Searched still confused on Pushrod length
Originally Posted by bigbipo
I also am doing a cam swap and need two differnt length pushrods (intake/exhuast) I went to my local speed shop and picked up a pushrod length checker (adjustable rod)...
Their machine shop guy told me to "PRE-LOAD" The lifter to .060" then adjust to what length would be correct.. [.060"] seems a bit much and I would like to confirm this??...
PLEASE HELP....
I asked him also about measuren the base-circles and subtracting the difernce and he told me not to chance ordering pushrods based on that method....
Their machine shop guy told me to "PRE-LOAD" The lifter to .060" then adjust to what length would be correct.. [.060"] seems a bit much and I would like to confirm this??...
PLEASE HELP....
I asked him also about measuren the base-circles and subtracting the difernce and he told me not to chance ordering pushrods based on that method....
Last edited by mattr228; Jun 23, 2005 at 03:29 PM.
OK THX GUYS!!
Also the reason I rather not just do the math is cause im adden LS6 cnc ported head, they arent milled but still.. I rather be safe then sorry...
.030" - .060" is a HUGE JUMP? I guees it realy isnt that criticial after all? That machine shop guy said if its .010" off dont worry about it but .030 seems a bit much... But ill let u guys know if I have any problems... Should be done by this weekend I HOPE..
Also the reason I rather not just do the math is cause im adden LS6 cnc ported head, they arent milled but still.. I rather be safe then sorry...
.030" - .060" is a HUGE JUMP? I guees it realy isnt that criticial after all? That machine shop guy said if its .010" off dont worry about it but .030 seems a bit much... But ill let u guys know if I have any problems... Should be done by this weekend I HOPE..
Originally Posted by PREDATOR-Z
Ok, give me the measurements (lifts at cam), I'll calculate and you measure it and we see how close we are to each other. Kinda like a field test.
MTI Cam = 1.475" / 1.450"
Would be a differnce ofcourse of .075" / .10"
Plus what ever differce of the LS6 heads/valves would be. The head does NOT look milled, its brand new and still has some sort of anadized finish on gskt surface.. I do not know what my stock pushrod length is cause I dont have a caliper that is bigger then 7" LOL!!!
THX for the help, if you tell me how much to add to my stockpush rods ill be sure to start the pushrod checker in that length. I gotta kick mself in the rear to finish my long block first hehe :-p
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From: BFE
The 02>04 LS6 valves are .024" taller than LS1
so you'll need (according to my calc)
(.075-.024)=.051 + 7.38 = 7.431 intake
(.100-.024)=.076 + 7.38 = 7.456 ext
So, in a nutshell:
with adjustable rockers 7.425 it is
and with non adjustables 7.425 int and 7.50 ext
It doesn't make sense on the non adjustables but that will get the set up really close to stock specs with minimal valvetrain noise increase (if any).
Ideally, a custom p-rod setup of 7.431 int and 7.456 ext would get them as quiet as the stock set up with non adjustable stock rockers.
so you'll need (according to my calc)
(.075-.024)=.051 + 7.38 = 7.431 intake
(.100-.024)=.076 + 7.38 = 7.456 ext
So, in a nutshell:
with adjustable rockers 7.425 it is
and with non adjustables 7.425 int and 7.50 ext
It doesn't make sense on the non adjustables but that will get the set up really close to stock specs with minimal valvetrain noise increase (if any).
Ideally, a custom p-rod setup of 7.431 int and 7.456 ext would get them as quiet as the stock set up with non adjustable stock rockers.
Last edited by PREDATOR-Z; Jun 24, 2005 at 09:49 AM.
Why does everyone beat themselves up over "Pushrod Length" when all it takes is a $10 adjustable pushrod from comp and a black marker. With deck height differences, head thickness diffrences, base circle differences, rocker pad height differences there is no way unless you are working on that particular engine that you can guess over the net to what it needs. Sorry, I like buying parts once.
Chris
Chris
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From: BFE
Originally Posted by Cstraub
Why does everyone beat themselves up over "Pushrod Length" when all it takes is a $10 adjustable pushrod from comp and a black marker. With deck height differences, head thickness diffrences, base circle differences, rocker pad height differences there is no way unless you are working on that particular engine that you can guess over the net to what it needs. Sorry, I like buying parts once.
Chris
Chris
given that the p-rods are sold in .025 increaments, you never get the exact length needed (unless custom).
I do my calcs, buy all my parts and when I install, i only do it once.
Why do do it this way? Because i live outside US and I need to order package all at once. I do not have the luxury to drive to any store over here.
Also keeps me fresh on my algebra
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Can someone clarify the pre-load part? If I get the adj.p-r to zero lash, with lifters on the heel of cyl 1, do I simply take the zero lash and add .030-.060" for the "preload" or what? I have checker springs, and the adj p-r.
Charlie
Charlie
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Verdad Gallardo ok preditor,
I just dont understand your measurements first u said "in a nut shell" 7.425/7.50 Then u said to go with 7.431/7.456... How much pre-load do u factor in... Or is that only something u need to do with pushrod checkers?
*** Let me know how much to add to my stock pushrods ?*** since I can not measure total length of them but I have a checker. When im ready I will add your measurements...I.E. If you say I need a .030 or w/e longer rod ill make the checker .030 longer then stock....
I just dont understand your measurements first u said "in a nut shell" 7.425/7.50 Then u said to go with 7.431/7.456... How much pre-load do u factor in... Or is that only something u need to do with pushrod checkers?
*** Let me know how much to add to my stock pushrods ?*** since I can not measure total length of them but I have a checker. When im ready I will add your measurements...I.E. If you say I need a .030 or w/e longer rod ill make the checker .030 longer then stock....
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From: BFE
(.075-.024)= 0.051 + 7.38 = 7.431 intake
(.100-.024)= 0.076 + 7.38 = 7.456 ext
These are the differences in p-rod length vs your stockers.
Do you have stock rocker arms??
If so then put you p-rod checker at 7.425 intake / 7.450 exht and measure the lifter preload on these. pre-load should be between .030 and .060 on stock lifters.
If your measurement of preload are between these numbers, then you have the correct length.
If preload is more than .060, then decrease the p-rod checker untill you are in those margins, the read the length displayed on the checker.
If it is less than .030, then increase the p-rod checker until you are in those margins and read the length displayed.
Once you have those measurements, get the p-rod length that is the closest to those readings without going over.
Does it make sense?
(.100-.024)= 0.076 + 7.38 = 7.456 ext
These are the differences in p-rod length vs your stockers.
Do you have stock rocker arms??
If so then put you p-rod checker at 7.425 intake / 7.450 exht and measure the lifter preload on these. pre-load should be between .030 and .060 on stock lifters.
If your measurement of preload are between these numbers, then you have the correct length.
If preload is more than .060, then decrease the p-rod checker untill you are in those margins, the read the length displayed on the checker.
If it is less than .030, then increase the p-rod checker until you are in those margins and read the length displayed.
Once you have those measurements, get the p-rod length that is the closest to those readings without going over.
Does it make sense?
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**** me on this pre-load ****...I dont understand it. So hows this:
I try the a-p-r at say 7.300" and run the rocker to 22ftlbs, conduct wipe test and the wipe looks good, stick with it, or do I need to go through some counting of the rocker bolt to find out how many turns from Zero Lash I am? Head hurts.
I try the a-p-r at say 7.300" and run the rocker to 22ftlbs, conduct wipe test and the wipe looks good, stick with it, or do I need to go through some counting of the rocker bolt to find out how many turns from Zero Lash I am? Head hurts.
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Well, got everything needed and went to town tonight checking length. I must have done it about 6 times each on int&ext. Wipe looks best with the 7.350. Wipe starts slightly on the interior, centers nicely and rolls over towards the exterior and back, resting more so on the interior from centerline. So, feeling comfortable with that, I will be ordering the 7.350" tomorrow.
Thanks to everyone here, I greatly appreciate the confusion I created...nothing like making an easy task difficult.
Thanks to everyone here, I greatly appreciate the confusion I created...nothing like making an easy task difficult.
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From: BFE
Originally Posted by CAT3
Well, got everything needed and went to town tonight checking length. I must have done it about 6 times each on int&ext. Wipe looks best with the 7.350. Wipe starts slightly on the interior, centers nicely and rolls over towards the exterior and back, resting more so on the interior from centerline. So, feeling comfortable with that, I will be ordering the 7.350" tomorrow.
Thanks to everyone here, I greatly appreciate the confusion I created...nothing like making an easy task difficult.
Thanks to everyone here, I greatly appreciate the confusion I created...nothing like making an easy task difficult.
The wipe test on pedestal rockers has nothing to do with p-rod length.
wipe test will determine if your rockers are at proper height (which they are as you say).
Wipe test determines correct geometry and preload to a certain degree, p-rod length only affects lifter pre-load (this is because we run hydraulics, ie LSx specific with pedestal rockers).
Now with stud mounted rockers (Comp Magnum), your method is correct.
Now that you know that your geometry is correct, you need to measure your lifter preload to determine what length rod you should run. I would say ~ .060 cold.
Try to do other p-rod length (7.40) and (7.30) and a wipe test, you'll see it has no effect on your geometry (centered wipe), but will have dramatic effect on lifter preload..
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Actually, I did see a difference b/w the 7.3/7.35/7.4 on the wipe test. .300 barley made it past center mass of stem. .400 went onto the outer edge of the stem. .350 was pretty much centered throughout the range.
Ok, other than using a dial indicator, how do you test preload?
Ok, other than using a dial indicator, how do you test preload?
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From: BFE
Was this with stock rockers?
You can ask Tony Mamo about what I've told you and that was his reply.
He actualy summarised it by saying: "do not use wipe test to determine p-rod length on pedestal style rockers, use it to determine proper rocker height (geometry), then user preload measurement to determine correct p-rod length.
Preload measurement:
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 straightedge 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 carefully 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
You can ask Tony Mamo about what I've told you and that was his reply.
He actualy summarised it by saying: "do not use wipe test to determine p-rod length on pedestal style rockers, use it to determine proper rocker height (geometry), then user preload measurement to determine correct p-rod length.
Preload measurement:
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 straightedge 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 carefully 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
gotta dig this one back up.
How can you have proper geometry with non-adjustable rockers and the pre-load be off?
seems to me if the wipe is centered, then the geometry would be correct.
How can you have proper geometry with non-adjustable rockers and the pre-load be off?
seems to me if the wipe is centered, then the geometry would be correct.