Unique method for rocket arm adjustment?

I have read many articles and post about how to adjust the rocker-arms on my 235 L6. I have tried them all and not happy with any of the results. So, I sort of come up with my own method and it seems to work the best. I’m curious if anyone has heard of this method and are there any major potential issues that might arise?

Method:

1. Adjust the rocker arm clearance “cold” to .016 exhaust valves, .006 intake valves.
2. Readjust “at temp” to same specs.

Note: At this point I noticed it was still ticking and ran a little rough. If took my hand, and held it at the exhaust pipe I could feel and hear some slight coughing.

The final adjustment:

Using a vacuum gauge of the intake manifold, and while the engine is at idle 450 RPM (and at temp), I would loosen each rocker adjustment, one at a time, just enough so a “clicking” noise can be heard. Then tighten “just enough” to eliminate the clicking noise while maintaining the maximum level of vacuum.

It seems to work great! The noise is gone and runs smooth! I noticed, if I tightened any even “one-iota” to much, the engine would run rough.

After final adjustment it feels like a constant smooth breath of air out the exhaust. No coughing! My vacuum gauge and RPM gauge are steady as a rock!

Is this a known method? Anyone ever heard of it? Anyone ever used it?

 

I've never read anything about doing it that way but if it works for you good enough. You may have stumbled on some late 40's early 50's tune up specialist's secret method of getting the stovebolts of that era to purr.

 

Your clearances are backwards. .006 on the exhaust will burn valves ...

 

Exhaust is always looser than intake.

 

Oooops! typo! Thanks 302 GMC I will fix the post!

Since the final adjustment is done with a vacuum gauge, I wonder what the final gaps are? I wonder if it is consistent or all over the place?

I think I will record them and post them here for the hell of it.

 

Do something like that, on my old pushrod engines. i picked it up from Royal Enfield and Triumph motorcycles. The R.E. you adjust the clearance until the pushrod just turns freely. On the Triumph you tighten while moving the rocker back and forth until the clicking sound disappears. I always adjust cars with running engine.

 

I always just back em off till they clacked then slowly tighten them till they stopped making noise.Never had a problem.
When setting up the engine I use the "Valve overlap" method.Ya cut the firing order in half( for a GM V-8 ) ya take ..1-8-4-3-6-5-7-2 & write them down over each other so...
1 8 4 3
6 5 7 2..... Then set # 1 on valve overlap & snug #6, # 8 valve overlap & snug #5,etc.That will get ya started Then adjust them normally.
JimV

 

I had one early chev 6 like that here for some work, and it was way too fussy on the valve adjustments to try to quiet it down. I did doing it by ear to get the clacking gone, but some were what I thought were too tight to last very long..so..


I put some exc used rockers and shafts on it, and then I could do the settings by the book.

 

F&J I think you make an excellent point if it doesn’t tune to specs without some type of witchcraft, chances are something is wrong or worn-out. I did notice some of my push-rods are not as straight as I would like to see, and it make sense that the hardest ones for me to adjust, are the more bent ones. There is a variation of about 1/32” (I think), as you can see them spin “out-of-round” if you look close.

I ordered a set of rods today.

I will say, the engine does purr like a kitten, however being on a stand with no load may mean something also. Like you said it might not last. I’m afraid, first it will be the push-rods, then adjusters, then lifters, then rocker assembly, and dare I say cam?

This '54 235 is an (extra) motor from my restoration project, I don’t want to spend a ton of money. (How many times have I said that...geeesh!)

 

I have used the vacuum gauge method on a SBF while setting valves and agree it is a great method and really opens your eyes as to how a small adjustment to even one of the 16 valves, can really make a huge difference on how smooth the engine idles.

 

Valve overlap? I wonder if it will work with a straight-six?

(I adjust each cylinder in the order of firing? I don’t know if it is important, I just learned to do it from one of methods I read about. So I do it.... Seems like a plan.)

Overlap on a straight-six would look some thing like this?

153 ...........153
624...then? 624 again for the next 3 cylinders?

Or how about?
153624
624153?

Or?
624153
153624?

The numbers stagger me! (Curly)

 

I use a similar procedure on my 289 ford . I carved the top off of a valve cover to keep the oil mess to a minimum

 

I've used the vacuum gauge method setting hydraulics, never tried it with solids. I have also listened at the tailpipe while someone did the adjusting. Both methods also work great on carb adjustments.

Bob

 

Go back over them all with a feeler gage and see what you adjusted them to. Don't readjust them, just measure them.

Let us know.

Usually replacing the worn out parts will help keep the noise down.

 

Well I tried to measure the gap when cold and hot after adjusting for best performance and noise. It appears to "click" at times, then not?

It is not consistent when I measure, and re-measure again. Come to find out, some of the push-rods are so bent, it depends where it lands. If I manually spin the push-rod in the "valve closed" position, the measurement will change up to .002-.003 in some cases.

My new set of push-rods are due to come in today's mail. I will install them and see if things get better. The new one's DO NOT have a hole down the center? I'm told by the seller that it is ok? You can use hydraulic push-rods in a solid get-up but not the other way around?

Anyone know about this?

Thanks!

 

I believe that solid and hydraulic push rods are different lengths for a 235

 

I have heard of fellas using a vacumm gauge to adjust about everything on the engine. I use them to trim the carb or carbs myself, as well as a diagnostic tool.

Unless you engine is new and tight you will have to compensate for valve train wear. In essence what you are doing is compensating for the wear. You have managed to teach yourself a vital part of the tunning process. A good tunner doesnot take a book and do exactly what it says, the book is just a guidline for you. A tunner makes it run the best it can in a given situation, in your case that would no doubt be valve train wear.

 

I find this to be interesting.

I have an OT 351M engine in my early Bronco that is supposed to have a non-adjustable valve train, you just tighten each rocker down to the inch pounds and it is done.

However, the engine went from running well to running poorly over a period of time and with the help of an old timer, we tracked it down to just ONE rocker arm that needed a slight shim under it. The standard shims you could buy through Moroso, etc were way too huge. We had to custom make a very thin .007 shim to eliminate the problem.

I am sure this is an indication of something else that is worn, but the single shim has made all the difference. Runs great now. I would have never have guessed that this very minor difference could make the change from un-driveable, to running and driving great.

 

That's great to hear, and yes I have learned a lot about how important rocker-arm adjustment can be. In my newly rebuilt 216 (I replaced the 235 with the 216 in my '48 with for period correct reasons) the noise is "nil" and it runs sweet.

Rusty they claim the length is the same on these rods and that is why they selected them for me. But yes, I suspect it is a critical to have the right length.

Red, cool I didn't know they had shims for that? How do the shims keep from falling out? Just curious?

 

That is the only way to adjust them unless you opt for an adjustable rocker arm kit. Making your own shims is a very old practice. I keep various thickneses of shim stock in the shop for just that reason. A good tool box will actually have cutters in it for making gaskets and cutting shims.

Valve trains wear, that is why rocker arms are adjustable as a rule. The cam lobes will get some wear in time as well as the pocket in the rocker arm and the push rods, the contack that the rocker makes on its pivot. Hydraulic lifters get weak even solid rollers get worn. All the oil does is slow the process, it does not stop it for happening.

Something that really makes me happy is to see when a newer to the game mechanic begins to figure this stuff out. I always like to hear hay I figured this out instead of I don't know what to do. They used to call us grease monkeys and it was a put down like we weren't as good as anyone else, but the truth is that you have to think all the time if you are going to get it right.

I keep a card in my tool box that my grabdad left stuck in my carburater when I was a kid. All it says is "THIMK"(sic)

 

The rockers are pedestal mount meaning there is a rocker and then also a squared off pedestal and the bolt goes through both into the head. The pedestal fits into sort of a keyed catch area for location.

You just cut a piece of shim to length, punch a hole through it for the bolt to pass through and then It goes in between the rocker pedestal and the head with the bolt sandwiching it in place.

It effectively raises the rocker slightly.

 

Your correct it works exactly the same,I just didn't know any 6 cyl. firing orders!!Never owned one!!lol
JimV

 

I installed the replacement pushrods last evening and wow! So much better behaved! But not perfect. After bring up to temp, adjusting by vacuum, I recorded the gaps:

1 .016 Exhaust .005 intake
2 .015 .005
3 .016 .006
4 .015 .006
5 .017 .005
6 .016 .005

Cylinder 3 exhaust adjustment, requires a bit of a “knock” in order to achieve the highest vacuum? If I adjust it as quiet as the others, It causes an otherwise nonexistent mild cough...I found a happy compromise.

Just happen to have a copy of Popular Mechanics Nov 1948. Talks about wedging a screwdriver in the valve spring to increase tension to eliminate a knock, then shim to tighten spring. Screwdriver on Cyl 3 exhaust spring made a difference. Let’s see what happens before I pass out cigars. I will post the result.

Posted some photos and videos. One photo shows the difference in the quality of the new push rods,another how I use a very large 12” screwdriver and a 5/8” combo wrench. In a video I show how I take the oil temperature. I use a lab thermometer with the tip in the stream of oil coming from the valve train over-flow pipe. (I don’t adjust anything unless I see 140 deg F first, requires frequent reheating.) You can see a couple old push-rods spinning out of round.Another video shows the adjusted result. (Don’t know if you can hear what it sounds like?) Also shown a rigged up a piece of cardboard to amplify the vibrations coming out the exhaust. Luckily with only 2 steps be outside and feel it with my hand. These coughs may or may not show upon the vacuum gauge.]

I appreciate the comment about giving it a go, rather than ust ask how to do it. However, You obviously haven’t read some of my first posts to the HAMB….lol. I will say, I have made great progress as an amateur mechanic since. Yes, Oil seems to find its way into the air especially at warming RPM’s. It appears to be non-existent at first. The cut-out on a spare-valve-cover is a great idea. I wish I had an extra. Great explanation for shimming, a good thing to know! As far as order of adjustment, this time I use the firing order, and always adjust the exhaust valve first.

I am including some other data (for those interested)

Cold Crank Compression
1. 130
2. 130
3. 130
4. 125
5. 130
6. 120

RPM @ idle 450 / Vacuum @ idle 18.25 / Max Vacuum ~20 Hg @ RPM / Oil Pressure 45 lbs @ idle 50+ at speed / Regulator voltage 7.2 Volts @ idle / Ignition Timing dead on flywheel ball @ idle / Ignition point gap .018 / Spark plug gap .035 / Oil 10W-40 detergent with 1/2 pint zinc additive and a few tbls of mystery oil.

I can’t thank all of you enough! The HAMB is the balls!

 

I wonder about the significance of getting perfect smooth idle at 450 rpm.

What does the vacuum gauge reveal at fast idle ? Do fine adjustments of .001 still register?

Can you feel, hear or measure that difference under load and driving on the road ?


I wouldn't use Marvel Mystery Oil as a permanent oil additive, although that small amount probably doesn't hurt.

 

Great questions!

Would it be fair to say, that any vibrations and coughing is carried along at higher RPM’s regardless? As your RPM’s increase so does the frequency. I can raise the Idle speed to 500? But I can’t adjust them at that speed.

I’m getting a slight increase in vacuum as I increase idle, The vacuum advance smoothly. Max vacuum @ high RPM’s is ~20. If I slide the .006 gauge in any exhaust the motor begins to stall. I’m not sure what you mean by still register .001“?

You got me there. Yeh...no load. I’m just guessing, but I would expect to adjust them one more time after running under load. If it doesn’t blow up, after all that, I’ll probably have a good running 235? I just need something to put it in, or perhaps sell it as a turn key?

A good post might be"How many blown engines does it take to learn to be a good mechanic?"

It has done its job. I won't even use it next time I change the oil.

 

I remember one of the old gas station mechanics in my hometown had a spring-loaded screwdriver that he used to adjust valves on running engines. The blade would move up and down with the rocker, and the handle stayed still in his hand. The blade end was recessed into a collar that fit around the adjuster screw to keep it from slipping off.

 

It is interesting you mentioned that, and while it was running too! I was wondering how I was going to compress the spring, and hold the valve up at the same time to slide a shim with out scratching, breaking or bending something? I hope I don’t have to buy a tool?

 

All of the old Motors repair manuals that I have say to make the valve adjustments a little wider gap for an engine that is regularly driven harder and at higher speeds. My grandfather was a mechanic in the 40's,50's and 60's and his standard valve setting on a 235 Chevy with non-hydraulic lifters was .016 on exhaust and .008 on intake. He told me you can tighten the valves to the point that they make almost no noise, but then under a load it will run hot and have no power. I never tried the vacuum gauge method, but I did tighten my valves without a feeler gauge once until they made almost no noise at all. The engine ran super smooth under no load. As soon as I drove the 54 car around the block, it heated up and had no power. I loosened them off to the settings he said and big power jump.
One other valve issue that can make setting your valves a nightmare- make sure that the rocker arm shafts are not worn. Often the bearing surface of the rocker arms wears out, eggs the rocker arm and cuts into the shaft. It will big time reduce power and make setting the valves next to impossible.
I always set them with the engine running and with a screw driver and box end wrench. Its a pain in the butt, but it works.

 

Sucking a valve would really suck! I think I will take your advise on riding a a bit noisy at first, then quiet to taste. I do know in the 216, I had professionally rebuilt (Now in the car), whispers. Granted all new components and I haven’t adjusted anything to screwed it up yet. Still great point!

I would love to know more about this old mile-o-meter? What does it do? Measure miles by vacuum? Miles vs. average vacuum? Perhaps provide acceleration feedback for fuel economy?

I still stand by the thought that if all components were up to spec, and not worn, a warm engine off adjustment with feeler gauges, would be all one needs to do. This engine is pretty good now with new rods. The new gap data appears to be within tolerance.

Just a little glitch to fix (I hope) and I will know it is capable of quiet and the motor is still adjustable to shop manual specs. I wouldn't want to sell or own anything else.

Nice! I notice my measurements are reasonably close to grandpa's and shop-manual settings. I will start by loosening each exhaust .002" and open intakes a bit more. If the people in the car next to me are not ducking for fear of shrapnel, It should be a good place to start!

Thanks! Far better to be safe than sorry!

 

The rocker adjustment specs for the big trucks with 261 are .018 for the exhaust, so the valves stay cool.

I have .008 Intake and .014 Exhaust on my 261 with an RV cam and it's fine around 3000 rpm on the freeway.

I wouldn't worry if the exhaust sound at 450 rpm is not smooth or even and wouldn't tune for that, but instead to the recommended specs for a car engine and its cam - 216/235/261

If it runs even and smooth at fast idle (around 700 rpm) and higher and especially under load, you are good.