moving powerband with solid cam?
#1
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Car: 87 formula and 85 olds delta 88 2 d
Engine: 60's 350 holley carb and intake
Transmission: muncie 4 speed with centerforce
Axle/Gears: 3.42 99 camaro rear w/ discs
moving powerband with solid cam?
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...
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Car: 82 Berlinetta/57 Bel Air
Engine: LS1/LQ4
Transmission: 4L60E/4L80E
Axle/Gears: 12B-3.73/9"-3.89
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.
You can't decrease the lash below the minimum recommended if you expect your valves to close fully.
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Car: 1982 Trans-Am
Engine: 355 w/ ported 416s
Transmission: T10, hurst shifter
Axle/Gears: 10 bolt, true-trac, 3.73
Re: moving powerband with solid cam?
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.
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.
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Car: 1988 Trans Am GTA
Engine: 350 4BBL
Transmission: 700R4
Axle/Gears: 3.27
Re: moving powerband with solid cam?
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?
Which way moves the powerband which way?
Advancing the cam moves the powerband higher?
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Car: '82 Sport Coupe/'89 bird/'77 280z
Engine: 355/2.8/L28E(t)
Transmission: TH350/T5/4 spd
Axle/Gears: 3.73/3.42/3.54
#6
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Re: moving powerband with solid cam?
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.
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.
#7
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Car: 87 formula and 85 olds delta 88 2 d
Engine: 60's 350 holley carb and intake
Transmission: muncie 4 speed with centerforce
Axle/Gears: 3.42 99 camaro rear w/ discs
Re: moving powerband with solid cam?
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
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thanks bird and other gurus
Last edited by drex; 10-25-2007 at 09:40 PM. Reason: Automerged Doublepost
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#8
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Car: 82 Berlinetta/57 Bel Air
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Transmission: 4L60E/4L80E
Axle/Gears: 12B-3.73/9"-3.89
Set the lash where the cam is meant to have it. That's your best bet for power for the longest time.
#9
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Re: moving powerband with solid cam?
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.
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