here is the real skinny on chromolly pushrod valve lash Thursday, 02-Nov-00 14:20:06 writes: earlier today i made reference to this link, here it is again with a couple of updates. the bottom line: you should always set street engine valve lash at the factory spec of .006", even with chromoly pushrods. anything less than .004" is a fool's game :-) i think that most people who read this faq will learn something new from some of the links. dan dan

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oops! (n/t) (dan) (02-Nov-00 14:23:49)

Nice to know someone agrees with me (there are so few). A lot of people may run zero lash and get away with it UNTIL something unfortunate happens. Also, picture this: you set your valve clearance to .0005" on a nice fall Sunday evening, say 65 degrees farenheit, and that night a cold front comes through and when you go out to start your car in the morning it's 28 degrees. Betcha it won't start... valves may not close completely and without compression the mixture won't light off. (n/t) (george brown) (02-Nov-00 15:59:15)

Nice work Dan. You are helping the whole VW community with your data logging and efforts to present info like this on your website. (n/t) (Steve Arndt) (02-Nov-00 16:01:02)

Re: Dan...good input...but what about those of us who have run "0" lash with chromoly pushrods for years...and no problems? I guess our years of experience is lucky? We all need to be sure that our opinions can be substantiated with facts. (Rick M) (02-Nov-00 16:04:43)

i tried to do this faq with an open mind, but i was unable to dig up any scientific, logical, or factually-based evidence in favor of zero cold valve lash... nobody but acvw's does it!! my berg chromoly pushrods do make more noise, but after running 'em for over 80k+ miles, i have not seen any evidence of damage caused by .004"-.006" of lash... to each his own, i guess :-) i just wanted to post what relevant info that i found. (n/t) (dan) (02-Nov-00 16:51:12)

Re: Good input George...If we make our comments relevant to the conditions...then there is accuracy. We live where the median temperature is always somewhere between 60-80. If I lived where colder I would use a little different approach. However..... (Rick M) (02-Nov-00 16:10:05)

Re: 0 LASH? well its not really, set the lash at .000 -.001and i have found my valves to settle at .011 at full operating temp. so its not 0 lash, this is the same as I have found with alum. push rods set at .006. To each his own, (n/t) (Art Thraen) (03-Nov-00 00:16:02)

RATTLE, RATTLE, RATTLE, RATTLE, RATTLE (n/t) (Wayne) (02-Nov-00 16:12:20)

Re: The Bottom line for me...>> ( Mark H) (02-Nov-00 16:33:02)

the factory changed the valve lash because.... (John Connolly) (02-Nov-00 23:36:36)

I think it's hard to use research done on water cooled heads and use it on a aircooled Vw engine, especially a engine which is all aluminum. The head expands at a faster rate than the steel ex valve. When it expands, it has a counter effect of pulling the stem deeper into the head, and making it effectivly shorter. The perch on which the rocker arm is attached is also expanding. This increases the valve lash. I know the valve lash is greater on a hot engine than on a cold engine, you can measure it yourself and verify that. It's not like you are running zero lash, you're in reality running .007-.008 lash, you are just setting it at zero when the motor is cold. I keep hearing horror stories about zero lash, but I haven't seen anybody who has burnt a valve running zero lash. (n/t) (James2) (02-Nov-00 16:41:05)

All aluminum? James, Iron cylinders, magnesium case, forged steel rods and crank? (n/t) (Steve Arndt) (02-Nov-00 16:50:13) james2, your logic is flawed because your opinions differ from the facts stated in the bentley manual... i always thought that air-cooled hot running valve clearances increased because the engine gets noiser, but the bentley sez otherwise!... you also failed to mention that all valve stems grow in length with the heat, which decreases the lash. (n/t) (dan) (02-Nov-00 16:58:28) The Head and case are cast from material that grow at a much faster rate than the steel rod or the valve. If you have aluminuim rods then go with the factory settings. If you have chrome moly rods then do this, check your valve clearance with the engine cold. Go drive it 10-15 miles. Hop out and recheck your clearance. I'll bet anyone here that it is at least .005 greater than when the motor was cold. (n/t) (James2) (02-Nov-00 19:31:38)

EARTH CALLING DAN. bently is referring to aluminum pushrods, NOT CHROMOLY! two very different things. i agree w james. jim kelly (n/t) (jim kelly [the crow]) (02-Nov-00 17:21:41)

EARTH CALLING "JIM" :-) without mentioning pushrods, james gave us logic claiming that "this increases the valve lash"... the only increase in overall valve lash is due to the expansion differences of the chromoly pushrods. (n/t) (dan) (02-Nov-00 19:15:02)

No, there is increased lash also because you have a steel valve in an aluminium head. The head grows faster than the valve. The test done in the article where done on water cooled heads, which run at 180-220 degrees and don't grow that much. The VW head runs much hotter and grows more and faster. That's why the valve isn't held off the seat with during warm up with zero lash. BTW, it's not a big deal to me, I'm going to run zero lash because it's worked for me. It it gives you piece of mind to have more, than it's not going to keep me from being your friend. (n/t) (James2) (02-Nov-00 19:37:37)

the valve is MUCH hotter than the head will ever be... 1200+ degrees vs. 400(?) degrees... guess which one expands more? the exhaust valve is very hot within seconds, so it expands immediately, i.e., the valve stem lengthens immediately to take up the cold valve lash... if there is any :-) meanwhile, the head takes a lot longer to heat up than the valve, because of it's much larger mass and the fact that it isn't surrounded by hot exhaust gasses... but i know what you mean about running the cold lash that works for you, i just wish someone could provide the science to back zero valve lash :-( (n/t) (dan) (02-Nov-00 21:16:17)

I guess I can't explain the period between the time both the valve and the head reach full tempature, and I think that is the strong point of your debate. I can only say that if the valve was being held off the seat, then it would have shown up in shorter valve life. I think we can pretty much agree that there is valve lash once the whole engine reaches operating tempature with the chrome moly pushrods.. I also know you went to the trouble of finding this info because you didn't want me to burn a valve, thus it shows you care about my valves. Thanks :0). (n/t) (James2) (02-Nov-00 21:28:48)

YO, dan dude.... 1200 degree exhaust valves??? commonnn!! the valves are cooled thru the seats and guides and dont get that hot! if the exh got 1200 and the intake was cooler they would be MILES different in lenth according to your theory..hey boys, 006 on intakes 044 on exhaust !! ha ha the valves DONT GROW MUCH!! the changes happen in the head/pushrods.. no being a smartass but things are gettin' a LITTLE TWISTED... FRED (n/t) (FRED STANSKI) (02-Nov-00 21:42:05)

"...Exhaust valves usually have to endure temperatures that are generally in the range of 1000-1500 F." please guys, READ THE FAQ, FOLLOW THE LINKS! :-) yes, the head will soon expand more than the valve stem, but NOT during the initial cold startup period :-)) (n/t) (dan) (03-Nov-00 02:15:55)

here is the rest: "...(exhaust)valves typically run 150-250 degrees(f) less than egt(exhaust gas temperature)" (n/t) (dan) (03-Nov-00 02:24:01)

Mabye we could get a government funded grant for few million or so, call the grant bug endangerment grant.. premise could be how heat effects the general nature of a bugs ability to perform under high stress situations. (n/t) (dean n.) (04-Nov-00 10:44:43)

"To each his dagnab, blue-eyed own..." Pogo Possum (Walt Kelly) (n/t) (george brown) (02-Nov-00 17:26:47)

I think I'll check a steel and an alum. pushrod for growth...... (Tom H.) (02-Nov-00 17:45:09)

Now there is a scientific approach, I got money that the aluminium rod grows .004 more than the steel. Wait, what temp are heating to? (n/t) (James2) (02-Nov-00 20:15:13)

And the results are in........ (Tom H.) (02-Nov-00 21:50:07)

Tom, could that be because of the short time the engine is run drag racing as opposed to a street driven motor? or is that irrelevant in this case? (bugly) (02-Nov-00 23:41:09)

thanks tom, for the real-world test! so, at 250 degrees, the measured hot expansion difference is .008"/alum vs. .017"/chromoly, right?... that ain't worthless trivia! :-) check out the link where they built a machine that measures the actual running valve clearances at high rpms, see what happens to exhaust valve lash under heavy race loads... then your training as a jedi knight will be complete :-) just don't go back to the dark side of zero valve lash! :-)) (just kiddin' guys!). (n/t) (dan) (03-Nov-00 03:02:31)

15 alum....7 c/m. not too scientific but building jets has taught me a lot about metals............. (Tom H) (03-Nov-00 07:49:17) Thanks for your efforts Dan! (n/t) (Don Jiskra) (02-Nov-00 17:55:22)

let me get this straight.all these differing opinions and NO flame war?whats up with THAT:-)? (n/t) (bartman) (02-Nov-00 18:48:04)

HERE is my thoughts.... on my drag car i set my chromoly p/r lash at 0-1 [pushrod turns/no real lash] when it gets real hot it gets real noisy[big lash] and i cool it off in the pits...on street cars w/chromoly i set at 1 or 2 thousandths so i dont wipe the lube off the cam,never had any problems,george has a point about temp getting colder and valves gettin tight but the valves wont burn because they arent hot enough when first started.... may cause some popping in the carbs or exh. my opinion it probably makes no measurable difference either way. do what works for your car. dennis valley vw (n/t) (dennis valley vw) (02-Nov-00 22:03:19)

Whoopie! another "debate" sure to get someone mad, how about: if it works for you, just do it? Believe it or not, you'll never convince an "expert" that his method is wrong, all that can come of this is: somebody is gonna get pi$$ed, start some $#it, and we're going to have to be censored again. I value this forum too much to see it destroyed by bickering. (n/t) (bugly) (02-Nov-00 22:26:42) BUGLY, GO BURN..... (th) (02-Nov-00 23:31:15)

Re: BUGLY, GO BURN..... (bugly) (02-Nov-00 23:42:11)

hey bugly it's all in good fun :-) controversy causes discussion, discussion causes people to think... and maybe we all learn something! (n/t) (dan) (03-Nov-00 02:37:13)

No one is getting mad Bugly, we are just hashing out our differences. The problems come along with some who think there way is the only way. I'm sure that Dan is just trying to caution us as to the risk we are taking if something should close up and we end up with NO Lash. I'm sure his way is safer, especially for people who don't adjust their valves very often. (n/t) (James2) (03-Nov-00 07:26:10)

Re: No one is getting mad (bugly) (03-Nov-00 20:29:34)

Re: hey bugly it's all in good fun :-) (bugly) (03-Nov-00 20:31:17)

Re: FYI aluminum grows 12 millionths per degree F per inch of length, Steel grows 6 millionths per inch per degree F. I think you may be interested in the delta between the two. If the oporating temp is 250F, then a 10" pAl pushrod should grow by .024", a carbon steel pushrod should grow by .012. the engine is Aluminum, cylenders cast iron (grows at almost the same rate as steel) then you have the ratio of the rocker to consider, I think. Do the math and decide for yourself (n/t) (Tom Simon) (03-Nov-00 00:34:26)

I have run zero lash since1982 with no problems.I cringe when a valve clattering VW pulls up in the parking lot with 4-6 thou lash. Mine are adjusted slightly warm at zero. (n/t) (04-Nov-00 14:49:53)


Re: Dan...good input...but what about those of us who have run "0" lash with chromoly pushrods for years...and no problems? I guess our years of experience is lucky? We all need to be sure that our opinions can be substantiated with facts.

Thursday, 02-Nov-00 16:04:43 writes:

I have run "0" lash with chromoly pushrods for years and will continue to do so. With aluminum I run factory specs. Everyone can do what they want to do here. I will continue to do what has worked successfully for me. The growth rate of chromoly is much different than aluminum when hot. So, I still don't see where everyone is coming up with their recommendations to run factory lash on chromoly pushrods. My motors sound like thrashing machines when I set them at .004-.006. Come on guys....listen to a few people who can conclusively show that their results are factual. There need to be a little less ego and stubborness here and a little more flexibility to try and accept new learnings. Do what you all like. I like the quite, smooth sound of my engines the way I set my lash with chromoly pushrods. Too much clearance can result in parts slapping each other and inordinate wear or damange.



Re: Good input George...If we make our comments relevant to the conditions...then there is accuracy. We live where the median temperature is always somewhere between 60-80. If I lived where colder I would use a little different approach. However.....

Thursday, 02-Nov-00 16:10:05 writes:

On our trip to Detroit in 1997...I drove my 2110cc motor with 48s cross country. In Wyoming, we woke to a 32 degree morning. My motor and Art Thraen's both fired on the first pop. We both run "0" lash, had big motors and run 48's. So, I think we need to maintain a broad and open approach to this issue based on where we live, ambient temperatures and how we drive. Again, different conditions allow different things. There is no 100% absolute rule on this unless we just choose to believe that way.



Re: The Bottom line for me...>> Thursday, 02-Nov-00 16:33:02 writes: I`ve also run zero lash on chrome moly pushrods for so many years I can`t remember. I have driven my VWs daily up to 100 miles for a long time. Personally though I run obsolete Sig Erson dual tapered Aluminium pushrods when ever I can, set at the factory .006 setting. Much quieter that way. By the way its interesting that the factory changed there official valve lash settings from .004 to .006 . It depends how old of a manuel you have. Mark H


the factory changed the valve lash because.... Thursday, 02-Nov-00 23:36:36 writes: people weren't adjusting their valves within the recommended interval. Since valve lash gets SMALLER (not tighter folks) as the engine wears, some people had lash at 0 or negative, and were burning valves. Increasing the lash gave more "margin for error", and had less of a problem. It's interesting to note that VW did a similar thing with the oil drain plate starting around 73' models, eliminating the drain plug. This was intended to "force" guys to clean the strainer, instead of just draining and changing the oil. John Connolly


I think I'll check a steel and an alum. pushrod for growth...... Thursday, 02-Nov-00 17:45:09 writes: ....heated at the same time in the same oven and measured with the same 12" dial caliper. Think this would be quantifying, factual data? I'll let ya'all know what I come up with. TaTa Tom H.


And the results are in........ Thursday, 02-Nov-00 21:50:07 writes: Not really surprising to me. I can set the valves at .004 on our drag Ghia's 1776 and after a pass, if I pop the v/c there must be at least 12-14 thou clearance, maybe as high as 18. I believe that the old crafty Herr Dr. Porsche was taking in to consideration the expansion of his motor when he specifed the alloy that was used in the push rods. Yes, different alum. alloys expand slighly differently, rate and total. That has to be allowed for in aircraft design and engine design, not much of a problem with cast iron and water cooling and 6" or shorter steel push rods. ......................Alum..........C/moly

room temp--11.060---------10.945

150 F.-----11.068---------10.948

200 F.-----11.075---------10.952

250 F.-----11.077---------10.953

Well, who won the bet? I used a stock 15/1600 push rod dug out of a scrap pile after work tonite, must have been 50 to choose from. And the C/M one is out of my 2017, a Berg one set up for ratio rockers on an engine that only needed .030 barrel shims to get my desired comp. Alum. expands at a much higher rate and higher total than steel (but we all knew that, right?) Here's a bit o trivia to go with this. Did you know that the Concorde (the supersonic jet) expands like 18" in length at cruising speed and altitude from heat? And burns 93 TONS of fuel from Heathrow to JFK!!! Caution : these results may be repeatable in your oven, just make sure there is no oil in them, or you could be in the dog house. :-0 Tom H.

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