Positive Stop Rockers????
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Senior User
Joined: May 2004
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Positive Stop Rockers????
I have "positive stop" rockers on my 73 302 F100. No adjustment. Just tighten them down.
My lifters (new) are clattering on startup for a few seconds, then they quit. It runs good, but doesnt seem to sound right at an idle (lope) and seems to be choked some while driving. It just doesnt seem to run right.....
Does anyone have any experience or ideas on these rockers? Do they work? Do I need to adjust them like normal hydraulic lifters to get the zero lash effect?
I am thinking I need to loosen them, let the lifters relax, and snug them back up til I get the lash out and then tighten them and lock them?
Any ideas here from someone who has had them or messed with them?
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My lifters (new) are clattering on startup for a few seconds, then they quit. It runs good, but doesnt seem to sound right at an idle (lope) and seems to be choked some while driving. It just doesnt seem to run right.....
Does anyone have any experience or ideas on these rockers? Do they work? Do I need to adjust them like normal hydraulic lifters to get the zero lash effect?
I am thinking I need to loosen them, let the lifters relax, and snug them back up til I get the lash out and then tighten them and lock them?
Any ideas here from someone who has had them or messed with them?
Thanks,<!-- / message --><!-- no sigs except when logged in -->
Elder User
Joined: Apr 2004
Posts: 970
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No you shouldn't have to make any adjustment. The geometry is figured out by the
engineers to center the lifter's travel when the nut hits the stop. You may get noise if a stud pulls out of the head allowing lash on that rocker, while it happens it is not too frequent. I would investigate carburation as the cause of your lope and choking up.
As far as the clatter on start up I would guess you may have a delay in the oil
pressure getting to the engine (oil filter draining back). Hope this helps.
engineers to center the lifter's travel when the nut hits the stop. You may get noise if a stud pulls out of the head allowing lash on that rocker, while it happens it is not too frequent. I would investigate carburation as the cause of your lope and choking up.
As far as the clatter on start up I would guess you may have a delay in the oil
pressure getting to the engine (oil filter draining back). Hope this helps.
Logistics Pro
Joined: Jan 2002
Posts: 4,907
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From: suburban atlanta
If you have had the heads worked on, you may have the valve stems too high, thus the rocker pushed higher on the valve side, thus lower on the lifter side... This could prevent the valve from closing all the way leading to lope, overall low performance, etc. If the seats were ground and the valves refaced you lose metal, and it all adds up over time. Each loss will move the valve stem further up.
You can test by loosening all rockers until they clack, tighten back down 1/2 turn or so, and taking it for a spin. If you loosen the rockers and the lope goes away immediately, you have found a problem. You *can* use lock nuts on the rocker arm studs if you want to keep the rockers where they are, should bringing them up from the positive stop help your engine. It is not warranted... but should work.
tom
You can test by loosening all rockers until they clack, tighten back down 1/2 turn or so, and taking it for a spin. If you loosen the rockers and the lope goes away immediately, you have found a problem. You *can* use lock nuts on the rocker arm studs if you want to keep the rockers where they are, should bringing them up from the positive stop help your engine. It is not warranted... but should work.
tom
Elder User
Joined: May 2006
Posts: 938
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From: Outside Boise, Idaho
Positive stop means just that, the nuts thread down until they stop. No adjustment. If you have a performance cam, or the heads were shaved, etc...it will be an issue.
You can always pull those studs, and cut threads for new threaded rocker arm studs (with hex nut is the easiest to use) and have the bosses machined if you want to use push rod guide plates and then with hardened push rods and poly locks you will have maximum flexability in adjusting your valve lash.
Did I spend enough of your money?
You can always pull those studs, and cut threads for new threaded rocker arm studs (with hex nut is the easiest to use) and have the bosses machined if you want to use push rod guide plates and then with hardened push rods and poly locks you will have maximum flexability in adjusting your valve lash.
Did I spend enough of your money?
Posting Guru
Joined: Mar 2005
Posts: 2,068
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From: western montana
I know this is a little late but want to add to thread.
As you know hydraulic lifters need to be 'pumped up' to get the proper geometry so that would explain why the problem goes away but not for the clatter. For some reason those rockers are not quite adjusted to those lifters which likely means the tolerance is off on the studs. The concept is the same between all rockers in that they should be exerting a bit of pressure on the lifter when tighened down aith the valve completely closed.
So i would check that first ie is there vertical movement in the push rod when the valve is closed. ( on adjustable rockers you usually adjust until play is gone then turn and additional 3/4 turn so that the push rod is embedded into the lifter a bit even when the valve is closed- ie no slack no clatter. I'd also measure the tolerance of those studs as far as distance from the spring seat to the stop on the stud.
hope it helps.
As you know hydraulic lifters need to be 'pumped up' to get the proper geometry so that would explain why the problem goes away but not for the clatter. For some reason those rockers are not quite adjusted to those lifters which likely means the tolerance is off on the studs. The concept is the same between all rockers in that they should be exerting a bit of pressure on the lifter when tighened down aith the valve completely closed.
So i would check that first ie is there vertical movement in the push rod when the valve is closed. ( on adjustable rockers you usually adjust until play is gone then turn and additional 3/4 turn so that the push rod is embedded into the lifter a bit even when the valve is closed- ie no slack no clatter. I'd also measure the tolerance of those studs as far as distance from the spring seat to the stop on the stud.
hope it helps.
