Pushrod length checking - questions - help needed
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Pushrod length checking - questions - help needed i'm a bit lost if i'm honest as to some specifics of how to check preload and pushrod length.
i've read the guide and had a go myself yesterday, but keep getting varying results on the dial test indicator, which must be due to the lifter bleeding down etc.
i know how much preload i need to be at, and i'm getting results between .035" and .090" and it seems to depend on how well you set up the "zero lash" to start with.
if i wind in the rocker bolt by hand till it seats hand tight the variances are less. if i wind it down just until i get no rock on the rocker then i get bigger bleed down results.
also, my understanding is that the lifter bleeds down each time you torque up the bolt, so how long do you wait, it seems to take ages on the dti with the gauge still slowly moving.
finally the guide doesnt make reference to if you should do it and re-charge the lifters with oil or not? ie do you have to crank it over and get oil pressure up before you start measuring?
my engine had been stood a month, the lifter bled down a lot first time then sort of settled out, but i think i am causing variations in result myself by how i set the "zero lash" start point before torquing down.
any help or experience to make it clearer would be great.
i think my current pushrods may be slightly too long as my new engine has LS7 lifters now and the old setup had a 7.425" rod on a 22/220 cam and worked ok. i reused these rods when i didnt realise the slight height difference from ls1 to ls7 lifters.
cheers
chris
i've read the guide and had a go myself yesterday, but keep getting varying results on the dial test indicator, which must be due to the lifter bleeding down etc.
i know how much preload i need to be at, and i'm getting results between .035" and .090" and it seems to depend on how well you set up the "zero lash" to start with.
if i wind in the rocker bolt by hand till it seats hand tight the variances are less. if i wind it down just until i get no rock on the rocker then i get bigger bleed down results.
also, my understanding is that the lifter bleeds down each time you torque up the bolt, so how long do you wait, it seems to take ages on the dti with the gauge still slowly moving.
finally the guide doesnt make reference to if you should do it and re-charge the lifters with oil or not? ie do you have to crank it over and get oil pressure up before you start measuring?
my engine had been stood a month, the lifter bled down a lot first time then sort of settled out, but i think i am causing variations in result myself by how i set the "zero lash" start point before torquing down.
any help or experience to make it clearer would be great.
i think my current pushrods may be slightly too long as my new engine has LS7 lifters now and the old setup had a 7.425" rod on a 22/220 cam and worked ok. i reused these rods when i didnt realise the slight height difference from ls1 to ls7 lifters.
cheers
chris
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dial indicator is set on the pushrod side of the rocker as per the guide i have, and initially set it to zero, at the point when i have wound down the rocker bolt to eliminate any lash (ie zero lash). i'm trying to ascertain then as i torque down the bolt to 22ft/lb how much preload it gives, and the lifter bleeds down etc,
regards
regards
Sounds like you are doing it correctly. Make sure lifter is against the cam on the base circle of the cam. Finger tighten the bolt to make sure you just take the slop out of the setup. Make sure the dial indicator is aligned with the pushrod (same angles). Make sure the dial indicator is not sliding on the rocker (I usually try to get it in the oil hole at the top of the rocker on my Yella Terra's). It will take a minute or so to bleed down, the dial indicator will stop. The more you do it to the same lifter the quicker you will get the measurement.
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should i do it though after the engine has been run and the lifter has been pumped up?
at first i got big variations in result, then after a bit it didnt really bleed down or alter.
and when i release the rocker pedestal bolt does it need some time to let the lifter expand out again? i am doing it as you describe with the dial test on the oil hole and in a straightline. what i am seeing is about 25 tho to 95 thou results on the same rod, so its not repeatable in any way. i think its to do with the point i set "zero lash" or the effect of lifter bleed down?
if it needs pumping up with oil i'd have to put the covers back on and coil packs so i cant see it needs to have run inbetween? or should i crank it over on the starter to ensure the oil pressure has been pumped up again or not?
at first i got big variations in result, then after a bit it didnt really bleed down or alter.
and when i release the rocker pedestal bolt does it need some time to let the lifter expand out again? i am doing it as you describe with the dial test on the oil hole and in a straightline. what i am seeing is about 25 tho to 95 thou results on the same rod, so its not repeatable in any way. i think its to do with the point i set "zero lash" or the effect of lifter bleed down?
if it needs pumping up with oil i'd have to put the covers back on and coil packs so i cant see it needs to have run inbetween? or should i crank it over on the starter to ensure the oil pressure has been pumped up again or not?
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You can adjust them cold,but are you making sure the lifter is on the base circle of the cam? It sounds like you are having a hard time finding Zero Lash.Also are you using the Pushrod drag method when adjusting Lash?
If you follow the correct adjustment procedures you should get an accurate lifter pre-load.
If you follow the correct adjustment procedures you should get an accurate lifter pre-load.
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You can adjust them cold,but are you making sure the lifter is on the base circle of the cam? It sounds like you are having a hard time finding Zero Lash.Also are you using the Pushrod drag method when adjusting Lash?
If you follow the correct adjustment procedures you should get an accurate lifter pre-load.
If you follow the correct adjustment procedures you should get an accurate lifter pre-load.
at the minute i am trying to measure what the preload is on my 7.425" pushrods, i have a set of 7.400" if need be, and a pushrod lenght checker to try and get the right length anyway.
when you say adjust them cold, does that mean it doesnt need to have run recently so the lifters arent pumped up then?
cheers
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no its stock rockers, stock ls7 lifters, i am thinking the engine needs to have seen some oil pressure thats all to get into the lifters or doesnt that matter?
i havent turned it over in ages you see, maybe a month or more.
i think its all down to where/how i start from at "zero lash", its quite easy to hand wind down the rocker bolt and i'm not 100% sure where to start measuring from when i start to torque up. a turn either way makes massive difference to the measured preload result on the dial test
i havent turned it over in ages you see, maybe a month or more.
i think its all down to where/how i start from at "zero lash", its quite easy to hand wind down the rocker bolt and i'm not 100% sure where to start measuring from when i start to torque up. a turn either way makes massive difference to the measured preload result on the dial test
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result!
the problem was i wasnt aware how fine the point of zero lash could be, it is easy to wind a little too far in initially on the rocker bolt without realising which misleads your result. once i had a light "zero lash" setting i found my measured preload was 0.150" so too much.
i swapped for my shorter set of 7.400" and got a prelod of about 0.090" which is about right for now, i've no other rods currently anyway.
thanks for the help !
the problem was i wasnt aware how fine the point of zero lash could be, it is easy to wind a little too far in initially on the rocker bolt without realising which misleads your result. once i had a light "zero lash" setting i found my measured preload was 0.150" so too much.
i swapped for my shorter set of 7.400" and got a prelod of about 0.090" which is about right for now, i've no other rods currently anyway.
thanks for the help !
LOL I was gonna mention how tempermental that dial indicator can be as I got about halfway thru reading this thread. Very easy to crank some false initial preload into the lifter even turning the nut with your fingers. Zero lash is basically resting the rocker arm on the pushrod . Glad it's sorted out
