Stovebolt.com Forums The Shop Area The Engine Shop valve adjustment (baby steps)

Running valve adjustments are for people who don't know any better, or don't care about doing quality work.
Jerry

On later model engines with individual rockers, I do the prelim adj;s with engine off and a feeler gauge. I then start it up, warm it up then work the tappers out by sound, feel and smoothness. Both solid and hydraulic.Crank them down until the engine misses then back off until it smooths and doesn't tap.

On common rail rockers I haven't mastered the running technique so it's engine off and feeler gauge. Both my 216 and 235 don't expand much from cold to hot so cold I add only 0.002" to the factory spec., and readjust when warmed up (if needed, i.e. noisey valves).
Ironically, this Magic Hands video at the 15:05 time mark shows the engines getting their valves adjusted via the "running" method.

My 216 was so noisey I couldn't tell if it had internal problems or not. I then pulled the rockers and ground them smooth, taking care to maintain the tip radius, reinstalled and re adjusted, talk about a world of difference, the engine actually "sang" LOL. There were some grooves worn in the tips that had to have been at the least 0.004" deep....

FIRST-TIME TUNEUP COMPLETE!

I adjusted the valve clearance on a COLD engine by adding 0.005 to the recommended clearances (Volfandt, interesting that you've found 0.002 might be better on a 216/235. Maybe for extra credit I'll look at the tips of the rockers). I'll readjust valve clearance after I can take it for a spin and warm it up.

I have now set the ignition timing, adjusted valve clearance, and installed new spark plugs (and adjusted idle speed and mixture, with the aid of the tachometer built into my new timing light). She sounds really good, although I maybe should refer to the truck as a "he", because the new glass-pack muffler has revealed some cajones in the old boy!

I wish I had made an observation of running smoothness after each tuneup operation, but for various reasons, mostly impatience, I did not. As a purely academic exercise, I'm going to assign the following percentages of "contribution to better running":

New spark plugs - 60% of the improvement. The old ones were highly fouled. And because the windshield wiper vacuum hose had been open to atmosphere for about 5 years, I gather that I had too much fuel to the plugs.
Set ignition timing - 30% of the improvement. Before the operation, the octane selector had been set to 8 degrees retarded, and the BB was about 1 inch to the left of the pointer. I set the octane selector to 0 and set the timing.
Valve clearance adjustment - 10% of the improvement. On this cold engine, most of the exhaust valves were fine without adjustment, though a couple had to be loosened. and about half of the intake valves were too tight. None was too loose (needed to be tightened).

The above is just a hunch. I'd be interested in ya'lls comments.

“Actually what I learned was that it was a great way to find out that my rocker arm tips were badly grooved. They chewed up the feeler gauge right quick.”

Carl,

This discussion reminds me of an amusing incident that occurred when I was putting together the engine for my ’36 pickup in the early 1970s. I was able to find everything NOS for a complete head and valve train except the exhaust valves. Being out of options I decided to inquire at the Chevy dealer.

So I went to the dealer parts department and asked the counter man about the availability of 1935-40 Chevy exhaust valves. Typical of the know-it-alls of this world he let out a big guffaw at me even asking about such an obsolete (in his vast knowledge) part. Then he rounded up some of the other parts guys so they could share in his glee. When they were all done enjoying my foolish inquiry I said “Now that you’ve had your fun would you please look up my part?”

It suddenly got real quiet as Mr. Know It All found the part I was looking for, PN 838717, in his then-current parts book. Apparently GM discovered that there was sufficient demand to put those valves back into production. I placed the order and a few days later the valves showed up in a freshly minted GM box. Another example of the value of ignoring the "experts" and doing a little independent inquiry.

Because all these parts were NOS when I started there was no problem with feeler gauges being marred at the valve stem-rocker arm interface.

My '36 engine idles down to such a low RPM that it's super easy to feel the gap with a feeler gauge and get it just right.

Easiest way is to buy the special tool.

The parts guy should have known what virtually everyone with 3 brain cells to rub together here at Stovebolt knows- - - - -the exhaust valves are identical to the ones in most small block V8's. Only anal-retentive purists care about OEM part numbers.
Jerry