lifter preload
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Senior User
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From: FLOWER MOUND,TX
lifter preload
i have read almost every post on this subject and i don't want there to be any i think i got it right facters in my mind...
comp says my lifter preload should be .020 to .040
this is with comp lifters,stock pushrods 1.73 roller rockers,and heads r&rd
when i first installed the lifter with no shim it looks to be about .060 (using double mark process on my pushrod and a feeler guage eyeballing)
i figured i needed a shim...after calling around all over no one locally had them and i don't want to wait for mail order...
i used my old oil deflecters that were on the old rockers(looks to be about .020 i think if anyone knows for sure that would be cool)) with a little bit of sanding to get them to fit into the pedestal area and they fit perfect...
now i know there is a science to how many turns on the rocker arm bolt equals
something like .055 and a half a turn equals so much...(TORQUE)
i guess my question is how much of a turn would be to get the .030 i need???
i thinkin about 3/4???the reason i ask is i remember some of them turning a full turn which would be .055?? which would be out of the ball park...
does any one know what i'm talking about??thanks
comp says my lifter preload should be .020 to .040
this is with comp lifters,stock pushrods 1.73 roller rockers,and heads r&rd
when i first installed the lifter with no shim it looks to be about .060 (using double mark process on my pushrod and a feeler guage eyeballing)
i figured i needed a shim...after calling around all over no one locally had them and i don't want to wait for mail order...
i used my old oil deflecters that were on the old rockers(looks to be about .020 i think if anyone knows for sure that would be cool)) with a little bit of sanding to get them to fit into the pedestal area and they fit perfect...
now i know there is a science to how many turns on the rocker arm bolt equals
something like .055 and a half a turn equals so much...(TORQUE)
i guess my question is how much of a turn would be to get the .030 i need???
i thinkin about 3/4???the reason i ask is i remember some of them turning a full turn which would be .055?? which would be out of the ball park...
does any one know what i'm talking about??thanks
Lead Driver
Joined: Nov 2000
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From: Albuquerque
Adjustable rockers would be set from 3/4 to 1 and 1/4 depending on who you listen too. This should hold true for non adjustable. So if the lifter is on the cam base circle, after all the slack is out of the push rod and rocker about 1 turn would be perfect.
Laughing Gas
Joined: Nov 2002
Posts: 1,198
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From: Fairmont
The oil deflector is .022" thick. One turn of a 5/16-18 bolt would be .056". The setting of "3/4-1 turn" is usually with a 3/8" stud, that equal .042"= 1 turn and .032" = 3/4 turn.
.020"-.060" is the preload spec I use.
.020"-.060" is the preload spec I use.
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From: FLOWER MOUND,TX
so one turn on a 5/16-18 is .056...which means .014 a 1/4 turn sounds like i may have to have just over 1/2 turn .028 + a little to get to .030 (does that sound right??) hummm i wonder if i could go with shorter pushrods and do away with the .022 shim???i will double check tomorrow to see how many turns i have now...a'm i going about this the right way???
Lead Driver
Joined: Mar 2004
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Just remember one thing: The more you shim a rocker, the more you throw the geometry off. Leading to more problems.
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Posting Legend
Joined: Sep 2001
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Actually with the 1.73:1 ratio of the rockers the motion induced at the lifter will be 2.73/1.73 or 1.578 x the motion at the screw. With a 5/16-18 screw one turn would be 0.056 x 1.578 = 0.088". 1/2 turn would be 0.044".
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Senior User
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From: FLOWER MOUND,TX
ok...now one turn would be .088" at the bolt or at the lifter plunger...i'm trying to figure out how to get .030" at the lifter plunger...i didn't consider (and truthfully didn't know how to figure the math)with the rocker ratio...you would think i could eye ball .030"..i was thinking i could go by the rocker bolt some how..it is an allen bolt head so i thought it would be easy see...come to think of it... without the shim being close to .060" preload..an undersize .030" pushrod would be just about right...i have to recheck in the morning...thanks guys
Laughing Gas
Joined: Nov 2002
Posts: 1,198
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From: Fairmont
Wow, good one Eric.
I plumb forgot about the ratio.
Have you ever heard of "dry lash" It is the amount of clearence between the tip of the valve and the tip of the rocker, when the rocker is pulled back all the way to bottom out the lifter. This lash is around .150-.175" Now I would like to see it writing, I had just heard of it. I suppose it could be figured out.
Full travel of a lifter is typically around .187" If I remember right.
I plumb forgot about the ratio.
Have you ever heard of "dry lash" It is the amount of clearence between the tip of the valve and the tip of the rocker, when the rocker is pulled back all the way to bottom out the lifter. This lash is around .150-.175" Now I would like to see it writing, I had just heard of it. I suppose it could be figured out.
Full travel of a lifter is typically around .187" If I remember right.
Posting Legend
Joined: Sep 2001
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Figuring the math was why I got paid the big bucks -hehe!
One turn at the bolt is 0.056". One turn of the bolt would be .088 at the lifter. I thought the math was clear... I guess I have been doing it to long. And yes the bolts are actually screws.
Technically a socket head cap screw.
If the lifter travel is 0.187" then the dry lash would be 0.187 x 1.73 = 0.324" Sounds like your lifter travel figure is a bit large. Check with a lifter manufacturer. As the lifter and cam wear the lifter preload will be reduced. I would suspect the total lifter travel is around 0.090. That way if the lifter preload is set at 0.060 then it would allow some "fudge" factor. In fact 0.090 x 1.73 = 0.156" which is close to your "dry lash" figures.
One turn at the bolt is 0.056". One turn of the bolt would be .088 at the lifter. I thought the math was clear... I guess I have been doing it to long. And yes the bolts are actually screws.
Technically a socket head cap screw.If the lifter travel is 0.187" then the dry lash would be 0.187 x 1.73 = 0.324" Sounds like your lifter travel figure is a bit large. Check with a lifter manufacturer. As the lifter and cam wear the lifter preload will be reduced. I would suspect the total lifter travel is around 0.090. That way if the lifter preload is set at 0.060 then it would allow some "fudge" factor. In fact 0.090 x 1.73 = 0.156" which is close to your "dry lash" figures.
Last edited by Torque1st; May 12, 2005 at 01:09 AM.
Posting Legend
Joined: Sep 2001
Posts: 30,255
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0.152 x 1.73 = 0.263 at the valve. There seems to be plenty of travel in the lifter so why specify so little preload? I would assume it also varies with lifter brand and type also. So it would seem that "dry lash" has little to do with setting up an engine.
