The Stovebolt Site Forums The Shop Area Engine Shop 2002 5.7 vortec

looking for info to make sure i dont mess things up. i bought a 02 5.7 vortec that came out of a 3500 box van the guy i bought it from had it rebuilt and put this cam in it.

valve lift intake exh.
.480 .480
cam lift .320 .320

duration[sae]287 287

valve lash hyd

centerline 107 111

spread 109

timing event @.050 cam lift
opens BTC 8 BBC 46
closes ABC42 ATC 4
duration INT 230 EXH 230

using rosker ratio 1.5

can anyone tell me if this set up is going to be ok for the stock 5.7 that has been converted to carb. i need any and all input.

Thanks
John

_________________________

You didn't mention the compression ratio, or whether it's going to be used with a standard or an automatic transmission. IMHO, it's going to need increased compression, around 10:1 minimum, and it will have a pretty lumpy idle with very high exhaust emissions. You'll be lucky to make it idle below 1200-1500 RPM, and manifold vacuum will be too low and erratic to handle power brakes without a big reserve tank. Use a standard transmission, or a torque converter with about a 2,000-2,300 RPM stall speed, and a 4.10:1 rear end or lower ratio.

In my opinion, it's way too much cam for smooth engine performance on the street. It would make a pretty good cam for marine use, or maybe a weekend cruiser with a low-restriction dual exhaust system and a 600-650 CFM 4-barrel carb. Low speed to midrange performance will suck like a Hoover upright, but it should come on strong above 3,000 RPM.
Jerry

Its something that you will never be happy driving on the street. Listen to Jerry's advise.

It'll never be easier to put a nice conservative cam in it than now while you have it on the stand.

regards,
Leon

i did not rebuild thi engine but i think i could install another cam im not a mechanic im a woodworker but i think i could acomplish puting a cam in but i dont know what size cam to get i do want a good lop tho. any recomendations on a cam would be greatly appreciated i am using a th350 and 273 rear end. seems like i read some where this engine had 9.4.1 compression not sure tho. thanks for the advice.im also going to use corvette style rams horn maifold.

John

The only "good lope" is the one that's not there at all. A Comp Cams 268H cam is about the most radical thing I'd reccomend for street use. It will also have somewhat less lift, so the valve spring retainers don't crash into the tops of the valve guides or chew up the valve stem seals if positive stem seals have been installed. If you decide to stay with the lumpy cam with the high lift, be sure the valve guides have been shortened about 1/4" on the top.

If the engine has been run to "break in" the cam, be sure you change both cam and lifters if you downgrade the cam specifications. If the engine hasn't been run for even a few minutes with the radical cam, the lifters won't need to be changed.
Jerry

Thanks Jerry it hasnt been run at all i think ill probably dowu grade the cam took 3 years to get this far . when i do get it on the rod i want to be able to drive it and enjoy it.

Thanks
John

Being a 2002 engine that engine should be a hyd. roller. And new lifters are not needed and I agree with Jerry, 268HR cam is a great cam to use.

the guy that built it put jb817 flat tappet lifters carbureted 4 barrel intake is the 268 still going to be ok.

Yes! Its the right cam!

I'm going ro suggest the 260H cam myself. For the reasons I said in another post about Vortec heads and valve seal clearance issues. Plus, it's a little more streetable, with a good mid range.

Jerry may be able to enlighten you more on the seal issue than me.

I've used both the 260 and the 268 cams, and they're both good choices. The 260 works best in trailer-towing situations, while the 268 gives a little more scoot for passing, etc. The 268 has enough idle lope to declare "I've got a cam", while the 260 resembles a stock engine with a slight miss. Both work well with basically stock torque converters, but the 268 can benefit from a slightly increased stall speed.

Valve guides- - - - -The only problem happens when valve lift approaches .450" or more. Then the valve spring retainer squeezes the umbrella seal or positive stem seal, and might get metal-to-metal contact, which can bend pushrods. The fix is to shorten the top of the valve guide a little. The 260/268 cams don't have enough valve lift to be concerned about interference.
Jerry

Thanks Jerry, Im going to use the 268. i appreciate the help!

John

I'm curious why your engine has flat tappets and not roller lifters. Rollers are the way to go.

not sure why he did that unless it was the cost. do you know i they make the 268 in a roller or what roller cam is equivalent to it.

John

Comp makes a hydraulic roller cam with similar timimg specs, but a LOT more lift. It's their XR-264-HR. It has 264 degrees of intake duration and 270 degrees of exhaust, but the valve lift is .487/.495. That would require valve guide modifications, and probably stronger valve springs, since the rate of lift woule be pretty extreme. It would be quite a bit more radical than the flat-tappet version, even if the idle lope is not very noticeable. It's going to cost considerably more because of all the high-tech gizmos the roller lifter setup needs. I'd hesitate to use that one for a daily driver.
Jerry

Thanks Jerry, I yhink im just gona use the flat tappet 268 with .456 lift this engine was supposed to be ready to go and i dont want to sink a bunch more money in it. will i have a problem with the cam retainer plate if i use the flat tappet cam.

Thanks
John

As long as you use the correct cam sprocket, the retainer plate won't pose a problem. If I remember it correctly, the sprocket used with the retainer plate has a stepped-down section that fits through the retainer and sets the proper cam position and end play. Before that feature was added to the small block engine, we had to fit a thrust button between the cam and the timing cover when we used a double-roller timing chain to keep the cam from "walking" back and forth and changing the ignition timing. I always brazed a heavy washer onto the outside of the timing cover to keep it from flexing and cracking the sheet metal. The thrust plate solved that problem.
Jerry

do you think this will be a good choice. 268h

High energyC.A.R.B. approved hyd flat tappet camshaft. fits 262- 400 cubic in.smallblock 1955 - 1998.
good street perfomance with stock converter, choppy idle.
RPM rang 1500-5500
Valve timing 0.006
Lobe seperation 110
intake centerline 106
valve lash hyd.
duration 268 268
duration @ 0.050 218 218
valve lift 454 454
lobe lift 0.303 0.302

Thanks
John

That's an excellent choice. It will work with stock compression, and even a standard stall speed torque converter, although a slightly higher-stall unit will really make the engine come alive. Don't go overboard on the carburetion- - - -a 600 CFM 4-barrel would be about right. A stock-calibration quadrajet for a pre-electronic 350 engine will also work well if you don't intend top go with an aftermarket intake.
Jerry

i have the satin cyclon non egr manifold says goog to 5500 rpm all ready on the engin.

John

I've dyno-run similar manifolds to 6500-7K with very good results. That's a pretty conservative speed rating! On the "cheater" engines we ran on the 1/2 mile round track, the ignition would crap out long before the carburetion got marginal. We were running 355 cubic inch small blocks to 6200 RPM on a 300-CFM Holley 2-barrel! Not the world's best choice, but that's all the track rules allowed.
Jerry

Hey, Jerry thank you for all your help now maybe ill be able to enjoy this truck. sorry about all the questions i just dont anything about building engines just trying to put something together for a nice daily driver.

Thanks
John

Well, 50+ years of building round track and street engines has made me an opinionated old coot, but I'm happy to share what has worked for me. Hope you enjoy the ride!
Jerry