Too little preload?
Too little preload? How would the preload of .045 on the intake and a little less on the exhaust effect power. I know too much hurts power, but does too little hurt. I've seen guys say .030 to .060 is the area you want and others say .060 to .080 is the magic number. Just looking for some input. Thanks Fellas!
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Happy 4th LS1Tech!
TECH Senior Member
Joined: Mar 2004
Posts: 14,620
Likes: 17
From: BFE
There is the dial indicator way and there is this way if you don't have one:
Preload measurement:
I normaly prime the motor at this time with coil pacs and pump still disengaged and fuel line disconected (use container for any remneants in fuel line), butwith covers on (not to make a mess).
Once I have done 2>3 cranks with a few full revolutions and i see oil pressure for a few seconds, then I remove covers:
Hand rotate the engine in its normal direction of rotation until both valves are closed. You are on the compression cycle for that cylinder. (At this position the valve springs are at their least amount of tension making the job a little easier to do.)
Wait a few minutes, allowing the lifters to bleed down. Now, lay a rigid straight edge across the cylinder head, supporting it on the surface of the head where the valve cover gasket would go. Using a metal scribe and the straightedge, carefully scribe a line on both pushrods. Now slowly remove the torque from all valve train bolts, removing any pressure from the pushrods. Wait a few minutes for the pushrod seat in the hydraulic lifter to move back to the neutral position. Carefully scribe a new line on both pushrods.
Measure the distance between the two scribe marks, it represents the amount of lifter preload. If the lines are .030” to .060” apart you have proper lifter preload. If the lines are the same or less than .020” apart you have no or insufficient preload. (warm measurement)
Preload measurement:
I normaly prime the motor at this time with coil pacs and pump still disengaged and fuel line disconected (use container for any remneants in fuel line), butwith covers on (not to make a mess).
Once I have done 2>3 cranks with a few full revolutions and i see oil pressure for a few seconds, then I remove covers:
Hand rotate the engine in its normal direction of rotation until both valves are closed. You are on the compression cycle for that cylinder. (At this position the valve springs are at their least amount of tension making the job a little easier to do.)
Wait a few minutes, allowing the lifters to bleed down. Now, lay a rigid straight edge across the cylinder head, supporting it on the surface of the head where the valve cover gasket would go. Using a metal scribe and the straightedge, carefully scribe a line on both pushrods. Now slowly remove the torque from all valve train bolts, removing any pressure from the pushrods. Wait a few minutes for the pushrod seat in the hydraulic lifter to move back to the neutral position. Carefully scribe a new line on both pushrods.
Measure the distance between the two scribe marks, it represents the amount of lifter preload. If the lines are .030” to .060” apart you have proper lifter preload. If the lines are the same or less than .020” apart you have no or insufficient preload. (warm measurement)
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ill check this tomorrow. I was thinking a while back and doing some calcs. Basically if the cheatr cam has a .030" reduced base circle and if in fact 5.3L heads have a 63cc chamber unmilled, coupled w/ my .040" cometics, id need a pushrod of 7.443 or 7.45". I got this calc like this: Graphite gasket " .053 vs .040 (-.013") and base circle difference of -.030" Of course the valve seat and stem height will affect this but in my prelim calcs, the pushrod may be too short if these heads are infact unmilled. Now my question is, is a 5.3L head rocker pedistal the same height as a 5.7L pedistal height? This would explain my loud valvetrain during acceleration..
Dave
Dave
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Originally Posted by TT_Vert
ill check this tomorrow. I was thinking a while back and doing some calcs. Basically if the cheatr cam has a .030" reduced base circle and if in fact 5.3L heads have a 63cc chamber unmilled, coupled w/ my .040" cometics, id need a pushrod of 7.443 or 7.45". I got this calc like this: Graphite gasket " .053 vs .040 (-.013") and base circle difference of -.030" Of course the valve seat and stem height will affect this but in my prelim calcs, the pushrod may be too short if these heads are infact unmilled. Now my question is, is a 5.3L head rocker pedistal the same height as a 5.7L pedistal height? This would explain my loud valvetrain during acceleration..
Dave
Dave
I'm hopefully going through the same exercise here in a few weeks. I've got 5.3 heads milled about .008" with graphite gaskets.
I need to start to study up on what I need to do to for proper assembly.
TECH Senior Member
Joined: Mar 2004
Posts: 14,620
Likes: 17
From: BFE
Originally Posted by TT_Vert
ill check this tomorrow. I was thinking a while back and doing some calcs. Basically if the cheatr cam has a .030" reduced base circle and if in fact 5.3L heads have a 63cc chamber unmilled, coupled w/ my .040" cometics, id need a pushrod of 7.443 or 7.45". I got this calc like this: Graphite gasket " .053 vs .040 (-.013") and base circle difference of -.030" Of course the valve seat and stem height will affect this but in my prelim calcs, the pushrod may be too short if these heads are infact unmilled. Now my question is, is a 5.3L head rocker pedistal the same height as a 5.7L pedistal height? This would explain my loud valvetrain during acceleration..
Dave
Dave
(7.38 + .030) - .013 = 7.397 so 7.40 p-rod should be your length.
Can't you get he true base circle figure from TR? I think it would be more than .030 on a .600 lift
ive read that 2 people recently have measured their OEM pushrods out at 7.398" I dont have the cam out or id mic it. I have a call into TR for this info as its not on the cam card. There was a mistake in my math though thanks. I need to reduce pushrod length due to a thinner gasket, not add. Ill call TR again.
Dave
Dave
unfreaking believable. The guy i talked to therdidn't know what the base circle of the damn cam is. He's forwarded my email to Jason. All he can tell me is he designs all his cams to work w/ stock pushrods. Even on milled heads! This helps me absolutely none and it isnt even on the cam card. I shoulda mic'd it while it was out of the car but didnt think it'd be something i'd have to deal with.. Strike 2 against these guys..
Dave
Dave
Originally Posted by TT_Vert
unfreaking believable. The guy i talked to therdidn't know what the base circle of the damn cam is. He's forwarded my email to Jason. All he can tell me is he designs all his cams to work w/ stock pushrods. Even on milled heads! This helps me absolutely none and it isnt even on the cam card. I shoulda mic'd it while it was out of the car but didnt think it'd be something i'd have to deal with.. Strike 2 against these guys..
Dave
Dave
I'm hoping mine works out, I bought the pushrods with the cam kit from Futral. Since I'm going 5.3 heads I'm only milling about .008" max off the heads so I should be close to stock geometry barring any major cam base circle changes on the F14 from the stock cam.
Good luck
Launching!
Joined: Apr 2005
Posts: 205
Likes: 1
From: Atlanta area, GA
Originally Posted by TT_Vert
unfreaking believable. The guy i talked to therdidn't know what the base circle of the damn cam is. He's forwarded my email to Jason. All he can tell me is he designs all his cams to work w/ stock pushrods. Even on milled heads! This helps me absolutely none and it isnt even on the cam card. I shoulda mic'd it while it was out of the car but didnt think it'd be something i'd have to deal with.. Strike 2 against these guys..
Dave
Dave
So it's clear that even well known and respected tuners are more than willing to "let it ride" when it comes to the small technical details like choosing the correct push rod length for a given combination. The assumption (I guess) is that it will last long enough to not blow up in the first 30K miles or so.. By the time something bad happens you are convinced that "it's all part of the modding game, you take your chances, blah blah blah", and you'll probably head right back to the same tuner that was really responsible for the failure in the first place, so they can fix you up with a "new and improved" package.
Originally Posted by Dan_the_C5_Man
Well, if it's any consolation, LPE's techs will swear up and down (and sideways) that they re-use the stock pushrods on GT2-3 cam swaps all day long. We already know the FACTS.. The FACTS are that the LS6 cam has a smaller base circle than the LS1 cam, and the LPE cam has a smaller base circle than the LS6 cam. We also know GM engineers accounted for the smaller base circle of the LS6 cam w/ longer valves.
So it's clear that even well known and respected tuners are more than willing to "let it ride" when it comes to the small technical details like choosing the correct push rod length for a given combination. The assumption (I guess) is that it will last long enough to not blow up in the first 30K miles or so.. By the time something bad happens you are convinced that "it's all part of the modding game, you take your chances, blah blah blah", and you'll probably head right back to the same tuner that was really responsible for the failure in the first place, so they can fix you up with a "new and improved" package.
So it's clear that even well known and respected tuners are more than willing to "let it ride" when it comes to the small technical details like choosing the correct push rod length for a given combination. The assumption (I guess) is that it will last long enough to not blow up in the first 30K miles or so.. By the time something bad happens you are convinced that "it's all part of the modding game, you take your chances, blah blah blah", and you'll probably head right back to the same tuner that was really responsible for the failure in the first place, so they can fix you up with a "new and improved" package.
This is one of the most well thought out replies I have seen in a long time. Stateed facts, as well as speculation leaving the question/doubt in the readers interpretation. I love it. Thanks for sharing.
I agree that the guesstimating "base circle should be .xxx smaller (equals longer pushrod) and the gaskets are +/- .xxx from stock + sotck vs. milled heads" is a crap shoot at best. But now I ask this:
My combo, cam is larger than .600, we'll say .6307/.6222 duration around 231/242 on 114*, should be pretty small base circle (need to contact Ed). Gaskets are .040" (-.014 from stock) 5.3L heads milled .010" ( -.010 from stock). So, 7.398+ .050 (guesstimation of base circle) = 7.448 - ((-.014 + -.010) or just say -.024) = 7.428. Not sure what Morel Lifters like on preload but we'll go with the .30 - .60 like stock warm. What would be the outcome if ran with a 7.400" pushrod, then checking the wipe and dialing and either getting 7.350/7.375/7.425/7.450" afterwards? is there potential for limited use using it this way? I ask because my engine sits on a stand, waiting for an oil pump and of course pushrods. I havent seen too many people address the lifters being preloaded dry before.
I am using stock rockers for this combo, used a stock spring and measured with an adjustable pushrod, and came up with 7.350", contrary to the guesstimational math or 7.425". Maybe the Morels like more preload, less preload, and base circle could be less or more than estimated. I would hate to put the 7.350" in, although I feel I'd rather be short in this case than to have longer then needed, and have something get ruined.
Advice?
Charlie
Originally Posted by Unaffiliated Racing
CAT3
1. The best thing to do is ,always use a pushrod length checking tool and adjust for the proper geometry.
YEP, I USED AN ADJ PROD, SETUP AS DESCRIBED ABOVE, BUT WAS CONCERNED ABOUT THE LIFTERS NOT BEING PRIMED OR ANYTHING. I WENT AHEAD AND ADJUST IT OUT FROM 7.450 DOWN TO 7.350, TURNING THE CRANK OVER EACH TIME, SCARY WITH IT BEING FRESH *OUCH*. THE BEST WIPE PATTERN CAME FROM THE 7.350, ALTHOUGH I THINK OPTIMAL WOULD BE 7.375. I HAVE A SET OF 7.400 NOW AND A FRIEND HAS 7.350, SO FIGURE I CAN TRY THE 7.350, SHORTER BEING SAFER AND THEN SEE HOW IT GOES FROM THERE ONCE IT ACTUALLY RUNS. WHAT DO YOU THINK?
2. On a camshaft of that caliber.....why on earth are you not using an adjustable rocker?
SEEMS TO BE A LOT OF HASSLE WITH ADJUSTABLES, SOME ARE HEAVIER THAN STOCK, OR NOT RELIABLE. MY PLAN IS TO GET THE HS MODIFIED STOCK ROCKERS W. LARGER TRUNIONS AND CLIPPED ENDS. I DO BELIEVE A TRUE ROLLER TIP ROCKER WOULD BENEFIT MY COMBO, BUT I AM NOT FEELING GOOD WITH TOO MANY OF THE PRODUCTS OUT THERE YET, EXCEPT JESELS. AND I REALLY DONT BELIEVE THE ADJ. ROCKERS ARE AS NECESSARY AS IT IS "PIECE OF MIND" BUT THATS ME. AGAIN, I OPEN TO SUGGESTIONS, BUT HAVE A HARD TIME BUYING INTO "YOU GOTTA HAVE *insert anything from rockers, oil pump to dbl roller timing chains* FOR *fill in your combo here*. I'VE HAD 3 CAMS IN MY CAR, MY BUDDY 4, AND OTHERS AS MANY IF NOT MORE, AND NONE OF US HAVE SWAPPED OIL PUMPS OR TIMING CHAINS. OLD SCHOOL FOR ME, MEASURE STRETCH AND REPLACE AS REQUIRED, IF ITS CLOSE AND I AM THERE SURE....BUT 47,000 MILES ON MY CHAIN AND PUMP NO ISSUES AND LAST TIME I CHECKED THEM BOTH OUT DIDNT LOOK LIKE ANY COMING.
TT
It's hard to say how much it will vary. Like stated above, a checking tool and adjustable rockers is the best way. You can get correct geometry and preload at the same time. That may not be the case with a non-adjustable rocker.
I'm not sure about your second post. Typically the follower diameter is the size of the wheel on the lifter.
Thanks,
Brian
1. The best thing to do is ,always use a pushrod length checking tool and adjust for the proper geometry.
YEP, I USED AN ADJ PROD, SETUP AS DESCRIBED ABOVE, BUT WAS CONCERNED ABOUT THE LIFTERS NOT BEING PRIMED OR ANYTHING. I WENT AHEAD AND ADJUST IT OUT FROM 7.450 DOWN TO 7.350, TURNING THE CRANK OVER EACH TIME, SCARY WITH IT BEING FRESH *OUCH*. THE BEST WIPE PATTERN CAME FROM THE 7.350, ALTHOUGH I THINK OPTIMAL WOULD BE 7.375. I HAVE A SET OF 7.400 NOW AND A FRIEND HAS 7.350, SO FIGURE I CAN TRY THE 7.350, SHORTER BEING SAFER AND THEN SEE HOW IT GOES FROM THERE ONCE IT ACTUALLY RUNS. WHAT DO YOU THINK?
2. On a camshaft of that caliber.....why on earth are you not using an adjustable rocker?
SEEMS TO BE A LOT OF HASSLE WITH ADJUSTABLES, SOME ARE HEAVIER THAN STOCK, OR NOT RELIABLE. MY PLAN IS TO GET THE HS MODIFIED STOCK ROCKERS W. LARGER TRUNIONS AND CLIPPED ENDS. I DO BELIEVE A TRUE ROLLER TIP ROCKER WOULD BENEFIT MY COMBO, BUT I AM NOT FEELING GOOD WITH TOO MANY OF THE PRODUCTS OUT THERE YET, EXCEPT JESELS. AND I REALLY DONT BELIEVE THE ADJ. ROCKERS ARE AS NECESSARY AS IT IS "PIECE OF MIND" BUT THATS ME. AGAIN, I OPEN TO SUGGESTIONS, BUT HAVE A HARD TIME BUYING INTO "YOU GOTTA HAVE *insert anything from rockers, oil pump to dbl roller timing chains* FOR *fill in your combo here*. I'VE HAD 3 CAMS IN MY CAR, MY BUDDY 4, AND OTHERS AS MANY IF NOT MORE, AND NONE OF US HAVE SWAPPED OIL PUMPS OR TIMING CHAINS. OLD SCHOOL FOR ME, MEASURE STRETCH AND REPLACE AS REQUIRED, IF ITS CLOSE AND I AM THERE SURE....BUT 47,000 MILES ON MY CHAIN AND PUMP NO ISSUES AND LAST TIME I CHECKED THEM BOTH OUT DIDNT LOOK LIKE ANY COMING.
TT
It's hard to say how much it will vary. Like stated above, a checking tool and adjustable rockers is the best way. You can get correct geometry and preload at the same time. That may not be the case with a non-adjustable rocker.
I'm not sure about your second post. Typically the follower diameter is the size of the wheel on the lifter.
Thanks,
Brian
Used cap locks not yelling, but answering portion applicable to me.
i went ahead and checked preload w/ a dial. This is odd but this is what im coming up with.. I set the rocker to zero lash and tightened to 22 ft/lbs (took about 1.5 turns) and i get about .080" but it creeps back down to .020" in a matter of 10 seconds. I then rezero'd the DA at 22ft/lbs and loosened. I saw about .120". I think that could be because im loosening the rocker past zero lash when im loosening. Why would the clearance creep back down like that??
EDIT::
N/M i was reading that backwards. What is happening is the plunger is creeping down slowly and the dial is actually showing .080" after a few seconds. Is this normal?
Thanks
Dave
EDIT::
N/M i was reading that backwards. What is happening is the plunger is creeping down slowly and the dial is actually showing .080" after a few seconds. Is this normal?
Thanks
Dave
Last edited by TT_Vert; Jul 5, 2005 at 04:36 PM.