FSC Forum - View Single Post - Common performance-minded FAQs about 88-98 OBS trucks

Red94Chev · 05-30-2006, 09:13 PM

Can I install a hydraulic roller camshaft in my TBI engine? What do I need to know?
Yes, the TBI engine blocks have all the provisions for hydraulic rollers, including the bosses for the spider. Unfortunately, they are not pre-drilled. Therefore, you should disassemble the engine first to avoid getting metal shavings in your engine. There are two terminologies that you have to watch out for here: Retrofit roller cams are for pre-87 blocks: OEM roller cams are for 87 and later blocks. The best way to convert to a hydraulic roller is to buy a kit available from camshaft companies like Comp Cams (K-kit) that includes almost all the parts you need for the swap. The only additional parts needed are the spider, retainer plate, and the roller rocker arms. Total cost however is about $1000.
Read the following article for more info on installing a roller camshaft: http://www.chevyhiperformance.com/te...ler/index.html

An except from the article: “One of the more budget-oriented conversion kits from GM Performance Parts is the Hot hydraulic-roller cam. This particular cam was originally designed for the LT1 small-block and used 1.6 roller rockers. ... This is a great cam; in a 355ci small-block with Vortec heads and a GM Performance Parts dual-plane intake, it made 412 hp and 422 lb-ft of torque with 9.75:1 compression.”

Is there any way to predict what kind of hp I’d expect from my performance upgrades?
You bet. I did a series of common engine upgrades using the stock TBI engine to illustrate the utility of dyno simulation software. Here’s a link to the thread: http://www.fullsizechevy.com/forums/...d.php?t=194581. Engine sim software is an invaluable resource in helping to choose the right camshaft or the right performance heads. You can also couple your engine with the Drag sim software to see how your engine upgrades will perform on the street. You can try out different rear ends, transmissions, or higher stall torque converter with your engine/truck combo. Spending some quality time with this software could save you thousands of dollars in selecting the wrong parts. I can not say enough about the utility of this software.

What TBI and Vortec intake manifolds are available for my truck?
There are 3 aftermarket TBI intake manifolds that are out on the market today. Holley makes one that has 2” bores but requires you to use an older style EGR. GM performance parts make one that also has 2” bores but is designed to be used with Vortec heads. They will not work with non-Vortec heads since the intake runners are much taller. The only real bolt-on without any modification is the Edelbrock Performer TBI intake. It is a direct replacement for the stock intake manifold with no modifications required. Its only downfall is that it uses the stock size inlet bores that don’t allow you to use a larger TBI unit as previously mentioned. Your local machine shop can make easy work of this and the intake can be bored to accept 2” TBI units. The last option is to use an intake design to work with a carb and use a TBI adapter plate (i.e. GM or Trans Dapt). Some people go this route and have a tremendous amount of success.

The only direct Vortec-compatible intake is the marine version that I mentioned earlier. It allows the use of standard aftermarket fuel injectors. There are also some other modifications that are required to use this intake. The conversion link is here: http://www.pacificp.com/forum/viewtopic.php?t=317. There is also a Vortec-compatible TPI base manifold available if you'd like to switch to TPI induction.

Are there any other intake systems I could use for my Vortec engine?
Definitely. Some people have moved over to the GM RamJet for Vortec engines. Edelbrock also makes a MPFI system for Vortec heads. More and more manufacturers are making Vortec- compatible intakes and fuel injection systems. A less expensive option may be a TPI conversion (http://www.fullsizechevy.com/forums/...=marine+vortec). Visit Summit Racing for an up-to-date listing of Vortec-compatible systems. Weiand, for instance, has their new Stealth Ram for Vortec heads and even the weiand supercharger units for Vortec heads. Any of the products would be used with TBI engines that use Vortec or Vortec-style performance heads as well.

What about Edelbrock’s MPFI conversion for TBI engines or engines with Vortec heads? Is it worth it and how much power does it provide?
Another common question. Here is a good article on this kit: http://www.off-roadweb.com/tech/0310or_edel/. Edelbrock did their own testing using their performance parts (cam, heads, exhaust, etc.) and came up with about 270 hp. I use it, but I’ve matched it with Trick Flow heads and a cam from Comp Cams roller with more duration and higher lift. Here are the pro's and con's on this kit.

Pros:
1. I called Edelbrock and the supplied injectors are rated at 20.5#/hr at 43 psi. With tuning and maximal FP (~65 psi), these injectors are good up to 360 hp. You can also swap the injectors for larger ones, so you'll never exceed the hp limit of the fuel injectors,
2. Least expensive manufactured MPFI system on the market that's brand new.
3. Single plane intake design that works well with high flow heads/camshaft upgrades. Although torque is lower than a dual plane setup at lower RPMs, torque output is still significantly more than stock.
4. There is an aftermarket adjustable FPR available for it. There are several manufacturers, including Holley, Jet, Automotive, etc. I purchased the Holley one (512-502) and switched the output connector with an AN-6 one (Barry Grant 140028). Easy peasy. There is a schrader valve for a fuel pressure gauge off the driver's side fuel rail. It can be swapped out to work with an inexpensive underhood Autometer fuel pressure gauge. In order to make this work, you'll need to exchange the position of the fuel rails (driver's side fuel rail to passenger's side and vice versa for passenger's side fuel rail) and rotate them 180 degrees (Edelbrock engraving towards manifold). The fuel lines hook-ups will still be at the back, but on the opposite side. You will also need to create an access hole in the throttle cable mounting bracket to easily adjust the AFPR with an allen key.

Cons:
1. Relatively expensive for the performance gain on stock setup
2. Some improvement in highway fuel economy, but not much.
3. You can achieve similar performance from a TBI/chip for less money BUT you'll need larger injectors to match your power output.
4. Need a custom chip if you use any camshaft or cylinder head other than Edelbrock. The Edelbrock tune is not optimal anyway, and probably explains the poor performance some people have experienced. Save some money by ordering the 3502 kit, which is the same system w/o the Edelbrock-supplied chip.
5. Not a true PFI setup, since the PCM fires the injectors using the TBI firing strategy (twice as often as PFI). For a true conversion, you can use the PCM from a 94-95 truck (7427) and convert it to PFI: http://www.fullsizechevy.com/forums/...i-tbi-pcm.html. A good discussion topic on this can be found here: http://www.fullsizechevy.com/forums/...ur-trucks.html

So to answer the question - is it worth it? On a mostly stock engine with stock heads - no. Even on a performance motor, I'm not sure if the added expense justifies the minimal performance gains relative to a TBI setup. TBI is capable of supporting engines with 360+ hp with FP/tuning/injector upgrades. Some people, however, have reported rich idle that they cannot tune out due to the TBI injector firing strategy with high pressure stock injectors or with the 454 injectors. Converting to PFI mode and running MPFI would eliminate this problem and allow you remove the bottleneck of TBI in a performance application. Most people would consider other performance upgrades first before attempting this swap.

What is involved in a TPI swap for my TBI engine?
This was a popular swap about ten years ago. I still think that this swap is economical and it has an important application in trucks since it is designed to produce a broad flat torque curve. Read these articles for more specifics on the conversion: http://www.chevyhiperformance.com/te.../148_0207_tpi/ and http://www.chevyhiperformance.com/techarticles/90759/. There are also entire books dedicated to this swap, such as the Chevy TPI Fuel Injection Swapper's Guide available through Summit Racing or at your local performance parts store. There is more involved in this swap than a short paragraph will allow. Here is a well put-together article detailing the swap on a 94 Suburban: http://www.edgesz28.com/edgesZ28/sub...an-tpiswap.htm. If you’re thinking about a TPI setup, I would try to choose your components to maximize torque/power under 4500 RPM. There are ways to improve top-end breathing on TPI engines, but the parts are expensive and not readily available. Adding these components can produce a 400hp TPI engine, but the added expense of the components will no longer make this an economical swap. If you want a 400 hp small block or high RPM performer, I’d consider using the GM Ramjet or Holley Stealth Ram instead. It will be cheaper to buy these systems than modify the TPI system for high RPM power.

What cylinder heads can I use on my truck?
There are a few choices that you can go with. A popular set of heads are those found on TPI Camaros/Firebirds/Corvettes, called the L98 head. They do not have the swirl port style of the stock TBI heads, but have the same combustion chamber size as your stock heads. They can be found in cast iron and aluminum, the aluminum being the most desirable because of their smaller 58cc combustion chamber. IMO though, there are better aftermarket heads available for TBI replacements. Another cast iron set is the World Products SR Torquer heads. These heads have larger than stock valves, the same combustion chamber as stock, and provisions to accept cams up to .525” lift. Other choices include AFR, Edelbrock, Trick Flow, Pro Topline, and Canfield. Personally, I love the Trick Flow heads for a few reasons: 62cc combustion chamber, direct bolt-on design, excellent flow characteristics, aluminum design, and relatively inexpensive. They come with several spring options to support 0.500” lift hydraulic and hydraulic roller camshafts.

Vortec heads are a good head from the factory, but also have their limitations (see “What are the major troublesome areas to overcome in TBI engines to make awesome power? In Vortec engines?”). At minimum, I would upgrade the springs on these heads to support high lift roller camshafts. If you are looking for more power, you will need to upgrade or replace your fuel induction system and should consider aftermarket Vortec heads. There are many heads available and here is a recent article on some of the more common choices: http://www.chevyhiperformance.com/te...tec/index.html. To save you the extra reading, the Edelbrock 170 Etecs are the best performing head on the market right now with valve lifts up to 0.575”. Awesome head. These heads are used on Edelbrock’s EFI 440hp 350 crate engine, which would make an outstanding turn-key drop in motor for any 88-98 OBS truck.

I want to use Vortec heads on my TBI engine. What is involved with the swap and what kind of power increase can I expect?
Oh man, if I got a dollar for every time this question is asked…OK, this swap is not as easy as swapping heads as you’ve probably figured out. There are a lot of hidden costs involved that add up very quickly. You need: 1. Vortec-compatible TBI manifold – currently only GM Performance Parts sells this and it is pricey. 2. driver’s side manifold needs to changed to utilize EGR. Can be pulled from a parts yards or buy headers for 96-99 5.7L trucks. 3. EGR tube - again get from a wrecking yard. 4. Vortec heads have low lift potential and will require either machine work or different springs for high lift cams. If you're changing heads, you might as well change the cam at the same time. Summit racing and others sell Vortecs heads with these modifications already performed. 5. You will need a custom chip regardless of what you do in order to maximize the potential of your engine. 6. You may need to upgrade your fuel pump, run an adjustable fuel pressure regulator, or run larger injectors to make sure you have enough fuel to support a substantial increase in horsepower over stock. Just adding Vortec heads may add only 20 hp because the TBI camshaft is so weak. To take advantage of these better flowing heads, you need to change the camshaft in your engine. All told, it is going to cost more than $850-1000+, not including the cost of the heads to make it run right and to avoid disappointment. With careful parts selection, you can achieve 320+ hp easy with a performance exhaust setup.

I want to use a 4 barrel 900 CFM Holley TBI. Can this be done?
Sure! Some methods are easier then others though... You won’t need it until your pushing over 400 HP or 6000 RPM on an extensively modified engine. At power levels below this, an upgraded 2-barrel TB can meet the required demands. You can either run an external injector driver and learn prom burning or go promless and do your own source coding to control it, or you can use an aftermarket ECU. Your choice.

Fuel injection is not for me. How do I swap my TBI (or Vortec CSFI) for a carburetor?
I know – I get it. You have a ton of experience with non-computer controlled vehicles and when properly tuned, they can perform just as well as EFI, right? Plus, there is no dreaded computer to deal with and the thought of controlling your air:fuel ratio using metering rods and jets gets your heart pounding. While of course it is possible to run a carb on these engines, there are some things to think about before plunging into this swap. If you have the 4L60E transmission on 93 and later trucks, you will need to use an aftermarket controller kit with a specialized throttle position sensor designed for carburetor “retrofit” applications. As for the engine, the key to a successful swap is to remove control of the computer to engine parts. Therefore, you need to replace the EFI system with a carb/intake combo and replace your computer-controlled distributor with a non-computer controlled distributor, ignition module, and coil. You will also need to modify the fuel system by installing an in-tank fuel pump or installing a 3-port, return style AFPR inline before the carb to lower the fuel pressure to a carb-friendly 5-8 psi. There are also some minor modifications that need to be made, such as throttle linkage, vacuum lines, etc., but essentially you’re done. Ok, you’re still convinced on performing the swap. Instructions are here: http://www.thirdgen.org/carbswap. An article on the different types of carbs available is here: http://www.thirdgen.org/pickacarb.

Can Seafoam improve the performance of my engine?
Maybe. The reason to use Seafoam (or GM top engine cleaner) is to remove the carbon deposits from your combustion chambers. Why? Two reasons: 1) To promote cleaner combustion, and 2) Because these deposits can increase the compression of your engine by taking up free air space. You won't notice using the stock chip, but if you use a performance chip with aggressive timing, it may cause the engine to ping when under load (WOT) and using 87 octane fuel. On TBI and Vortec engines, there is a knock sensor that decreases the timing if engine knock is detected. Using Seafoam in this case, may remove engine deposits and lower engine compression back to the stock configuration, eliminating the engine knock. The result: you regain the lost power and performance of your engine.

What is a good exhaust system for my truck and will too big of a system take away low end power?
A 3” exhaust will not decrease low end power at all. A dual 2.5” exhaust system is optimum. Also, you’ll want to decrease back pressure as much as possible and many people get this confused with scavenging. A full exhaust from headers, dual or single high flow cat(s), and cat-back really provides a major power boost. The stock exhaust is horrendously restrictive. Buy a pre-fabricated exhaust kit or have an exhaust shop make your exhaust from scratch. It is not much more money believe it or not. A little reading in this exhaust section should help you make an informed decision.

05-30-2006, 09:13 PM	#3
Red94Chev Kick Ass!! Status: Offline Join Date: Sep 2005 Member ID: 33983 Pics: My Gallery Location: Edmonton, AB Age: 33 Posts: 930	Re: Common performance-minded FAQs about 88-98 OBS trucks Can I install a hydraulic roller camshaft in my TBI engine? What do I need to know? Yes, the TBI engine blocks have all the provisions for hydraulic rollers, including the bosses for the spider. Unfortunately, they are not pre-drilled. Therefore, you should disassemble the engine first to avoid getting metal shavings in your engine. There are two terminologies that you have to watch out for here: Retrofit roller cams are for pre-87 blocks: OEM roller cams are for 87 and later blocks. The best way to convert to a hydraulic roller is to buy a kit available from camshaft companies like Comp Cams (K-kit) that includes almost all the parts you need for the swap. The only additional parts needed are the spider, retainer plate, and the roller rocker arms. Total cost however is about $1000. Read the following article for more info on installing a roller camshaft: http://www.chevyhiperformance.com/te...ler/index.html An except from the article: “One of the more budget-oriented conversion kits from GM Performance Parts is the Hot hydraulic-roller cam. This particular cam was originally designed for the LT1 small-block and used 1.6 roller rockers. ... This is a great cam; in a 355ci small-block with Vortec heads and a GM Performance Parts dual-plane intake, it made 412 hp and 422 lb-ft of torque with 9.75:1 compression.” Is there any way to predict what kind of hp I’d expect from my performance upgrades? You bet. I did a series of common engine upgrades using the stock TBI engine to illustrate the utility of dyno simulation software. Here’s a link to the thread: http://www.fullsizechevy.com/forums/...d.php?t=194581. Engine sim software is an invaluable resource in helping to choose the right camshaft or the right performance heads. You can also couple your engine with the Drag sim software to see how your engine upgrades will perform on the street. You can try out different rear ends, transmissions, or higher stall torque converter with your engine/truck combo. Spending some quality time with this software could save you thousands of dollars in selecting the wrong parts. I can not say enough about the utility of this software. What TBI and Vortec intake manifolds are available for my truck? There are 3 aftermarket TBI intake manifolds that are out on the market today. Holley makes one that has 2” bores but requires you to use an older style EGR. GM performance parts make one that also has 2” bores but is designed to be used with Vortec heads. They will not work with non-Vortec heads since the intake runners are much taller. The only real bolt-on without any modification is the Edelbrock Performer TBI intake. It is a direct replacement for the stock intake manifold with no modifications required. Its only downfall is that it uses the stock size inlet bores that don’t allow you to use a larger TBI unit as previously mentioned. Your local machine shop can make easy work of this and the intake can be bored to accept 2” TBI units. The last option is to use an intake design to work with a carb and use a TBI adapter plate (i.e. GM or Trans Dapt). Some people go this route and have a tremendous amount of success. The only direct Vortec-compatible intake is the marine version that I mentioned earlier. It allows the use of standard aftermarket fuel injectors. There are also some other modifications that are required to use this intake. The conversion link is here: http://www.pacificp.com/forum/viewtopic.php?t=317. There is also a Vortec-compatible TPI base manifold available if you'd like to switch to TPI induction. Are there any other intake systems I could use for my Vortec engine? Definitely. Some people have moved over to the GM RamJet for Vortec engines. Edelbrock also makes a MPFI system for Vortec heads. More and more manufacturers are making Vortec- compatible intakes and fuel injection systems. A less expensive option may be a TPI conversion (http://www.fullsizechevy.com/forums/...=marine+vortec). Visit Summit Racing for an up-to-date listing of Vortec-compatible systems. Weiand, for instance, has their new Stealth Ram for Vortec heads and even the weiand supercharger units for Vortec heads. Any of the products would be used with TBI engines that use Vortec or Vortec-style performance heads as well. What about Edelbrock’s MPFI conversion for TBI engines or engines with Vortec heads? Is it worth it and how much power does it provide? Another common question. Here is a good article on this kit: http://www.off-roadweb.com/tech/0310or_edel/. Edelbrock did their own testing using their performance parts (cam, heads, exhaust, etc.) and came up with about 270 hp. I use it, but I’ve matched it with Trick Flow heads and a cam from Comp Cams roller with more duration and higher lift. Here are the pro's and con's on this kit. Pros: 1. I called Edelbrock and the supplied injectors are rated at 20.5#/hr at 43 psi. With tuning and maximal FP (~65 psi), these injectors are good up to 360 hp. You can also swap the injectors for larger ones, so you'll never exceed the hp limit of the fuel injectors, 2. Least expensive manufactured MPFI system on the market that's brand new. 3. Single plane intake design that works well with high flow heads/camshaft upgrades. Although torque is lower than a dual plane setup at lower RPMs, torque output is still significantly more than stock. 4. There is an aftermarket adjustable FPR available for it. There are several manufacturers, including Holley, Jet, Automotive, etc. I purchased the Holley one (512-502) and switched the output connector with an AN-6 one (Barry Grant 140028). Easy peasy. There is a schrader valve for a fuel pressure gauge off the driver's side fuel rail. It can be swapped out to work with an inexpensive underhood Autometer fuel pressure gauge. In order to make this work, you'll need to exchange the position of the fuel rails (driver's side fuel rail to passenger's side and vice versa for passenger's side fuel rail) and rotate them 180 degrees (Edelbrock engraving towards manifold). The fuel lines hook-ups will still be at the back, but on the opposite side. You will also need to create an access hole in the throttle cable mounting bracket to easily adjust the AFPR with an allen key. Cons: 1. Relatively expensive for the performance gain on stock setup 2. Some improvement in highway fuel economy, but not much. 3. You can achieve similar performance from a TBI/chip for less money BUT you'll need larger injectors to match your power output. 4. Need a custom chip if you use any camshaft or cylinder head other than Edelbrock. The Edelbrock tune is not optimal anyway, and probably explains the poor performance some people have experienced. Save some money by ordering the 3502 kit, which is the same system w/o the Edelbrock-supplied chip. 5. Not a true PFI setup, since the PCM fires the injectors using the TBI firing strategy (twice as often as PFI). For a true conversion, you can use the PCM from a 94-95 truck (7427) and convert it to PFI: http://www.fullsizechevy.com/forums/...i-tbi-pcm.html. A good discussion topic on this can be found here: http://www.fullsizechevy.com/forums/...ur-trucks.html So to answer the question - is it worth it? On a mostly stock engine with stock heads - no. Even on a performance motor, I'm not sure if the added expense justifies the minimal performance gains relative to a TBI setup. TBI is capable of supporting engines with 360+ hp with FP/tuning/injector upgrades. Some people, however, have reported rich idle that they cannot tune out due to the TBI injector firing strategy with high pressure stock injectors or with the 454 injectors. Converting to PFI mode and running MPFI would eliminate this problem and allow you remove the bottleneck of TBI in a performance application. Most people would consider other performance upgrades first before attempting this swap. What is involved in a TPI swap for my TBI engine? This was a popular swap about ten years ago. I still think that this swap is economical and it has an important application in trucks since it is designed to produce a broad flat torque curve. Read these articles for more specifics on the conversion: http://www.chevyhiperformance.com/te.../148_0207_tpi/ and http://www.chevyhiperformance.com/techarticles/90759/. There are also entire books dedicated to this swap, such as the Chevy TPI Fuel Injection Swapper's Guide available through Summit Racing or at your local performance parts store. There is more involved in this swap than a short paragraph will allow. Here is a well put-together article detailing the swap on a 94 Suburban: http://www.edgesz28.com/edgesZ28/sub...an-tpiswap.htm. If you’re thinking about a TPI setup, I would try to choose your components to maximize torque/power under 4500 RPM. There are ways to improve top-end breathing on TPI engines, but the parts are expensive and not readily available. Adding these components can produce a 400hp TPI engine, but the added expense of the components will no longer make this an economical swap. If you want a 400 hp small block or high RPM performer, I’d consider using the GM Ramjet or Holley Stealth Ram instead. It will be cheaper to buy these systems than modify the TPI system for high RPM power. What cylinder heads can I use on my truck? There are a few choices that you can go with. A popular set of heads are those found on TPI Camaros/Firebirds/Corvettes, called the L98 head. They do not have the swirl port style of the stock TBI heads, but have the same combustion chamber size as your stock heads. They can be found in cast iron and aluminum, the aluminum being the most desirable because of their smaller 58cc combustion chamber. IMO though, there are better aftermarket heads available for TBI replacements. Another cast iron set is the World Products SR Torquer heads. These heads have larger than stock valves, the same combustion chamber as stock, and provisions to accept cams up to .525” lift. Other choices include AFR, Edelbrock, Trick Flow, Pro Topline, and Canfield. Personally, I love the Trick Flow heads for a few reasons: 62cc combustion chamber, direct bolt-on design, excellent flow characteristics, aluminum design, and relatively inexpensive. They come with several spring options to support 0.500” lift hydraulic and hydraulic roller camshafts. Vortec heads are a good head from the factory, but also have their limitations (see “What are the major troublesome areas to overcome in TBI engines to make awesome power? In Vortec engines?”). At minimum, I would upgrade the springs on these heads to support high lift roller camshafts. If you are looking for more power, you will need to upgrade or replace your fuel induction system and should consider aftermarket Vortec heads. There are many heads available and here is a recent article on some of the more common choices: http://www.chevyhiperformance.com/te...tec/index.html. To save you the extra reading, the Edelbrock 170 Etecs are the best performing head on the market right now with valve lifts up to 0.575”. Awesome head. These heads are used on Edelbrock’s EFI 440hp 350 crate engine, which would make an outstanding turn-key drop in motor for any 88-98 OBS truck. I want to use Vortec heads on my TBI engine. What is involved with the swap and what kind of power increase can I expect? Oh man, if I got a dollar for every time this question is asked…OK, this swap is not as easy as swapping heads as you’ve probably figured out. There are a lot of hidden costs involved that add up very quickly. You need: 1. Vortec-compatible TBI manifold – currently only GM Performance Parts sells this and it is pricey. 2. driver’s side manifold needs to changed to utilize EGR. Can be pulled from a parts yards or buy headers for 96-99 5.7L trucks. 3. EGR tube - again get from a wrecking yard. 4. Vortec heads have low lift potential and will require either machine work or different springs for high lift cams. If you're changing heads, you might as well change the cam at the same time. Summit racing and others sell Vortecs heads with these modifications already performed. 5. You will need a custom chip regardless of what you do in order to maximize the potential of your engine. 6. You may need to upgrade your fuel pump, run an adjustable fuel pressure regulator, or run larger injectors to make sure you have enough fuel to support a substantial increase in horsepower over stock. Just adding Vortec heads may add only 20 hp because the TBI camshaft is so weak. To take advantage of these better flowing heads, you need to change the camshaft in your engine. All told, it is going to cost more than $850-1000+, not including the cost of the heads to make it run right and to avoid disappointment. With careful parts selection, you can achieve 320+ hp easy with a performance exhaust setup. I want to use a 4 barrel 900 CFM Holley TBI. Can this be done? Sure! Some methods are easier then others though... You won’t need it until your pushing over 400 HP or 6000 RPM on an extensively modified engine. At power levels below this, an upgraded 2-barrel TB can meet the required demands. You can either run an external injector driver and learn prom burning or go promless and do your own source coding to control it, or you can use an aftermarket ECU. Your choice. Fuel injection is not for me. How do I swap my TBI (or Vortec CSFI) for a carburetor? I know – I get it. You have a ton of experience with non-computer controlled vehicles and when properly tuned, they can perform just as well as EFI, right? Plus, there is no dreaded computer to deal with and the thought of controlling your air:fuel ratio using metering rods and jets gets your heart pounding. While of course it is possible to run a carb on these engines, there are some things to think about before plunging into this swap. If you have the 4L60E transmission on 93 and later trucks, you will need to use an aftermarket controller kit with a specialized throttle position sensor designed for carburetor “retrofit” applications. As for the engine, the key to a successful swap is to remove control of the computer to engine parts. Therefore, you need to replace the EFI system with a carb/intake combo and replace your computer-controlled distributor with a non-computer controlled distributor, ignition module, and coil. You will also need to modify the fuel system by installing an in-tank fuel pump or installing a 3-port, return style AFPR inline before the carb to lower the fuel pressure to a carb-friendly 5-8 psi. There are also some minor modifications that need to be made, such as throttle linkage, vacuum lines, etc., but essentially you’re done. Ok, you’re still convinced on performing the swap. Instructions are here: http://www.thirdgen.org/carbswap. An article on the different types of carbs available is here: http://www.thirdgen.org/pickacarb. Can Seafoam improve the performance of my engine? Maybe. The reason to use Seafoam (or GM top engine cleaner) is to remove the carbon deposits from your combustion chambers. Why? Two reasons: 1) To promote cleaner combustion, and 2) Because these deposits can increase the compression of your engine by taking up free air space. You won't notice using the stock chip, but if you use a performance chip with aggressive timing, it may cause the engine to ping when under load (WOT) and using 87 octane fuel. On TBI and Vortec engines, there is a knock sensor that decreases the timing if engine knock is detected. Using Seafoam in this case, may remove engine deposits and lower engine compression back to the stock configuration, eliminating the engine knock. The result: you regain the lost power and performance of your engine. What is a good exhaust system for my truck and will too big of a system take away low end power? A 3” exhaust will not decrease low end power at all. A dual 2.5” exhaust system is optimum. Also, you’ll want to decrease back pressure as much as possible and many people get this confused with scavenging. A full exhaust from headers, dual or single high flow cat(s), and cat-back really provides a major power boost. The stock exhaust is horrendously restrictive. Buy a pre-fabricated exhaust kit or have an exhaust shop make your exhaust from scratch. It is not much more money believe it or not. A little reading in this exhaust section should help you make an informed decision.