I cannot figure out why these motors need such excessive valve lash when hot. On a vw, you set them .006 cold, and as motor heats up with aluminum pushrods it becomes a "0" lash. With chromolly pushrods they don't expand so you set them "0" cold. Even on any motor with a hydualic setup there is no lash... lifters are preloaded quite a bit.
How does so much valve lash make it run correctly, are the cams not ground the same way as other motors? It seems we are loosing lift and valve timing is changed? I don't know I'm just stumped

They don't need "excessive" lash. They need correct lash, which is a function of camshaft lobe profile.
Yes, and when repairing a Proctor-Silex citrus juicer from the 1960s, you need to make sure the fibre washer is sandwiched between the two leather washers on the drive end of the motor armature. That bit of knowledge is just as apposite as your VW tidbit to the engines we discuss here on this forum. Fact is, when you're working on a slant-6, unless it's installed in a Valiant Wagon, it's not in a VW and so VW specifications are irrelevant.
No, we are not losing any lift by setting the valve lash to the correct figure.
All that's required is to shift your perspective a bit. You're coming from a completely different engine and reacting to what you perceive as "excessive" valve lash. All you have to do is realise that different engines with different architecture and different cam lobes and different valvetrain particulars have different lash specifications. Our 0.010" and 0.020" would be excessive on a VW motor. A VW motor's 0.006" would be insufficient on a slant-6. Use the lash specification for whatever specific camshaft you've got in whatever specific engine, without regard to specs that exist for engines other than the one you're working on, and there'll be no need for confusion or alarm.

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Too many people who were born on third base actually believe they've hit a triple.

I'm asking why are they like this... a cam is a cam i dont care if its a vw mopar or my scooter.... all you can do is change the lobes, but they all work under tyr same princapal. You can have a slant six with hydralualoc lifters and there is no lash needed... its all preloaded into the lifter. What is it that makes a flat tappet slant cam need so much lash. Other manufactures figured to use a "0" lash which to me makes more sense. More quiet less wear..ect.

And in my eyes it is exsessive if its possible to run 0.000. Obviously it is correct if runs best at such a high spec. Hell... if they can make the motor run at .010/.020 theres a way they can make it run .030/.050 but it would be loud as hell. What i want to know is WHY would they use such lash at a hot tempurature, and HOW, what in the cam allows the motor to run well at that spec.

Therr was no need for the wise ass remarks with the juicer, theres no fiber washer in a valve train in any motor, but yet there is a camshaft in both flat four and slant six. I can understand where your coming from, yes its obviously not exsessive and is obviously correct if that's what it was designed to run, but against another engine it is exsesive... you catch my drift. I'm typically a smart ass my self but i do like to learn, wether it be automotive related or cooking tips from my grandmother. And this question was intended to only gain some more knowledge... which i did.... i learned i need to make sure i have all my washers in order when rebuilding my grandmas juicer.

As for lift.... if a cam has a lobe lift of .400 and you multiply that to a rocker ratio of 1.5 you get a total lift of .600.... but if you have a motor that needs .020 of valve lash. Your now at .580 or am i crazy? Valve is closed, set at .000lash, roll motor over to top of lobe, you have "x" amount of lift, but oh wait! I forgot lash is at .020 now you back that adjuster off .020 and your valve closes ever so gently.

What determines the valve lash in a solid lift cam is how agressive the opening and closing ramps are in the cam profile, obviously the VW doesn't have or need as fast of a ramp on its lobes as many other engines, inline or V8's, since it has lash as small as .006 as you mentioned. Most Chevy and Ford solid lift cams have .018-.020 lash or more on both the intake and exhaust, and roller cams as much as .028-.030. So what you are seeing in the slant really isn't excessive at all when you look at other engines in comparison.

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There's no such thing as too much cam....only not enough engine!

Thanks for the info. I figured there would be other motors that would use more then slant.. just no experience of others. With solid lifters other then vw and the slant. Is there some kind of trick or formula to figure out what lash it would actually need? With my ocg cam their reccomended lashes where too tight motor ran like $#!+ at only 13/14 inches of merc.loosened them .006 and ran a lot smoother at 18/19".

What about spring pressures, wouldnt that help with the fast ramps? I know on my vw cam is fairly gnarly and was reccomended stiffer springs, lash is still zero with chromolly push rods, I'm running k800s on that set of heads, also to help 46mm valves to seat. And what is the reason for needing such quick ramps on a stock slant, is it the small bore vs larger stroke? Or does it have to do with being inline?

What they have tried to tell you is you are NOT comparing apples to apples. I am unfamiliar with Volkswagon engines, so If I were to have started running/working on one, from MY past experiances the .006 is WAY to tight. I understand WHAT they are doing ( clearances for 0 lash hot) but I dont know WHY they chose to do it that way, Its the same as you looking from the other side. The slant closes up some also when warm, altho it STILL has lash.

I am not sure why the aftermarket cams give such tight clearances but most of them do and end up being ran with 'looser' than stated figures. I am assuming it has to do with marketing and ppl trying to figure out how much lift is lost with looser figures. (as you are surmising now) Now when they finally started using hydraulic cams in them that all changed too....

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MRO....

Cheap, Fast, Reliable.... Pick 2...

Right, 'cause the slant-6 is known for wearing out and stuff.
Okeh, I'll shut up. I think you'll find if you adjust the lash on a slant-6 to the "more sensible" 0.006" VW figure it won't run very well.

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Too many people who were born on third base actually believe they've hit a triple.

The simple answer is "yes"... the lash clearance is determained by the lobe design used on the cam, the clearance ramp or "lash ramp" area is what deturmines the amount of lash that is "correct" for that lobe shape.

Truth is, you can take a VW cam lobe, copy it and grind it onto a SL6 camshaft "blank" and you will have your .006 lash clearances.
Trouble is... all the cam lobes are designed by smart engineers who spend a lot of time collecting date and calculating out the "best" cam lobe shape for a given engine, then testing it. In our case, one of the factors is a .903 diameter lifter found in Mopar engines, another is the expansion rate of the valves and with a SL6, valves with somewhat long stem lengths.

All this is the reason why I do not like a lot of aftermarket or reground cams and why I tend to not recomment any cams, based on the numbers people "throw around".
Good cam selection starts with good lobe profile selection, mostly driven by lifter diameter, engine layout, engine material type, valve train and intended operating range / vehicle use.
DD

Sure I'm comparing apples to apples, camshaft vs camshaft i wanted to know why one would need .020 compared to one thay runs at zero. Doesn't matter what engine its in.... I'm sure someone could grind a vw cam to require lash...

Dan. I never said adjusting .006 lash to a slant is better. I agree 100% .010/.020 is correct for a stock motor.

And thanks doc for the input. I knew it woiuld have something to do with the grind (obviously since its only a camshaft) just didnt know what parts of the lobe, and why would some manufactures want lash when zero proves fine on other motors. But some motors seem to need special lobe profiles that just require that lash.

Any idea if theres a way to figure optimal lash# on paper?

No. This is not a valid apples/apples comparison, any more than it's valid to compare the Briggs & Stratton on my lawnmower to the Pratt & Whitney on my flight because they're both engines.
Yes, it really does. You seem very resistant to that fact. Perhaps this will help: when designing the aluminum slant-6, Chrysler engineers thought they might have to go to hydraulic lifters because the greater coefficient of thermal expansion of aluminum vs. cast iron might make it impracticable to specify a solid-lifter lash adjustment that would provide suitable valve behaviour and noise control, cold and hot. However, in testing they found this theoretical concern did not translate to practice and so they kept the iron engine's same solid-lifter setup. I feel as though I am repeating myself when I say the lash setting is determined by the specifics(!) of the cam lobe profile, the valvetrain geometry, the engine architecture, and other factors.

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Too many people who were born on third base actually believe they've hit a triple.

You didn't understand, like doc said you can copy the vw lobe onto slant blank, whalah! Zero lash on a slant. Would it run well? No caise every motor doesn't use the same lobe characteristics. But it would have a lot less lash..... that's what i was saying rigjt there dan. Doesn't matter the engine a lobe is a lobe. Just ass my heart vs your heart. You could have a bigger heart with less blood pressure or the otherway around. Still a heart. I'm not a doctor so i could be wrong... but I'm sure you get it.

This whole question was just wanting to know why, and how. And i got my answer theres no need to try and out me. But i did have other questions that pertain to this topic such as how does a cam manufacture get there reccomended valve lashes. And why are people like ocg giving wrong tight numbers. Is there a specific formula

Im sure if you were to graph the opening ramps on a dozen or so different profile solid cams with varying valve lash you might begin to see a pattern of how fast or slow the rise rate is compared to that cams recommended lash. Its probably a rate vs. time(degrees)type of ratio that helps determine the lash.

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There's no such thing as too much cam....only not enough engine!

My personal experence... most of the cam grinders just pull the lash info. "off the top of their head". ( or right out of their a$$)
The better cam grinders know the designed-in lash range (yes, it's a range & not one set number) and the best cam people (usually lobe designers / engineers) can estimate a revised lash range when you use a .842 (GM) cam lobe with a .875 (F@rd) or .903 (Mopar) lifter.

For me, you measure it, in the engine, with your lifter size, using a dial indicater.
DD

What about the lifter diameter that makes a difference, is it just how much surface area it can support allows for more radical lobe profiles or something?