Valve adjustment

Welcome to 2CarPros.

It sounds like the additional half turn is not allowing the valves to seat fully. Can you explain the reason why for the half turn?

Let me know.

Joe

Different feller,

This puppy has solid lifters or tappets (hydraulic lifters)?

The Medic

I'm not really up on this adjusting situation.

Here's where I'm not following:

The tappet is designed to take up the slack or wear that occurs on the
cam
the tappet bottom
the tappet center (top)
both ends of the push rods
the center pivot of the rocker arms
either end of rockers
the valve stem

and

Kind of the reverse of the wear situation, the little bit that the valve's face sucks back into it's hole as it slaps the seat.

So, if the tappet's center is not bottomed out in the tappet's body at the bottom of it's stroke, I see no way that the valve will remain or be held open.

Just for giggles with Jeep CJ's six and eight cylinders I start with dry tappets (the centers will be springy top to bottom). I select my push rod length using a dial indicator and allowing/ leaving 100 thousandths in the bottom end of the tappet when each tappet is down.

When I fire it up, the tappets fill with oil and act like mini-hydraulic jacks when they push up and open the valves. When they drop back down into the oil galley they open up and re-zero.

They do this every time they go up and down.

Re-zeroing means my Free 100 thousandths remains as a buffer in the bottom, what's left above that point is used to make up for any wear.

To maybe make it clearer, and hypothetically, in a year's time my buffer my grow to 105 thousandths as wear in the system is replenished.

Of course, I can't check any of this unless the oil is out of the lifter.

This is why I do the homework in the beginning.

If you are doing your adjusting with the tappets full of oil, how do you know when they are bottomed or better still, how much buffer you have.

If you are bottoming the tappet's center out in the body, it won't take much to make your valve stay cracked open instead of fully seating.

The Medic

Welcome back:

Are the lifters you used solid or hydraulic? If they are solid, you are opening the valves for sure. If they are hydraulic, chances are the same because they will pump up with the engine running. Also, pre-load is the distance the plunger inside the lifter is depressed from the fully extended position. If you purchased solid lifters, there is no plunger to absorb the 1/2 extra turn you add. That would open the valve a bit. Valve lash is the gap between the rocker arm and the very tip of the valve stem. That is where, using a feeler gauge, we would set the valves. From that point, if there was a tick, we would slowly tighten the clearance until the tick was gone.

Do this. Make sure the valve being adjusted is fully closed. Then, tighten the rocker arm down until it makes contact with the valve stem and there is no play between the lifter, push-rod, and valve. See if that works. I used to use a.010" feeler gauge between the two to initially set them because if there wasn't any clearance, when the engine would get hot and the steel would expand, it could cause a rough idle or miss. Once the engine would start, then I would listen for noise indicating an issue.

If it runs bad the way you originally adjusted them, they are too tight.

I like what you did as far as the 1/4 turn. When we set valves years ago, literally, a feeler gauge was used. Let me know what happens.

I hope this helps and isn't making things confusing.

Take care,
Joe

Maybe I'm not up on these super high tech things.

But if I were to "preload" a tappet on my Jeep, the looks like I would be taking/ stealing part of my 100 thousandths buffer. In turn, the tappet would re-adjust to the new push rod depth and all remain the same--unless the preload bottomed out the center of the tappet.

This may sound dumb.

If we are (for some reason) shoving the tappet's center to bottom out in the body, whereas there is no buffer left at all.

Why are we not just using solid lifters in the holes instead of those pesky self adjusting tappets that normally and automatically take the slack/ slop out of the system (so you don't periodically have to manually adjust them with two wrenches, as I have to do with my '46 Willys Jeep). Pic down yonder!

If I were "winging" this with oil filled tappets (centers cannot be pushed down due to being in the "hydraulic jack mode") and having up and down adjustable rocker arms.

I'd bring each "filled" tappets to the top one at a time.

I'd measure (dial caliper) or guess how many threads on the rocker are studs would be close to 100 thousandths.

I'd screw the rocker down until it touched the push rod and valve stem equally.

This is where the 100 thousandths comes in!

Screw the rocker down an additional, let's guess 5 threads = 100 thou.

Think about this now.

That extra 5 threads opened up the valve because the tappet could not compress even though there is plenty of buffer below the fully extended tappet. Each valve is somewhat opened as we have things now!

When we crank the engine and oil pressure builds up and those pesky tappets drop into the oil galley.

Wow!

They open up and re-adjust for zero slop. That "cracked open" valve is now sitting on it's seat and the other goodies are tight against each other so there is no lost motion or racket! The extra 5 threads of "push" is now absorbed inside the tappet.

When they lift back up the next time, that extra 100 thousandths has been absorbed into the "buffer zone" in the tappets center portion that travels inside the body.

What we have now are "zeroed" tappets that can compensate for 100 thousandths of wear before they need replacing or the valve system becomes floppified/ ticking/ rattling.

Gosh! I know some junk!

Anybody else got better ideas or explanations?

The Medic

Think of the tappet (hydraulic lifter) as 5 gallon bucket with a 2 gallon bucket inside. The 2 gallon bucket is sitting on "bubble wrap".

If these are new (un-oiled/ engine not run) tappets and you tighten the rockers until there is no "give". Basically you have stepped into the 2 gallon bucket and shoved it to the bottom of the 5 gallon bucket, the bubble wrap is busted.

At this point you might say that you have a solid lifter per it's situation.

Right now you could say you are at rock bottom zero.

If you tighten the rocker any more, the valve will begin to open (as it should be 100% closed with the tappet "down") Open valves while it's running just ain't good at all!

Now that it has run, I'd get them (tappets) all down (one at a time) and adjust them one at a time.

Back the rockers out until the rocker and push rods are gapped apart. Run them back together until they just touch.

What we have now is "zero" with the tappet unable to adjust out any more to compensate for wear. (this is not what we want).

Tappets are not all the same as far as adjustments.

If you can/ even go to a parts store and measure the amount a plunger can push inward on a "Brand New" tappet exactly like yours.

This is a "make believe" number!

180 thousandths- plunge

I would rotate each rocker nut the number of threads equal to (make believe, lets say 5 revs) (120 thousandths). This would be 2/3s of the travel available, leaving 1/3 of the plunge unused.

It doesn't matter if there is oil in them. With the tappet "down" and the rocker completely having been backed completely out, the tappet's plunger should be all of the way up, before you tightened the additional (make believe) 5 threads.

Now when it is run, oil pressure will adjust everything as it should.

You now will have 2/3 of whatever travel to automatically adjust the system.

This may help some with the carburetor.

https://www.2carpros.com/questions/jeep-cj7-1985-jeep-cj7-stalls-when-hot

In jumping to a new subject, the big guy's S.O.P is to create a new question to keep different repairs from intermingling (messes up somebody performing a search at this site).

Not getting upset by no means! Just start a new question should the subject change. You can ask for specific people if you wish or you can let one of the many experts here jump in there!

Continue on this thread with updates about the tappet situation.

The Medic