Hi all. I have lurked around this site for a few weeks now and have finally decided to register. I know this is mainly a camaro site and all, but you guys have a heck of a good TBI section so I thought I would join up and ask a few questions about my truck.

I have a 1987 Silverado that I am restoring cause I love those old trucks. It has a 5.7L TBI engine. But what I am really looking to do, is build up a motor for it, that gets the best gas mileage possible. It's just a little project of mine, that I want to see if I can pull off. I have heard rumors in the past, that people who know what they are doing can squeeze a lot more gas mileage (and by extension, more power) out of TBI engines. I have even heard claims of 21 miles per gallon, in the city. Probly turn out to be something like 24 on the highway. Is there any truth to this? Does TBI hold a lot of untapped potential, when it comes to gas mileage?

I want to start my 5.7L build as soon as I can, however due to school reasons I am not entirely sure when that will be. So I have plenty of time to do all my research, which as we all know is a must. So a couple of questions first:

1. I have heard that TBI has a lot of untapped potential for gas mileage, sometimes a lot more than the engine came with from the factory. Is there any truth to this? Some people have even told me that just adding the right cam can earn you 2 MPG city.

2. Which block do I want, if I am going to be doing a junkyard build? And which vortec heads?

3. I do want votec heads, if I am doing a gas mileage build, right? LOL. I have heard that they are some of the best for mileage, even better than most of the advanced aluminum heads out there in the aftermarket.

4. Are there any other gas mileage tips/tricks/mods that you can think of, for a 5.7L TBI build? I hear tuning and ECM programming is a very big part of it. Again, this is all just sort of a personal project that I am going to undertake. I want to see if it can be done. The vehicle is a truck, not a sports car, so it's not some big loss if I don't try for all the horsepower that a man can possibly make. And hey, if I manage to pull out all the tricks for fuel mileage, I'm sure I'll have plenty of power for a half ton truck.

Thanks for reading, and I hope everyone has a wonderful day!

 

Hmm I guess that's not a real popular idea around here lol. Well how bout we start simple. Which block should I choose (junkyard) for a good 5.7L TBI build?

 

Take a look at my 'truck TBI smallblock build' here in the TBI section. I dunno about 20+mpg in a fullsize pickup, but mine gets 16 or so city and 19 highway, compared to 13 city and 16 highway when it was stock.
Yes-Vortec heads by all means!!- all you need to do is open up the exhaust ports a bit, clean the rough edges up in the intakes and theyre good to go. the 062 castings are the ones I like- you can really get some good exhaust flow numbers out of them! My truck has the 906 castings..they have a hardened exhaust seat which makes it hard to get a good seat profile for good flow, although I still managed to get another 27cfm out of mine.
Keep your cam small, and if you can get an 87-up block, you can drop a roller cam right in there. I used a 71 block and flat tappet cam, but the next build will be a roller. Run a split pattern cam with no more than 210 or so on the intake and slightly more on the exhaust, on a wide lobe sep.
Run some flat top pistons and get your compression up in the 9.5-9.8 range for a little more punch.
last but not least, go EASY on the converter if you change it ( a 2500 works REAL good and wont cost you much mpg in town...you still have lockup for the highway), keep your rear gears 3.42 or numerically lower (youll have plenty of torque to pull those wimpy gears) and swap over to synthetic oil in everything- even the wheel bearings. Keep a light right foot and a good tune, and you should be pretty happy with the mileage..................for a fullsize truck anyhow........
P.S.- ive also heard of guys running a stock lt-1 roller cam and getting real good mileage, but the power isnt going to be up there with a good aftermarket cam.......

 

Thanks for the help! I really do appreciate it. But yeah, Power really isn't an issue for me. I mean, anything I do will put me probly 50hp above my old wore out 220 hp stock motor lol. So I'd be plenty happy with that stock LT1 cam, if it bumped me up a little in the MPG. Cause let's face it, I'd be lucky if I'm still making 200hp. Oh well that's what new builds are for. But um, so the blocks are all the same from 1987, till they quit making the TBI? which would be what, 1999? So it doesn't matter what block I do? There isn't one block that is known to be thicker or better for whatever reason? And the 062 castings will fit just fine on any block?

 

87-98 blocks (tbi and vortec 5.7) block are basically the same. the vortec blocks do not have provisions for a mechanical fuel pump, where the 87-95 blocks just ran a blockoff plate. the 87-95 cars got roller cams, but the trucks did not, even though they are a 'roller' block. all vortecs were roller cammed.
you can pop a roller cam right in your TBI block, but you will need the cam and lifters and a lifter spider kit, which will have the spider type hold down, lifter tie bars, and a cam retainer plate. you will also need to run a timing set for factory roller equipped engines if you do this. However....although all blocks will accept a factory style roller cam, I HAVE seen one block that did not have the spider hold downs tapped, and many do not have the cam retainer plate holes tapped either.
As for the power.....I actually know a guy who ran a stock lt1 cam in his tbi truck, along with headers and ported TB...but kept his stock TBI heads...it made 200 at the rears (not sure how much torque) those TBI heads will not perform without some good port work, and even then id be surprised if they outperformed a stock set of vortecs. theres a few guys (on here I believe?), who have gotten real good results from working over a set of TBI heads, but unless you can do it yourself, its probably not worth the money versus a set of vortecs. they do claim the tbi heads are good for mileage and yes they are good for torque down low, but thats about it. the vortec heads are worth an easy 40hp and some torque, over your TBI heads. (you will have to change intakes to run vortec heads.)
Are you planning on doing a whole engine, or just a cam swap? If youre going to do the entire engine and yours is running fine as-is...find yourself a good rebuildable 96 or 97 vortec 5.7.....if its low miles you might even be able to reuse the lifters, pistons, and not need valve guides or anything. better yet..if you can find a low mile 5.7 in good running condition, get a carb'd intake for vortec heads, run a TBI adapter, chip it and drop it in.....itll run circles around your old tbi 350 and get better mileage....all for less than itll cost to rebuild your existing engine!

all of this info is from MY experiences in the business......im sure someone will chime in if anything is incorrect...theres some pretty smart guys on here who are hip to this TBI/vortec stuff.............

 

Thanks for the helpful reply. But to answer your question, I am wanting to just get a junkyard motor and rebuild it myself. Both for a learning experience, and so I can be driving the truck the whole time I am building the motor.

So just to clarify, I want to get the engine from a 97 TBI truck, so that I make sure I get the vortec heads, and a full roller motor. Does that sound right?

 

Your best highway gas mileage is going to come from swirl ports, a stock tbi intake, and a mild roller cam...

The vortecs are worth about 40 HP over the swirl ports on a mildly cammed, stock engine, but the 40 HP doesn't show up until 6,000 rpm.... At 4,500 the gains of Vortecs are NON EXISTANT. Below 3,500 you actually lose some with the Vortecs.