I don't fully understands valve springs. I just got some complete AFR heads. The springs have 120lbs at full height. I am also putting in an XE274 - Comp reccomends springs with 105 lbs seat pressure. My machinist figured I should have the springs for the XE284 (132 lbs seat pressue) because I'll need a little more with a 1.6 roller rocker. Is there more to the story? If not, I am pretty much in between the two sets of springs.

 

I think your mechanic is thinking about the Xe284 (986-16) springs for you because they have a slightly higher seat pressure without the expense of open pressure. More seat pressure means the ability to run at higher RPM's without problems. They also have a slightly taller installed height while retaining the same coil bind height as the 981's. That means that you can run higher lift without coil binding. That was probably another thing that crossed his mind considering as how you mentioned 1.6 rockers compared to 1.5. I see no problem in running the 986's in comparison to the 981's. They are both springs for hydraulic flat tappet cams. Its just one has a lower spring rate and a higher margin between the installed height and the coil bind.

But im no expert when it comes to hydraulic cam springs.

 

What about just using the AFR springs? I don't have a problem switching to Comp springs, but if the AFR springs will give me the proper seat pressure...

EDIT: THE AFR springs have 120 lbs seast pressure.

 

i wouldnt trust the AFR springs.

 

What about them is bad if they have the right pressure?

 

I have read/heard several stories about them failing due to poor quality.

 

The bottom of the line AFR springs are crap from everything I have read. For sure don't run over .480" lift w/ those, or you are asking for a spring failure. Get a set of COMP springs, that match up well w/ the cam you are running. That or get the upgrade AFR springs.

 

The heads came complete with:

 

Ok... those aren't the baseline springs though. IIRC, they come baseline w/ 1.25" spings that are good to like .500" lift they say... I could be wrong...

 

So do ya figure that is the correct seat pressure for my application?