Modding a 98 Vortec 5.7 Silverado X-Cab
 

I assume this is the area I should be asking questions for my 98 Silverado X-Cab with a Vortec 5.7.
Well my tow truck has a whopping 52,000 miles.
Let me give you a little history on the truck.
3.42 posi
Hypertech
K&N filter
Gibson exhaust.
I'm not looking to make it a race truck but I've been thinking about doing some more mods like: Cam, porting heads maybe change some induction but I still need to tow my Chevelle.
Any suggestions?

Thanks
Dave

Re: Modding a 98 Vortec 5.7 Silverado X-Cab
 

first, yank off the hypercrap, second, get a full intake and exhaust setup before touching heads and cam. the heads and cam wont do anything unless you can get the air into and outta the engine. weight loss is prolly the most important factor for you to be aware of. you are a truck and will be heavy as crap, start looking for ways to lighten your truck A LOT. as for being in the rightplace to ask the question, well, this isnt exactly the wrong place. you might want to try the Truck Performance area but im pretty sure they are LS1 derived motor specific but it wouldnt hurt to try. they would probably be able to provide you with better help than we could even though your motor is more similar to ours.

Re: Modding a 98 Vortec 5.7 Silverado X-Cab
 

Thanks....but like I said this is my tow truck and I really don't wan't to shedd a bunch of stuff off it for weight reduction. I just wan't to make some more power and keep fuel injection on it. It gets pretty descent mileage.
The "HyperCrap" <img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" /> really picked the motor up from stock. As for the exhaust with the fuel tank inside the frame rails there's not enough room for true duals or I just haven't seen any done.
Maybe I'll just put a 540 in it <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />

Re: Modding a 98 Vortec 5.7 Silverado X-Cab
 

HPP helped a lot, did you do the 160 t-stat tuning?

I have a 99 Tahoe with the same engine, the undersung L31 which is a great engine, rated at 280hp and 330tq.

L31/Vortec heads are pretty decent from the factory. I'd look into doing a small cam and some valvesprings. I'm not sure if the L31 can share cams with the LT1 or with a traditional SBC.

I know a guy around here selling a used Powerdyne blower for our setup, email me if you want his contact info, I think he wanted $1400 for it and the blower has been refurbished. His marine company had it on a 98 Surburban for towing purposes.

Re: Modding a 98 Vortec 5.7 Silverado X-Cab
 

Well I put the 160 stat in but I've heard that it's really too cold for the system to close the loop.
I've thought about the blowers but I haven't done much research on them. I was just thinking more along the lines of maybe Port matching the intake or possibly getting another one and maybe doing some bowl work on the heads and change cams.
I guess the thing is I know me and I don't wan't to turn this trunk into some unpractable vehicle to drive.
I've got one of those already in the garage!

Re: Modding a 98 Vortec 5.7 Silverado X-Cab
 

Heyy I found someone with the same truck as mine. I got many ideas for your truck. I have a 97 C1500 5.7 L31 too. Well first I wanna say that there is a true dual exhaust. I have a factory true dual exhaust setup on my truck. Idid replace the tips and the muffler though. I recomend picking up a truckin magazine for ideas on the engine. I tried looking for cams, heads, intake manifolds and such didnt have any luck. The only heads and intake manifolds for our engines was from edelbrock but its for the engine only and it will have to be converted into a carb. So the only thing will be like shorty headers, intake, pulleys, and any other bolt-on part.
I know websites if you wants some.

Re: Modding a 98 Vortec 5.7 Silverado X-Cab
 

Ive got one of these trucks and have thought about the same thing so I'll give you what I dug up. The stock vortec heads flow excellent, but there is a problem. They will only accept around .460 lift before they run into retainer to guide clearence issues. Most performance roller cams, even small ones have more lift than this so if you want a cam your gonna have to yank the heads and have the guides cut down. That being said, heres what I may do some day: stock heads with bowl work, mild cam, somewhere around 212 218 little under .500 lift, and 1 5/8 primary headers with dual exhaust. The duals are real easy to run because there is already 2 pipes to the muffler. You just cut the pipes into the muffler, mount two small case mufflers(I like flowmaster) virticly(SP) then run the pipes out the back.

Re: Modding a 98 Vortec 5.7 Silverado X-Cab
 

I have a ATI procharger off a 97 regular cab that went 12.85 at Hattisburg dragway. The truck towed cars all over the southeast and was great. Let me know if you would like to know more.

Clyde

Re: Modding a 98 Vortec 5.7 Silverado X-Cab
 

The easiest and most cost efficient process is to put a self contained centrifugal supercharger on the truck. Either that or an eaton type roots blower, both of which have easy bolt on kits.

Now this, coupled with the full exhuast would give your truck the best seat of the pants kick for driving and the best towing capabilities without putting you through a bunch of labor of replacing heads and cam.

Just keep in mind the uses of the truck and what your actually doing the mods for.

Re: Modding a 98 Vortec 5.7 Silverado X-Cab
 

Thanks,

I appreciate the info.

Dave

Re: Modding a 98 Vortec 5.7 Silverado X-Cab
 

I have a guy at the shop with the same problem.

Our solution, a 383 bottom end.

A Caomp 4x4 Cam and a Scat 383 bottom ends should solve your problem, we are going to build one up fro him soon.

Let me know if you have any questions on it, just drop me an e-mail.

Bret Bauer

Re: Modding a 98 Vortec 5.7 Silverado X-Cab
 

I have a 97 L31 vortec also. I have also performed the mods that you are looking into. I made the mistake of over-camming my truck with the LT4 hot cam. Our trucks use hydraulic rollers and LT1/LT4 cams work. However, due to the drastic differences in the intake and fuel injection systems I would not get an LT1 cam again.........because our trucks are so heavy. Due to the cam I had to get a 3000 Vig converter (which I love) and I run 1.9x 60' times with it. I would suggest Doug Thorley headers! These work awesome on our trucks!!!! Forget shorties completely. The thorleys will be more labor intensive, but they are worth it! Alot more torque. If you want to get into the heads (I ported mine also) focus on the exhaust. The intake is not very restrictive, but there is alot to gain in the exhaust ports. For your purposes I would suggest a blower. Our trucks have been much more successful with superchargers than the new LS1 style engines. A supercharger will give you more power and torque without the hassle and work of a heads/cam deal.......which then has to be tuned by Ed Wright or Z industries. I had to buy a maf translator to get mine dead on....ran lean with Ed's tuning. Good luck, if you have any more questions email me!

If someone still has a supercharger kit for a 98 5.7 vortec c1500 i am interested. thanks

holy 7 year old thread

You can run beehive springs with 795 retainers and +.050 locks and then there's room for about .550 on the lift. Comp cams used to send me a lil rag once in a while. The addressed this issue in one of those. They were makin 400hp with a hot cam. A good friend of mine is currently using the same setup with a 503 cam.

A good valve job on the heads really helps alot. Torque is gonna be what moves it so look into makin yourself a 383 if ya got the money. I would also try a Comp 4x4 cam w/1.6 rocker 7 ma custom tune. Exhaust is a given!!

:lol:

I bet this guy didn't think he'd still be getting advice 7 years later...hahaha! :)

Hey it's good advice, I've got a 98 that I'm looking to mod since I can't leave anything alone LOL

I have a 98 vortec that I've worked on over the years and gotten some good performance out of.
Here's my advice:
1. Dont waste your money on any intake modifications unless you're going to get rid of the stock intake manifold/injectors and go with a GM marine or comparable intake. The intake plumbing, MAF sensor and TB are capable of more than you will ever push through the stock intake manifold. Plus the stock injectors at 19 lb/hr wont support more than about 325 rwhp. I swapped to a ZZ3 cam, and the motor still seems to be done pulling by 5300 rpm. With the stock cam, it was done by 5100. It will rev past those numbers, but those are optimum shift points.
2. Go to longtube or TriY headers, and for ease of exhaust routing bring them into a single 3" system. Of course, if you're building more power than the stock intake manifold allows and ditching that, then you'll want more exhaust flow too.
3. Get custom programming, get rid of TM, and install a Transgo HD2 kit.
4. Install a tight 9.5 or 10" converter, 2600-3000 stall'

Following the above recipe, I'm happy with the performance of mine, 14.8 NA and 13.6 on the 75 shot, in a 5000 lb vehicle, with excellent driveability and towing manners. Just want to point out the limitations of the stock Vortec intake system.

I know this is a dumb question, but what kind of MPG's do you get?

19 hwy. 17 mixed. 1 less mpg than with the stock cam