drex

iTrader: (1)

i heard you could "move" a powerband by adjusting your valve lash smaller or bigger? is this true and which way does what? i want my power to come in a little higher up in the revs...

five7kid

iTrader: (14)

Increasing the lash decreases the duration, which moves the powerband down slightly.

You can't decrease the lash below the minimum recommended if you expect your valves to close fully.

Sonix

iTrader: (1)

Also, the wider the lash, the noisier it'll be. It may wear faster also.

Eg, if you normally race in xxx location, and then go to to zzz location, 3000' higher in elevation, you can loosen up your lash to gain more cylinder pressure, and also shift the powerband lower.
A few thou' can actually make a difference. You can rig up your dial gauge to find out how many thou will change how many degrees.

Supervisor42

I'd like to step in and substitute advancing and retarding cam timing instead of changing lash.
Which way moves the powerband which way?
Advancing the cam moves the powerband higher?

327???

I think retarding the cam moves it higher.

F-BIRD'88

advancing the cam favours the lower end of the the torque curve.
Cause the intake valve closes sooner. Retarding the cam in a motor makes the intake valve close later, adding top end power at the expense of low end torque.

tighter valve lash make the effective valve timing longer = more top end

looser valve lash shortens the valve timing making more low end power but trimming top end power a bit.
both are a subtle but effective tuning aid.

generally you can tighten a motors valve lash quite a bit but can only loosen it a few thousands of an inch. a XE solid cam with its tight lash clearance ramp design wants a lash between .012" and .020" a cam with a more conventional longer lash ramp design like .026" wants a .020 to .030" lash adjustment window.
You have stay with-in a lash varience window that keeps the lifter on the camshaft lobe lash clearance ramp when it opens and closes.
if you want to know the allowable lash varience window you can use as a tuning aid, phone or email the camp company that made your cam.

You cannot make a little cam into a big cam by adjsutiong the lash or advance. You're just dialing it in within its basic rpm range.
if you have a medium sized cam and want a big cam to match your big racing intake manifold, you have to change the camshaft.

drex

iTrader: (1)

i just got the cam and lifters and i will change back to the performer rpm but if i bring the cam from .016 to .012 or so..id get lil more top end ?
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thanks bird and other gurus

five7kid

iTrader: (14)

Set the lash where the cam is meant to have it. That's your best bet for power for the longest time.

F-BIRD'88

yes but only as a tuning and evaluating tool to help you pick the next better cam you really need. if you wer to pull the timing cover and retard the cam you'd notice more of a power shift then varying the lash of a already tight lash design cam.

I suspect that from your other posts that you have a fuel volume delivery issue more than a cam problem. killing the top end. Typical on these cars.