Zero Valve Lash

Advokat · Post by **Advokat** » Mon Jun 17, 2002 4:47 pm

I know this is a reply to an old post, but can the h/d aluminum push rods John sells be used with a head running dual springs?

Also, if this is possible, since these p/rods are aluminum, does the valve lash go back to being set at .006?

If not, and chromoly ones are used, does that mean that it is safe to set rocker arm geometry using the .004 number Jake mentioned?

Thanks
Thanks

Marty · Post by **Marty** » Mon Jun 17, 2002 7:32 pm

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Advokat:
<B>I know this is a reply to an old post, but can the h/d aluminum push rods John sells be used with a head running dual springs?

Also, if this is possible, since these p/rods are aluminum, does the valve lash go back to being set at .006?

If not, and chromoly ones are used, does that mean that it is safe to set rocker arm geometry using the .004 number Jake mentioned?

Thanks
Thanks</B><HR></BLOCKQUOTE>

I am using Johns' HD aluminum pushrods with dual springs that measure 340 pounds at full lift. I am not sure what the recommendation is but I set them at .004.
I also set my chromoly ones at .004 but this is for 1/4 mile at a time.

------------------
Marty Staggs
www.staggsracing.com

petevw · Post by **petevw** » Tue Jun 18, 2002 1:21 am

is the "zero" lash with stock head studs or chromo studs?

any difference?

pete

[This message has been edited by petevw (edited 06-19-2002).]

ppp · Post by **ppp** » Tue Jun 18, 2002 4:21 am

is there a difference in the spec's if your running roller rocker arms?

Pablo · Post by **Pablo** » Tue Jun 18, 2002 2:04 pm

"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."

Interesting. I gotta wonder why my engine ran so smoothly when cold, while set at zero. Perhaps I wasn't as meticulous at the zero adjustment, or perhaps my cheapo valves didn't expand immediately. Whatever the reason, "ya learn something new every day". Thanks, Dan.

Paul

danimal · Post by **danimal** » Wed Jun 19, 2002 7:04 am

zero valve lash is always a fun thread

john c. did a decent job of summing up what is in my valve lash faq.

however, bruce, he's wrong to infer that the valve will not suffer any damage from overheating... it may not "burn", per se, but constant overheating like that will decrease the longevity of the valve... that probably isn't something that will show up in the lash adjustment, but it may make parts of the valve brittle.

and just for the record, ollie frey and fred simpson busted my chops big time at the last sac race for advocating some valve lash w/chromoly pushrods

)

dan
oceanstreetvideo.com

Bruce2 · Post by **Bruce2** » Wed Jun 19, 2002 11:15 pm

But in order to make hi carbon steel brittle you first have to heat it up to about 900F (that's glowing orange) and then quench it in oil. I'd have a hard time believing the exh valve could get to even tempering temps (~600)
FYI, since my first post where I set the valves and noticed for the first time ever that the lash didn't change, I set them again in early June and found for the second time the lash didn't change. After the 1500 mile round trip to Sur Califa for the Classic, I checked them again yesterday, and for the third time, no change. Engine now has 15k miles on it since new in January, all at zero lash.

danimal · Post by **danimal** » Thu Jun 20, 2002 9:24 am

sh$t happens all the time on stock motors, when valves get out of adjustment with aluminum pushrods... they stay open part or all of the time, and eventually pieces break off of the head of the valve... i know you've seen that before... you don't believe that it's due to the valve overheating??

i can see the point that john is making about 'em not being open long enuf to cause serious damage, but if you've ever had a motor that sucked a valve, you're liable to feel a bit more cautious about it

dan
oceanstreetvideo.com

Bruce2 · Post by **Bruce2** » Fri Jun 21, 2002 1:17 am

Those stories of stock engines way back are due to owners of aluminum pushrods who never set the valves. They go into negative lash and stay there for thousands of miles. That's what causes a valve to drop. Not 30-45 seconds when dead cold.

petevw · Post by **petevw** » Fri Jun 21, 2002 11:03 pm

so......

setting valve lash different when using stock or chromo headstuds?

what the diff?

later,
pete

Bruce2 · Post by **Bruce2** » Sat Jun 22, 2002 12:33 am

This has nothing to do with headstuds.
We're talking about different lash when comparing stock aluminum pushrods to steel pushrods.

MASSIVE TYPE IV · Post by **MASSIVE TYPE IV** » Sat Jun 22, 2002 7:56 am

Yes it does have an impact on valve adjustments with steel pushrods....Chromo studs do not expand, stock do....

Bruce2 · Post by **Bruce2** » Sat Jun 22, 2002 8:51 am

Chromoly is a slang term for the headstuds available for VWs. A better term is Chrome molybdenum steel. The minute amount of Chrome or Molybdenum alloyed into the steel does not change the coeficient of thermal expansion. Chromoly head studs expand the same as stock.
Where's Shad when we need him?

s,axel · Post by **s,axel** » Thu Jul 11, 2002 1:21 pm

i run a .004" lash w scat steel rods it lattles a tiny bit when cold .
and a lot when hot.

maybe i should have fitted strait cut cam gears to hide the noise.

lol

ghiaracer70 · Post by **ghiaracer70** » Thu Jul 11, 2002 1:52 pm

I set rockers at .002 with chromoly push rods since when they expand at a different rate than everything else does I wont here them clink since Im always around seven thousand rpms any way I dont always want to be adjusting them every two weeks. Before I had to at .004 end play.