VW 044 Heads - Valve Train Geometry

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Booga-dune-poon
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VW 044 Heads - Valve Train Geometry

Post by Booga-dune-poon »

My 1914 engine has developed a loud noise from the top end on the drivers side. Sounds like the valves need adjustment. But I just adjusted them. Double checked them again. Right side fine, left side not so much.

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The old girl is trying to tell me something. Pay me now or pay me big time later. What I have now are. stock dual port heads. push rods and rocker arms. I know, these probably shouldn't even be on top of the 94mm cylinders anyway. Ports and valves too small. Time to upgrade.

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I hate opening up the engine running the risk of getting sand inside. So, I used a brush, vacuum cleaner, compressed air and extreme caution.

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Got everything all cleaned up and began the mock up assembly of the upgraded heads, push rods and rocker arms. Things don't look right. The geometry of the rocker arms to the valve stems are not lined up. Time to do a little research. Looks like I'll need to take some precise measurements. Borrowed a dial indicator and verier caliper from work. I'll go take some photographs to document now. Post them when I get back.
Kevin

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Re: VW 044 Heads - Valve Train Geometry

Post by Booga-dune-poon »

The new style rocker arms have swivel adjusters (foreground) compared to the stock adjusters (background). As you try to install the arms it's easy from them to get bumped and spin around and not have the flat side facing the valve stem. I had to remove and re-install them several times during the process of shiming / alignment and caught myself not paying attention to the swivel adjusters and had to loosen everything back up to get them aligned properly.

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After several attempts and getting the rocker arms ajusters to line up to the valve stem at 1/2 lift (more on that in a minute), I finally settled for .105" of shims per stand. This is to say that I used 1 each .060", .030" and .015" shims and stacked these to raise the rocker arms solid shaft higher from the valve stems. You can see the shims mounted on the rocker studs in the following photo. Notice the adjustable push rod tool compared to the stock push rods.

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The point of this whole exercise is minimize side thust on the valve stem caused by the rocker arm adjuster misalignment. If this detail is not addressed during assembly, premature valve guide wear will occur and the engine will not deliver peak performance.

If the rocker arm / adjuster do not make a perpendicular line to the valve stem centerline at 1/2 valve lift, the side load to the vavle guides will cause the guides to wear out causing excessive oil consumption. The excessive side load creates horsepower robbing friction. If the rocker arms are not set up to the proper height, total valve lift will be decreased thus limiting both intake and exhaust port function. Another horsepower robbing side effect.

To measure the valve lift (linear movement) caused by the rocker arm pushing down on the valve stem it is recommended to use a precison measuring device called a Dial Indicator. This tool must be securely positioned so as not to move inadvertently during measurements. Normally Machinists use what is called a Magnetic Base to hold the dial indicator securley in place. This works very effectively as long as you have something magnetic adjacent to where you wish to mount the dial indicator.

As VW heads are made of aluminum (not magnetic) so a temporary solution is called for. I fabricated a simple right angle bracket that bolts up to the exhaust port stud.

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Kevin

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Re: VW 044 Heads - Valve Train Geometry

Post by Booga-dune-poon »

As I stated earlier, I test fit the rockers with no shims and stock push rods. If you already know how to adjust valves, finding where each cylinders valves are both closed is essential. In the following photographs I'm working on the exhaust valve of cylinder #2 (right side / rear of car). Open the distributor cap, look for the hash mark on the rim of the distributor (about 5:00 position), rotate the crankshaft until the rotor cap is pointing near the hash mark and the crankshaft pulley is at TDC (0 degrees). This is set up for #1 cylinder. Now rotate the crankshaft 180 degrees counter clockwise to BDC (180 degrees shown on the pulley). This is set up for # 2 cylinder.

With the dial indicator mounted on the magnetic base and lined up with the exhaust valve, rotate the engine and measure the total lift of the valve. That is to say watch the needle sweep the dial and count the number of times it orbits until it stops moving in one direction. On my dial indicator, each complete sweep of the dial = .100". I counted four complete orbits and .035" before it stopped. So my total valve lift was .435". Do the math for 1/2 lift. Rotate the engine back to the 1/2 lift measurement and stop again.

Valve Closed Positon - notice angle of rocker arm / adjustment screw
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At 1/2 valve lift is where you want to line everything up visually. That is to say, you want to verify if the rocker arm adjuster screw appears to be aligned to the centerline of the valve stem. Looking at the cylinder head from the side, you can see the valve stem just sticking up above the valve spring keeper. Notice that you can also see the valve stem through the exhuast port. It appears the valve centerline is projected at an angle about 10 degrees upwards. When I got here the first time without the shims, the angle of the rocker arm / adjuster screw was way off line. I tried to sneak up by adding various thickness shims on each sucessive attemp. You could see the difference by just adding .030" of shims under the rocker arm shaft. To get it to where I was satisfied I ended up adding .105" of shims.

1/2 Valve Lift Position - Using the fabricated bracket, I angled the magnetic base in line with the centerline of the valves. Notice the angle of the rocker arms adjustment screw. As close as I could get it.
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Full Valve Lift Positon - It should appear to be the inverse of the full closed positon.
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*** IMPORTANT NOTE *** As you add shims to line up your rocker arm adjuster screws at 1/2 lift, the screws also need to be adjusted more and more extended. This creates a new problem. The adjuster screw is now severly weakened because of all the additional leverage caused by the side loads at full lift and closed positions. To fix this, the push rods must be lengthened so the adjusters don't have to be extended excessively. How much adjustment screw extention is excessive? I'm told that more than two (2) turns out is maximum. That is plenty enough for valve adjustments later.

This is where the adjustable push rod tool comes in. After you have shimed the rocker arm assembly, back the adjuster screw all the way in. Then turn it out 1 1/2 turns. Use the adjustable push rod tool and adjust it to take up all the slack to create a zero clearance valve lash. Now cycle through to full lift, take measurements and go back to half lift. I literally gained an additonal .015" to .020" of lift as I changed shim thickness. When you finally get everything all lined up, stop, disassemble the rocker arm assembly and measure the adjustable push rod tool. Yes, it's longer than the stock push rods. Next, install the push rod tool in another valve location.

Wash, rinse, repeat.

If the new length adjustable push rod tool works in other locations, BINGO we have a winner! I purchased a set of "cut to length" chromolly push rod tubes. Subtracking the tip lengths (x 2), I now know what lenth I need to cut the tube to equal the new length.

I'm off to cut these push rod tubes to the new length. I'll post photograhs when I get back.
Kevin

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Re: VW 044 Heads - Valve Train Geometry

Post by Booga-dune-poon »

The lathe at work did not have enough clearance to hold the push rod tube close to the jaws of the chuck. The machinist improvised and made a fixture to hold the tube extended from the jaws (see the tube extending from the fixture).
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Once the overall length was cut, the i.d. of the tube needed the edge to be chamfered to allow the push rod ends to get pressed on later.
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Using a vernier caliper the machinist measured the overall length for my push rod tubes at 10.300". When I got home I pressed on the ends and they matched the length of the adjustable push rod tool.
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I re-assembled everything and adjusted the valves. Much better.

Just got back from Glamis over the Thanksgiving holiday. Drove the buggy on 9 "runs" over 5 days from wash 10 to Flag Pole, China Wall, Osborne Lookout, Oldsmobile Hill, the Sand Drags and everything in between. I'm happy to report that all went well. The car ran better than ever and no more unusual noises coming from the top end.
Kevin

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Re: VW 044 Heads - Valve Train Geometry

Post by kaiyara »

I appreciate all the posts in this forum... thanks everyone... Have a good day.

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