Cam help

[Tyler09]

I'm wanting to do a cam, I don't know anything about them. Never really kept a truck long enough to want to do them. But I want to do a nice cam, not choppy. Just a street cam that'll give me a good sound and gain some power. Also what lifters and timing chain would I need. I have a '96 Sierra 350 vortec btw. Help would be appreciated tons!

 

[am92]

Well, what cam you get depends a lot on how much you're willing to spend/do to accomodate it. If you stay under .470-.480 lift, the stock heads will work fine (check clearances to be sure though), but performance gains will be limited. If you want to go with a higher lift cam, you'll need new valve springs and retainers, machining for screw in rocker studs, and possibly a little clearancing of the guides. I'm pretty sure you can get up tp .550 lift with new springs/retainers on otherwise stock vortec heads. Finally, depending on the power curve of the new cam you'll most likely want a higher stall torque converter. The real question is what do you use your truck for and how much do you want to gain?

 

[Tyler09]

I use the truck daily just a drive won't ever haul trailers, I don't go to the track,just hot rod around town. Just want a little more power and a good sound. I don't wanna pay out the a$$ for one. Seen some on summit racing, for fairly cheap.

 

[big_mike]

Then your gonna want a cam that will work within the stock spring rates. You can achieve more lope with moving the LSA on the cam from say a 114 to a 112, but this will also shift the power range of the cam. You can have a nice idle sound with a 114 LSA cam with the right exhaust & tune. The lower the idle is set in the PCM the more you'll hear the lope at idle as well.

For instance, I run a 224/224 .581/.581 114 cam in my 99' TA. Its got a ton of useable power, its doesnt lope like a Pro stock car but you can definetly tell its not stock. Its easy on my valve train since I tossed a set of Patriot Gold dual springs rated at over .600" lift.

Always keep in mind, if you put alot of miles on you want a cam thats not gonna be close to max spring rates. You'll go through springs a few sets a year. Again, for example, I have put 60K+ miles on my Patriot springs b/c the lift on my cam is well below the spring max lift rating. So I got more life from my springs. Now there is a point where you can have too much spring but I dont think your gonna worry about that with what it sounds like your wanting to do. Also keep in mind your stock stall converter, you dont want to over-cam it.

Id just get a mild off the shelf cam & set of Comp 918 springs & call it good. Dont forget all the gaskets, new bolts (if any stockers are TTY) for the swap either. Sometimes the nickle & dime stuff will eat you up if you dont account for it.

 

[DieselPower]

Another option is going with roller rockers, swapping out to a slightly higher ratio (1.6 or 1.7), it'll give you a bit more valve lift and your stock cam will perform better. Your stock vortec heads should provide adequate air flow - they aren't your limiting factor yet. I'd suggest starting with a good filter setup, an exhaust system that provides the tone you are after then move on to engine internals. I replaced a holy (hole-y!) stock exhaust on my wife's C1500 with a 3" Summit Racing "Cat back" system and the sound is far more powerful than the stock engine can match! It's got adequate power for her as it is.

Cam selection is an art - it's best to read up on the details of how they work and select one that matches your needs and your current engine configuration. David Vizard's book on building SBC's on a budget has a pretty good chapter on cams and valvetrains - I'd suggest picking up a copy and reading through it before you make any decisions. Getting lots of low to mid range torque and good fuel economy should be a reasonable target, I'd skip on the high rpm, high HP cams as they will result in power that is not "compatible" with the aerodynamics of a truck. You want 0-80 mph performance for around town or highway use, speeds above that are better suited for more aerodynamic vehicles. Torque is what you feel!

 

[Tyler09]

Thanks for explaining it all, i dont know jack about internals. I wouldn't need lifters or a timing chain?

 

[am92]

No, to use 1.6 roller rockers you just pull the cover, take the old ones off and put the new ones on and adjust them. The highest you can go is 1.6 ratio but you'll need to check clearance of the pushrods in the pushrod holes. The different ratio rockers move the pushrod closer to the stud so you may have to drill out the holes to 1/2"(with the heads off the engine of course)

 

[big_mike]

Honestly for a guy at your level I'd avoid rocker ratio swaps. You can run into a few issues goin that route. The most important things to watch for when swapping a cam & leaving everything else to stock specs are:

pushrod length
piston to valve clearance (PTV)

I'd be willing to bet Comp already has several grinds right off the shelf for exactly what your looking to do. You can call them, tell them exactly what your looking for, how your engine is set-up & they will give you a grind number that will get you where you wanna be.

Also watch the degree of timing ground into the cam. For example some will say +4 which means its got 4* timing ground into it when installed dot to dot.