The I6 170 in 64.5 had adjustable valves, requiring a feeler gauge to set the valve lash. I presume you are talking about adjusting the preload on the hydraulic lifters. The symptoms you describe are not "normal". If a valve is adjusted "too loose" you get the tappet noise, and if too tight, the lifter could collapse , thus not actuating the valve correctly. 1/8th of a turn or even 1/4 is generally not enough to make a major difference. On my mercedes diesel, where adjusting the valves is how you tune the engine, 1/4 turn does make a difference, but not to the extent of causing the engine to sputter, and that is a 4 cylinder engine.

A turn of 1/8th to 1/4 should not have a dramatic effect, such as stalling the engine, particularly if these are the exhaust valves. For example, if you pulled the spark plug wires from those two cylinders, the engine should run, but run roughly. I think you have a combination of things happening.

First, at 100 miles on a rebuild, it is likely that your rings have not yet seated. Thus, the compression would be down in varying amounts from cylinder to cylinder. Running with a lot of blow by at the rings would make the engine more susceptible to stalling.


Second, were the lifter's replaced? If you are using the original 40 year old lifters, it is possible that they are not pumping up with oil or otherwise bad. Cam replaced? If not, maybe a cam lobe has been wiped. What type of head work was done? Valve job? new springs, seals, valve guides, valve seats? retainers? push rods? Did you check to learn whether the push rods on the offending valves are bent? ARe the retainers properly installed on the valve stems?

Normally, the first thing I would suggest is to run a compression check, but with only 100 miles, it might not indicate whether there is a problem, other than the rings not seating. Wouldn't hurt to check the compression anyway and see if these two cylinders are lower than the others.

Got me baffled here. You've got a problem beyond adjusting the preload. Don't know what it could be.

 

I have heard that some of the early I6 engines had individually adjustable hydraulic rockers, but I've never seen one of them. My 65 200 is the same as the manual describes, which is, there is NO adjustment to individual rockers. The entire shaft bolts down solidy, and the only way to adjust lifter preload is by installing a different length pushrod. I put mine together in 1978, and have had no problems with them.

Here's what the manual says (somewhat abbreviated):
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1. Rotate crank to TDC compression stroke where by using the procedure in step 3, you can check #1I, #1E, #2I, #3E, #4I, #5E.

2. Rotate crank 360° (#6 @TEC), where by using the procedure in step #3, you can check #2E, #3I, #4E, #5I, #6I, #6E.

3. Using tool 6513-k, apply pressure to the push rod end of the rocker arm to slowly bleed down the valve lifter until the plunger is completely bottomed. Hold the lifter in this position, and check the available clearance between the rocker arm and the valve stem tip with the feeler gauge. If the clearance is less than 0.066 inch, install an undersize push rod. If the clearance is greater than 0.216 inch, install an oversize rod. [/quote]

So, I'd check the clearance on the offending part compared to some of the others. It could also simply be a bent or worn pushrod, or a defective rocker! I'm still not sure what you're talking about when you say you readjusted them. I'll leave it to you to figure out how to sidestep buying the tool they referenced, but it just torques the rocker over to put lots of pressure on the rocker end to compress the lifter. Nothing a good imagination can't overcome! :lol: Good Luck!