Jake Widman

Ive got 91 4wd 5.7 and I wanna put a bigger cam in her to get a some more power out of it. I don't know to much about which cams are good and what size would be best for my application, so ill tell you a little about it and what I want to do.
All I've got done to the engine is bigger air intake filter, msd wires and distributor, and headers/exhaust.
I plan on rebuilding the engine before putting the new cam in, I want something that I can daily drive but still spank other trucks and have an awesome sound. Im assuming im going to need a new computer chip too.

any suggestions are helpful, thanks

Chughes

max lift on tbi heads is pretty low
i would say 450-460 lift is about the most you can run.

if you are going to rebuilt it, i would just put different heads on it. Tbi heads dont flow well at all. Vortecs heads from 96-98 trucks are cheap but they need machined to run over 480 lift cams.

The tbi system in general is very good for stock application, but its going to be a headache to make power with it.

if you wanted to stay fuel injected i would look at the Fast ez-efi setup.

i have a 91 c1500, i got sick of the tbi, i just put aluminum heads, 550 lift cam and a carb on it, and im glad i did.

hope this helps a little.

05GMC4.8

Look for some.vortec heads off the 96-98 trucks and get a tbi/vortec intake. I remember the lt1 cam out of the camaros/firebirds were a popular choice for a decent cam that was cheap. The tbi heads make great torque down low but lack on the top end. You can also swap on a t.p.i system from the thirdgen camaro/firebirds to gain about 20rwhp over the stock t.b.i. systems if you stick with the stock tbi heads. They can be worked over to get decent numbers out of them. If your really serious about making some decent power with the tbi system go over to thirdgen.org. there used to be some pretty knowledgeable people over there a out the tbi stuff. Lots of old posts on making power with them.
After its all said and done, you might be better off swaping in an ls motor though. That would def. Be faster that most/all tbi setups and more efficient.

hammered94

iTrader: (8)

If you put the right combination together, a tbi 350 can be a real torque monster from idle to about 4000 rpm. It all depends on what your looking for, I've played with tbi's for years and they can be a lot of fun if you know the head/induction/injectors/pcm limits ahead of time and dont try to do something beyond its limits. Ive seen many people in person and online that have overcammed and put expensive heads and big bore tbi's, etc, but have not addressed chip tuning, hoping for a 12 second truck and are usually left with a slower than stock truck that has zero drivability. Mail order chips are hit and miss with tbi, it really needs to be tuned in person by someone that knows these systems in and out.

With that being said, my favorite setups so far were:
.030 350, 9 to 1 comp, stock swirl port heads, 206/212 cam .42x/.43x cam, edelbrock intake, perfect tune(really torquey, tire shredder, got 20+ mpg mixed in a rcsb 2wd)

Stock 350, stock comp, bowl blended and lightly ported swirl port heads, edelbrock intake, ram jet cam, tri-y headers (slightly less torque than above, really good combo for a work truck used for pulling etc)

This setup would still be in, if I didnt lose a cylinder on the 250000 mile shortblock, it's got an lq4 in it now!

hog

Good results with Vortec 350 heads on a TBI setup with the stock 1996 LT4 production 203º/210º 0.476"/0.480"(with 1.6 ratio rockers-0.446"/.450" with 1.5's).

peace
Hog

Widman350

Kind of forgot I posted this, but after learning a little more about my engine and what not, ive decided when I get enough money to swap the TBI system for an Edelbrock efi system with edelbrock performer heads. Now that ive changed up the injection system im thinking about a bigger cam, I want to be around 350 rwhp and 400 trq.
Would a chevy performance cam 220/230 be a good cam with the heads ive chosen?

Thanks for all the help

hog

Are you planning on swapping from teh stock GM TBI to the Edelbrock TBI to MPFI conversion? If so I would have to suggest that you avoid that kit, many people have done that swap and were disappointed with it.

However, if you a talking about some of the newer Edelbrock Pro flow systems thats different, some of them are fine. Just avoid the specific TBI to MPFI conversion.

If you want that kind of power, you will need their Performer RPM heads and kits, the straight Performer kits will not support what you desire.

Personally if I were you, I would get an 0411 PCM, a Ramjet 350 intake manifold, some fuel rails(use LT1 or TPI rails as the Ramjet 350 rails are $475 actually) some injectors, and get EFIConnection to make you up a custom harness for whatever engine you wish to use.

A brand new Vortec 350 engine can be had for $1800 for a 2 bolt main setup, add $75 and you can get a Vortec 350 with 4 bolt mains.


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12530282
L31 Vortec 350 LD 1/2 ton trucks 3/4 ton trucks under 8600lbs GVRW
5.7L 350 96 (L31) (Vortec) light duty, 2-bolt main.
12530282 350 CID New 5.7L
1999-2000 Chevrolet, GMC CK1 (L31) M30 (exc. NM8)
1996-98 Chevrolet, GMC CK1,2 (L31)(5.7R) M50, M30 (exc. NM8)
1996-2002 Chevrolet, GMC G1,2 (L31)(5.7R) M30
Engine-Specific Content: Crankshaft Hub, Front Cover, Oil Pan, and Valve Rocker Cover
Notes: For 2001 G-van application, service engine block contains English threads. May require Valve Covers to be transferred from original engine for some applications.

12530283
L31 Vortec 350 HD 3/4 ton and 1 ton trucks over 8600gvrw
5.7L 350 96 (L31) (Vortec) (HD), 3/8” stem exhaust valves and hardened inserts installed, 4-bolt main.
12530283 350 CID New 5.7L
1996-2000 Chevrolet, GMC CK2,3 (L31) MT1 (exc. NM8, KL5)
1996-2000 Chevrolet, GMC CK2,3 (L31)(5.7R) MW3 (exc. NM8)
1996-2002 Chevrolet, GMC G2,3 (L31)(5.7R) MT1
1996-99 Chevrolet, GMC P3 (L31)(5.7R) MW3, MT1 (exc. NM8, KL5)
Engine-Specific Content: Crankshaft Hub, Front Cover, Oil Pan, and Valve Rocker Covers
Notes: For 2001 G-van applications, service engine block contains English threads. When used for 2001 and 2002 vehicles, must also use 2000 MY Starter/Trans/Eng mounting bolts.
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx xxxxxxxxxxxxxxxxxxxxx

These engines come with:
-nodular iron crank (stronger than cast iron, just below forged steel cranks)
-forged Powdered Metal (PM) connecting rods-these rods are stronger than the older GM Performance Parts "pink" rods
-hypereutectic pistons these are high silicon cast aluminum pistons, they dont expand and shrink like a forged aluminum piston, but are stronger than normal cast aluinum pistons.

The Vortec 350 (L31) heads that are on these engines, are the highest flowing cylinder heads ever installed on a production GEN 1 V8. Better than the old Z28 302 heads, the 370hp LT-1 heads, and all the double hump heads. They even out flow some of the Bowtie racing heads. There was substantial development on these heads. And they are installed on both the 12530282 and 12530283 Vortec 350 engines.

Both of these engines also come equipped with all the roller cam equipement, and also have a windage tray from the factory.
Stock Vortec 350 windage tray(not the best, but better than nothing, esp. from the factory)

I ahve pulled these engines apart with over 400,000miles on them and they still have the crosshatching on the bores, and there is no typical piston ring rideg at the top of the cylinder bore. These engines are the pinnacle of the GEN 1 head.
I have over 500 1/4 mile passes 27 in one night, with 10's of thopusands of street 0-60 acceleration blasts. I havent had to have the valvecovers off to do anything.

These engines are rated at 255 sae net hp, which is about 310-320 gross hp.
These Vortec 350's have a roller hydraulic camshaft with 191°/196° duration at 0.050" with 0.412"/0.428" lift with 1.5:1 rockers and 111° LSA. This cam was used in the 1994-96 GEN 2 iron headed LT1 engine(260hp/330 lb/ft torque), and the 1994-96 4.3 V8(Vee 8) 200hp/240lb/ft torque) and well as the 1996-2003 Vortec L31-350 and Vortec L30-305
Take that stock roller out and drop whatever you wish in, heck even the very healthy sounding and torquey LT4 Hotcam with 218°/228° duration @ 0.050" lift and 0.525"/0.525" with 1.6:1 rockers or 0.492"/0.492" lift with 1.5:1 rockers with a 112° LSA.

The Ramjet 350 is pretty much a Vortec 350 with a fuel injection intake and electronic with a GM MArine.HT383 roller cam with 196°/206° duration @0.050" lift and 0.431"/0.451" lift with 1.5:1 rockers, but the Ramjet 350 actually uses the full roller rocker with a 1.6:1 rocker ratio which bumps lift to 0.460"/0.481" lift with a 109°LSA. Point being, is that the LT4 hotcam when used with 1.5:1 rockers the lift is 0.492" and with the Ramjet 350 using 1.6:1 rockers the max lift is 0.481" are within 11 thousands of an inch. Be sure to check the retainer to valve seal clearance. If there isnt enough clearance, look to a set of Beehive springs with 787-16 retainers and then you can run the full LT4 hotcam's 0.525" lift with 1.6:1 ratio rocker arms.


Here is a dyno chart showing the difference between the locked and unlocked 4l80e torque converter clutch. These results were through a 4l80e and 14 bolt rearend.
-stock LT1 Camaro cast exhaust manifolds and a single catalytic converter
-small 4x4 CompCam 258°/262° dur/ advertised 206°/210° dur@0.050" 0.458"/0.458" lift 110° lsa grind p/n 08-409-8
-self PCM tuned
-Mercruiser Marine intake

Just imagine what a set of headers and exhaust and a cam would do?

As it sits it's making stock LS1 power.



Here is a cross ram marine intake


Vortec 305/350 intake(left), next to crossram Marine Intake(right)


You can spend a lot of money in shiny cylinder heads, and have them not work as good as a set of $700 Vortec L31 heads.
A mild roller hydraulic cam, in a Vortec 350 will give you hundreds of thousands of trouble free miles, making great torque and decent power. An easy 390-400hp are to be had from the listed engines. They even come with a 3 year/60,000mile warranty, so long as you stick with the stock Vortec 350 cam. Plus you have all GM parts pretty much.

The stock Vortec 305/350 intake manifold, tiny 1 7/8" headpipes that crimp down to 1/2 of that size in the bends, and small roller cam contribute to poor comparative performance in a stock Vortec 350 setup.

here is a pic that evidences tha bad 1/2 ton Vortec 350 headpipes, the larger pipes ar the stock Vortec 350 3/4 ton exhaust


And hear, look at the horrible crimp bends that crimp down MUCH smaller than the 1-7/8" on the 1/2 ton setup, the stock 3/4 ton 2-3/4"-3" Vortec 350 exhaust is much larger.



Ramjet 350 intake manifold in a GMT 400 truck with CNP ignition(24x-coils mounted on firewall) with twin turbo on a Vortec 305 that runs 12's in 1/4.


Ramjet 350 intake alone


p/n 12498032 $1800
This unit includes the following parts:
(1115498 coil)
(12097982 marine spark plug wire kit)
(12489371 intake manifold)
(1104060 distributor)
(10456126 knock sensor)
(17096144 throttle body)
(12553918 fuel injection rails)
(17124248 eight injectors)
(16249939 map sensor)
(17123897 fuel pressure regulator)

12489371 $475 Gets you the intake manifold alone


Or ****** a GEN 3/4 engine, run it with an appropriate GEN 4 engine ECM, or use an 0411 PCM with a GEN 3 engine, a GEN 4 engine with a 24x to 58x reluctor swap on the crank, and changing the cam sprocket from a 1x for GEN 3 to 4 x for a GEN 4 engine. Or use the 0411 PCM with a Lingenfelter Perormance Engineering (LPE) 58x to 24x and be ahead so far as power/fuel economy.

Here is an article that gives some basic details of all the GEN 3 and GEN 4 engines made.
Performance Chevy LS Engine Comparison - Chevy High Performance Magazine

And an article which compares every single GEN 3 and GEN 4 camshaft that GM used in an original GM application.
LS Cam Test Comparison - Car Craft Magazine


Its all up to you.

peace
Hog

94dreamK1500

First I would start with a set of aftermarket Vortec heads that are extrude honed, ported and Port matched.
Next is the cam: For maximum thermal and volumetric efficiency, the cam will need to be a four-pattern design with single-pattern duration at .050 lift. Consider modifying a L31 Vortec 350 cam to 197@.050 on the inboard cylinders and 199@.050 on the outboard cylinders. It has a 111° LSA, so it will pull exceptional vacuum for the MAP sensor. I mentioned this type of Cam profile because of the difference in length of the intake Runners on the TBI intake manifold.
Follow that with 1.6 ratio roller tip roller-rocker arms, 1 inch throttle body spacer and injector pod spacer. Top that with a salad bowl and high flow filter. Through JEGS, find plug-and-play modifier enhancement harnesses for the major sensors connected to the ECM. Then go through Tom Miller at Turbo City for a custom tuned prom chip.
Then headers, flowmaster Y-pipe and 3 inch exhaust.

VR,
Matt

1991C1500