VW Rocker arms: Loss of power due to broken adjuster. Install 'em right!

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delta

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I just checked the valves on my 1700cc vw engine. This is a full vw engine not the 1/2vw. But I found on each side one intake valve that the adjuster was turned all the way in. I needed a little more clearance and could not get it
I know next to nothing about these split case air cooled engines and have no problem admitting that. Why I post here. Why I refuse to try and built one to put into the air. I can do some maintenance but that is it. It would be nice if someone offered training for these VW engines that go into the air. I would be standing in line for that training.

Tony
I find your statements not only confusing but disturbing. If the adjuster was all the way in, one would only have to loosen it to get clearance. What clearance are you adjusting them to and how often do you check them. Are you positive that you are adjusting the cylinder that is tdc and on the compression stroke? If you rock the prop a tad when you're at tdc and there's valve movement, you're on the wrong cylinder.
I would run a compression check before I went anywhere (even around the patch). If it's had tight valves and bipasssing gas through them for any length of time, you have the potential for them burning,stretching, and/or breaking. A leak down compression checker would be best. Someone on the field should have one.
I hope you have a cht and egt monitoring system. If you get that baby to hot, it will fail.

Rick
 

N8053H

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I find your statements not only confusing but disturbing. If the adjuster was all the way in, one would only have to loosen it to get clearance. What clearance are you adjusting them to and how often do you check them. Are you positive that you are adjusting the cylinder that is tdc and on the compression stroke? If you rock the prop a tad when you're at tdc and there's valve movement, you're on the wrong cylinder.
I would run a compression check before I went anywhere (even around the patch). If it's had tight valves and bipasssing gas through them for any length of time, you have the potential for them burning,stretching, and/or breaking. A leak down compression checker would be best. Someone on the field should have one.
I hope you have a cht and egt monitoring system. If you get that baby to hot, it will fail.

Rick
Only disturbing because you do not understand what problem I have. If the adjuster is all the way in no way to adjust for you can not go in anymore to get the clearance needed. I wanted .06 thousands clearance and could only get .05. Seeing how this effected intake valve, heat will not be a problem. The length of time between adjustment has nothing to do with this. But I check these every 25 hrs. But sometimes I do it early if I feel the need.

If you move the prop a "tad" and a valve moves..You are in over lap and not at TDC on compression stroke.
 

TFF

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Overhead valve engines normally wear to open lash clearance when run. If it is closing up clearance, you do have a problem somewhere. overhead cams with the cam directly on the valve usually close up clearance when run. I would swap a rocker from a cylinder that is normal and see if anything is different. It can be anything from wrong pushrod length or rocker slightly different to OMG. I would bet its a small problem than a large one.
 

Pops

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Overhead valve engines normally wear to open lash clearance when run. If it is closing up clearance, you do have a problem somewhere. overhead cams with the cam directly on the valve usually close up clearance when run. I would swap a rocker from a cylinder that is normal and see if anything is different. It can be anything from wrong pushrod length or rocker slightly different to OMG. I would bet its a small problem than a large one.
VW engines normally tend to close valve lash clearance when run. That is the reason for the close monitoring of the clearance.
 

Jerry Lytle

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Only disturbing because you do not understand what problem I have. If the adjuster is all the way in no way to adjust for you can not go in anymore to get the clearance needed. I wanted .06 thousands clearance and could only get .05. Seeing how this effected intake valve, heat will not be a problem. The length of time between adjustment has nothing to do with this. But I check these every 25 hrs. But sometimes I do it early if I feel the need.

If you move the prop a "tad" and a valve moves..You are in over lap and not at TDC on compression stroke.
Something here I don't understand. On my VW I had to back off the screw to get more clearance, not in.
 

TFF

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Almost all my cars have been solid cams. So is the wear in the seats or valve face making the stem protrude more? Most other car engines wear the stem tops faster than the seats, hence my opening clearances. Now car engines like my Alfa Romeos close clearance as the stem top never has any rubbing; only the cam to tappet bucket and valve/valve seat wear. it does sink the valve in. Many times you are stuck with new valves at rebuild just for the clearance.
 

N8053H

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Something here I don't understand. On my VW I had to back off the screw to get more clearance, not in.
I am speaking from the rocker arm. The adjuster is screwed in towards the rocker arm to get more clearance. In other words you are removing or screwing in this adjuster to get more clearance. Screwing the adjuster out reduces this clearance. The OP showed these screwed out to far. They needed to come in to get the oil holes in the correct position. I had two screwed all the way in and no adjustment was left to get more clearance.

Tony
 

Pops

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Almost all my cars have been solid cams. So is the wear in the seats or valve face making the stem protrude more? Most other car engines wear the stem tops faster than the seats, hence my opening clearances. Now car engines like my Alfa Romeos close clearance as the stem top never has any rubbing; only the cam to tappet bucket and valve/valve seat wear. it does sink the valve in. Many times you are stuck with new valves at rebuild just for the clearance.
I really don't know for sure. After driving in front of a VW engine :) for about 1.2 million miles, I have found the normal wear is about 1.5 thousands per 10K miles. IF more than that the valve stem is stretching from worn valve guides and the valve face hitting the seat on one side before the other that will lead to a valve head breaking off.
On a fresh overhauled VW engine, if driven correctly, I usually could plan on 200K miles on the engine. I always used straight weigh Valvoline racing oil, changed oil at 3k and at 10K would install new plugs, points and condenser. If I didn't change the plugs, points, etc, the fuel mileage would go from 33 mpg to 28 mpg on a 1600 cc engine. Engine timing is very important for good mileage and power. Always kept the points dwell on 50 deg and make sure for full timing advance per specs. Set total advance timing at 2500 rpm's at 28-32 degs, 28 for low octane and 32 for high octane with a VW dis. If using a 009 distributor use 3000 rpm's to check total advance. Always use Bosh ignition parts.
 

N8053H

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Pops after speaking with Jerry the owner of this airplane since the engine was built, it has 117 hr on it now. I believe this has been an issue since the engine was built. These two intake valves did not have a lot of adjustment. I will keep an eye on these. But like I said this engine is getting new heads this winter and a complete inspection.

Tony
 

Pops

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Pops after speaking with Jerry the owner of this airplane since the engine was built, it has 117 hr on it now. I believe this has been an issue since the engine was built. These two intake valves did not have a lot of adjustment. I will keep an eye on these. But like I said this engine is getting new heads this winter and a complete inspection.

Tony
Tony-- You can get small caps that go over the tip of the valve stem. Check to see if the caps are used on all of the valves or just some of the valves.
 

N8053H

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Tony-- You can get small caps that go over the tip of the valve stem. Check to see if the caps are used on all of the valves or just some of the valves.
Pops thanks for this info. I did not notice any caps, but then again I never really looked to see if these had caps, I never knew they used caps on these. All engines I have build do not use anything like this. Like I said, I know nothing about these engines and don't pretend to know anything about them. Why I posted here for some help.
I would like to thank everyone for trying to help. Explaining something like this over a forum like we have here and finding a fix, is tough at the best.

Tony
 

N8053H

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Pops no they did not have anything like those on the valve stem ends. Today I went out and rechecked the valves. This time I set them to .08 as you recommend. She has never started so easy. the forth pull of the prop and she was running. She also seemed to have more power. Before I had to throttle up to around 2 grand before she would move. Now she moves a little over or above idle setting. I hope to put some time on her tomorrow around the pattern. But she has never sounded better. Jerry told me he was having problems starting her and not sure why. I believe I found the problem. Jerry had this engine built for him by a vw shop out in Arizona in the early 90's. I can not believe they would have set this engine up like this. If these where exhaust valves I would be real concerned about stem stretching. But the intakes should not do this. Is this correct Pops?
Thanks again.

Tony
 

Pops

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Pops no they did not have anything like those on the valve stem ends. Today I went out and rechecked the valves. This time I set them to .08 as you recommend. She has never started so easy. the forth pull of the prop and she was running. She also seemed to have more power. Before I had to throttle up to around 2 grand before she would move. Now she moves a little over or above idle setting. I hope to put some time on her tomorrow around the pattern. But she has never sounded better. Jerry told me he was having problems starting her and not sure why. I believe I found the problem. Jerry had this engine built for him by a vw shop out in Arizona in the early 90's. I can not believe they would have set this engine up like this. If these where exhaust valves I would be real concerned about stem stretching. But the intakes should not do this. Is this correct Pops?
Thanks again.



Tony
Correct. The intake run a lot cooler than the exhaust valve and far less valve guide wear.
 

N8053H

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Pops this is why I believe the intake valves where set-up this way. Or the rockers anyway. I am having one valve cover leaking. It needs to come back off. When I do this later today, I will take pics of what I have here. I should have done this when I repaired this. A post like this is useless without pics. IMHO

Tony
 

N8053H

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After looking at this again. These rails or rocker assemblies need shimmed out some. Where do I get these shims?

The second one in line here is the one I repaired. I need to move the rail out some. IMHO

SAM_7114.jpg
 

TFF

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I wonder if the cause was new valves in an old head. Not bashing the old head its self, but grind the seats and the valve sinks a little. There is built in depth you can do this, but if on the deep side the stem is sticking out more. Old valve being reused, which is normal for car on a budget rebuild, would have the tip trued on the valve machine, knocking the length down a little.
 

N8053H

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TFF I agree. But the fix could have been to shim the rocker shaft away from the head. I believe Pops pointed me to the correct part for this, I just have not gone back through the thread. I was hoping he would just post this again for others looking for this same info. Or maybe someone else is having this same issue.

IMHO the builder who built this engine for Jerry should have known to shim this rail away from the engine for valve clearance in the future. This engine only has 118 hrs on it today. It was build in 1993 and then hung on the airframe as said airframe was being built. It did not get any use until 2013 when the airplane was finished. The man who built her was a Lt. Col. in the airforce and life stepped in the way while he was building this, why it took 20 years. He is one upstanding man. I will handle this little issue. Not a real big deal, but why I want the engine gone through by Scott Casler. He will or see anything of issue and repair and or replace what is needed. This engine may go to him sooner then I thought.

Tony
 

Pops

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After looking at this again. These rails or rocker assemblies need shimmed out some. Where do I get these shims?

The second one in line here is the one I repaired. I need to move the rail out some. IMHO

View attachment 62942
Tony those are not stock valve adjustment screws, those are aftermarket swivel feet adjustment screws. Because they are longer between the rocker arm and the valve stem they require a spacer under the rocker arm. If I remember correctly the thickness of the spacer is .062 . As you can see in the ad the spacers come with the swivel feet screws.
I have use those but took them off and used the stock VW screws. The stock screws hit the valve stem face slightly off center to slowly rotate the valves when the engine is running. The swivel screw that I had seem to hit the valve stem face more in the center so I didn't know if the valves were rotating correctly so I went back with the stock replacement screw. Never had any problem with the stock screws.
http://www.cbperformance.com/product-p/1523.htm
 

Hot Wings

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Could just be the photo, but that first valve spring looks to be upside down. Not a big problem but if it is then it's an indication there may be other details missed.
 
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