Cam choice?

GavinJansma · May 2, 2022

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.

Erik the Awful · May 2, 2022

I prefer to always put new, quality valvesprings in a rebuild. If your rocker arm breaks, you're down a little power. If a valvespring breaks your valve hits the top of the piston. If you're trying to keep the stock injection, I'd just go with a set of factory-style springs. RockAuto has Mellings for $1.70 each - $27.20 for a set. The GM springs are $9.42 each - $150.72 a set. The factory rockers are a little short on lift, but a larger cam will fix that, and won't cost any more than a normal cam. Reusing the factory rockers is budget friendly, and if the pushrods are in good shape, they aren't bad for a mild build.

As far as a cam, call your favorite cam grinder and tell them what you're looking for. Their advice will be better than internet advice. That Melling kit you're looking at is for a flat-tapped hydraulic cam and your motor has hydraulic roller lifters. You definitely want to stick with a roller cam. Three times the price, but significantly better. Clean the factory lifters, dog bones, and spider and reuse them.

I didn't bother with a higher volume or pressure oil pump on my build, and I have plenty of oil pressure. The dash gauge reads in the high 50s at idle.

Schurkey · May 2, 2022

GavinJansma said:
I'm rebuilding a 1998 5.7 Vortec...

...i want to put a slightly better cam in than stock I'm thinking a stock L31 cam

Don't you already HAVE an L31 cam in that Vortec 5.7L?

Be careful on the rocker arms. They're likely too worn to re-use--depending on the mileage/condition of the engine.

GavinJansma · May 3, 2022

Erik the Awful said:
I prefer to always put new, quality valvesprings in a rebuild. If your rocker arm breaks, you're down a little power. If a valvespring breaks your valve hits the top of the piston. If you're trying to keep the stock injection, I'd just go with a set of factory-style springs. RockAuto has Mellings for $1.70 each - $27.20 for a set. The GM springs are $9.42 each - $150.72 a set. The factory rockers are a little short on lift, but a larger cam will fix that, and won't cost any more than a normal cam. Reusing the factory rockers is budget friendly, and if the pushrods are in good shape, they aren't bad for a mild build.

As far as a cam, call your favorite cam grinder and tell them what you're looking for. Their advice will be better than internet advice. That Melling kit you're looking at is for a flat-tapped hydraulic cam and your motor has hydraulic roller lifters. You definitely want to stick with a roller cam. Three times the price, but significantly better. Clean the factory lifters, dog bones, and spider and reuse them.

I didn't bother with a higher volume or pressure oil pump on my build, and I have plenty of oil pressure. The dash gauge reads in the high 50s at idle.

ok, I wasn't sure if I should buy new springs or what kind I should buy.

This is my first time going this far with rebuilding a truck engine. I don't really have a cam grinder that I know of but I will call around and try to find someone.

GavinJansma · May 3, 2022

Schurkey said:
Don't you already HAVE an L31 cam in that Vortec 5.7L?

Be careful on the rocker arms. They're likely too worn to re-use--depending on the mileage/condition of the engine.

I do not know if it already has one in it as I'm not sure how to tell. And he engine has roughly 180-210k (bought from a dude that didn't know)

Erik the Awful · May 3, 2022

If you have a Vortec, you have an L31 cam.

"Likely too worn to re-use"? Inspect the rockers carefully and judge for yourself. Look carefully where they capture the pushrod to ensure they aren't eating through the metal. I haven't had an issue, but some of these guys have more experience than me.

Gmc3500HD · May 9, 2022

Pacesetter longtubes, comes with egr and get the sp357 cam it will work and you will be happy

35olds · May 10, 2022

So what is the best cam to use if you don't want to machine the heads ? I'm doing the same thing , I'm thinking of just using the factory cam because I do not find any answers . Thank You

Schurkey · May 10, 2022

Whatever cam has the appropriate valve-timing events, but not more lift than your heads can accept.

You'd still need springs to suit.

And machining the valve guides to accept greater lift is just not that difficult.

Vikingdude · May 10, 2022

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.

Cam choice?

GavinJansma

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