Valve Train Question, One won't hold adjustment-- Knowledge Base Chime In Options

[Robarabian]

A few weeks ago I posted a photo of some heads I pulled off a motor I had purchased from another member that had some heads with valves that were not in alignment with each other. They were GEX heads, and all the postings agreed, don't waste too much time on them. I saved them for another day.

I had a set of AA 2.0 heads (brand new) that were slated for another motor but this is a stop gap engine to use till that one is built. I swapped heads, cleaned everything, and re assembled. Valves adjusted and mounted to my test stand. Fresh oil, O rings etc...

Engine fired quickly and got the webers to the point where it idled reasonably and I was going to start adjusting them. At about the three - four minute point of idling and goosing the throttle a bit, I heard a bit of valve train noise, almost like a "POP" and I could hear clickcty Clack so I shut it down. I set the crank back to TDC #1 and checked the valves. (cold) 1,2,4 were good. #3 the intake valve was out of spec so I re-adjusted. re-checked the other three again, rotated the motor through and buttoned it back up. This was a week or two ago.

Today, I decided to tinker again and same thing happened. All was good, engine was running real smooth. Goosed the throttle, started tuning carbs and again, "POP". #3 is loose.

When I say "loose" it is going from .006 adjusted to .008 so it is loud enough to hear. Putting it another way, it sounds as a proper air cooled type 4 should, and then clickety clack, loud valvetrain. Cyl's #1, 2, 4 are in spec. I am setting Intakes at .006 and exhaust at .008.

I replaced all the valve adjuster tappets when I swapped the heads with stock ones, not swivels or anything weird.

This one is baffling me. Could I have valve adjusters out of alignment? Is the head just going through a normal cycle of stretching new valves when it got to operating temp? Am I losing my mind?

I appreciate the input from the knowledge base here. Im a garage mechanic, not a pro shop and Im only recently delving back into the mechanicals of the 2.0...

[porschetub]

Wow hard to nail this one down,never had this before,I will throw out the following;
Did you check the lifters and cam for wear? were all of the pushrods straight?
Are the adjuster ok or look crappy? good luck.

[burton73]

I am going to through this out. In 1979 I had a 1974 2.0 that I rebuilt and the vales kept going out of adjustment in a short amount of time. I readjusted it over and over each 200 miles or so. The problem was the lifters where not hardened by the factory that made them.

I had to take down the Eng. and found that the new cam and lifters had to changed because the lifters would mushroom. Very mad

Maybe something like this is happening on just one of yours or some reason that the one may be wearing fast?

Just putting this out there. All of my machine and balance work was done at a top shop. Bieker Engineering by Harry Bieker

Bob B

[porschetub]

I am going to through this out. In 1979 I had a 1974 2.0 that I rebuilt and the vales kept going out of adjustment in a short amount of time. I readjusted it over and over each 200 miles or so. The problem was the lifters where not hardened by the factory that made them.

I had to take down the Eng. and found that the new cam and lifters had to changed because the lifters would mushroom. Very mad

Maybe something like this is happening on just one of yours or some reason that the one may be wearing fast?

Just putting this out there. All of my machine and balance work was done at a top shop. Bieker Engineering by Harry Bieker

Bob B

(IMG:style_emoticons/default/agree.gif) lifter and cam wear seem to be rather common on t4s,cam go's flat in the centre of the lobes and the lifters wear concaved and no rotation ,no favours to the rest of the valve train besides (IMG:style_emoticons/default/sad.gif) .
Yes cam to lifter match is very important.

[Robarabian]

Thank you for the insight.

So I did change out all the adjusters because the original ones were pretty buggered up, given the heads they came off of, I was not surprised.

I did pull one lifter out of its bore while I was going through things just to look, and it looked good. Was flat, no scoring etc. Flashlight into the bore and I did not see anything that would have caused concern,.... It was on Cyl#2 intake.

Today, I pulled the valve covers off and pulled all the rockers and reinspected everything. They looked good (no uneven wear, cracks etc...). Pushrods are straight. It was Cyl #4 intake that was the loose one.

I had a Type 4 store set of bushings, so I spent the day fitting them and re-assembling the valve train.

Before disassembly, I did look at everything and re-measured clearances cold. Everything but two were within spec, and at that, the .008 became .009, so not by much, but enough to be louder than it should when running. I think I found 2 that had "moved".

Also, and I believe this is normal, not all the tappets hit the valves dead center, but are offset slightly, which I think I read was to allow the valve stem to rotate.

Reassembled it all and ran it. I ran a solid 5 minutes and got the webers a bit more dialed in (flat spot so I am lean) but nothing went boom or click. Also re-pulled the valve covers and made sure all the adjuster nuts were tight (actually got some turn out of two of them). I will try it again next Friday, maybe I licked it. Then again, it could go pop, and I could be in to pulling all the lifters out to look at them, and the cam.

You guys gave me some leads to pursue, Ill know more next week when I get shop time again. Thank you for chiming in.

[Jake Raby]

As a general rule, loose valves occur from cam/lifter wear, and tight valves occur from valves stretching, and seats moving.
What oil did you break it in on? What cam/lifters were used? What oil is it running now?

[Mark Henry]

Check your valve cover for the adjuster touching it. It will leave only a tiny mark, but if an adjuster touches the cover it will loosen off every time.

[VaccaRabite]

Check your valve cover for the adjuster touching it. It will leave only a tiny mark, but if an adjuster touches the cover it will loosen off every time.

Wouldn't this make a good bit of noise? It did in my case.

Zach

[Robarabian]

Thanks Jake, always honored to have your expertise. The motor was someone else's, and I am trying to ensure it will run before putting it in the car. So it was a motor with approx 8,000 miles on it according to the seller, so I don't really know its internals, running dual weber 44's. I put 40's on it cause I think the 44's are overkill..96MM Jugs on a 1.8 crank. I noticed the heads were GEX when I popped the valve covers off to adjust the valves, and the valves were not sitting at the same height. So I swapped heads with some new ones (AA bolt ons) again, just as a temporary motor till I can do something more significant. Pistons looked clean, cylinders were not polished smooth. I pulled one lifter and it looked good. Cam didnt look scored looking through with a flashlight. Once the new heads were on, everything went back together smooth and then this little hiccup has occurred.

So my thought is that if I run it again next week and it happens again, then lifters / cam issue and the motor wont do what I had intended it to do and I have a rebuildable core...

Valvoline High Zinc 20-50

As a general rule, loose valves occur from cam/lifter wear, and tight valves occur from valves stretching, and seats moving.
What oil did you break it in on? What cam/lifters were used? What oil is it running now?

[Mark Henry]

Check your valve cover for the adjuster touching it. It will leave only a tiny mark, but if an adjuster touches the cover it will loosen off every time.

Wouldn't this make a good bit of noise? It did in my case.

Zach

Depends, it could be barely touching, but it would be enough to loosen the screw. Start the engine up and look to see if the cover "dances" a little bit.

Every possibility must be eliminated, no matter how unlikely. It's my experience that the one check you skip has a good chance of being the issue.

[Robarabian]

Check your valve cover for the adjuster touching it. It will leave only a tiny mark, but if an adjuster touches the cover it will loosen off every time.

Wouldn't this make a good bit of noise? It did in my case.

Zach

Depends, it could be barely touching, but it would be enough to loosen the screw. Start the engine up and look to see if the cover "dances" a little bit.

Every possibility must be eliminated, no matter how unlikely. It's my experience that the one check you skip has a good chance of being the issue.

Thank you Mark, I will check this Friday, (hopefully)