exhaust at a starting point (cold after a rebuild?) and to look at a sticker on the valve cover for the values when warm. I don't have a sticker so went with 0.012" and 0.020" for now, better a little loose than too tight. They were all quite loose, they all needed adjusting.
Next points and timing,
Grigg
