What bolt on mods have you made to your gas powered tow truck that truely helped power and fuel mileage? I have a stock 1990 3/4 ton 350tbi. The cat has been removed but still has single exhaust with a Dynomax Super Turbo and the air intake silencer has been cut out. I've been thinking about headers and electric fans.

What about one of the programmers you can buy.Like the hypertech plug in type?

I don't think there is one for my truck, I've only seen 96 and up.

You have the LO5 350, factory rated 200 HP.

They run 1.94"/1.5" valves, 64 cc chambers, and 9.3:1 compression.

You can not plug in a programmer, but you can burn a performance chip, or purchase one. I researched this a while back for my '95, and many people with performance chips, particularly hypertech, complain of pinging, even running 92 octane.

If you're up to the task, you can buy everything you need to burn your own chip for around $300. Check out www.thirdgen.org (http://www.thirdgen.org) for additional information.

I think a good set of headers would compliment your 3" single exhaust system well, but only if you installed a chip to alter the fuel and timing curves to work with the free flowing exhaust.

Enen if you put forth the effort, don't expect a night and day difference. The cylinder heads don't flow that well, the factory cam is tiny, and I understand the 2 bbl TBI is rated for 400 cfm or less.

I friend of mine built a vortec roller 383 TBI for his '93 suburban that tows his 3000 lb boat no problem while getting 12-13 mpg. This, of course, required a custom burned chip.

If you get into programming your own chips, there's a few parameters in there for "highway mode" that GM never enabled. Some folks have claimed quite noticable gains in mileage in cars by tuning with it, but I don't know how it will affect a truck. Like said before, you can get all the info you need HERE (http://www.thirdgen.org/techbb2/forumdisplay.php?s=cd94a791c43b350ae70a1f4e2c8b3b2 5&forumid=16) and HERE (http://www.thirdgen.org/newdesign/tech/promintro.shtml) You can get the software for free at www.tunercat.com (http://www.tunercat.com) and then you'll just need some blank chips ($5-8) and an eprom burner. I use the Pocket Programmer (http://xtronics.com/memory/EPROM.htm) . It's definitly worth the effort. You can also go to the TBI forum at thirdgen and check out the throttle body mods.

I don't know if I would want to tackle the chip idea, I may be scared of something I don't know. Would the truck not see an improvement with 1 1/2 headers without the computer changes? Seems like it could adjust its self some.

The heads are a real stumbling block on those engines. 1/2 the port is blocked off near the valve guide to promote swirl.

The intake manifold is infamous for mixture distribution problems.

Add in the small throttle body, and it's a recipie for poor power. My 1/2 ton has the GM Caprice roller cam crate long block, Edelbrock headers, high flow cat, Flowmaster cat-back exhaust. Still has less than optimum power, although better than the stock flat-tappet longblock originally installed in '88.

Edelbrock sells a $1000 port-injection upgrade, using the stock computer. That would totally solve the mixture distribution problem. I think a set of Vortec heads would do wonders, too.

I have owned several of these trucks. As stated above, the heads are your main problem. I would avoid aftermarket PROM's too, as they tend to increase HP through ignition timing, and require premium fuel. Your first upgrades should involve airflow. Headers, and high flow 3" exhaust will make a significant difference. I have also noticed an improvement after installing an open element 14" air cleaner. On the TBI side, an injector pod spacer and throttle body spacer will make a noticable difference as well. An aftermarket ignition coil and module should increase economy. An adjustable fuel pressure regulator will allow you to "fatten" it up a little to compensate for the increased airflow. If you really want to go for the gusto, drop in a little bigger cam, some better flowing heads, and a Performer manifold with a 4BBL-TBI adapter and no EGR. By this point, downloading WINALDL and playing with PROM's is going to become mandatory. Finally, a Holley replacement throttle body will help feed your new found ponies. Some sights of interest are: CFM tech (http://www.cfm-tech.com/catalog/gm_tbi_performance_parts___accessories_126905_prod ucts.htm) Howell (http://www.howell-efi.com/) TBI chips (http://www.tbichips.com/) turbo city (http://www.turbocity.com/) and finally, the best TBI site on the web, Thirdgen.org (http://www.thirdgen.org/techbb2/) I love TBI motors, they have LOTS of potential.

Thanks for the info guys. I did not know these engines were as stopped up as the mid 80's smoggers.

Look for a company called Performance Resource,they make great chips.I put one in my 90 454SS truck.I liked it a lot :D

Simple solution. You need...

http://www.qis.net/~geislert/truck1.jpg

graemlins/thumbsup.gif

Only 6 cylinders, 5.9L and gets 16 mpg on it's worst days driving around town. 19-22 mph highway is typical :eek: graemlins/thumbsup.gif ...and thats dragging the 4x4 running gear around.

Sure beats my old '89 3/4 ton Suburban with a tbi 454/th400 which typically got between 8 and 10 mpg at best (2 wheel drive).

IMO, there is not a lot you can do with this truck. a combination of the heads & EFI setup, you are kind of hozed. look @ the newer trucks, they dont get much better than what your getting now. However, if you wanted to drop a good chunck of coin into it you could eek out a few more MPG's.

Im right behind you 10secBU in my 99, 3/4 T, Quad Cam. I LOVE this truck.

Bob

I can buy a lot of gas for what a new truck costs.

Originally posted by Dragn70:
I can buy a lot of gas for what a new truck costs. I though so too, but my old Suburban was costing me a pretty penny in maintence and upkeep ($3k for reman engine, $3k for new paint, new tires, new brakes, blah, blah, blah), not to mention the fact that it was an '89 and while the outside body was in very good shape, the underside was just rotting away. It was simply time to let it go.

I don't know if this is an option for you and what you pull however, I'll throw in my $.02. I have a 97 Chevy 1/2 ton 4x4, vortec 350, 4L60E, 3.73 gears with the towing package. It pulls my full weight 70 Chevelle and open car trailer, about a total of I think 5500 lbs, great! It might be easier to run down one of these instead of sinking a bunch of money in modifications. It has 155,000 on it, but has been well taken care of. Still has even the original tranny in it. I get 13-14 mpg towing the chevelle or the fishing boat. While at college I average 16-17 running back and forth to work 80 mile round trip. It doesn't pull my car at any fast speeds but will cruise down the highway at 70 mph without a problem, and with the 3.73's gets up to speed great! Maybe this could be an easy way since these years of trucks aren't terribly expensive!

Matt

Originally posted by 70ss496:
I don't know if this is an option for you and what you pull however, I'll throw in my $.02. I have a 97 Chevy 1/2 ton 4x4, vortec 350, 4L60E, 3.73 gears with the towing package. It pulls my full weight 70 Chevelle and open car trailer, about a total of I think 5500 lbs, great! It might be easier to run down one of these instead of sinking a bunch of money in modifications. It has 155,000 on it, but has been well taken care of. Still has even the original tranny in it. I get 13-14 mpg towing the chevelle or the fishing boat. While at college I average 16-17 running back and forth to work 80 mile round trip. It doesn't pull my car at any fast speeds but will cruise down the highway at 70 mph without a problem, and with the 3.73's gets up to speed great! Maybe this could be an easy way since these years of trucks aren't terribly expensive!

Matt While I agree a newer truck from 96+up is the way to go, these year trucks are EXTREMLY expensive used. They hold resale like a honda, at least around here they do. A 96 extended cab with 100,000miles will get an easy $10,000 if its in good condition. Way overpriced.....