at what point is a cam going to need a different size pushrod other than the stock 7.4

 

The stock Gen 3 camshaft has a base circle of 19.7mm. Most after market cams are smaller than this ('02 on ZO6 cam is 19.0mm for example).
This would need a pushrod length change.

Also if you mill (skim) the cylinder heads, or change the installed height of the rockers or change the length of the valves.
Anything in fact that alters the relationship of where the lifter sits to where the rocker pad (or roller tip) position is.

 

Depends on what you do.

 

most aftermarket cams have a smaller diameter base circle...depending on which lifters you use, you may or may not need to change the PR length....use a length checker to make sure u got it right...

 

Its just something you have to check....No one can give you and answer, only a guess.

 

^x2, i just had to check the length for mine, ls7 heads are a totally different beast

 

7.4's are for aftermarket cams. Different lengths would be for different heads or milled heads.

 

Not sure what you are saying here.......

 

he saying "typically" 7.400s are used on unmilled heads, but you still need to check for yourself.

I have Comp .105 wall, 7.400s pushrods in mine, but I havent swapped the cam yet so I didnt need to check. Ill be getting new pushrods soon since my truck is torn apart for a heads/cam/intake/header/exhaust swap

 

i went with 7.4s but i have heard 7.425s are a bit quieter.

 

To the op sorry to but 01ssreda4 is this on stock heads and what cam?

 

yeah stock set-up on a tr224. base circle is a tad smaller on aftermarket cams. i know this for sure bc i compared measurements.

 

Heard about that too,

It generally costs a not insignificant amount of duration and lift because the normally recommended amount of lifter pre-load has been ignored.

Bit like going forward three steps and back one.