Zero Valve Lash

Greg Ward · Post by **Greg Ward** » Wed May 15, 2002 11:00 pm

Thanks Shad, but I already have a set

John has sponsored my Hillclimb race Beetle over here in Australia for the last 2yrs....

Shad Laws · Post by **Shad Laws** » Wed May 15, 2002 11:13 pm

Hello-

Thanks Shad, but I already have a set

Always gotta be one step ahead of me, dontcha? Whyioughta...

Take care,

------------------
Shad Laws
LN Engineering
http://www.lnengineering.com

mharney · Post by **mharney** » Wed May 15, 2002 11:52 pm

not enough lash will definitely burn the valve, and cause it to run hot... the excess lash that comes with chromoly pushrods on a warm motor will not hurt parts at all, even tho it's way beyond the factory clearance you get with aluminum pushrods on warm motor.[/B]

No, you're right, but I meant on a standard valvetrain...even with chromoly pushrods, too much lash (grossly too much) will beat up your adjusters and valve stems in the long haul.

Bruce2 · Post by **Bruce2** » Thu May 16, 2002 12:36 pm

The BMW motorcycle example is completely meaningless to ACVWs since we don't use alum cylinders. There are hundreds of testimonials out there advocating zero, are they all wrong? Why haven't they all burnt up their heads or valves? I ran my 2 liter to Mexico and back through all extremes of temps at zero lash with no problems. Just yesterday I checked the valves and it was the first time I've ever found them to be exactly unchanged. If there were some detriment, wouldn't I see something in the lash setting?
My observations: With regular lash the engine starts and runs nice from dead cold. With zero lash, the engine runs like crap for the first 20-30 sec. This may be where the valves aren't sealing properly as Dan states, but IMO, 30 sec isn't enough to burn a valve. Want to test this? You can hold onto the exhaust pipe for that long. If the thin pipe isn't getting hot, the valve ain't either.

JohnConnolly · Post by **JohnConnolly** » Thu May 16, 2002 1:24 pm

Another viewpoint:

The only reason we need lash is so the valve always fully contacts the seat (this cools the valve off, heat transfers to the valve seat where the head moves it the fins). The valve temp doesn't care if lash is .000 with clearance, or .040".

Now, the valve tip is another story. Too much lash and it will mushroom from the pounding (and you lose duration from too much lash too).

The VW factory used Al pushrods because valve clearances were more consistent from cold to hot. Once you use steel, all that goes to hell, since steel has a much lower rate of expansion compared to aluminum. This is alse the same problem Titanium WOULD have if they were used in the VW engine. Hydraulic lifters adjust for these changes, and if you have Hydrualics, you can run any pushrod you want (wood?

).

Back to the beginning: VW used to recommend .004 in and .006" exhaust clearances. They changed this to .006/.006" because lazy VW owners weren't getting their valves adjusted at the recommended intervals, and their intakes were going tighter then .000 clearance, and they were burning valves. Since you can't change customer habits, you change the spec to .006", which gives them 50% more time before they are at 0 clearance.

Now, early engines used .010", but that's a different deal due to rocker studs, I won't go there.

The reason we need clearance (besides the heat transfer deal) is because the valve stretches over time (the spring is lengthening the valve). Also, the valve pulls into the seat, the seat pulls into the head, etc, etc. All this is worse the more spring pressure you have. Stock springs are easy on valves, Chevy or VW triples are harder. Lastly, if you run 9K RPM, the valves don't like that as much as a 4500 redline. Get the point?

All that being said, there's nothing wrong with running .000 clearance, but you damn well better check it often. Most of the CLF gearheads check their valves a LOT because they have a lot invested in their engines, and to not do it is $$$. I regularly ran .001 on my turbo engine with chromoly, never a problem and was much quieter then .004 or .006" (which was closer to .030" when hot BTW).

So, Al pushrods are the best, but until recently, they all sucked nads (too soft) for serious performance use (the term "noodle" comes to mind). Recent metalurgy has provided some killer heat treatings and alloys, that solve the problem for everyone, but they are about $100 a set instead of the $45 for chromoly. Al is QUIET at all temps, and due to this you can run .006" for valve safety, and have a beer instead of always crawling under every 3-500 miles to adjust the .000-.001" chromoly PRs, I have better things to do with my time!

Hope this clears this topic up a little, these are my opinions, you are entitled to your own.

John
Aircooled.Net Inc.

James2 · Post by **James2** » Thu May 16, 2002 1:49 pm

Totally, 100% agree with John. zero is fine for ChroMo pushrods, if you are willing to check lash often. I ran it with no problems, just be sure the pushrod spins freely.

That being said, the new al push rods sounds to be the ticket. I have a set and hope to have them running soon.

Pablo · Post by **Pablo** » Thu May 16, 2002 4:04 pm

Quite obviously, a freely spinning pushrod means that there's SOME clearance, even though we call it "zero" (imperceptible) lash. So long as there is SOME clearance, there is no danger in burning an exhaust valve. (The valve sits on the seat with only marginally shorter duration with no lash, and in this situation, more than adequate lash will quickly develop.)

Hell, I see heads from the factory with .030" wide sealing surfaces. Those seats are going to burn a heck of a lot quicker than .055" seats on an engine with properly adjusted steel pushrods.

If an engine with steel pushrods runs rough when started, then either those pushrods are NOT spinning freely, or there is another unrelated issue. The engine should purr when started --- so quiet and smooth that you only WISH it would stay so quiet.

Obviously, high quality aluminum pushrods are best. But we got so fed up with "bad batches" of supposedly "aircraft spec aluminum" pushrods, that we eventually gave up on them. I'm sure that's changed today. There seems to be a greater emphasis on true quality than hype in today's market, fostered by the fact that people seem more willing to pay for high quality than they used to be ---

JMHO, Paul

MASSIVE TYPE IV · Post by **MASSIVE TYPE IV** » Thu May 16, 2002 7:13 pm

Dan,
set those valves at .006 cold and watch them have .015 when they are hot, and even more....They sound like hell, and lose power.It's okay, we all know that you are great with a video camera so we'll overlook that clakety clack...LOL

Anyway, I run zero lash all the time with chromolys, when the engine is hot I have .004-5 and if the P/rods are cryoed i maintain a constant .004.

Too much lash makes your cold rocker arm geometry settings useless, and wears the guides. When I do geometry I use .004 as a baseline and go from there. Loud valvetrains suck, and wear alot of parts out fast.

I have used Jonhs aluminum pushrods and give them rave reviews, I just put a set in an 80,000 buck beetle, (TIV POWER of course) and they are quiet as a mouse..

------------------
Jake Raby
Raby's Aircooled Technology
www.aircooledtechnology.com

danimal · Post by **danimal** » Thu May 16, 2002 11:24 pm

>>>No, you're right, but I meant on a standard valvetrain...even with chromoly pushrods, too much lash (grossly too much) will beat up your adjusters and valve stems in the long haul<<<

i ran stock lash on chromoly pushrods for way over 130k miles with no problems... if you are worried, run lash caps to protect the valve stem ends... quality adjusters should not get hurt, but then again, if you want to run triple springs on a serious daily driver, good luck, lol...

wrt lash settings, read my link to the martel site for reasons why they advocate running up to .030-.032" of lash for serious competition... there is nobody in our industry that has done that kind of research, so don't get blinded by the status quo out here

keep your mind open.

funny how this subject just came up on the clf:

"When valve lash is set at "0" when the engine is cold, is not good for the exhaust valve. When the engine is first started, the exhaust valve heats up immediately, holding the valve open. The exhaust valve is held open until the head and cylinder heat up enough to overcome this situation."

most of you won't have a clue who harold washington is, but what he said there is exactly what all the r&d in my faq shows... most especially, if you have a serious daily driver, zero valve lash is a fool's game.

one thing that was interesting in that clf thread was the response from george brown, it's the first time i've seen evidence that someone besides acvw guys has our bastard combo of aluminum heads and steel pushrods on an ac motor:

"Bruce, When I was a BMW dealer I saw problems on BMW /5/6/7 motorcycles from too-tight valve clearances. These are air-cooled boxer twins with steel pushrods and aluminum cylinders, heads, and cases"

dan
oceanstreetvideo.com

fastfood · Post by **fastfood** » Fri May 17, 2002 1:34 am

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by MASSIVE TYPE IV:

I have used Jonhs aluminum pushrods and give them rave reviews, I just put a set in an 80,000 buck beetle, (TIV POWER of course) and they are quiet as a mouse..

[/B]<HR></BLOCKQUOTE>Jake is that 80,000 buck beetle a typo?

------------------
Rice, it's what's for dinner!!!

danimal · Post by **danimal** » Fri May 17, 2002 8:31 am

>>>The BMW motorcycle example is completely meaningless to ACVWs since we don't use alum cylinders.<<<

it is still a good example of what happens with different rates of expansion between steel and aluminum in an aircooled motor... and yes, with aluminum cylinders, they probably had it worse than we do.

>>>With zero lash, the engine runs like crap for the first 20-30 sec.<<<

thank you for providing a perfect example of why you should NEVER run zero valve lash on an aircooled motor... i couldn't have said it any better myself.

perhaps pablo should re-read the part where your valves were perfectly adjusted... but the engine ran like crap because they were being held open during warmup.

>>>This may be where the valves aren't sealing properly as Dan states, but IMO, 30 sec isn't enough to burn a valve.<<<

the pushrod faq indicates otherwise.

>>>Loud valvetrains suck, and wear alot of parts out fast.<<<

loud valvetrains suck so bad that i've ordered up a set of john's aluminum pushrods... but i've never had a problem with "parts wearing out fast" on the motors i build.

if you can back that up with some logic, we are all ears.

dan
oceanstreetvideo.com

Shad Laws · Post by **Shad Laws** » Fri May 17, 2002 10:15 am

Hello-

Jake is that 80,000 buck beetle a typo?

Yep, it was a typo. He meant to say $84,700+.

-$54,000 for Car (1980 VW Convertible, Triple White number three of three)
-$12,000 for full leather interior (including headliner, seats, doors, and even a car cover... EVERYTHING)
-$18,700 for imacculately detailed (i.e. work of art status) 2270cc T4 engine

I'm sure there are other expenses, too. I just don't know about them

.

BTW, the car costs $54,000 because it is TRIPLE WHITE NUMBER THREE. Remember the famed 1980 Triple White Convertibles, the ultra-special edition cars that were the LAST aircooled vehicles ever sold by VWoA in the US? This was the very _last_ one of those three. It had 27 miles on it when purchased.

Take care,

------------------
Shad Laws
LN Engineering
http://www.lnengineering.com

bayareathrasher · Post by **bayareathrasher** » Fri May 17, 2002 10:25 am

ive seen it in person, although it didnt have any motor in it when i saw it. without a doubt in my mind, that is the most beatiful car on earth - that leather is sinful!

john

JohnConnolly · Post by **JohnConnolly** » Fri May 17, 2002 12:23 pm

I don't want to see an argument show up again.

Here's what's going on, and Dan hasn't explained too well.

When you start the engine, the valve heats up first. The valve gets longer. After 45 seconds or so the engine starts to heat up, and IT expands.

In this period, the zero valve clearance goes negative (valve held open) for 30-60 seconds, IF the valve is growing more then the valve clearance, which is part of why 0 clearance cars can run like shite for the first minute or so. As the engine continues to warm up, the engine's expansion is greater then the valve, so you have valve clearance.

I would bet my reputation that you ain't gonna' burn a valve with an engine that cold, especially only running for a minute or so with the valve not seating, so it's not harmful, just annoying.

John
Aircooled.Net Inc.

[This message has been edited by JohnConnolly (edited 05-17-2002).]

Bruce2 · Post by **Bruce2** » Fri May 17, 2002 11:34 pm

You didn't answer my question, Dan.
If there were some detriment, wouldn't I see something in the lash setting?