type 1 valve clearance issue

Hi,

With a stock type 1 motor, will the valve lash increase or decrease as the engine heats up?

I ask because on my motor, I installed new factory heads, and after the install, as the engine warmed up, I began to notice excessively louder valve train noise (as compared to when the old heads were installed). The valves were adjusted cold at 0.006". I drove the car a few miles and rechecked said valves (cold). After I put about 100 miles on the car, I re-checked the valve lash with the engine warm. I was able to squeeze 0.017" worth of feeler gages between the rocker and stem!

The motor was a rebuilt deal that came with the car. One of the old heads was cracked, so I replaced both. I reused the rockers and push rods.

In case I am missing something more obvious, the motor is configured as follows:

-1600 cc

-stock cam

-stock intake and 34 carb (rejetted for exhaust)

-bugpack hide away exhaust with heaterboxes

-new 36mm/32mm Brazilian heads

-stock single vacuum distributor with Pertronix ingitor, coil and wires

-initial timing set at 7.5 BTDC

-stock air filter

-all stock cooling tin, vanes, gaskets and t-stat in place

-mobil 1 oil

Thanks in advance for any help,

Tom

Reply to
Tom Jordan
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Virtually all metals expand as they get hotter. All of the metal used in the VW engine follows this rule.

Ideal valve lash is zero, achieveable only hydraulic tappets.

With solids, the cold lash setting of .006 is a compromise, intended to get you close to zero lash when the engine heats up.

If you're seeing .017 hot after setting the thing at .006 cold then you've either mistaken your cold reading, your adjuster screws are trashed or you're not doing the adjustment properly -- using the wrong setting-point or failing to maintain the setting whilst tightening the lock nut.

(I'll assume the adjuster screws AND the heads of the valve stems are not trashed... but you should know that you need to replace the stock adjuster screws about every five adjustments... the cambered end of the screw becomes faceted due to wear and dishes-out the head of the valve stems, leading to Chunkie Attacks :-)

Here's how real mechanics do it:

Set the pulley at or near TDC. Remove the valve covers. (Engine is cold; has not been run for at least four hours.) By touch, identify any valve that is NOT tight. Loosen the lock nuts on those valves, turn the adjuster screw until it makes contact with the valve stem, then back it off an estimated 45 degrees... one eighth of a turn and tighten the lock nut while holding the adjusting screw in position. (Be as precise as possible in your degree estimate. Do just one bank at a time.)

Do the other bank. Then rotate the engine one full turn... bring the pulley back to the same mark as before.

Now repeat the procedure. This time, all of the valves that were tight will be loose.

Replace the valve covers.

(This procedure works -- and is the method taught at the factory school -- because of the pitch of the adjuster thread, one eighth of a turn being approximately .006" of linear travel.)

The method described in St. Muir and other manuals is the procedure used when ASSEMBLING an engine -- when the valves are adjusted for the first time. With an engine that is already assembled, thanks to the characteristics of the Otto cycle, the valve lash may be adjusted ANYTIME the cam-follower is riding on the heel of the cam.

-Bob Hoover

Reply to
Veeduber

Valve clearance should DECREASE as the engine warms up. That's why you need to adjust them with the engine dead cold. In your case, something is probably not tight. Check all the locknuts on the valve adjusters, and check the bolts holding the rocker assemblies to the head. One may have loosened and caused all your valves to have way too much clearance and make a lot of chatter.

~Anthony

Reply to
Anthony

Check in the John Muir How To Keep Your Aircooled VW Alive book and in the Roberta Haynes repair manual that applies to your vehicle. Wherever three or more agree right?

Reply to
Sleepy Joe

Check the Bob Hoover manual. It seems to be more precise.

Lane

Reply to
Lane Jennison

Thanks for all the responses!

I assumed the clearance decreased as well, but considering the steel jugs with aluminum heads with steel studs and push rods, expansion is not exactly uniform, so I wasn't sure if there was some phenomenon going on that I wasn't aware of. I have heard of some of the old porsche engines having expansion problem....

Here's the deal with what I have done so far. I double checked the valve clearance cold several times, so I am confident we can rule out the a mistake with the initial adjustment (.006"). I also double checked the rocker arm nuts and the adjuster nuts before and after, so I know we can also eliminate that variable.

The adjuster screws have a few thousand miles on them, so I guess they can be potnetially in need of replacement. They are somewhat faceted.

I still don't see how trashed screws could create a hot clearance of

0.017".

I was wondering if there is an issue with newer Brazilian heads being made from a different alloy than old German heads, but i couldn't imagine how there could be that great a difference in expansion between various aluminum alloys.

Thanks again,

Tom

Reply to
Tom Jordan

do you have "chromoly steel" pushrods? if the answer is yes, you will need to learn to love noisey valves or switch back to alluminum pushrods...

------------------- Chris Perdue

"Sometimes you're the windshield, sometimes you're the bug!"

Remove "PANTS" to e-mail

Reply to
Chris Perdue

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Dear Tom,

You've missed the point (and the reason I described the most common method of adjusting the VW's valves).

The valves should only be adjusted when the cam-follower is riding on the heel of the lobe. The pulley is a demountable item. Over the years it's quite possible for the pulley from another engine to be substituted for the original. Even if everything is all-original the marks on the pulley are only an APPROXIMATION to be used only for IGNITION timing.

(Accuracy of the notches on the fan pulley is usually +/- 1.5 degrees, close enough for the engine to start. Once started, the ignition timing is dialed-in using a stroboscopic timing light.)

Another assumption embodied in your original message is that the cam is stock and the engine has been properly assembled. The limitations of email make it wildly impractical to try and nail down such assumptions but the described method of valve adjustment will work in any case.

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The faceting of the cambered face of the adjusting screw is just the tip of the iceberg. Once the face is faceted any future adjustment is liable to bring the EDGE formed by two facets into contact with the valve stem. Having a significantly smaller area, the edge wears at an accelerated rate, often needing only a few miles to open the adjustment beyond spec. The other part of the problem is that the edge also greatly accelerates wear/deformation of the head of the valve stem, making first a groove then folding the edge of the valve stem outwards until it cracks. When the valve stem is worn in this fashion -- even moderately -- and when the adjuster screw is faceted, it is impossible to accurately set the valve lash using a feeler gauge, since it simply bridges the groove in the one while touching the edge of the other. You may think you have a nice .006 fit when in the actual dimension is much greater.

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Automotive engineering has nothing to do with your confidence (nor that of your pet mouse :-) Having the valve lash open up when hot is the symptom of a problem. Until the problem is defined it would be unwise to rule out anything based on human perception.

If that sounds a bit harsh please understand it not meant as a put-down. A few minutes poking through the archives will show you literally hundreds of requests for help from people who have already decided what the problem can and cannot be -- "I know it can't be that because..."

Such determinations are not up to us. The engine or the chassis or the electrical system always has the final say. All we can do is try and interpret the symptoms -- as colored by your perceptions.

That's like saying your girl friend is slightly pregnant :-)

Faceting of the adjuster screws is normal. The service manual says to replace them 'as required' which works out to about every fifth valve adjustment. This chore may be eliminated by using swivel-foot adjusters, assuming the face of the valve stems are still true. (Back in the Good Ol' Days... whenever that was... the parts-guy kept adjusters bagged in sets of eight right there on the counter. I can't recall the price... I think it was about a buck per set.)

-Bob Hoover

Reply to
Veeduber

hmmmmm that reminds me... I need to adjust my valves and tighten the fan belt. I may as well just do a complete tune up and oil change while I am at it...

Reply to
dragenwagen

8< snip >8

Considering you have so many new parts and work done on the heads, I'd say this is normal during the first couple hundred miles. All the parts wear in and seat themselves for a while at first, until they settle. Keep a close eye on the valve clearance for the first 2k miles. If one or two valves seem to *lose* clearance repeatedly, you may be looking at a stretching valve... about to snap. Usually happens to old valves though.

Jan

Reply to
Jan Andersson

I just thought of something: If he used steerl pushrods to replace old aluminum pushrods with (by someone's recommendation perhaps) then the lash would get bigger as the engine heats up....

Jan

Reply to
Jan Andersson

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Dear Jan,

Here... put on this tall, pointed hat. Now go stand in that corner over there... no, facing the wall.

(For your supposition to be correct the steel-tube push-rods would need a negative co-efficient of thermal expansion. But they don't. Steel expands when it gets hot, just like aluminum... only not so much. The hot valve lash would still be something less than .006" rather than more.)

-Bob Hoover

-PS -- If you're running steel push-rods of stock length, start with a cold lash of .004, check to make sure that you still have some clearance when the engine is hot.

Longer than stock? Then try a little less. How much? You'll have to work it out empirically. But steel push-rods, be they in a Buick or a bug, ALWAYS expand less than aluminum push-rods in the same engine. So take it into account. Or buy ear muffs. Your choice; you're the Mechanic in Charge.

Reply to
Veeduber

Bob, I agree with what you said, the theory of it is correct. But at the same time you yourself explained why the clearance GROWS. It's indeed because of the slower/lesser expansion of steel vs. aluminum. You still have a huge lump of an aluminum head sitting on top of the cylinder, expanding as usual. Factory stock engines had aluminum pushrods, carefully designed to make the valve clearance get just a tiny bit smaller when the engine warms up. It really only takes a material change from aluminum to steel (pushrods) to go the opposite direction, the steel rods dont expand enough to allow the gap to get narrower, but instead will "fall short". Then you have the head that still expands, more than the now steel rods.. taking the rockers further away from the rod tip. It's all very minimal, but it is noticeable to a trained eye. Ear. Or feeler gauges (you have to be real fast if you plan to measure HOT valve clearance though.. man what a pain). What I'm saying is that the difference in expansion rates is enough to not only negate the "closing" effect, but also make the clearance actually grow. I've built countless engines with these, and it's just something one has to accept. Or go to high $ special parts or hydraulics or... ;)

Right. No argument there.

Jan

Reply to
Jan Andersson

The adjuster screws have a few thousand miles on them, so I guess they can be potnetially in need of replacement. They are somewhat faceted.

Worn adjuster screws will give you inaccurate readings and will cause premature engine wear. Just replace 'em and check the valves with the engine completely cold.

Replace the screws or get some elephant feet adjusters from cbperformance.com or aircooled.net . Do not use the Empi brand elephant feet adjusters. They fall apart fairly easily. Well mine almost fell apart, but I caught it in time. No problem with C.B.'s feet for over 10 years now. For engine break in, First I would take it slow. Drive through a residential area and do plenty of stop and go driving for at least 30 minutes at under 1500 rpm. Park it. Let it sit over night or at least 12 to 14 hours and check the valves with the engine completely cold. Then change the oil. Then drive it for a week and change the oil and check the valves with the engine completely cold. Then drive it for a month and change the oil and check the valves with the engine completely cold. After that follow the usual oil change interval, which for an aircooled VW with no oil filter, the strainer screen does not count, should be at least every 1000 miles, but I would recommend at least evcery 850 miles, and check the valves with the engine completely cold. I just drive mine on weekends but I still change it at least every 3 months even if that is less than 400 miles. And I check the valves with the engine completely cold about every three months if for no other reason, just to practice doing it.

Reply to
Sleepy Joe

Bob, I'm going to have to stick with Jan here. With stock pushrods the extra expansion coefficient of the Al makes up for the fact that the oil-cooled pushrod doesn't get nearly as hot as the cylinder and the head studs. It's just enough extra that the lash can close down close to zero when fully warm.

With a coefficient of expansion 1/3 that of Al, the steel pushrods can easily expand less than the cylinder and cause an actual increase in lash, even though the pushrod still expands somewhat.

We know that all these parts don't come to equilibrium at the same temp, don't we?

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----------------------------------------------- Jim Adney snipped-for-privacy@vwtype3.org Madison, WI 53711 USA

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Reply to
Jim Adney

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