Common Performance Enhancing Mods
 

Post your common performance enhancing mods here.

I'll start with a few things which show little to no gain and, IMHO really aren't worth the cost of the packaging they come in:

• Intake Air Temperature Resistor Mod - Those things that are offered on eBay for $20-$40 that say they alter the IAT temps for a performance gain... This is something that the PCM will eventually correct for, negating any supposed gains that may have been.
• Throttle Body Spacer (~$90 or so) - This mod works on many other vehicles that have relatively low plenum volume and produce peak torque at a relatively high RPM. In principle, this works by increasing the volume of air between the throttle blade & the intake valve, lowering the RPM at which peak torque occurs. The 4.3L engine, however, produces peak torque very low in the RPM band already and with a rather large open plenum intake design, the increase in plenum volume is very small.

Now some mods that have shown some 'gains' whether those gains are in perception, performance, and/or mileage:

• Cold Air Intake ($60-$250 depending on source) - The stock air box does a decent job at supplying air to the engine that is at or close to ambient temperatures. One of the most common mistakes that people make when moving to an open element air cleaner is the lack of proper shielding to ensure that the new intake does not suck in hot engine bay air. Hot air with less restriction most often is worse than cold air with a bit more restriction. Cold air is dense air.
• Tune ($150-$250) - Probably the best mod that can be done to these vehicles is a tune. Factory tuning is conservative at best and decent gains in both power and mileage can occur if your vehicle is tuned properly. For the maximum benefit, get a dyno tune after other modifications are done. But mail order tunes still give noticeable gains. PCMforLess.com, BlackBearPerformance.com, & Wait4me.com are a few businesses that do mail order tunes.
• Headers ($200+) - Headers flow better than the stock cast iron exhaust manifolds. Coupled with a larger y-pipe & high flow catalytic converter, exhaust restrictions can be minimized which will result in better power & efficiency.
• Cat-Back Exhaust ($200+) - Mostly done for a better sounding exhaust, it also removes restriction from the exhaust system. Care must be taken when choosing the design of the system as there is such a thing as too large of an exhaust pipe.
• Throttle Body Blade Mod (Free) - Basically removing or trimming down the deflector on the underside of the throttle blade. Good if you are looking for increased throttle sensitivity, but I had no gains in wide open throttle performance or mileage after I did this mod to my old '00 Bravada. Scans pre-mod & then post-mod showed nearly identical 0-60 times with the same ambient temps on the same road. Throttle sensitivity definitely increased to the point of being annoying to me. I also noted a difference in deposits on the 'front' plugs vs. the 'rear' plugs after 15k miles which I attributed to an uneven distribution of EGR gases which the deflector helps push to the center of the plenum during normal cruising.

I tossed the throttle body blade mod on the second section after initially wanting to put it in the first section. This has been a contentious mod in the past with my views being on the 'doesn't do enough to be worthwhile' side. I keep very detailed records on all of my vehicles and had recorded my runs before & after this mod with my scan tool (AutoTap at the time) showing no difference in WOT performance.


So post up your ideas for common performance enhancing mods. Please try to include the cost, gains or other observations you noted, possibly a link to a thread here discussing the mod, and anything else that would help in the discussion.

Change the distributer cap and rotor. Yes the 4.3l engine still has a distributer cap and rotor. I bought my 1997 Blazer with 105,000 km on it and it was running rough. Found out by accident that it had a distributer cap and rotor - I thought that it was a coil pack as it doesn't look like a traditional distributer. As part of my routine maintenance I decided to change it out. Well, I'm pretty sure that they were the original parts as the rotor and cap were extremely pitted and corroded. Now the engine idles smoothly and I have a little bit more power all for about $20.

I bought this inexpensive Walker Dynamax cat back 2.5" dia exhaust kit from Rockauto. The stock exhaust goes from dual 2" pipes from the manifolds to a single 2.5" collector to the cat then 2.5" to the stock monster size muffler and then exits the muffler back down to a 2" exhaust pipe! What is with that? That's a 60% restriction just by pipe size.

The Walker kit is inexpensive and very easy to install. Fit perfectly. I put the passenger side up on jack stands and took off the passenger rear wheel. The hardest part was removing the 3 bolts at the header style connector at the cat. I ended up breaking the nuts off. The rubber exhaust hangers required lots of WD40 and wiggling back and forth to get them off. The sound is a very mild rumble while driving and quiet at idle. The engine feels more responsive now where before it felt very choked.

I wanted to second the post by Blanchae. If you shop around you can get this exhaust for about $140. It is super easy to install. You just need to purchased the three bolts and nuts necessary to attach it to the flange.

I can't say I've noticed much improvement in performance. I purchased it for its ease of installation, only discovering later that it was considered a bit of an upgrade.

The best you can do if you have the money( what ive done) is, Cam, headers and high flow exhuast, CAI, Higher output coil, removed AC and installed electric fan, then have your computer flashed/tuned to accept these mods. I gain about 35-40 HP. Doesnt sound like much but you will notice it.
Agree, throttle body spacer, throttle blade mod, ebay chips are useless. Pretty much much any mod will net little gains as the computer will adjust to changes bringing it back to stock.

Came across this youtube video with a free mod to the throttle body plate to improve performance.
For some reason, Chevrolet decides to put a wide "deflector plate" on the throttle plate to interrupt the air flow at part throttle. Before the mod, I found my throttle response to be sluggish, removing the "deflector plate" off the throttle valve made the engine responsive like it should be and removed the sluggish feeling. Highly recommended.

I did it a bit different from the video. I removed the throttle body off the intake, disconnected the wiring but left the throttle cables connected. I covered the intake opening with a rag and used a socket as a spacer to keep the throttle plate opened while I ground off the rivet heads with a dremel tool. Used a punch to punch the rivets out and removed the plate. Plugged each of the holes with a large pop rivet and washer. Blew out any filings and put it back together. It was simple. Tricky part was to grind the rivet heads off without scratching or damaging the throttle plate.

like the 2 posts above say, it does nothing and can end up damaging your motor

Actually, having done the mod, it does improve the response as I've stated. Does it improve performance - yes, with better low throttle response. As I've stated, my Blazer felt sluggish, I had to bury the pedal to get acceleration. Now it responds as it should. Does it improve gas mileage or make more hp? I don't know and never stated that it did. It improves driveability as far as I'm concerned.

As for damaging your engine? Really? That would mean that every time you push the pedal to the metal, the butterflies would open wide and damage the engine. Same effect.

Seems to me that what is accomplished with that mod is a greater open cross-sectional area versus throttle position curve. I.e. at a smaller throttle plate angle there is a greater open cross-sectional area. How this affects the computer is hard to know. The person who posted the video is convinced that it makes the motor more more responsive.

But for anything that is engineered, there are reasons something is done and there are always trade-offs. These can be:

1. cost of production,
2. optimization of fuel efficiency,
3. reduction of emissions,
4. tuning for a combination of power or torque,
5. drivability, or
6. something else??.

Considering the design, of these I doubt 1 applies here. My guess is that it has something to do with 2, 3, 4 or 5.

With almost or over 20 y.o. vehicles, we may not care much about emissions and doing this mod could increase mileage, power or torque. Then again when you modify one part of a system, there could be unforeseen consequences in other parts of the system. Whatever these changes are, they may be good or bad depending on your point of view.

It is interesting that I find the mod more responsive and to my liking and Swatlkk found it too sensitive. Also, historically there is no deflector plate on the throttle butterflies. I agree that the deflector plate is attempting to change the cross-sectional area versus throttle position curve at low positions. My preference is to remove it as it makes the truck more responsive at the low throttle positions where I drive 90% of the time.

Since we like controversy here. What do you think about blocking the EGR valve off? Just taking a plate and blocking it off then reinstalling the EGR valve.

If you do that and don't have the PCM tuned for it, you'll probably get engine knock. Best case, the knock sensor detects it and backs off your timing to correct it. That way, you only get worse performance, but no damage. Worst case, you chew up one or more pistons.

It can be tuned out, but I don't know if it will give you any real performance gains, since it's normally closed at WOT, anyway.

has any one gotten a throttle body from the 7.4L swapped the injectors off there 4.3L TB and installed it I know it changes the opening to 2" each and the 4.3/5.0/5.7 are all the same and smaller 1.5" or 1.75" if I remember correctly but dont hold me to that. Just curious if any one has tried this, also what cams/durration are most people running?

Dont know about the throttle body but doubt the injectors would work. computer controlled engine remember

The injectors would run but would flood the motor/ run extremely rich, remember reading up on it and the injectors on the 7.4l run close to double what the 4.3 run at slightly higher pressure. To me it makes sense believe the cfm on the 7.4l t/b was in the 400s around 450. Just figured I wasn't the first person to have this hair brained idea

I wouldn't consider it at all for a TBI 4.3L v6 as it would require a fairly wild build to need a larger throttle body. For a TBI 5.7L, you need some fairly large heads, a big cam, and an intake that would support a higher RPM range to really need the larger TB. I have read many accounts of people performing the swap on TBI 350's and state that their engine bogs at low RPM WOT which is likely because they did not change anything in the ECU, but who knows.

I have a bunch of TBI parts that I've collected over the years for when I get around to putting the '90 TBI 5.7L engine I have into my '74 K5. I recently picked up a spread-bore to TBI adapter found on the many of the early 454 TBI motors that would allow me to swap between the stock quadrajet and TBI with relative ease. I also picked up a very nice Holley TBI unit at a swap meet for $25 probably 10 years ago now.

I may end up ditching all of that and using the $30 LM7 (5.3L LS engine) in the K5 instead. But that brings along the added headache of either changing it over to carb'd with aftermarket DIS or getting the wiring & ECM to control it with more or less stock parts.

I know the only difference between the 350 and 4.3L tb is the injectors they run a higher fuel flow rate and cause the engine to bog and run rich, other than that it's the exact same physically. I've been researching what hot rod did on there 4.3 build they did a long time ago. They used a custom intake as it was before the the use of vortec heads and Edelbrock performer intakes. They upgrade to a 650 cfm carb don't think that much is actually required for a v6 as that would hold over most mild to decent built 350s. Does any one have the flow rait on a set of vortec heads guess that should really be what I'm looking for that would determine if it's worth it or not.

Ok so found data I was looking for the pre vortec heads flow at a miserable 138 cfm intake and 116 cfm exhaust the vortec heads off the 200hp 4.3( Silverado, sieera) flow at 202cfm intake and and 190cfm exhaust. The 4.3/5.0/5.7 tbi has a flow rate of 490 cfm with a bore of 1 11/16" and the 7.4l is 645 cfm with 2" bore. The huge difference is the injectors 4.3 runs at 48#/hr 5.0 is 55#/hr 5.7 is 61,65,68#/hr and 7.4 is 75,81#/hr at stock psi. So stock tbi should suffice most v6 builds. This explains the bogging and running rich when guys do tbi swaps and don't change injectors if possible.

I know, this is a old thread. The throttle blade mod throws off the cruise control. Makes it almost useless.