Carbureted Vortec 454 in a 95

[Chillin Dylan]

Hey guys. I’ve got a 95 TBI 454 with an NV4500 and I’m looking to get some more pulling power out of it. I know that the TBI motors are limited on upgradability and what is available is pricey. I also know that the Vortec heads are way better than my peanut ports. I see and read a lot that with a simple torquey cam, a good distributor, and a good tuneup on the carburetor, 400hp, 500lb-ft is easily achievable on a Vortec head 454.

Now here’s why I’m even considering this. I’ve got a buddy that has a perfectly good Vortec 454 with 100k less miles on it than my TBI 454 that he’s agreed to sell to me $500. That’s a hell of a deal. To put a mild “RV” or “4x4” cam in it, plus the manifold, a good distributor and carburetor, I’m looking at a little less than $1k. So for $1500 I could nearly double my factory power numbers.

Is this worthwhile? Will it work correctly? I don’t want to end up spending a month figuring out electrical problems. I’m not that concerned about being able to get it in the truck and hooked up. I’m more concerned with the rest of the truck staying working. I’ve got several people in real life telling me to leave it alone, and several people saying it’s a great idea especially for the price and to go for it. Multiple people on each side have a lot of experience and knowledge too. BTW yes I’ve looked into doing a true Vortec swap and keeping the fuel injection, and converting to OBD2. I absolutely do not want to get into that kind of headache. One guy suggested putting the TBI on the Vortec motor and getting a chip/tune if need be.. but if I’m gonna do that what benefit would there be in getting the whole Vortec motor besides the lower miles?

Has anybody on here done this? What does it take to work? Lemme know what y’all think and if you’ve got any experience with this, thanks.


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[Allen4rmGromLak]

Some people are due hard TBI fans. Personally I HATE the TBI. My computer when the humidity is high does something weird and throws all kinds of codes and acts a fool. I threw a cheap carb setup from Craigslist and HEI dizzy and running mechanical fuel pump (as a test to see it was in fact the ECM issues). Drove it in the rain today and no issues. Truck doesn't hesitate or randomly die. It's like a new truck. Other than the normal smoke screen that it does constantly. Oh. And ran the entire engine on one wire hooked directly up to the battery.

So I say go for it. 454 is a torque monster and the opportunity to build massive amounts of power is there for ya. (Dont see anyone running a blower with GM TBI).

The next weak link will be that NV4500. My buddy has one in his Cummins. He's blown two 3rd gears. Hes a jerk to his transmission but still. I baby mine because mine needs ALOT of work soon.

 

[Chillin Dylan]

Don’t get me wrong, I like my TBI. My 95 350 served me well for years and this 454 has been great so far. I think it’s great, in a stock application. But with me wanting to make more power, the TBI becomes difficult to work with. If it was OBD2, I could tune it with my HPTuners, but I can’t since it’s not.

So you’ve done a carb swap, what year is your truck? Because mines a 95, it has the interior and a lot of the electrical stuff that the OBD2/Vortec trucks have, from my understanding at least. I could be wrong. I don’t want to run into issues with things like my gauges not working, accessories not working, and other random electrical stuff not working because it slightly has something to do with the ECM.


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[Allen4rmGromLak]

Mines a 94. There's a guy on YouTube from texas (blue sticker in the windshield, Spanish speaking guy in the background) who did it to a vortec engine truck. It was the speedo wasn't working. He used a US shift controller for his trans. Maybe I can find it.

Edit: found it. Guy named "Tim G" he does it to a 1999 vortec

 

[RichLo]

I would say go for it and eventually get a stand alone EFI throttle body like FiTech or similar if you drive it in a range of temps and/or altitudes.

The gauges should be fine as long as you keep the stock computer in there and obviously put all the sensors on the new motor where they were on the TBI motor. Water temp, Oil pressure, RPM, voltage, etc. All shouldn't be effected with essentially a carb swap and HEI. The motor swap is just a bonus.

 

[Chillin Dylan]

Doesn’t the RPM signal come from the distributor? If I leave the ECM in there it’s gonna throw all kinds of codes


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[Allen4rmGromLak]

With a HEI and Carb, yes you will throw codes but the engine won't be controlled by the ECM. So remove the light. Your timing advancement will come from the carb vacuum source.

With a manual transmission, manual choke and HEI and Carb, you can run the entire drivetrain without a computer. All you need is a ignition source to the HEI.

On my 94, everything else works fine. I have a service engine light.

Oh and if you use the factory fuel pump relay you have to wire up the relay differently. You can find videos and diagrams online. You need fuel pressure regulator if you use factory pump.

 

[Chillin Dylan]

Why would I need to change the fuel pump relay? It comes on with they key.. does it turn off if certain check DTCs are tripped? I was thinking a manual choke on a large 2 barrel or smaller 4 barrel. Really just thinking 650-750 CFM and not too concerned about the number of barrels. It’s a truck, I’m not concerned about the last few horsepower


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[Allen4rmGromLak]

From what I've gathered is the ECM controls the relay, so yes you turn your key and the ECM then makes the relay come on. I believe that through the negative side of the relay. So you have to disable one wire and jump another wire and connect another wire directly to your hot source. Easy way to test that as I did was to unplug the ECM and see if the fuel pump kicks on.


That what I did yesterday since I'm keeping my carburetor, I wired in aftermarket relay and it connects to the fuel pump harness right below your steering shaft. Doing that allowed me to put in a kill switch to kill the power to the fuel pump even while the ignition is on. You know it prevents someone from taking a joyride with it

It's not a hard conversion at all, as long as you get fuel to the engine, then all you need is a way to start it, and a ignition hot to the distributor.


Check out this video.

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[Chillin Dylan]

Okay so in your experience the only change that has to be made to the truck is the fuel pump relay correct? Everything else is motor stuff and all the trucks components and **** still work?

I definitely wanna keep the fuel system stock and just run a regulator and re-utilize the factory return line for the extra fuel the carb doesn’t need.

The distributor drive setup did or didn’t change when they switched to Vortec? I’ve seen mixed answers on that.

I also saw some people say the TBI motors still had the provisions for a mechanical fuel pump but with a block off plate. Some people say they don’t. However, I just pulled the TBI 350 drivetrain out of my other 95 to sell and noticed that it’s block still had the mounts cast into it, but the machining process for the hole was skipped. So I’d have to cut a hole in the block and then maybe I could slap the pushrod and mechanical pump on it. That’s if they didn’t also delete the lobe off the cam.

I’ve already looked at my 454 TBI block and there’s not even the mounts cast into it. I just mentioned that as an example of mixed information I’ve been seeing.

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