Here are some rambling thoughts on the subject.

The main thing with setting the valve lash is consistency in the method being used.  I’ve found slight variances in lash when checking by the different methods and part of this goes back to non-contricity or out of roundness in regards to the base circle of the camshaft.  It’s not unusual to find up to 0.002”-0.003” of non-concentricity on even the higher end camshafts and this by itself is why setting the valves with the engine running tends to be a less accurate method than setting the valves with the engine shut off.  Other problems that crop up with the running method is oil getting to where it doesn’t belong and worn rocker tips beating up what started out being a good feeler gauge.  A P&G valve gapper will compensate for some of this so all is not lost in regards to setting the valves with the engine running if one of these gauges is available.  For myself and especially on engines with flat or adjustable tappets, I use several of the non-running methods for setting the valves and avoid setting the valves with the engine running.

Setting the valves is obviously not rocker rocket science and although missing the adjustment by a couple of thousdandts in either direction is not a show stopper, it’s still desirable to get that measurement as ‘dead on’ as possible and especially if experimenting with different lash settings in which to optimize performance and/or economy.  In theory, if the base circle of the camshaft was perfectly round, then it would make absolutely no difference where the lifter placement on the base circle is when tappets are adjusted as long at the lifter is not on the lobes or ramps.  But this is not the case so just insure that you’re using the same adjustment procedure so that the results are consistent.

With the recently introduced Y aluminum heads, the temperature of the head itself has become a major player in the lash setting.  Although iron heads don’t grow enough to be a major consideration in the lash settings, the ~0.003”-0.004” net growth seen in the lash adjustments when using aluminum heads from cold to hot is just another factor that must be taken into account.  I’m currently setting the valves on the aluminum headed engines with the engine itself being hot soaked.

Lorena, Texas (South of Waco)

The only thing i can think of is the position of the lobes. That's why ?? for example when the exhaust just starts to open then set the intake, their not saying wait till the exhaust is all the down. Maybe Ted can fill us in alittle more of why the position of the lobe matters???

-Gary Burnette-

I have been setting valves with the engine running at a slow idle for over 50 years on both Y-Block and GMC. Is there any particular reason that anyone knows of as to why this is not an accurate way of setting them?

Kenneth

Fredricksburg, Texas

Here’s the link to the aforementioned post.  I couldn’t get to post #45824 by doing a search either.

Setting the valves

Lorena, Texas (South of Waco)

The method I use is when the exhaust just starts to open adjust the Intake as John said too .019 , then when the Intake just starts to close adjust the exhaust too .019 as well.

-Gary Burnette-

Hey Rick! 45824 does not bring up that post.I tried it.

  

In answer to your question, the lash is .019, intake and exhaust.  Hot or cold doesn't make enough difference to worry about.

John - "The Hoosier Hurricane"

Further to what I put in earlier go to search and type in setting the valves. There is a good deal of info in that post.

Regards


Rick - West Australia
Do Y Blocks Downunder run upside down? Gravity Sucks!!

The litters in a block are solid.

Enter the post number I gave you earlier in the search box and press return it should come up.

Regards

Rick - West Australia
Do Y Blocks Downunder run upside down? Gravity Sucks!!

thanks.

i tried posting for Post #45824 but it wouldnt show up.

so, are they hydraulic lifters with 0 lash ?

someone once told me they were solid lifters....

thanks



leonard