Because I have a 1975 250 in my 1965 C10, I have both the 1963 & 1974-76 shop manuals. I think it interesting that they contain a different method for adjusting valves.
The 1963 manual says to adjust both valves when cylinders are at top of compression stroke. The 1974-76 manual says to adjust both valves of Nos. 1 and 6 like that, but the others one at a time as shown on attached.
I was just wondering why the change? In the end the results are the same.
One method you put the desired cylinder at TDC and adjust intake and exhaust on that cylinder, the other method you put #1 at TDC and adjust the valves specified because those lifters are on the base circle of the cam.
The are the same as you said. It's probably quicker to do it in batches instead of one cyl at a time, perhaps that's part of the change? Time is money!
There's a very accurate method of assuring all the cam lobes are on the base circle of the cam when the adjustment is made, but I've wasted a few billion keystrokes over the past 20-something years explaining it, and nobody is willing to try it. Search "companion cylinder valve adjustment" in the site archives, and you'll probably find it. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
Don't consider the billions of keystrokes wasted. I have actually saved your explanation in my reference folder. Critical info and I for one appreciate you sharing it.
I have adjusted the valves on my ‘59 235 with hydraulic lifters several different ways, from starting at #1 (TDC) them rotating thru the firing order and adjusting each cylinder individually, to the rocking method and finally to starting at #1, adjusting valves 1,2,3,5,7,9 then rotating 360 degrees and adjusting 4,6,8,10,11 and 12. I found the last method for me to be the least confusing and quickest by far. JMHO
Phil Moderator, The Engine Shop, Interiors and Project Journals
1952 Chevrolet 3100, Three on the Tree, 4:11 torque tube Updated to: ‘59 235 w/hydraulic lifters, 12v w/alternator, HEI, PCV and Power front Disc Brakes Project Journals Stovebolt Gallery Forum
I have done them a couple of ways with the engine off. But sometimes, every once in a while, doing them with the motor off just will not work. Lifter bleeds down too fast and you end up over tightening them, or for whatever reason. It happens sometimes.
So it has to be over 40 years ago now, a really good mechanic showed me how to adjust them with the motor running. So if you are adjusting hydraulic lifter valves and for whatever reason the motor is still running badly or still tapping, get the motor running, turn the idle down until the motor is just about stalling, like a tractor, lol, flop a welders glove on the rockers so you don't burn your arm or bump the moving parts, wear some mechanic's gloves, use a wrench and a screw driver, loosen the adjuster until it taps, then tighten 1/4 turn at a time until it stops tapping, then tighten 1/2 more. It takes a little bit of practice to get use to the wrench and screwdriver moving up and down, but once you get in the groove, you are good to go.
I have tried the EOIC method that Competition Cams recommends for any 4 cycle engine. You would have to look it up, but basically you set the exhaust valve when the intake is just opening, and the exhaust when the intake is just closing. Or something like that. It works perfectly though.
