Do you recommend changing stock PR's with a 40k mile car, I have a ticking noise at WOT maybe PR's , but I am planning on doing the MS3 and I had heard about needing shorter than stock PR's to eliminate valvetrain noise, so shoukld I maybe change these? and if so go shoirter?

 

With a stiffer spring used with a bigger cam you will need hardened pushrods. I would run a 7.4" length. If you have milled heads a smaller PR would be better.

 

actually people sometimes use a longer PR (7.425) with the MS3 to eliminate the valvtrain noise.

 

Geometry dude, the best way is to buy a pushrod length checker and find out for sure. If your motor and heads and rest of valve train are stock that is a base line, take in consideration the cam specs and you can get in the ball park for which pr lenght checker to get and verify it. The only way to know for sure is using this method. I trusted a vendor on this board with it and their guess was just a waste of time and uneeded valve train noise. They got it right on the second try and it didn't seem like a big deal to them. It was to me.

 

stock style lifters and MS3 use 7.425's

 

what is better than stock? why longer? eliminate noise, and what? or why are they wanted more?

 

Because an XE-R aftermarket cam has 1.4x base circle (depending on lifts) which is on average ~.090 smaller than stock.
This translates in ~.045 average smaller effective radius on pushrod length.
Stock is 1.55
So you need to elongate your p-rods by that much to dublicate stock preload.
Now off shelf p-rods come in .025 increaments.
so 7.425's are the closest we get without going over.

 

is that gonnna be true with any after market cam since most will have a smaller base circle ?

 

Im running the 7.40s on my setup. Unmilled TSP LS6 heads, Comp XER 228/228 .588/.588 and PRC dual gold Valvesprings. My car makes excellent power and torque but we noticed I get some slight valvetrain instability around 6500 - 6600 rpms. Its after peak power, so it doesnt cause an issue as far as power, but nonetheless I do not like it. Point is I ordered some 7.425" Comp PRs and Im going to replace them and see if it helps. I'll let everyone know how it turns out....

 

cool