Join Date: Apr 2009
Location: Benton Harbor, MI
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Thanked 0 Times in 0 Posts
That isn't a cut and dry answer. The rockers for Iron heads, need to be self aligning. So if you continue to use stock iron heads, you will need SA rockers. Otherwise, it is generally said that the NSA rockers are better for higher performance cams, as they are aligned by plates, that are sandwiched between the head and the screw in rocker stud like on aluminum heads. The plate maintains the push rod in that same plane.
Then there is the whole issue, about how some after market cams can have too much lift with 1.6 rockers, on the stock iron heads. The GMPP "845" cam in my 96 9C1 was one of those that was really border line on the exhaust. Many said you could not use 1.6 rockers on the stock press in studs on the exhaust. But... 20k-50k later, I bought the car, and it's fine. The valvespring retainer gets close to the valve stem seal(which is a shorter blue band seal), but otherwise it all seems ok.
The valvesprings, they are a lot of variables. You need to have them setup at the correct install height so you have the right pressure, and also have enough movement to allow the amount of lift you need them to allow. Meaning, you could have a spring that allows .600" of lift, but it needs to be setup at 1.6" height. On the stock iron heads, they might be setup at 1.5" height, so the spring no only has a max lift of around .500". That is the exact case with the Comp Cams 26915/26918 beehives springs.
Buffmans car has some springs sold under the number CMS614, for the stock cam. The 96 9C1, had some springs sold under the number CMS613, for the GMPP 845 cam, which is one step stronger. Unfortunatly, Combination Motor Sports went out of business, so I have no idea what springs they actually are, or what the rates are. They were popular springs for a while in the early to mid 2000's on ISSF, so maybe somebody there knows the answer.
~Cory Magner "My name is Cory, and I'm an addict."
95 DCM Buick RMS 14.21 @ 91.79 "Jesus" Blown Engine at 85k
95 DCM Buick RMS 13.52 @ 99.33 "The Doctor" Blown Engine at 180k
96 DGGM Buick RMW. 263k, still on the factory tranny.
And 5 other LT1 powered land yachts Is there Rehab for this Sh*t?