I'm looking at replacing the engine in my 2001 ZR2. I have a 20,000 mile 2001 4.3 that I want to replace it with. I want to replace the cam and springs with a Comp Cams 260 kit. It has .500" lift. I want to use the stock roller rockers. Does anyone have experience using these rockers with this much lift and did they have any issues? Also did you have to cut the valve guides for added clearance?

Ken

 

Comp Cams says that you will need to have adjustable rockers with this cam - stock roller rockers are not adjustable. It is common knowledge that you will have to cut valve guides for .500 lift on V-8 Vortec heads. It would be the same on the V6 heads.

 

I did contact Comp. They did recommend their adjustable rockers but said that the stock ones should work ok. The problem with the adjustable ones is that it appears that no one makes an attachment bolt adapter for the 2001 and newer factory roller rockers. There is a stud available for the non-adjustable old style rockers with a 10mm threaded end to go into the head. The roller rockers use a 8mm threaded end. This is why I'm asking about the factory roller rocker since they are in excellent shape due to low mileage. I don't really need the adjustable rockers due to the valve stems are at stock height which leaves the geometry from the stem to the rocker pedestal at factory settings. The only thing that might change is the cam base circle and I can fix that with different length push rods. I'll check the retainer to valve stem seal when I put on the new springs and fix if needed. Thanks for the input. Still looking if anyone has experience running the stock roller rockers.

 

I'm building a 4.3 V6 and one other issue with adjustable rockers is the clearance in the valve covers.
I will need at least a 1/2" spacer for the covers.