I just picked up a 94 GMC Z71 ext. cab w/ 108k. It is just going to be an extra vehicle, so besides wheels and tires and a few other odds and ends I've already got coming for it, I don't want to blow alot of money on it or undertake any huge upgrades.
I do, however, want a little more umph from the old TBI 350. Right now I'm thinking about a K&N open element air cleaner, a throttle body spacer, set of shorty headers and a flowmaster mufler. I was wondering if anyone still made an intake manifold for these things? if anyone on here has one? and if anyone is also running the Holley 670 throttlebody and if it makes any difference?


Ideally I would like to put a cheap set of vortech heads on it and keep the TBI so I wouldn't have to get into a bunch of computer and wiring issues. Is that possible? anybody done it?

 

sounds like a good plan.

 

I've got a '94 RCSB z-71 with a TBI 350, and not only the best bang for the buck, but THE best thing you could ever do to that truck, is get a real, in person computer tune. hell, it doesn't even have to be on a dyno, anyone with some common sense on tuning can make a night-and-day difference with your truck.

dyno numbers may not be reflected all that well from a tune, but day-to-day usage will be tremedously changed IMO.

I know it made a world of difference in my truck, and all I had was a K&N and flowmasters at the time (so nothing worth talking about really)

 

I've got a couple of buddies who work at Hypertech and I think I found a set of lightly ported Vortech heads off a local mud racer's truck. I think Edlebrock makes the TBI intake that will fit those heads. Just those mods and a set of shortys should be sufficient to give it at least as much power as the 96-98's, and I had considered that it would need to be retuned or have a chip made for it.

 

Ditch the throttle body spacer. Basically doesn't do enough to make a difference.

The shorty headers and muffler is a good start. Also, do a high flow cat or no cat will make a good difference as well.

Generic hypertech chips are junk....you can gain a lot from a custom tune suited to your engine like Wester's, TBI-chips, etc. PCMforless also does them.

A set of vortec heads would be a great start on the engine. Now, a good cam would be a 206/212 or something in that ballpark and remember that its a flat tappet cam.

As far as the intake manifold, Edelbrock makes one and save your money on the 670 throttle body. Get a ported out piece from cfm-tech and have your injectors flow matched with an adjustable fuel pressure regulator and you'll have a good start.

 

Thanks for the info

Any idea what kind of power that should make? I'm wanting to make at least as much as a 96-98 Vortech 350, a little more would be nice, but not at great expense or loss of usability.

 

Stock 350 is 210hp. Vortec heads are worth 30hp (in stock form). So, 240hp then headers, exhaust, open air element, custom tuning, cam, throttle body mods, and e-fans(possibly), and underdrive pulleys would give you close to 275hp-290hp which would be more than the 255hp 5.7L vortec engine(96-99).

However, GM Performance parts makes the vortec TBI intake.

 

I have just spent about 2k on my 350 tbi build up. I am now looking about swaping a 4.8/5.3 into my truck.

My engine- stock short block rebuilt, camshaft stock used lt1 from a 95 camaro, heads new vortec, intake new GM tbi to vortec heads with egr, had tbi bored to 50mm, reconditioned injectors and 18psi spring in the regulator to make 70lb injectors and a custom chip. The engine runs very well has lots of power but with 11mpg at the best (in town is 8-9) I am very diaappointed with the mileage. This is the 3rd chip and the guy that made them says this is as good as it will be.

My truck- 1992 Silverado 1500 4X4, automatic, 3.42 gears, regular cab long bed.

Good luck with your project.

 

That truck should be knocking out about 14-15 mpg. Your tune is way off. You need to get a custom tune done in person or a person that knows what they are doing.

You did convert to hyd. rollers for the LT1 camshaft correct...just didn't see that in your list. You cam is on the small side for what I would have like to see. LT4 cam would have been a better choice.

 

Before I started the project (about 1 yr ago) I contacted tbichips and he said he was getting 20mpg with a similar setup. So this was the direction I went.

Yes it has been converted to roller lifters. This is the cam that he recommened.

I have been thinking about putting it all stock or a 4.8/5.3 swap. The truck is not driven very much 2000 miles a year. I have sent lots of data to him and this is as good as it gets.