OK, after counting nickels and only being able to do little mods since I bought my Trooper, I recently got a promotion/raise at work <img src="/forums/images/graemlins/smile.gif" alt="" /> AND one of the two kids in college will be graduating soon... <img src="/forums/images/graemlins/kewl.gif" alt="" />

Sooo...dad may finally be able to spend some of what is nominally HIS $$$ <img src="/forums/images/graemlins/rolleyes.gif" alt="" />.

One of the mods I've wanted to make is an upgrade of the throttle body. I was leaning towards the Holley, but in a recent post someone mentioned they had problems with the Holley unit, replaced it with a 4.3 one and have been much happier.

Has anyone else run both? From the posts here most people who have done the 4.3 TB are happy with it, how about the folks running the Holley?

As near as I can tell, I'll probably be looking at about the same $ by the time I rebuild the 4.3, so the issue(s) are performance, day to day driveability and reliability.

Opinions welcome. Thanks,

Jay

I have been running the Holley since 1999. I had a real run of problems, but when I eventually diagnosed it correctly, it was my problem not the Holleys. I had a bad connection in one of the splices of the wiring, so once that was resolved, I have had no other problems.

I'm quite happy with the Holley, I ran it atop my 2.8 and now it's on my 3.4 and still working great. If I recall I bought it in 2000 from Jegs.

One nice thing about the Holley, aside from being Brandy-New, is the adjustable fuel pressure regulator.

Of course there are ways to make a standard 4.3 TBI's regulator adjustable, but it does require some welding skills and a bit of other finagling.

Knowing what I know now about the 4.3 TBI, and with increased availability of used ones, I'd probably go that route. But nothing wrong with the Holley if you want to lay the $$$ out for it.

HTH & IMHO.........ed

The throttle body from a GM 4.3 should be about $30. Holley TBs are like 5 times that. Used ones are just as good as new, I don't see the Holley unit being worth the cash.

You'll spend more on getting the IM bored out. I spent $130 for the machine work, by a guy who needed like 3 hours to do it. That is too high, shop around for someone to do it cheaper.

Also, Make sure you do something to your exhaust since this mod should go in conjunction with something on the other side.

Really incredible improvement in power, might I add, for a simple and cheap mod.

here's my wrietup i edited some of it, in case you havent read it:

http://www.4x4wire.com/forums/showf...5&o=&fpart=&vc=1

Being a pessimist, I'm assuming that at least some parts (injectors, IAC, etc.) would need to be replaced during a rebuild, which would add a couple hundred $ pretty quick.

EDIT: Printed out the write up and read it last night. The injectors and IAC get reused from the 2.8 TB - sure makes this option look better!

I might luck out, but Mr. Murphy and I are old friends! <img src="/forums/images/graemlins/lol.gif" alt="" />



Took care of that when the muffler blew out, high flow 2 1/4" cat and turbo muffler, 2 1/4" pipe from the "Y" out the back.



Thanks...

Jay

Man, around where I live used TBI's are $100-$150, how on earth did you get one for $30.00?? Also, does it matter what vehicle you get the 4.3 TBI from? I did see one TBI for a lot less that was from a 1991 Astro with the 4.3 engine.

One more question- you reinstalled your old injectors, why not use the 4.3 injectors?

I got an intake manifold for $25 too. Here in MA, I think junkyards are really unpopular they sell you anything just to make a dollar. Sometimes they don't even charge for little things if you buy something big with it. There's only like 20 I think in the whole state. I think people here kind of look down on them and they don't get alot of business. The EPA in Mass is cracking down on them because I think MA is so eco-oriented and yards are looked at as really damaging to the environment.

Injector size on an EFI controlled vehicle does not matter since the computer makes fuel measurements based on sensor feedback. Since TB mods don't affect displacement, you use the same amount of gas. If I put in 4.3 injectors the comp would compensate and run them really stingy to get A/F ratio in spec. the comp doesn't know how big the injectors are on an efi system. The sensors provide feedback based on MAP, TPS and O2 readings.

Now with MPFI vehicles the comp controls fuel delivery based on pulse width (time) and not on orifice size. So on MPFI vehicle, a bigger injector will spray more gas, since the injector is open the same amount of time but puts more gas in the cylinder. BUT, no matter which system, the comp is still going to seek a medium based on feedback. Bottom line is injector size is not a modification, since fuel delivery is ultimately controlled by the comp. The only way to get more gas in an efi engine is to rewrite the ecm tables or alter the sensors to produce different outputs.

Now swapping to a 3.4 engine or modding an engine by replacement pistons with different cc volume etc. it is encouraged to jump up in injector size to handle the fuel delivery load the ecm will ask for.

Choosing the right injector size is based on which one can handle the range of gas the ECM will request so as not to cause a limiting factor. Too small and they can't deliver gas quickly or efficiently enough, and too big the computer will struggle at idle or low speed since they won't be accurate enough.

This TBI mod increases engine efficiency by reducing the amount of load on the engine during the intake stroke. It increases Wide open throttle performance, and allows for quicker throttle response.

Think of engine power mods as two types, type 1 creates more power, and the type 2 prevents the engine from wasting as much power so it can put it to the wheels. The net result of both is an increase in HP, but they are different.

TB and exhaust mods fall into type 2, as well as intake mods, high flow cats and air filters.

Type 1 would be like increasing combustion ratio, changing cc volume, forced induction, ignition mods etc.

Kind of a shaky analogy but sometimes it helps to oversimplify things.

Thanks CPOM, I was getting my mods mixed up... Thanks for straightening me out! One more question, would a TBI from a 1991 Chevy Astro with the 4.3L V6 work? I usually hear about people using S10 TBI's.

Thanks again, and excellent write up! <img src="/forums/images/graemlins/kewl.gif" alt="" />

I got mine out of a 4.3 Blazer. I don't think it matters, just get one that's clean and cheap.

One more question- what range of years should I be looking at? My Trooper is a 1991, so is it best to look for the same year? I recall reading something about different TPS connectors? I will try to find that info...