Stock LS6 Lifter Questions
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Stock LS6 Lifter Questions Does anyone have accurate measurements of the following on the stock LS6 lifters in a 2002 Z06 Vette.
1) Total lifter plunger travel range.
2) Lifter pre-load distance with all stock valve train components.
I'm trying to determine if replacing the OEM pushrods with 7.375" gauge length or 7.400" gauge length aftermarket pushrods will give me the best lifter pre-load.
I'm told the OEM pushrods are ~7.385" gauge length (7.400" actual tip-to-tip length).
I need to order pushrods ASAP and need to decide which length would be best for a direct OEM replacement.
1) Total lifter plunger travel range.
2) Lifter pre-load distance with all stock valve train components.
I'm trying to determine if replacing the OEM pushrods with 7.375" gauge length or 7.400" gauge length aftermarket pushrods will give me the best lifter pre-load.
I'm told the OEM pushrods are ~7.385" gauge length (7.400" actual tip-to-tip length).
I need to order pushrods ASAP and need to decide which length would be best for a direct OEM replacement.
Last edited by ZeeOSix; Jul 8, 2011 at 03:20 AM.
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I'm trying to do a little engineering analysis. Please see attached table showing supposed LSx OEM lifter travel and pre-load (in millimeters). Not sure if this is accurate or not, but it's the best info I could find so far.
Looks like there a huge difference in plunger travel distance between the lifter GM p/n 12576400 and lifter GM p/n 17122490. Anyone know why?
The 17122490 lifter with 4.22 mm (0.166") of plunger travel would make the use of any pushrod that was +/- 0.015" different from OEM a non-issue IMO.
I'm assuming my 2002 LS6 probably has the 12576400 lifter (?). If so, then the total plunger travel is reduced to 3.20 mm = 0.126", and pre-load distance is 1.58 mm = 0.062". This makes things a little "tighter" in terms of how far you could deviate from OEM pushrod length on the stock lifter.
Based on the OEM LS6 pushrods being 7.385" gauge length, and an OEM pre-load distance of 0.062", then:
a) If I used the 7.400" gauge length pushrod, the pre-load would increase to ~0.062" + 0.015" = 0.077".
b) If I used the 7.375" gauge length pushrod, the pre-load would decrease to ~0.062" - 0.010" = 0.052".
Which would be the better setup ... a) or b)? I've read some old threads here, and it sounds like if the pre-load is slightly past the mid-point towards the bottom of the lifter then the valve train seems to run quieter ... true? If that's the case, then it seems setup a) would be better then b).
Maybe I'm over analyzing this ... but I want to get this right the first time and not have to worry about any problem down the road from using the wrong length pushrod.
Please chime in.
Looks like there a huge difference in plunger travel distance between the lifter GM p/n 12576400 and lifter GM p/n 17122490. Anyone know why?
The 17122490 lifter with 4.22 mm (0.166") of plunger travel would make the use of any pushrod that was +/- 0.015" different from OEM a non-issue IMO.
I'm assuming my 2002 LS6 probably has the 12576400 lifter (?). If so, then the total plunger travel is reduced to 3.20 mm = 0.126", and pre-load distance is 1.58 mm = 0.062". This makes things a little "tighter" in terms of how far you could deviate from OEM pushrod length on the stock lifter.
Based on the OEM LS6 pushrods being 7.385" gauge length, and an OEM pre-load distance of 0.062", then:
a) If I used the 7.400" gauge length pushrod, the pre-load would increase to ~0.062" + 0.015" = 0.077".
b) If I used the 7.375" gauge length pushrod, the pre-load would decrease to ~0.062" - 0.010" = 0.052".
Which would be the better setup ... a) or b)? I've read some old threads here, and it sounds like if the pre-load is slightly past the mid-point towards the bottom of the lifter then the valve train seems to run quieter ... true? If that's the case, then it seems setup a) would be better then b).
Maybe I'm over analyzing this ... but I want to get this right the first time and not have to worry about any problem down the road from using the wrong length pushrod.
Please chime in.
Last edited by ZeeOSix; Jul 8, 2011 at 02:44 AM.
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Called the local Chevy dealership this morning and talked to the parts guy. He tells me the lifter p/n that should have come in my car when manufactured (in July 2001) would have been the 12564012, and that p/n was superseded to 12576400 on Mar 01, 2002. In any case, both those lifters have the same plunger travel anyway.
On lifter 12564012 or 12576400, pre-load center would be 0.063".
So for a lifter that has a total travel of 0.126" ... which pre-load position would be better?
a) Pre-load of 0.077"
b) Pre-load of 0.052"
On a side note ... he said the 17122490 is shown as the current lifter p/n for the LS1/LS6, and that lifter is also shown for the LS7. Note the 17122490 has more plunger travel for some reason (maybe to cover more engine models?).
On lifter 12564012 or 12576400, pre-load center would be 0.063".
So for a lifter that has a total travel of 0.126" ... which pre-load position would be better?
a) Pre-load of 0.077"
b) Pre-load of 0.052"
On a side note ... he said the 17122490 is shown as the current lifter p/n for the LS1/LS6, and that lifter is also shown for the LS7. Note the 17122490 has more plunger travel for some reason (maybe to cover more engine models?).
Last edited by ZeeOSix; Jul 8, 2011 at 02:04 PM.
FWIW, just finished a cam-head swap this weekend, I don't have the part number but I measured .220" of plunger travel with the LS7 lifters, recomended preload was .062"-.110" from the cam grinder.
