HEI swap

[indyboy]

Hello everyone. I apologize in advance if this question has been answered before but I am brand new to this site and don't quite know my way around yet. I have a 1994 C1500 with a V6 that I am swapping out with a 454. I am going with an HEI and carb set-up. From what I've read I need to hook the red wire from the existing coil up to the BAT terminal on the HEI and the white wire up to the TACH terminal. Is there an additional wire that needs to be hooked up to the HEI for the stock electric fuel pump to operate? Thanks in advance!

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[1owner1990]

Hello everyone. I apologize in advance if this question has been answered before but I am brand new to this site and don't quite know my way around yet. I have a 1994 C1500 with a V6 that I am swapping out with a 454. I am going with an HEI and carb set-up. From what I've read I need to hook the red wire from the existing coil up to the BAT terminal on the HEI and the white wire up to the TACH terminal. Is there an additional wire that needs to be hooked up to the HEI for the stock electric fuel pump to operate? Thanks in advance!

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Maybe this helps? @1:28 mentions a ppl/wht wire. When I converted from TBI to carb, I first did so without without connecting this wire, but because I felt she was cranking too long, I did some investigating and came across people talking about this wire, so I added this connection. I honestly dont think it made a difference. As the truck cranks and oil pressure builds, the oil pressure sending unit will energize the pump circuit regardless of whether this connection is made, and the truck will run. Maybe someone else will chime in and shed light on this, but I haven't seen a reduction in crank time with this wire connected. I'm planning to just to wire the pump circuit directly to a 'hot in crank and run' circuit and quit fooling around with this.

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[Schurkey]

Perhaps a moderator will move this thread to the LSX + Carb Swaps sub-forum.

I have a 1994 C1500 with a V6 that I am swapping out with a 454. I am going with an HEI and carb set-up. From what I've read I need to hook the red wire from the existing coil up to the BAT terminal on the HEI and the white wire up to the TACH terminal.

The 4-pin module HEI needs to have the red power wire connected to the BAT terminal on the cap. The tach in the dash needs to have the white wire connected to the TACH terminal, just as you said.

Is there an additional wire that needs to be hooked up to the HEI for the stock electric fuel pump to operate?

Good luck.

The fuel pump relay will not be powered except at initial key-on (two-second "prime") because the ECM is not getting an RPM signal from the original 8-pin module wire harness.

This means you'll have extended cranking time because other than "prime", the fuel pump won't run unless the engine has oil pressure.

I have no idea how you're going to make the transmission work. If it's a manual, the big-block torque will destroy it. If it's an automatic, you'll need the computer to control the shifting, and then the big-block torque will destroy it.

 

[PlayingWithTBI]

There's a safety factor in how the fuel pump is controlled. If you get in a wreck, the engine stops running, the Oil Pressure Switch doesn't see pressure and the PCM doesn't see any Distributor Reference Pulses so, the fuel pump shuts off and saves you from a magnificent bonfire.

 

[1owner1990]

Perhaps a moderator will move this thread to the LSX + Carb Swaps sub-forum.


The 4-pin module HEI needs to have the red power wire connected to the BAT terminal on the cap. The tach in the dash needs to have the white wire connected to the TACH terminal, just as you said.


Good luck.

The fuel pump relay will not be powered except at initial key-on (two-second "prime") because the ECM is not getting an RPM signal from the original 8-pin module wire harness.

This means you'll have extended cranking time because other than "prime", the fuel pump won't run unless the engine has oil pressure.

I have no idea how you're going to make the transmission work. If it's a manual, the big-block torque will destroy it. If it's an automatic, you'll need the computer to control the shifting, and then the big-block torque will destroy it.

If you know which wires from the original harness, would you share that? It sounds like the answer TWO of us are looking for.

 

[1owner1990]

Perhaps a moderator will move this thread to the LSX + Carb Swaps sub-forum.


The 4-pin module HEI needs to have the red power wire connected to the BAT terminal on the cap. The tach in the dash needs to have the white wire connected to the TACH terminal, just as you said.


Good luck.

The fuel pump relay will not be powered except at initial key-on (two-second "prime") because the ECM is not getting an RPM signal from the original 8-pin module wire harness.

This means you'll have extended cranking time because other than "prime", the fuel pump won't run unless the engine has oil pressure.

I have no idea how you're going to make the transmission work. If it's a manual, the big-block torque will destroy it. If it's an automatic, you'll need the computer to control the shifting, and then the big-block torque will destroy it.

@Schurkey could you share the wisdom please?

 

[GoToGuy]

Really, your doing these mods you should take look at the wiring diagrams. Nobody wants to die or burn up parts. Are you using your intank electric fuel pump with carb' ? Service manuals are free to download here on this forum. You won't have to guess what senders and sensors do for you.

 

[1owner1990]

Really, your doing these mods you should take look at the wiring diagrams. Nobody wants to die or burn up parts. Are you using your intank electric fuel pump with carb' ? Service manuals are free to download here on this forum. You won't have to guess what senders and sensors do

 

[1owner1990]

Could someone on this forum... just once... answer a question without going down rabbit holes? No one asked whether or not a mystery transmission would hold up to a 454. For all we know, he's using a chain-driven rear setup from the 1800's. No one asked to move this to an lsx / carb swap forum. No one asked about fiery explosions, reading wiring schematics, passive-agressively questioning peoples' skill set or guesswork over sensors. No one asked where to download service manuals. From all the replies, it sounds like everyone knows the answer to everything, so would you kindly go back, read the questions and just answer them? Please? I mean really, are we here to help one another?

 

[GoToGuy]

There is not always just a single short answer. For you it may be easy. I can't see what you doing. I don't know your skill level. I don't know your knowledge level. Things I see as an easy problem others don't.
You ask for help, great were here, but do something dumb and get called out for it, that's life. It's a learning experience.
All good mechanics, technicians use whichever service manuals applies to what they work on.
I can give you a fish, or I can teach you to fish. What's better for you long term?
We will give you answers and the knowledge, manuals for free.