TheSamba.com :: View topic - No clearance between valve stem and adjust screw- HELP!

Fri Apr 13, 2012 11:31 am

Hi-
Just adjusted the valves for first time on my '74 Thing (Dual port, AM numbered engine block) and ran into a problem. When I got to the cylinder #4 intake valve, I could not get any clearance between the valve stem and the rocker arm. I had to pull the rocker arm a bit to get the feeler gauge in there, but it still was too tight when I pulled the .006 feeler gauge out. I adjusted it as best I could, but I know it is too tight. The cylinder 4 exhaust valve was a little easier to adjust (little more room); I think it is OK, I am going to check again.
I adjusted the valves STONE COLD. The engine sounds good (I originally heard a tapping sound, but that went away after I adjusted valves), but I do not want to drive around and make things worse. Should I buy shims to put under the rocker arm shaft? Did the valve stem stretch and needs to be filed down? Do I file down the push rod? This is all new to me and I have no info from previous owner (i.e. were the heads re-done?). Any help would be greatly appreciated! -Thanks, Greg74

Fri Apr 13, 2012 1:13 pm

Let me understand. The rocker itself, and not the tip of the adjustment screw is actuating the valve? That is, you cannot back the screw out sufficiently to get the correct clearance?

It is possible to mess up rocker geometry with aftermarket parts during a rebuild. Are the rest of them close to similar? If its one valve only, I'd be concerned. Stems dont stretch, but valve and seat wear is what causes the clearance to shrink over time. All other wear, cam and lifter, pushrod and rocker cause the clearance to increase.

Fri Apr 13, 2012 2:59 pm

I had same problem, seats were falling out, not letting the valves fully close, ended up destroying a head.
something is wrong! figure it out before you drive it

Fri Apr 13, 2012 4:52 pm

Thank you for the replies! Yes, I cannot back the adjusting screw out any more to gain any clearance. I rechecked the valves and noticed the rocker arm shaft has been shimmed once to raise it (the rectangular shims). All the parts look similar, the head is stamped VW and appears to be OEM... again, I do not know if it was ever "remanufactured" in a machine shop. I also noticed the #3 cylinder exhaust valve also had a clearance problem. I just could not back out the adjuster enough to slide a feeler gauge through. I ended up pulling on the rocker arm, slipping the gauge through, and trying to get some clearance (got a little- do not know if it will keep) before tightening the nut. The engine sounds very good, but I have read a tight valve won't give a warning sound. Should I drive it around enough to warm it up for a compression test? This is frutstrating...

Fri Apr 13, 2012 5:57 pm

Make double sure you engine is at TDC on that piston, before you check it. Then if you are sure try rotating the engine with the feeler gauge in place, just a little both directions to see if you can feel it getting a little more loose when you rotate it. If it does I have an idea.--Larry

Sat Apr 14, 2012 7:39 am

if you are on the correct cylinder when adjusting and the engine is running ok it sounds like when the engine was rebuilt the heads may have been flycut or because of a different cam someone installed shims under the rocker arm shaft You may only need to install a larger shim. They are available in different thickness like the ones from bugpack.

Sat Apr 14, 2012 10:30 am

You may well be seeing the affects of some form of valve train recession. Valves recessing into the seats, the seats working loose, or the valve stems stretching/heads deforming. Pull the rocker and put a straight edge across the valve stems to see how things compare. I would not start adding shims unless you are absolutely sure its a build problem and not a wear problems. Type 1 heads are cheap, you don't want to do irreparably damage your bottom end to get a few more miles out of your heads.

Sat Apr 14, 2012 6:14 pm

as wildthing says make sure it is not just one valve that is down and you dont have a problem with a seat first. Also to be on the safe side also make sure that you have the same compression on all cylinders. This will give you another check that there is not a problem on one cylinder.

Sat Apr 14, 2012 7:17 pm

Yes that is exactly what I was thinking the valve being pulled back into the head. You know it's a wonder more of these Thing with the stock engines in them don't have more of this type of problems. Burning lead free gas and all. Other older cars types from the 60 and 70, have hardened valve sets installed in there heads.

Sat Apr 14, 2012 10:44 pm

livy wrote: Other older cars types from the 60 and 70, have hardened valve sets installed in there heads.

Ever seem an ACVW engine without hardened seats installed in the heads? I haven't. :wink:

Sun Apr 15, 2012 5:56 am

Steel inserts in aluminum heads are not the same as hardened steel inserts, put into aluminum heads.

Sun Apr 15, 2012 6:01 pm

Thank you for the info. Looking at the valves on both sides- again- I noticed that the rocker arm shaft on cylinders 1 and 2 had two shims under each side of it. The rocker arm shaft for cylinders 3 and 4 only had one shim on each side, and these were slipping downward at any angle. I loosened the rocker arm shaft nuts and tried to push the shims up and square as much as possible. Things were still tight to no clearance on cylinders 3 (exhaust and intake) and 4 (intake).
The part numbers on the heads both read "040.101.375.2" have 2BR stamped on each, with driver side stamped "59" and passenger side "58." They look clean and new.
I plan to order shims, but I realize new heads (L3 stock from aircooled.net) may be needed sooner than later.
Larry- (livy) I checked again for TDC at #3 and moved the engine back and forth a little: it did not move the valve.
Wildthings- I plan to put the straigt edge across the valve stems as soon as I remove the rocker arm shaft-and will do a compression test soon.
On the local front, an 87 year old machinist is making me a 90 degree feeler guage. I also learned that a Budweiser can is .006" thick.

Sun Apr 15, 2012 11:59 pm

You might want to read up on checking and setting valve train geometry.

Mon Apr 16, 2012 6:13 am

Here is a great article on VW aircooled engines and head design.

http://www.ratwell.com/technical/Heads.html

Mon Apr 16, 2012 8:35 am

If it was an exhaust valve I'd worry it was stretching and getting ready to loose a head....... If your engine has a mismatch of shims, they are there to adjust for something. I agree with the others, verifying your geometry is the place to start.