Why does valve lash change?

Cogburn · Post by **Cogburn** » Wed Mar 11, 2009 2:22 pm

If you check the clearance with the EOIC method and compare it to a different method the clearance could well be different.

If you set the opposite valve when one valve is at max lift the lifter will be on the edge of the opening or closing ramp and not the bottom of the base circle.

Also, at this point the force on the cam from the valvesprings is different.

Grab a cam and take a look at what is going on when you are setting valves by different methods.

Keep in mind you can waste a set of cam bearings turning the engine over without oil pressure. Turning the engine over should be kept to a minimum.

David_D. · Post by **David_D.** » Thu Mar 12, 2009 3:55 pm

It appears it is a difference in how he was adjusting them. Use one method, get x amount of lash, use another, get a different amount of lash.

I went back to the firing order method and set them that way. He's been doing it for years, and it's never not worked for him. He was just wondering why there would be a difference, but the assumption was that the cam would be exact on the base circle no matter the method. It appears this is not the case.

Thanks for the replies! Very helpful info.

af2 · Post by **af2** » Thu Mar 12, 2009 4:08 pm

David_D. wrote:It appears it is a difference in how he was adjusting them. Use one method, get x amount of lash, use another, get a different amount of lash.

I went back to the firing order method and set them that way. He's been doing it for years, and it's never not worked for him. He was just wondering why there would be a difference, but the assumption was that the cam would be exact on the base circle no matter the method. It appears this is not the case.

Thanks for the replies! Very helpful info.

Hard to know without seeing it.. You Have to adjust the valves 1 way and stay with it right or wrong to see changes.
I adjust valves as Joe does it works for me. If I were to change that I would stay with the change to make sure the lash is the same. It sounds like you are checking in 3 different places and will never get the same #.

I meant to say the firing order doesn't work with the cam I run.

David_D. · Post by **David_D.** » Thu Mar 12, 2009 7:29 pm

I personally use the EO/IC method and it works for me. My friend uses the firing order method where he adjusts both the intake and exhaust on the TDC for that particular cylinder.

I agree, you have to check it one way, or you will never get consistent results.

Barry_R · Post by **Barry_R** » Thu Mar 12, 2009 8:53 pm

I get eased a lot about my lash setting technique. My buddies refer to it as a "St Vitas dance" as I go from side to side with feeler gauge, Sharpie, and tools in hands.

I start off doing the IC/EO deal and put a Sharpie mark on each rocker. Then I rotate the engine a random bit and recheck the "loose ones", repeating the process for several revolutions. At this point I will not loosen one - knowing I am at least gonna have the desired clearance - but I inevitably find one or two that needs to be tighter.

bigjoe1 · Post by **bigjoe1** » Thu Mar 12, 2009 9:15 pm

I have done all of that that Barry said too. BUT the engine does not run any better- My take on all of this is when you find out what setting makes it run the best, just remember how you set the lash

JOE SHERMAN RACING

fastvette · Post by **fastvette** » Thu Mar 12, 2009 9:44 pm

I have seen loose cam bearings cause the lash to change alot when not checking at the exact same spot every time.

David_D. · Post by **David_D.** » Fri Mar 13, 2009 2:38 pm

bigjoe1 wrote:when you find out what setting makes it run the best, just remember how you set the lash

JOE SHERMAN RACING

I think that sums it up the best right there!

af2 · Post by **af2** » Fri Mar 13, 2009 4:10 pm

Big time yes on that one!!!

Hard enough to get confused with trying 1 thing 3 different ways.