What the @!*%$ is going on with my valves?

[robertsapp]

I had to replace my starter solenoid (cracked bakelite) on my 3GM30F, so since I had the starter off I decided to take a crack at adjusting my valves. They are absolutely driving me crazy! After putting each cylinder on TDC according to the flywheel mark and then setting the valves to .008, I rolled the engine around again to check everything, and it was all completeiy off. I'd set #1, then #2, then #3, then go around to #1 again to check them, and they'd be way off. I'm not talking just a tweak, I'm talking like a full turn of the tappet screw. Digging deeper into the shop manual says to do #1 first, then roll 240 degrees and do #3, and then another 240 degrees to do #2. OK, can't see why that makes any difference, but I did it that way, and dialed them all in just right. Then on the next go round to check, they'd all be way way off again. What the hell is going on? The only thing I can think of is something wrong with the cam or the head that's changing the settings on each revolution. Am I missing something?

 

[Ed Schenck]

The only possible explanation is that you are not coming back to the same point on the cam. It has been a long time, 50 years or more, since I worked on my Hemi powered '34 Plymouth. But one crank revolution for example does not get you back to your starting point. If I thought about it long enough I think I could figure it out. It should be in the book.

 

[kloudie1]

Ed is exactly correct..
Interesting.. Was it running OK before ya messed with it?? If so then probably a technique problem.. forgive me if I start a little to basically.. First, the cam turns at half crank speed, so it takes two revs to get it back to exactly where it was.. It is critical to be rotating in the correct direction (usually clockwise when looking aft at the front pulley). Please pull out the fuel cutoff to keep the injectors from working.. The engine may fire and hurt you if this is not done. Set the crankshaft on a Top Dead Center (TDC) mark which should be visible through the starter hole..or on teh front pulley or in teh hole to teh right of the transmission. Note the difference between this mark and injection timing marks.. use only the TDC mark. That should put #1 at TDC.. but it may be on Compression stroke, or it may be at the end of the exhaust stroke and beginning of the intake stroke.. If the latter, one or both valves will be tight.. If correct, both valves should have a little clearance Set the clearance when exactly on TDC of the compression stroke only.. Next in order is #3.. You have to roll the crank 240 degrees to get the cam to turn 120 degrees because it is turning at exactly half speed. The #3 valves should both be a little loose then .. set them then go on to #2 in order.. To check them, the cam has to be in exactly the same place so back to TDC #1 marker and see if it is on compression or end of exhaust stroke.. Get it onto compression and then check.. Ya might want to get a gear headed friend to watch the process and help if necessary this one time until you feel comfortable with the process.. Good luck !

 

[Charlie13958]

Kloudie is right, must be done on the compression stroke. I used to do my 56 Merc with the engine running, little messy, but no epa then and lots of room.

 

[Allan12210]

I just checked my service manual...Kloudie has the correct firing order....1,3,2. If you adjusted 1,2,3 that may be your problem.

 

[Ed Schenck]

I had forgotten that Charlie. Oil squirting everywhere while we tried to turn the screw and lock the nut while the tappets are bouncing you all over. Anyone doing that with their diesels?

 

[kloudie1]

Had to learn how to do that when I was 14 to take care of my new 1962 Honda 305 motorcycle! It was 65 miles to the nearest dealer; I learned from my grandfather and the strange english translation in the manual, how to maintain the little jewel of an engine myself. I always wanted a well made diesel to play with, and the Yanmar fits that bill !

 

[Bill Roosa]

Technique

Ditto the above about having the cylinder on the TDC of the beginning of the power/end of compression stroke and disabling the fuel delivery to prevent engine start. Since you can’t see the camshaft lobes you have to watch the valves move as you turn the engine. As you turn the crankshaft ½ turns (TDC to BDC and BDC to TDC) you will alternately see the TDC, intake valve move, BDC, nothing, TDC, nothing, BDC, the exhaust valve move and then it repeats. You want to be TDC between the two nothings. As far as I know the only other way to make sure you are on the TDC of compression/power is to look at the cam itself. Don’t think that is possible with a non-overhead cam engine though.
There is a bit of an art to adjusting them however. I find that loosening the both intake and exhaust valve tappet lock nuts and the tappets then, as you have an assistant hold the gage in place, wiggling the valve train as you tighten the tappet and then lock it down to work the best. Note that tightening the tappet with the gage in place so that there is less than 0" clearance is very easy to do. It takes a light touch. The wiggling of the valve train helps to bring out the "looseness." You want to tighten just till all clearance is gone and no more. Also hold the tappet while tightening the lock nut so the tappet does not turn and change the clearance. At the proper clearance the gage will just slide between the tappet and valve stem. If you angle the gage you will drive yourself crazy so make sure the assistant knows what is expected of them.
Also, the camshaft journals may be worn. I believe the 3GM30F does not have an overhead cam so checking the camshaft play requires some additional disassembly.

 

[kloudie1]

Yanmar specifies set cold so it should not be running.. I think the old Mercs specified HOT.. (and messy) .. Some folks still set hydraulic lifters this way.. and it is still quite a mess!
Yeah.. Bill you are right!.. I meant to add the part about how the lock nut will change the setting and how to keep the nut snug while setting and holding the adjuster screw while tightening the locknut.. and watching the position of the screw slot carefully.. Whew..
It was a real job on the 16 valve Honda CBR motor whose valves and adjusters are tiny..

 

[Bill Roosa]

setting hydraulic lifters

for the record
you can't adjust hydraulic lifters. That is the whole point of having them. They adjust the valve lash automagicaly as the engine runs. Which is why engines with hydraulic lifters don't have tappets that are adjustable.

 

[kloudie1]

Not exactly, Bill.. you can adjust the travel of their internal piston so that it is close to top .. that way the lifter won't pump up at high rpm as a normally adjusted one would.. Talking older Chebby V-8 motors..

 

[Allan12210]

Honda 305! Wow that brings back memories Claude. I remember the street version with the front fender that flipped up. I had a 350 a few years later. But talking about adjusting the tappets hot and with the engine running...that's how I had to do my Mustang II (wonderful car, LOL) with the 2.8 liter motor and solid lifters. I cut the top off a spare valve cover and used it so the oil wouldn't run all over the place. I had about 5 sets of feeler gauges with the .014 and .017 all hammered up. When the tappets started clacking I finally just set them cold about .002 loose and they were fine. After I rebuilt the engine I got a set of Rhodes anti pump up hydraulic lifters. They were nice...more bottom end power as the valves didn't open as far..but I digress.

 

[Jim Seamans]

What are you guys talking about??? 305 what?
I didn't get my first car until I was 20 and it was a '49 4 door Dodge, flat head six....Would hold 12 people and a keg of beer....

 

[kloudie1]

Laughing, Jim.. One of the original Honda motorcycles.sold in the US. I have some (‘66ish) college memories from a friend’s 1948 Dodge Business coupe.. Probably the same flathead 6.. It drove the car through a regular 3 speed but had a torque convertor in addition to a regular clutch. A strange thing .. but the trunk was huge and could hold a keg !

 

[Allan12210]

Robertsapp,

I should have re-read your post more carefully. I see you did do the adjustment in the right order. Sorry about that. One other thing then is if you have a dial indicater with a magnetic base, you can put that on the rocker (push rod side). Hold the rocker tight against the push rod and it should read a minimum value when the crank is at top dead center for that particular cylinder. The push rod will be all the way down and the valve would be completely closed. You can rock the crank back and forth and make sure that the indicator is minimum and there is lash between the valve and rocker. This could be the best way to really be sure that the valve is all the way closed when you set the gap. The only other thing I can think of is that these engines have a lot of hours on them and the base of the push rod that rides on the cam might have some uneven wear. If the push rod rotates (which it is supposed to) maybe it is in a different position when you rotate the engine back around to double check your measurements. I suppose you could check that too with the dial indicator by taking a measurment on the push rod side of the rocker then unloading it from the push rod and twirling the push rod a little, then load it again and see if you get the same value. If there is a difference, is it in the same range that you observed when rechecking your valve clearance?

Allan

 

[robertsapp]

Thank you everyone for the information. One thing I already see is that the service manual never mentioned that the cam rotates at half the rate of the crank, though now I'm like "duh" should have thought of that. The manual just says to put the cylinder at TDC by flywheel mark, it never mentions that you have a 50/50 chance of this being right. So basically what I was doing was chasing my tail, because maybe I'd catch the TDC on compression, maybe not, but whichever one it was, I'd set the valves, then rotate the crank 360 degrees back to that cylinder expecting to see the same valve readings, and I was totally flabergasted that they weren't. So now I'm thinking I may have broken something, because here's the rest of the story: Just bought the boat last September. Have put less than 12 hours on the engine in that time. Still working though routine maintenance issues like fluid and filter changes, etc. Coming back in from a sail under power. Notice engine RPM falling off. I'm thinking "plugged fuel filter". Quick email to previous owner reveals primary fuel filter not changed for years. OK. Replace primary - very black. Replace secondary - looks OK. Bleed system. Noticed previously mentioned solenoid problem, which led to my tackling the valves. Decided to test engine thoroughly before taking her out again - terrified of having engine die while transiting narrow channel into/out of Bayou. Started engine - fired up immediately, ran smoothly at idle. Warmed up for five minutes, then increased power to half throttle. Ran for ten minutes. Ran smoothly, only very very light whitish smoke. I thought "great, doing well." Decided to run it up to full throttle for five minutes, then bring it back down. Ran at full throttle for two minutes or so, then engine started chugging and fell off to idle. Since then, it will start, runs somewhat rough, dies when I apply throttle. I figured "last thing you touched is probably the problem" so I re-checked the valves, and they seemed way off. I figured maybe I hadn't tightened one or more tappet lock nuts sufficiently, and they drifted at high revs. I've been chasing this ever since, and have finally given up and called a local diesel mechanic who is highly recommended, and who must be pretty good because he is "booked up for months."

So, some thoughts I'm having. Maybe I got lucky enough at first to get it ALMOST right, so that the engine fired up and appeared to run smoothly. Is it possible that running it that way at full throttle for a couple of minutes could break something? I wouldn't think I could have caused a valve interference problem. One thing a friend of mine who works on diesels has suggested I try (obviously once I'm sure the valves are right) is to put in an electric fuel pump, because he says he's seen diesels with plugged fuel filters overstress the lift pump enough to cause a fuel starvation problem once you get them running again. I don't know, sounds to me like the fact that it started and ran fine for over 15 minutes makes that unlikely, but he says he's seen it and it's an easy thing to check, could explain why I can fire it right up but it dies at any throttle. I have verified that I'm getting fuel at all three injectors. So many things to think about!

 

[Allan12210]

I don't know that you could have set the valves tight enough to interfere with the piston at its highest point because you would be trying to create a gap between the rocker and the valve stem. Possibly it is too loose and just isn't letting enough fresh air in and exhaust out for it to run well. The diesel works by adding more fuel to go faster. If the air charge is too little because of insuffient duration or high exhaust dilution (from excessive lash) it might run worse at higher throttle position. Should start smoking badly. That won't break anything for the length of time you have tried to run it (although the injectors might have sooted up). The best thing to do is to get the valve lash sorted out and try running it again. One thing that always confuses me is that the engine and the propeller shaft turn in opposite directions because the transmission reverses the rotation. So, if you are turning the engine the wrong direction, then the 240 degrees will put you on the wrong side of the cam lobe. Another reason why I like to use the dial indicator (they sell them at Harbor Freight) so I can see that it is doing what it is supposed to sequentially. It sounds like you may have hit on the issue by turning the crank only 360 degrees instead of 720 degrees for a full cycle (720/3=240 between each cylinder in order).

Once that is done, make sure there isn't any water in the fuel...if those filters weren't changed for a long time, maybe there is water present...more fuel is introduciing more water.

These engines are pretty robust. I don't think you have broken anything. It would have probably made a lot of noise and not fired at all if a valve was open during compression. No spark plug to ignite anything.

Allan

 

[robertsapp]

I'm pretty positive I'm turning the flywheel in the correct direction. Facing aft, I'm turning it clockwise. All the belt driven accessories are going the right way, and I see the injection timing mark appear before the TDC mark for each cylinder. I'm really anxious to get back down to the boat and try again now that I've been given hope again!

 

[robertsapp]

How tight on the tappets?

Oh, and another thing. I have two shop manuals for this engine, and neither says anything about how tight the lock nut should be on the tappet screw. Just past snug? Tight as you can make it? I've started really torqueing on them since I thought maybe one might have "slipped" at first, but I'm afraid if I tighten them too much I'll strip the threads on the tappet screw.

 

[Allan12210]

Just past snug. A rule of thumb for bolts and nuts is to tighten until they just make contact with the underneath surface, then an additional 1/2 of the distance between two adjacent points....i.e., 1/12 of a turn for a 6 point fastener. Check the lash after tightening and if the measurement changes, note by how much and just gap accordingly. If it is .002 tighter, then gap to .010 and it will be right on after tightening. Did you happen to note what the clearances were before you started? Just curious as to how much change occurs after some number of hours of run time.

Sounds good on the rotation. Put that mechanic on hold and take tomorrow off work. Its going to be too nice of a day to go into the office anyway (LOL).