SBC - More power without sacrificing towing/mpg?

I have a 1992 Chevy C2500 with what I believe is a 350 TBI, I am not sure since it got an new engine about 50k miles ago before I got it and I don't really know for sure, but we can assume it is.

I think I would like more power, but I also tow with this truck and don't want to sacrifice towing capability and gas mileage too much. I currently get 16-17 on the highway unloaded which I like, I don't want to drop to like 13 on the highway. What hop up options are there for me? I assume there are a lot but I really know nothing about these engines. This would also be my first foray into engine mods.

1992 would be TBI. For low buck gains, I would focus on airflow in and out of the engine. Less restrictive air cleaner and exhaust would help. Headers could help out as well.

After that you are looking at TBI mods and possibly a TBI intake like Edelbrock sells. A 454 TBI flows more air and is a popular upgrade as well. But you may want to consider, if you go as far as changine the intake manifold, to go ahead and upgrade to Vortec heads and get the vortec TBI intake to go with it. Or even just a set of Performer heads would be an improvement over your stock heads. It all depends on how much you want to spend.

What he said. Air in and air out improvements are your best bet. Just don't go too far or you will need a chip burned to compensate.

But really, how much do you expect to gain? Best WAG is maybe 10-15% improvement, goven your non aero box to push through the air.

http://www.carcraft.com/techarticles/ccrp_0406_1993_gmc_pickup_project_jake/

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http://www.carcraft.com/featuredvehicles/ccrp_0407_1993_gmc_350_pickup/

The only part I don't like is the Hypertech chip that requires premium fuel.

http://tbichips.com/

This has ALL of the information you will ever need. And its not BS, its all backed by dyno runs. By far the most comprehensive work done for TBI vehicles.

The short answer though is you won't see much of an improvement in power or mileage. I currently have a 1993 K1500 with under $2k into it including purchase price (had to get the tranny rebuilt). I've spent hundreds of hours seeing what I could do for a bit better towing power/better mpg. The answer is to buy a new truck.

By far the best bang for the buck is an exhaust (smallest primary sized headers you can buy), a cheap cam (comp cams 12-249 is the kit I'd go for), and a tune from tbichips. But all of this will probably cost you close to $1k when its all said and done. $1k is a LOT of gas (for me, about 5,000kms worth).

Edit- The reason you won't see much of an improvement is that the heads are just garbage, outdated technology. If you want better power and no improvement in mpg, swap to vortec heads... or just sell your truck and buy a vortec truck. If you want better power and slightly better mpg, go buy a 1999 or newer 5.3L truck. Its really the only GRM way to do it if you factor in your time as money.

Or swap in a 5.3L from a 99 and newer truck

^^ Thats what I was going to suggest. Since the GMT400 body style is way better looking than any of the newer designs, find a wrecked truck with a 5.3 or a 6L and boom, better power and mileage and you have a great looking truck.

While I agree that the 5.3 will easily make more HP, it is really hard to beat the GenI SBC TBI's for where the torque is made and how much it makes. It's all down low, almost diesel like. throw on a set of Vortec heads, vortec TBI intake, cam, 454 TB/injectors, headers and 3" single exhaust and you have a fantastic tow motor. No, it isn't going to win a lot of drag races. It won't sound as pretty and an LSx truck engine. It won't rev, or be anything other than what it is: A truck engine.

In reply to Bobzilla:

This is quite true, even the lowly 4.3 had silly grunt off the line, peak tq happened at 2000 rpm. You could overload the truck all you wanted to but it would still just kinda shrug it off and go, I once hauled a whole yard of damp sand in a 94 K1500 4.3 Auto, engine had no issue with it. By 4500 RPM they sound/feel like they're gonna grenade, but they dont, conversely the LSx makes its power higher up but is happy to do so.

As I recall comparing said 94 to whatever the new GM small pickup is, the TBI 4.3 V6 still has more tq than any 6 cylinder gasser GM currently offers, and makes it spinning half as fast.

Save your money and replace it with a 96-00 vortec truck. It'll probably be a $1500 step up.

Fobroader wrote: ^^ Thats what I was going to suggest. Since the GMT400 body style is way better looking than any of the newer designs, find a wrecked truck with a 5.3 or a 6L and boom, better power and mileage and you have a great looking truck.

Sure, but buying anything older than a 2010 chevy for towing long distances is just silly. Old trucks suck for driving long distances, the newer body styles with modern suspensions, comfortable interiors, rack and pinion steering, etc is really where its at. Chug along with the beater truck till you cant take it any more than then make a real step up. Do it right, do it once.

Bobzilla wrote: it is really hard to beat the GenI SBC TBI's for where the torque is made and how much it makes.

No, it really isn't. As my claims are backed up by dyno stats (facts) while yours are heresay. There is nothing good about the TBI trucks besides being cheap. Do they get the job done? Sure, but none of your mods realistically will provide a meaningful gain in mpg. They will make towing better (the vortec heads really being the main ingredient), but why spend that much money on a old truck? What you suggested is well and above spending $1k on a truck that probably isn't worth more than $3k on a good day and with no rust. At the very least, he might as well buy a vortec equipped truck (96 to 99) to begin with AND they have better interiors. It'll be cheaper than what you suggest.

Leafy wrote: Sure, but buying anything older than a 2010 chevy for towing long distances is just silly. Old trucks suck for driving long distances, the newer body styles with modern suspensions, comfortable interiors, rack and pinion steering, etc is really where its at. Chug along with the beater truck till you cant take it any more than then make a real step up. Do it right, do it once.

While I agree with most of your post, you will not find a nicer riding truck than a GMT400 2wd 1/2 ton. I also am of the opinion that when it comes to trucks, considering the OP can sell his truck for $2-$3k, sell it, take the modification money he was going to spend, and buy a 6 speed auto chevy (2009 or newer). Even if you have to finance a couple grand, you come ahead in virtually everyway and will definitely see noticeably better towing mpg. The 96-99 vortec trucks make great torque, but get horrible mpg.

Edit- "While I agree that the 5.3 will easily make more HP, it is really hard to beat the GenI SBC TBI's for where the torque is made and how much it makes. "

This is all just wrong. Please don't listen to this OP, whatever you do. A 5.3L chevy will outtow a modified TBI truck all day. If you put vortec heads on the TBI, it will do fine, but again, the mpg difference is substantial between the 5.3L and the vortec 5.7L (2-3usmpg while towing I've found).

Ha thanks for all the info guys. This is my grandfathers old truck and my first truck and I don't really want to be getting rid of it soon. I towed a couple of motorcycles from TN to IL and I had no comfort issues. I am sure there are many better trucks out there, but I don't really need a truck and certainly don't need a newer truck. I was just looking to see what fun I could have with what I've got. I'll check through the links over the weekend, and maybe I'll make some modifications or maybe just leave it. I won't be towing any more than it can already handle, I just sort of wanted to turn tires into smoke without killing other performance.

Leafy wrote:

Fobroader wrote: ^^ Thats what I was going to suggest. Since the GMT400 body style is way better looking than any of the newer designs, find a wrecked truck with a 5.3 or a 6L and boom, better power and mileage and you have a great looking truck.

Sure, but buying anything older than a 2010 chevy for towing long distances is just silly. Old trucks suck for driving long distances, the newer body styles with modern suspensions, comfortable interiors, rack and pinion steering, etc is really where its at. Chug along with the beater truck till you cant take it any more than then make a real step up. Do it right, do it once.

Hmmm. I didn't realize my truck was so terrible...Although I've only towed across the US back home to Alberta twice. It's a 2000. IMHO (and experience) the 99 up GMT800s are very nice long distance vehicles.

I have owned a dozen GM trucks in this era. I will offer my two cents.

The TBI trucks are really kinda junk. Seriously. I had an 88 K2500 that could barely muster 13 mpg empty and only made 180 hp. It was pathetic with a capital P. Combine that with the fact that it leaked oil past the valve seals at 20k miles, and it was a pretty E36 M3ty truck. If I'm going to have a 3/4 ton truck that gets 6mpg towing, I at least want it to HAVE ENOUGH POWER TO TOW.

That's just my personal opinion.

HiTempguy wrote:

Bobzilla wrote: it is really hard to beat the GenI SBC TBI's for where the torque is made and how much it makes.

No, it really isn't. As my claims are backed up by dyno stats (facts) while yours are heresay. There is nothing good about the TBI trucks besides being cheap.

Amen. Tiny ports, tiny hp, tiny torque.

I will share a wee bit of info. I spend 6 weeks a year camping/fishing with the guy who was head of Rochester/Delphi for many years. He was the mastermind behind the Qjet, and when the corporate brass ordered the EFI, they scrambled to make the TBI. He has talked to me about it frequently... the Qjet was the greatest and most accurately metering carburetor ever created and people call it the quadrabog, or the quadracrap. The TBI is the worst ever FI created and people pay big money for junkyard conversions.

I know a dozen guys who swapped their TBI for a Qjet and added 25+ hp and improved their MPG by about 10%.

In a nutshell, GM's TBI is a whopping pile of E36 M3.

HiTempguy wrote:

Bobzilla wrote: it is really hard to beat the GenI SBC TBI's for where the torque is made and how much it makes.

No, it really isn't. As my claims are backed up by dyno stats (facts) while yours are heresay. There is nothing good about the TBI trucks besides being cheap. Do they get the job done? Sure, but none of your mods realistically will provide a meaningful gain in mpg. They will make towing better (the vortec heads really being the main ingredient), but why spend that much money on a old truck? What you suggested is well and above spending $1k on a truck that probably isn't worth more than $3k on a good day and with no rust. At the very least, he might as well buy a vortec equipped truck (96 to 99) to begin with AND they have better interiors. It'll be cheaper than what you suggest.

Leafy wrote: Sure, but buying anything older than a 2010 chevy for towing long distances is just silly. Old trucks suck for driving long distances, the newer body styles with modern suspensions, comfortable interiors, rack and pinion steering, etc is really where its at. Chug along with the beater truck till you cant take it any more than then make a real step up. Do it right, do it once.

While I agree with most of your post, you will not find a nicer riding truck than a GMT400 2wd 1/2 ton. I also am of the opinion that when it comes to trucks, considering the OP can sell his truck for $2-$3k, sell it, take the modification money he was going to spend, and buy a 6 speed auto chevy (2009 or newer). Even if you have to finance a couple grand, you come ahead in virtually everyway and will definitely see noticeably better towing mpg. The 96-99 vortec trucks make great torque, but get horrible mpg. Edit- "While I agree that the 5.3 will easily make more HP, it is really hard to beat the GenI SBC TBI's for where the torque is made and how much it makes. " This is all just wrong. Please don't listen to this OP, whatever you do. A 5.3L chevy will outtow a modified TBI truck all day. If you put vortec heads on the TBI, it will do fine, but again, the mpg difference is substantial between the 5.3L and the vortec 5.7L (2-3usmpg while towing I've found).

Angry much? This was posted earlier, but I guess to you it;s just "heresy". http://www.carcraft.com/featuredvehicles/ccrp_0407_1993_gmc_350_pickup/

Makes it's almost 300ft/lbs of torque at the rear wheels (with the stock heads) at 3200rpm. A stock 5.3L makes 294tq at 4000rpm. That's 800rpm SOONER with stock heads and cam. A pair of used Vortec heads from the local scrapper is $300 complete. Cam is $150. gaskets and intake another $300. Used OBS trucks here are about half the price of their newer 99-06 brethren.

But hey, no one but you knows anything about TBI engines, we get it. They're obviously spawned from the devil and nothing in this world can make them acceptable in your world. We get it. I know this may come as a huge surprise to you, but not everyone thinkgs/feels the same way about them as you do.

All I know is, I wish I had more people around me that nicknamed car parts things like "quadracrap".

I linked to a couple Car Craft articles that show some great gains on a TBI 350 that don't involve going into the motor. None of it would be especially difficult to do. Seemed like good answers to the OP's questions, maybe that's not what we're here for?

pres589 wrote: All I know is, I wish I had more people around me that nicknamed car parts things like "quadracrap". I linked to a couple Car Craft articles that show some great gains on a TBI 350 that don't involve going into the motor. None of it would be especially difficult to do. Seemed like good answers to the OP's questions, maybe that's not what we're here for?

It doesn't fit with HTG's opinion, so it is obviously stupendously wrong. I would think putting 268ftlbs to the rear wheels at just over 3k rpms would make an excellent tow rig even better. But, obviously we're completely wrong.

TBIs in trucks have swirl-port heads that are chevy's worst-flowing head ever. Even worse than the early 265 heads. The cam specs out to 181/187* duration with a 117 LSA. They are also 8.5:1 compression and the TBI has a wet-flow of 390 cfm.

What that means (unfortunately) is that there is no magic bullet to get more oomph out of a TBI. It takes a pretty comprehensive package to up the ante much.