Comp xr275hr
01-21-2009, 11:11 AM
#52
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What is the agreed pushrod length for this cam 7.4 length like stock or shorter. My heads are milled .045 with stock gaskets so I though I needed a 7.355 rod for the cam but you guys are saying you need a shorted one? Is the case circle different than a factory cam?
02-14-2011, 02:11 PM
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I know this is thread is over 2 years old, but i was wondering about the pushrod selection for this cam. I'm installing it in my 6.0 with milled .010 heads. what length pushrods should I be getting?
02-16-2011, 03:11 PM
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It really depends on how your valves sit in the heads. My heads had lots of hard miles on them so I needed shorter than normal rods to get proper lash. (or lack there of)
I cut one of my factory rods and built my own measuring tool. I recommend you measure instead of guessing or blindly putting parts in a motor because someone else got lucky with their build. There are lots of reports of people who want to know why theie motor "ticks" after a cam install.
I cut one of my factory rods and built my own measuring tool. I recommend you measure instead of guessing or blindly putting parts in a motor because someone else got lucky with their build. There are lots of reports of people who want to know why theie motor "ticks" after a cam install.
02-19-2011, 09:52 PM
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The XR275HR has a smaller base circle of 1.485" or -.065 shorter than stock.
I cannot seem to find exactly what length the factory push rods are, but are supposed to be 7.385.
So if this is the case and my math is right.....
7.385 + .065 -.010. = 7.44?
Does this sound right or am I way off base?
02-21-2011, 01:34 PM
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I don't plan on "blindly" putting parts in my motor. What I'm having an issue with is inconsistent information. According to SI, GM spec for lifter pre-load is .85 -.100". This is for use on a factory cam with a base circle of 1.550"
The XR275HR has a smaller base circle of 1.485" or -.065 shorter than stock.
I cannot seem to find exactly what length the factory push rods are, but are supposed to be 7.385.
So if this is the case and my math is right.....
7.385 + .065 -.010. = 7.44?
Does this sound right or am I way off base?
The XR275HR has a smaller base circle of 1.485" or -.065 shorter than stock.
I cannot seem to find exactly what length the factory push rods are, but are supposed to be 7.385.
So if this is the case and my math is right.....
7.385 + .065 -.010. = 7.44?
Does this sound right or am I way off base?
03-06-2011, 10:56 PM
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to what i was told is that ur right ur base circle is .065 smaller but ur only suppose to take half of that and add it to ur pushrods because the radius of the base circle only goes down by half. get me? so with that said its only .0325 smaller and when u add that to 7.385 u get 7.4175.... ur heads are milled .01 then ur back at 7.4075... in other words u will be fine with hardened 7.4s.. thats just how i would figure the math out.. but u need a pushrod length checker.
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