Ok, I need a sanity check here!

[Brian C]

I'm talking about the simplest thing here. Valve adjustment, mech roller cam. I go to adjust the valves, everyone says to adjust the intake just as the exh valve begins to open. I set the lash to .024" hot. When I continue to rotate the engine till exhaust is at full lift, while continuing to check intake with the feeler gauge, why do I have more lash on the intake (now .027")? Same situation on the exh adjustment. Do I go with the loosest clearance (exh at full lift)? Or do I go by the book knowing that it'll be looser at other points on the lobe? By the way, it was always this way even when everything was new so I can rule out worn components.

I've always done it by where I found it to be the loosest spot on the lobe and haven't had any issues but I'm trying to go by the book.

Thanks,
Brian

[grosspeed2k4]

Foreword  I know nothing but I have a theory.

I thought you were supposed to set lash cold because by the time you get to the end the temp has changed enough for them not to be the same.  (ie the metal has contracted by the time you get done.)

Summary  I know nothing but that is my theory.

[Richard Maitre]

agreed, always set cold.....when possible.

could it be a geometry bind (pushrod end to rocker arm cup conformity)?

Rich

[Starkravingmad]

agreed, always set cold.....when possible.

could it be a geometry bind (pushrod end to rocker arm cup conformity)?

Rich

Ditto on the cold setting.  The laws of physics and heat flow will never allow you to set all valves the same unless you actively heat the engine evenly while trying to set lash.  That just aint practical.

[Brian C]

Ok, let's forget about the hot setting. I normally set them cold, check them hot. The real question here is why do I see more intake lash after rotating the exh valve to max lift as opposed to when it's just cracked open which is setting lash by the book?

[1SlowFormula]

My guess is due tot he ammount of overlap in your particular cam, unless the "book" was written for that cam grind then you may have to go with the least measurable lash. Most of the rules or things you read in books and/or find online are general guidlines and most of the time are for stock motor combos. if you have more overlap on a tighter LSA your Intake valve may not be fully closed until after the exhaust valve opens, and just going by the rul of seeing it move, well that isn't an accurate way to measure is it? what if on one you saw something @ .015" of movement and the next .020? or better yet what if the exhaust valve you using as you mark has too much lash already and you have to rotate an extra degree or 2 to get the same 'Movement from that exhaust valve then the next?

I say set the lash when you know the valve is seated and off the lobe completely, normally when the exhaust (or opposite valve, intake when checking exhaust and vice versa) is fully open...

[RRCPERF]

WOW     all them replys and no answer

 

[1SlowFormula]

WOW     all them replys and no answer

 

and that added another, well so did this one, LOL...

[Brian C]

maybe my cam's just got some f-'d up odd shaped lobes???

[HS400]

Do the lobes look square?

[Richard Maitre]

Maybe there really isnt a RULE of anything in this world except our abilities to analyze and make our own assumptions from there. How about this....Back to back runs with it set the regular way and then try setting it when you know it to be at the max lash setting. Back to back runs should tell you et-wise which way the motor actually likes it. Again maybe there is no written rule of how things should be done and maybe you may find a unknown secret to unleashing more HP.....who knows?

also....would an inverted ramp camshaft make a difference in setting lash?

Rich

[Brian C]

Do the lobes look square?

Not sure, I haven't had this cam out yet since 1st installing it.

John P, I hear ya! There's gotta be a billion different lobe shapes out there. I'm sure like Rich said the rule may not apply for every single one. Besides, if I just crack open the exh valve so I can adjust the intake, "just cracked open" is arbitrary and is probably gonna be done differently by everyone. Just cracked open is not an exact spot. I think I'll just crack open another beer and go adjust my valves

Thanks Rich. Maybe it's time I experiment with different lash settings. I've always just set em and forget em. I guess I probably just answered my own original question. If I start playing around with different lash settings, then it doesn't matter cause I'll probably be changing it by 2 to 4 thousandths anyway. I just want to make sure I'm doing it the right way. I'm being hyper-anal about it 

Ah just finished my beer, time to go just crack open another............

[HS400]

Being super anal about valvetrain is always a good thing.  I always check my lash and seat pressure after every outing.