My car currently has a comp cams 264HR-12 which has a duration of 212/218 @ .050" and lobe lift is.488/.495 with 1.5 rockers. Lobe separation and advance is 112(+4). I now have 1.6 rr's installed.

When I had my valve job done and my heads built the machinist said they should be good for up to .550 lift. I'm assuming he was telling me what the springs would handle when he said this (a long time ago). I picked this cam because I wanted something extremely street friendly and something that wouldn't kill emissions (it passed). At the time I knew very little, and now after about 4 or 5 years I fully realize how small that cam really is! Now the car is not a daily driver and runs a best of 12.89@112 on drag radials with full bolt-ons and I want more.

What do I have to do to run the gm847 cam? I've seen it, heard it and I want it. Obviously I am going to need springs. Do I need to replace the retainers? Do I need to have anything done with the spring seats on the otherwise stock heads? What about my stock lifters? My current build has around 50k miles on it, but my lifters are stock original with about 150k on them. When I did the last motor they still looked GREAT so they went back in. Can I continue using the 1.6 comp rr's? Do I need to change my pushrod length or make any more clearance in my guideplates? Are the cam bearings that the machineshop put in reuseable when doing a cam swap? I know my way around my motor pretty well but valvetrain stuff just never seems easy to me. I know I am going to need a higher stall converter, I am only concerned about what I need to do to the engine for this cam....Hopefully I asked all of the right questions!

Also, my bottom end is stock reconditioned/rebalanced with arp fasteners everywhere...and speedpro hyperuetectic pistons..... Can it handle the additional rpms assuming it was well built and maintained?

 

Anyone want to give me some input?

 

all i have heard is u have to spin the gm847 real high to get its full potention.... 6500+ (from what i have heard)

 

Your pushrod length won't change if your not removing the heads, but I would not chance using 150K lifters on such an aggressive cam. You should buy at least stock replacement, or Morels would be better (but very expensive) It sounds like you already have NSA rockers with guideplates and betters studs so you should be good to go in that department. As fas as springs go, you'll most certainly need new retainers and seats, and you'll need to be sure that they are set up at the proper installed height.

Your bottom end sounds like it should be fine as long as your tune is good, and you don't plan to use a power adder

 

I would recommend, as I usually do, to use the Comp 918 beehives. They are lighter than a dual spring and they drop right into stock seats on the LT1. You will need new locators, retainers and locks to go with them and you should use the 10* +.050 locks. If you have stock length valves then you should be fine. They are good to .600 lift.

You will have to spin the motor up pretty high to make full use of that cam. Also, if your heads aren't ported, you might not be fully satisfied with the outcome. If you're not porting your heads and you don't have 100% faith in your bottom end, I'd say look at something smaller like the CC 503. Just my .02.