Pushrod Length
03-25-2012, 03:53 PM
#1
Pushrod Length I know this a beat the horse topic, but hear me out. It just really doesnt make sense to me.
If I have a completly stock LS1 with 7.400" pushrods, the only change would be milling the heads .010"
Wouldnt that mean I need 7.390" pushrods?
Of course many people will say what works in one engine doesnt work in another, does that mean all LS1s came from the factory with different length pushrods?
What I'm getting at is, if someone is running the exact same combo as person B, why wouldnt the pushrods be the same?
I also saw pushrods are not sold in a variety of lengths. Looks like "close enough" concept is at work here. Unless they are custom made $$$.
If I have a completly stock LS1 with 7.400" pushrods, the only change would be milling the heads .010"
Wouldnt that mean I need 7.390" pushrods?
Of course many people will say what works in one engine doesnt work in another, does that mean all LS1s came from the factory with different length pushrods?
What I'm getting at is, if someone is running the exact same combo as person B, why wouldnt the pushrods be the same?
I also saw pushrods are not sold in a variety of lengths. Looks like "close enough" concept is at work here. Unless they are custom made $$$.
03-25-2012, 04:18 PM
#2
You do have a "acceptable" window for pushrod length, as for any mass production unit like the ls motors you will have some on one end of tolerance and others on the other end....but when you start doing work that changes factors like pushrods length it is always best to check the measurement of "your" engine just to be sure...
For instance I personally think the GM specs for pushrod preload is a bit on the tight side to begin with and I only run about a half turn from 0 lash to 22flbs torque, so with even just .010" milled of of your head you are already adding .017" preload to an already too tight setting (rock ratio is 1.7:1, so if you mill your head .010", then multiply that times 1.7 you get .017")....in an engine where in some cases .005" difference can mean the death of the motor every change needs to be taken into account.
Hope that helps!
For instance I personally think the GM specs for pushrod preload is a bit on the tight side to begin with and I only run about a half turn from 0 lash to 22flbs torque, so with even just .010" milled of of your head you are already adding .017" preload to an already too tight setting (rock ratio is 1.7:1, so if you mill your head .010", then multiply that times 1.7 you get .017")....in an engine where in some cases .005" difference can mean the death of the motor every change needs to be taken into account.
Hope that helps!
