Im doing the MS3 PRC dual spring kit, which size PR's should I get stocklength? some guy earlier said to do 7.350? I am not sure on the size exactly but I think he said a shorter than stocklength. Anyway I was looking for less valvetrain noise, and if you recommend shorter or larger Pr's then stock, whats benefits/setbacks. I just dont want a realllly noisey valvetrain. thanks!

 

7.425 is the ideal setup for that cam from what I have searched on here.

I run the 7.400 PR'S with my MS3 and it is very noisy

 

If the only thing you are changing is the springs, why do you want different length pushrods then what you have already?

 

So they dont break, and go flying out the side of the block.

 

I don't know how you equate length to tensile strength, but whatever.

 

I want to know why TSP puts 7.4's in the package if that cam needs 7.425's.

 

thats what i want to know as well, i just put that cam in with 7.400 pr and it's noisey as hell and the guys at the shop told me that i need 7.425 pr and then there will be no noise so i ordered some and there on backorder wich sucks.

 

ive got 7.425's in mine and its extreamly quiet, its quieter than it was stock

 

i was also told stock 7.4 pushrods for my ms3 setup. Hmmmm

 

with the longer pushrods, do you have to worry about compressing(or colapsing) a lifter? Do they give us 7.4's for a reason?

 

Stick with the 7.400". I have the same setup and went with the 7.425" push rod. I found out last night that it is bleeding off cylinder pressure because they are too long. The reading with the 7.425 was 130 psi. I put in a shorter set and it jumped to 170 psi. Most aggressive cams will make valve train noise.

 

The real reason for longer pushrods is because the base circle on most aftermarket cams is smaller than stock. It is also a good idea to go to a hardened one with the much higher spring pressures.

 

OK first i hear use 7.425's to make it quiet, then i see use 7.4's so it wont bleed off pressure. I take it there is no pushrod that s between these lengths to find a happy medium.

 

I say just put-up with the noise

 

would that noise cause KR

 

I haven't heard of anyone ever having Knock Retard on a properly installed cam

 

the only reason mine was so loud at first was a header leak. It sounds like a champ now! I will see if I can post a video here in the next week or so.

 

For 1 that is BS,

Your sig says aftermarket heads, were they milled?
What gasket are you running?

Here try this calc for a rough idea, on cam only swaps with stock gaskets 7.425 are it.

http://ourworld.cs.com/ls1info2/Pushrod+calculator.xls

 

No BS. When I had the XER lobe cam I could not get it quiet for nothing. It always made some noise. The computer did not retard any timing though. My MS3 cam is quiet but it bleeds off cylinder pressure and leaves alot of HP on the table. I can live with a little noise. I am putting in a set of 7.400" pushrods this weekend. I will let you know what it does. I have the Patriot Stage II LS6 Heads that are not milled. I used stock GM head gaskets.

 

For a pushrod to be too long to hang a valve open and bleed pressure, believe me that it would be more than .025" too long
Think about it, that would mean that your lifters are overpowering your springs and opening the valve.
Something else is not kosher.