Cam choice?

[Frank Enstein]

I'm rebuilding a 1998 5.7 Vortec and I'm keeping stock heads, block, crank, pods, rockers, pushrods
along with the rebuild kit, I am going to be buying a high volume oil pump, a steel oil pump drive shaft, mid-length headers

i want to put a slightly better cam in than stock I'm thinking a stock L31 cam as I saw there just lightly better or I was thinking a melling 689-CL-MTF-2 cam kit with lifters I'm looking for something to get more torque and power in the lower rpm range, I want to keep the stock pushrods and rockers but if needed I will also buy new spings.

A 351M cam in a Chevy? You're gonna need a big hammer!

And it's a flat tappet cam too!

 

[Schurkey]

A 351M cam in a Chevy? You're gonna need a big hammer!

And it's a flat tappet cam too!

Nice. Good catch.

 

[lumpdog602]

No need for a high volume pump. You're actually better served by a stock style pump if your street driving.

For a very slightly larger then stock cam, lots of people use the GM "395" cam. Its the same cam in the HT383 motor GM sells for these trucks.
Its hard to say what your max lift is, since casting can vary. The valve retainers crash into the valve seals if you go past .475 total lift unless you do some extra machine work. Talk to your machinist, as they will know better than anyone here.

^^THIS^^
If you are going .030 over and buying pistons/rings, spend a little bit more and stroke that motor to 383(along with correct stroker pistons). Only costs a little more for new crankshaft and block clearance work. Use cam recommended above and have your 062 or 906 heads thoroughly inspected. The HT383e was GM's answer for everyone pointing out the dogshit low end torque of the L31. Don't cheap out on a full teardown. Will probably need to look at upgrading tranny to 4L65 specs or 4L80 swap as well.

 

[Frank Enstein]

Nice. Good catch.

That happens when you get part numbers from Jeg's!

 

[Frank Enstein]

Buy both of these and you can cut down your guides at home.

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Any cam other than stock will benefit from a tune. For that matter, a stock cam would too!

 

[Erik the Awful]

What's your purpose for your truck? Have a plan and call a cam manufacturer.

If you haven't done the MPFI upgrade on your injectors, you'll want it.

Stroking to a 383 is about $1000. You have to decide if that's something you want. If you're building for a budget, I'd skip it and use the very good stock bottom end as-is. I would take the time to balance the rod and piston assemblies. The cheap Harbor Freight scale will get you close enough for a home build and you'll be pleasantly surprised how much smoother the engine runs.

The valve retainers crash into the valve seals if you go past .475 total lift unless you do some extra machine work.

Yes, and no. With the stock valvetrain you're limited to .475-.480" lift. If you use LS2/LS6 beehive valvesprings with Comp Cams 787-16 retainers you can run up to .530" lift with no machine work. I'm running a set of untouched Vortec heads on my 350 and I have a .507/.515 lift Lunati cam. My research says the springs are about 10% stiffer than the factory Vortec springs.

 

[Frank Enstein]

I like this but it needs 1.6:1 rockers, new stronger pushrods, and valve springs to work.

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[Erik the Awful]

I wouldn't throw out a cam recommendation without knowing the truck's purpose first. Even then I'd recommend calling a cam grinder.

 

[0xDEADBEEF]

I agree with Erik. I'm kinda contrarian in that I don't think lift is all that important. The power gains from .050-.100 extra lift aren't that much.

Get the most duration you can that will work with your intended purpose.

Figure out where you want to make peak power and adjust the LSA appropriately.

 

[GavinJansma]

The purpose of the truck is a daily that will be pulling a decent-sized trailer about 2 twice a week.