1991 Suburban 3/4 ton: TBI to Holley Sniper conversion - stupid, or worth it?

[io6060]

First of all, I'm new to the forum, so, hi! I tried to do as much research as possible before wasting everyone's time with a post, but I still have questions...

So, we've recently pickup up a pretty clean 1991 Suburban 3/4 ton. We had an 89 3/4 Sub years ago, and so, here we are.

The head gaskets are about in need of replacing, so, that started us thinking about the TBI, and swapping out for a Holley Sniper. Not necessarily looking for loads more power, just a more efficient system. The old TBI was never great, it worked, but having had it on two trucks, I'd like something more modern.

If I understand correctly, it's not exactly a bolt-on. We'd need to:

1. buy the sniper kit
2. replace the distributor
3. replace the intake manifold?
4. new fuel pump?
5. a new controller for the 4L80E in the 1991 Sub.

Am I nuts to be considering this? Seriously, no ego here, the work isn't hard, is it just a lot $ and effort for no real benefit?

Thanks for your patience.

 

[CountKrunk]

I've seen maybe 70% love it and 30% hate it of the reviews I've read or watched on YouTube.

 

[77Dmax]

Step backwards over a TBI. Thats all those systems are. A good tune on your existing setup would be worth more.

 

[Bextreme04]

First of all, I'm new to the forum, so, hi! I tried to do as much research as possible before wasting everyone's time with a post, but I still have questions...

So, we've recently pickup up a pretty clean 1991 Suburban 3/4 ton. We had an 89 3/4 Sub years ago, and so, here we are.

The head gaskets are about in need of replacing, so, that started us thinking about the TBI, and swapping out for a Holley Sniper. Not necessarily looking for loads more power, just a more efficient system. The old TBI was never great, it worked, but having had it on two trucks, I'd like something more modern.

If I understand correctly, it's not exactly a bolt-on. We'd need to:

1. buy the sniper kit
2. replace the distributor
3. replace the intake manifold?
4. new fuel pump?
5. a new controller for the 4L80E in the 1991 Sub.

Am I nuts to be considering this? Seriously, no ego here, the work isn't hard, is it just a lot $ and effort for no real benefit?

Thanks for your patience.

What are you looking to get from this? None of this will be simple or a bolt on, and in the end you will still be left with a fairly tired TBI 350. If everything drives fine but you want a bit more pep, you could probably just do a mild RV cam and slightly better heads when you do the head gaskets. The factory TBI is going to give you better drivability than a Holley sniper ever would and the 4L80 is gonna be a problem for swapping to anything else.

 

[io6060]

Huh, I would have thought the Holley would provide better driveability, but, that's why I'm asking. I had a manual controller with a 4L80E in a previous truck, so, that's not that big of a deal to me.

Anyhow, appreciate the thoughts. Thanks for your help.

 

[daveca]

Good idea to change the system for parts availiability- I bot a NOS TBI for my 95 S10 15 +years or so ago, cant get them now.

Our favorite old vehicles are getting harder to find parts for.

 

[Ricko1966]

I would think in 10 more years,it will be easier to find real deal TBI parts.GM made and sold millions of them. When the Holley system gets obsolete,good luck finding parts .On another note if something goes wrong today,tomorrow,or 1/2 way across where ever you are going. If you break down with factory GM TBI you can probably have parts in a few hours,not so with Sniper. You know Sniper is TBI if I were going to that much trouble,I'd be looking at a mpfi,cpi, sfi,or tpi system.

 

[dd1990]

If your trying to build an engine for power sure, but you wont get the reliability of a gm TBI....and I don't see Holley supporting this system in the long hall.

 

[75gmck25]

To some degree, a Holley Sniper on the stock TBI heads and cam is like putting lipstick on a pig. Lots of shiny new parts, but probably not that much difference in power with stock cam and heads.

To get more out of the sniper you will need more cam, but not one that goes beyond the compression and flow of TBI heads - so maybe something in the 214-218 @ .050 duration range. And after you get everything installed you will be wondering what it would have been like if you also swapped to aluminum heads. It’s a slippery slope.

 

[Frankenchevy]

I’d stick with the GM TBI over swapping if you aren’t trying to go crazy with other power adding modifications. The sniper will flow much better, but it’s a moot point if you aren’t seeking to bump the HP by much.

As most have said, you’ll be swapping TBI for TBI. After having driven our new to us suburban with GM TBI, I’m really quite impressed with it’s efficiency.

Three things I will say about the sniper that some aren’t:

1. The install is not difficult.
2. Holley isn’t going anywhere and I’m guessing the sniper isn’t either for quite some time.
3. Holley built the system to use off the shelf parts…at least in the original sniper I had a few years back. The sensors the same sensors you’ll find on factory vehicles. Somewhere on the Sniper forums you can find the p/n list for all the components to write down or print and throw in your glove box. In the event of a failure, unless it’s the ecu, any local auto parts store should have what you need. Also, the Terminator X shares many of the same parts.

 

[Tonimus]

I've done some Holley systems for a friend, and I like them. I'm actually looking at trying an Aces kit on my burb, too. Not because I don't like the Holley, just that what I'm looking for is more my price range with Aces.

What I have learned:
-Install is pretty straight forward if you're mechanically inclined. Some electrical knowledge is good for helping with the install. Just good practices for splicing and things like that. If things go sideways, proper use of a multimeter is recommended.
-Holley's tech line is great. Was able to fix a crank-no start due to a firmware issue in about 30 minutes.
-Once installed, the system was pretty okay. I expected better, but it was decent.

Then we did a full system upgrade on that Holley. Changed the CDI box parameters, Holley dual sync distributor, new software. Set it up so the Holley ran the entire ignition system and timing, as well as fueling. That made a HUGE difference.

Based on what I have seen, when doing aftermarket EFI, you shouldn't do JUST fueling. It's only half the equation. If you're going to throw the money at it, get the full ignition system too. There's no way it isn't going to run better when the single ECU is running the whole getup. If you want to get real fancy, you can go with a Terminator X and it can control the trans, too.

Parts availability: Most of the hard parts that wear are based on OEM stuff. The injectors, IAC, and TPS can all be had easily. Sensors are just as easy to come by.

The learning curve for "tuning" a Holley system is also much shallower than learning how to tune an early GM ecu. I've started the journey to learn the 1994 GM 3.4L tuning stuff. It's not super simple. Part of the cost of going with a Holley system is you're also paying for all the software R&D that goes with it. And there is definitely value there. I've thrown a couple hundred dollars at learning to tune that 3.4L. Harness, adapter, software, and a spare ecu so I don't melt something that's hard to get.

Ultimately, do what you want. Just like anything in life, it could go either way. Don't let strangers on the internet tell you one way or the other.

 

[YakkoWarner]

I have considered this myself because the factory TBI isn't bad when it works, but because its all based on propritary OBD1 systems troubleshooting it is really, really difficult unless you know someone who has a unicorn-horn level rarity of a functioning OBD1 data reader.

For me the biggest detrator from moving forward with it was the fuel system - the Holley needs fuel piping for 60 or so PSI, the factory lines are designed for the factory TBI's 15 PSI - so everything fron the tank forward (including the pump) has to be changed over to handle he 4x increase in fuel pressure.

I am perfectly happy with the performance and power from the factory system when it is behaving, so the only reason I even think about changing it is for ease of diagnostics when something goes wrong. Being able to read the system in real-time and actually detect what is out of spec rather than depend on vague 2 digit codes would be the motivation to switch in my mind.

Right now my factory TBI is more or less happy so I'm leaving it alone and I'll reconsider the options the next time it starts giving me problems.

 

[77Dmax]

I'm actually working on retrofitting a GM tbi to an old Buick. I think I'm going to use a megasquirt controller. I have the capability/software to tune the early computer but it is a pain. The megasquirt seems like a good option to use GM parts and bring the ecm into the 21st century

 

[TotalyHucked]

The TBI is not a bad system as others have said. However, if you have plans to keep improving upon the truck, the Holley could be beneficial later on. My buddy put a Holley Sniper in his '86 454 crewcab longbed and loves it. He plans to do heads/cam/headers in the next couple years. He also upgraded to a 6L80 when he did it and LOVES the combo since the Holley can control the trans too. Truck has much better drivability and jumped from 8mpg to 11-12.

 

[YakkoWarner]

I'm actually working on retrofitting a GM tbi to an old Buick. I think I'm going to use a megasquirt controller. I have the capability/software to tune the early computer but it is a pain. The megasquirt seems like a good option to use GM parts and bring the ecm into the 21st century

I looked at the megasquirt - it seems like a cool idea but unless I was seeing things completely wrong - they send you a bare circuit board and you have to source/assemble the whole thing from zeo yourself - the odds of me having a functional ANYTHING after that would be pretty slim to none.