heads milled + new lifters = new pushrods, yes?
#1
heads milled + new lifters = new pushrods, yes?
so my heads were milled .040" while i was having them checked for warping/cracks & a bent valve replaced to get rid of a fire ring indent....i am also replacing the stock LS1 lifters with LS7 lifters, which from what i've gathered (with others posting measurements using dial calipers to back it up), are .050" taller, resulting in approximately .090" shorter clearance overall
the shop i had do the work (before they knew i had different lifters) said that i should be fine with the stock length pushrods with just a .040" difference, but i'm not convinced on that, given that many people on here have said that .050" shorter rods are needed when using the LS7 lifters.
.010" or .015", i could see as being negligible, and the stock pushrods would probably be OK....but .040" or .050"? not so much.
and definitely ~.090" as in my case with the heads + lifters? fuggedaboutit!
thoughts?
the shop i had do the work (before they knew i had different lifters) said that i should be fine with the stock length pushrods with just a .040" difference, but i'm not convinced on that, given that many people on here have said that .050" shorter rods are needed when using the LS7 lifters.
.010" or .015", i could see as being negligible, and the stock pushrods would probably be OK....but .040" or .050"? not so much.
and definitely ~.090" as in my case with the heads + lifters? fuggedaboutit!
thoughts?
#4
yeah, i've already got the adjustable rod length checker and i plan on measuring....my main question, i guess, was whether or not .040" worth of milling is enough to warrant shorter pushrods, or if the stock length 7.4" rods would work?
i would think i would need to go down to either a 7.375" or 7.35", assuming a .040" decrease in head height, all else being equal?
i would think i would need to go down to either a 7.375" or 7.35", assuming a .040" decrease in head height, all else being equal?
#7
OK, guys....i'm going to check...i've already stated that, & that's not my issue/question.
let me rephrase the question another way:
would a difference in height of .040" absolutely require a shorter pushrod, or would a stock-height 7.4" pushrod work fine in that scenario? this is with stock everything, rockers, springs, valves...the only thing not going back in from what was already in the car is the LS7 lifters.
if there's more to it than just a yes or no answer, can anyone explain why they might work in one scenario with a .040" difference, but not in another?
how much were your heads milled?
let me rephrase the question another way:
would a difference in height of .040" absolutely require a shorter pushrod, or would a stock-height 7.4" pushrod work fine in that scenario? this is with stock everything, rockers, springs, valves...the only thing not going back in from what was already in the car is the LS7 lifters.
if there's more to it than just a yes or no answer, can anyone explain why they might work in one scenario with a .040" difference, but not in another?
how much were your heads milled?
Last edited by 02Z28LS1; 05-19-2013 at 11:38 AM.
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#10
TECH Senior Member
iTrader: (39)
I'm going to say yes it would, My heads were milled from 64cc down to 59cc, I can't remember how much were taken off but around .040-.050 sounds right. With a small EPS cam I ended up w/ 7.350 pushrods, in a stock application Geoff says 7.40 would be fine.
#11
TECH Fanatic
iTrader: (45)
So what IM saying is, any little change can NEGATE changing pushrods for proper preload. MEASURE.
#12
TECH Senior Member
iTrader: (39)
And there is no real answer to his question unless he checks. Every single application is different, when I went from my stock heads to my patriots which were also milled to 59cc, I went from factory pushrods to 7.3 while keeping the same cam. When I called to order, TSP said there was no way. I went with what I measured and 500 miles later, car runs and sounds great.
So what IM saying is, any little change can NEGATE changing pushrods for proper preload. MEASURE.
So what IM saying is, any little change can NEGATE changing pushrods for proper preload. MEASURE.
#14
TECH Resident
iTrader: (20)
OK, guys....i'm going to check...i've already stated that, & that's not my issue/question.
let me rephrase the question another way:
would a difference in height of .040" absolutely require a shorter pushrod, or would a stock-height 7.4" pushrod work fine in that scenario? this is with stock everything, rockers, springs, valves...the only thing not going back in from what was already in the car is the LS7 lifters.
if there's more to it than just a yes or no answer, can anyone explain why they might work in one scenario with a .040" difference, but not in another?
how much were your heads milled?
let me rephrase the question another way:
would a difference in height of .040" absolutely require a shorter pushrod, or would a stock-height 7.4" pushrod work fine in that scenario? this is with stock everything, rockers, springs, valves...the only thing not going back in from what was already in the car is the LS7 lifters.
if there's more to it than just a yes or no answer, can anyone explain why they might work in one scenario with a .040" difference, but not in another?
how much were your heads milled?