Valve Adjustment Experiment

[Amskeptic]

I burned up three exhaust valves driving from Pennsylvania to Los Angeles in 1986. The dynometer said the engine was putting out 7 horsepower. The guy wanted to know how I made it across the country. I told him a JB Hunt driver agreed to let me draft behind him all the way across on I-40, we did pretty good all things considered until I had to go down I-15 and he continued on up to Salt Lake. The crawl over the El Cajon Pass was excruciating.

The reason I burned three valves is because I had made a bad decision that affected all of my clackityclacky valves. The valve stems were a bit stoved in from both the approximately 70,000 miles since the prior rebuild and the fact that the rockers had not been shimmed to ensure that the adjustment screws were slightly off-center . A flat feeler blade only contacts the outer circumference of a stoved in stem and covers up the "bowl" underneath. Even with a serious drag on the blade, the adjustment screws were pounding the centers of the bowls. I don't remember exactly what decision I made to compensate, but it was wrong . . .

. . . yesterday, I realized that I have some valve stems on Chloe that are a bit caved in as well. The engine had developed quite a tackitytack at idle, even with draggy feeler blades. So I thought to create a new method of valve adjustment that would be similar to the hydraulic valve adjustment method, so I would not have a feeler blade acting as a plank over a bowl.

If the valve adjustment screws are a 1.00mm pitch, and our adjustment specification is .15mm (.006"), why not back the screw out a precise number of degrees? Then I won't get thrown by a dished stem.

1mm pitch / 360º = .0027 X 55º = .015mm required clearance.

So, that is what I did.

A turn adjustment screw with fingers until it contacts valve stem

B turn backwards 55º (I did 60º)

(I will bring a spare set of heads* with me, just in case I have screwed up again):



*the heads that were originally on my engine got their seats destroyed by too-small fuel injected beetle exhaust valves. Now they are languishing in a box with new Osvat exhaust valves and new exhaust seats that hopefully will know how to stay in place. I have never owned or driven a VW with replacement seats . . . but if this experiment goes awry, the above *heads will have their next chance to hit the road.

[hambone]

It's nuts...you are trying to pre-compensate for expansion and dishes etc. But you are nuts too so it may work. But what if the threads are slightly off? I don't like it.
On this note, would it help a 1600 engine to have the intakes set at 0.004"? It used to be that way, didn't it?

[Amskeptic]

This is where I say, "what a great idea!"
Ha

It's nuts...you are trying to pre-compensate for expansion and dishes etc. But you are nuts too so it may work. But what if the threads are slightly off? I don't like it.
On this note, would it help a 1600 engine to have the intakes set at 0.004"? It used to be that way, didn't it?

We can trust the thread pitch far more implicitly than chinese feeler blades that have been bitten by adjusting screws, etc . . .

I am making a degree scale on a CD disc to see if I can make a system of it.
ColinByCracky

[SlowLane]

How about calling in a dial indicator to confirm your analysis?

[wcfvw69]

Someone (I think Glenn) on The Samba posted about this, suggested using chrome-moly pushrods and setting them to loose zero. Would that provide the same outcome? Would the chrome-moly rods and this loose zero adjustment be more accurate?

My bus has chrome-moly push rods installed when the previous owner had a shop rebuild the engine. It apparently has heavier than stock springs and swivel feet adjusters on it. I was just adjusting the valves on this engine a couple of days ago. It does seem to be easier to adjust them to loose zero than fiddle farting around with feeler blades like on my stock engines in my bugs.

[asiab3]

Someone (I think Glenn) on The Samba posted about this, suggested using chrome-moly pushrods and setting them to loose zero. Would that provide the same outcome? Would the chrome-moly rods and this loose zero adjustment be more accurate?

My bus has chrome-moly push rods installed when the previous owner had a shop rebuild the engine. It apparently has heavier than stock springs and swivel feet adjusters on it. I was just adjusting the valves on this engine a couple of days ago. It does seem to be easier to adjust them to loose zero than fiddle farting around with feeler blades like on my stock engines in my bugs.

I do not consider "ease of valve adjustments" to be a desire or factor in my parts selection. I want the expansion and compatability of expansions to be correct through 100% of driving conditions. I have not yet seen hard-core research that chrome-moly pushrods work 100% as well as, or better, than stock pushrods through every condition I drive through. (Remember, I have been known to take my bus snow skiing and surfing on the same tank of gas...)

Robbie

[Amskeptic]

Someone (I think Glenn) on The Samba posted about this, suggested using chrome-moly pushrods and setting them to loose zero.

I like my VW engines the way they were delivered. They have never let me down. If chrome moly would have saved VW from the endless grief of tight valves in the 1960s, why did they not use them?

Is it because the factory wanted the pushrods to expand sooner to help hold the clearances down as the head-to-rocker arms heated up in the first phase of warm up? Is it because aluminum tubes hold more oil by far and shed that heat more effectively? Just wondering . . .
Colin

[wcfvw69]

Someone (I think Glenn) on The Samba posted about this, suggested using chrome-moly pushrods and setting them to loose zero.

I like my VW engines the way they were delivered. They have never let me down. If chrome moly would have saved VW from the endless grief of tight valves in the 1960s, why did they not use them?

Is it because the factory wanted the pushrods to expand sooner to help hold the clearances down as the head-to-rocker arms heated up in the first phase of warm up? Is it because aluminum tubes hold more oil by far and shed that heat more effectively? Just wondering . . .
Colin

Note to self... Colin is NOT a fan of chrome-moly push rods.

[Amskeptic]

Note to self... Colin is NOT a fan of chrome-moly push rods.

Aw, here's a cold washcloth . . .

I LIKE chrome moly pushrods on a Raby engine, what the heck, he has done his home work. I have adjusted many chrome moly push rod equipped engines.
BUT . . . (there's always a Kim Kardashian moment)
A loose zero CAN become a slightly open valve, i.e. too tight and nowhere to go.
It can catch you unaware during an engine changing moment like my Chloe and PluckyTheSquareback had when their seats eroded. With a .006" clearance closing up, I had all the time in the world to catch the trends before they gave the valves a lick of trouble.

Hey. Who here *doesn't* like the clickitty clackitty of oem VW engines?
Colin

[wcfvw69]

Note to self... Colin is NOT a fan of chrome-moly push rods.

Aw, here's a cold washcloth . . .

I LIKE chrome moly pushrods on a Raby engine, what the heck, he has done his home work. I have adjusted many chrome moly push rod equipped engines.
BUT . . . (there's always a Kim Kardashian moment)
A loose zero CAN become a slightly open valve, i.e. too tight and nowhere to go.
It can catch you unaware during an engine changing moment like my Chloe and PluckyTheSquareback had when their seats eroded. With a .006" clearance closing up, I had all the time in the world to catch the trends before they gave the valves a lick of trouble.

Hey. Who here *doesn't* like the clickitty clackitty of oem VW engines?
Colin

Glad you get my humor. :)

I've never experienced any issues w/chrome moly's over the years though I have bent an aluminum push rod before. They were installed on this engine when I purchased this bus. Yes, they are a bit louder than aluminum as well.

I do watch trends while adjusting them as well. My last adjustment found a couple of exhaust valves a bit tight and required loosening them. I'm going to recheck those valves in 1000 miles to insure nothing fishy is going on.