93lt1fun

I'm considering a cam upgrade for my LT1 396. My current cam is:

GM Perf Hyd Roller cam (12370846) (Same grind as Crane HR-284-2S-12 IG)
222 / 230 @ .050 .509 / .528 1.5r ( .542 / .563 w/1.6r ) 112

Upgrade to:

GM Perf Hyd Roller Cam (12370847). (Same as Crane HR-296-2S-12 IG)
234 / 242 @ .050 .538 / .558 1.5r (.573 / .597 1.6r) 112

Some other miscellaneous info:

- Heads are LT1 stock CNC'ed with 2.02 / 1.57 valves
- Non-self aligning Crane Gold 1.6r 7/16" stud with guides
- Double springs with titanium retainers
- Hardened pushrod's 5/16" 7.150"
- Pistons are JE SRP dished
- LT4 .050 head gasket
- Hyd. Roller lifters (of course!)

Question is, Can I just swap them out or will one or more of the following be true and required for the swap:

1. Piston-to-valve clearance issue possible solved with thicker head gasket
2. Push rod length change
3. Spring size / pressure change
4. All of the above

-WhItE_NoIsE-

Do you have a video of it idling?

93lt1fun

No but, I could make one. The idle is just slightly rougher the stock but, not really that noticable to me at least.

rodj

"Double springs with titanium retainers"

You need to know exact specs of current springs to see in suitable for your new .600 lift.

steve40th

There are many people using Comp Cams 918 springs. Get the ones made from Pac racing.
These are US MADE , not Mexican made Comp Cams crappy ones. This company originally made them for Comp Cams, then CC sent them out to Mexico to save a buck, and the top of the spring started breaking with several people. This happened around 2006. Pac racing is a higher quality steel and manufacturing process.
http://www.pacracing.com/Valve_Sprin...e_Springs.html

racebum

we definately need the seat and open pounds per inch of your springs. also, you have ported LT1 heads. how many cc's runners? 190 maybe? those are good to 6500 or so on a 350. on your 396 that number is lower. that cam you posted is one hell of a beast but not out of line for a 396. have you considered buying a nice all out 210-220 cc head? AFR use to have {still might} a 227cc head that would be a lot more inline with that massive cam you plan and also 396 cubic inches.

Curveit

Unless you really prefer GM/Crane cams...Comp Cams has quicker acting lobes; smaller total duration to .050 numbers. Same top end power, with better bottom/mid range. If you do a lot of street driving a 230/236 should work well. For more of a top-end power motor, maybe a 236/242. You should check your Piston/Valve clerance, unless you hear from someone with the same combo. Depending on what you already have; springs are matched with the Cam used. Check Pushrod length. I've never used Ti Retainers, but somebody on the Forum had major problems with his not long ago. Comp Cams makes some steel Retainers nearly as light as Ti.
AFR makes some very nice heads, but I think the 227CC heads require offset Rocker/Lifters, and a Shaft mount setup is preferred. 195s or 210s can support over 600HP, so unless you're building a Race motor they should suffice. Doesn't matter... Just checked AFRs site and the bigger heads are for LT4s.