1980 C3 Corvette to LS2/T56

**Myko** · 09-16-2013, 03:24 AM

Originally Posted by reedld

Mike,

Little late here but.....have you been to vetteworks.com? I used their fuel bucket mod in my 78 fbody. I bought it for simplicity...but ended paying someone to build a recess in the tank so it did not hit my trunk. The GM fuel bucket works great....no problems...even down below a quarter tank. The fuel bucket takes care of fuel starvation rather than tank baffling. I do not know any common daily drivers with factory tank baffling...the fuel bucket is what the car manufacters do.

If you have questions...let me know...I hope to help!

Look under "engine conversion", C3, fuel systems

Leon

Leon,
I had been over to VetteWorks and CustomImage a while ago but it looks like they have some more stuff online then the last time I checked. I have the 1980 tank with a plastic lining so I am reluctant to do any cutting mods. Here is what I fabricated using a Walbro 255 gph in-tank pump, a 58 PSI in-line regulator, and the stock lines.

The wiring connections will be outside the tank. Now I need to determine the best route for wiring to have the pump run when the key is turned. And decide if I need to run the ground with the hot wire or ground to the frame. What do you think?

**reedld** · 09-16-2013, 01:39 PM

Originally Posted by Myko

The wiring connections will be outside the tank. Now I need to determine the best route for wiring to have the pump run when the key is turned. And decide if I need to run the ground with the hot wire or ground to the frame. What do you think?

My ground is to the frame...here is a pic of my old setup...NOISEY!!! , but worked well.

I'd worry about your pump getting hot or sucking air, both will cause the pump to fail prematurely. The OEM setup uses a bucket to prevent this. I don't know if you can put some kind of container in the tank...then put your walbro inside that. It will work without the bucket ...but you will not be able to let your fuel level get low.

**Myko** · 09-16-2013, 03:45 PM

Originally Posted by reedld

My ground is to the frame...here is a pic of my old setup...NOISEY!!! , but worked well.

I'd worry about your pump getting hot or sucking air, both will cause the pump to fail prematurely. The OEM setup uses a bucket to prevent this. I don't know if you can put some kind of container in the tank...then put your walbro inside that. It will work without the bucket ...but you will not be able to let your fuel level get low.

I can't imagine a pump getting hotter in the tank then outside it? The NOISE was the major factor for choosing an in tank pump.

I am still thinking of a way to get the bucket in there. I guess that was what I was thinking of but called it "baffles". Any pics of a homemade bucket?

**reedld** · 09-16-2013, 05:48 PM

The comment about the pump getting hot is only from what I've read...but makes sense the pump, submersed in gas would be cooler, than in open air. I don't know how you would fit a bucket in there without cutting a hole. Is the tank partially plastics? I understand your concern about cutting into a used tank, that's why I bought a new one to modify. Depending on where you live, if you have a radiator shop near by....they may be able to cut a hole in the used tank.

**Myko** · 09-16-2013, 06:46 PM

The tank has a plastic lining. A bladder,so to speak. I could make the existing hole larger but would worry about trying to make a different hole. It would be nearly impossible to weld on the bottom of the tank. An older C3 tank would work to modify, if necessary.

I was trying to think of a bucket design that would fit and attach to the pick up. I'll probably make something. It won't need to be pretty, just effective.

**reedld** · 09-17-2013, 03:36 AM

I found a pic of the 80 tank with the "bladder" you are referring too. I think the best way to do it is from the top....off to one side like vetteworks did.

**Myko** · 09-20-2013, 03:15 PM

The tanks from Vetteworks and others are made from the older style tanks. I think I'll hook this setup up and check pressure and flow. If it looks good I'll rerun high pressure lines.

I just ordered the radiator so after I get the water pump finished I'll be ready to start it.

**pajeff02** · 09-20-2013, 04:37 PM

The joy of installing the C3 radiator. My brand new one leaked after 2-3 years and I had to pull it to get it fixed. Not a real fun job.

**Myko** · 09-21-2013, 04:41 AM

Originally Posted by pajeff02

The joy of installing the C3 radiator. My brand new one leaked after 2-3 years and I had to pull it to get it fixed. Not a real fun job.

I found a small hole in my original one so I bought an aluminum replacement. I plan to make any adjustments to the brackets needed for easier removal now. The brackets are rusted and will need welded anyway so I might as well plan on the future leaks and put in some time now to make it easier when everything is back together.

**pajeff02** · 09-21-2013, 05:23 AM

I went with a copper/brass replacement and it works great. I think it was a seam that leaked on ours, so I had it repaired. While it was out of the car, I bent the outlet up to gain some more clearance by the front suspension and fan shroud, and then had that re-soldered as well. That has been at least 4 years ago and it has held up well.

Here's my C3 puzzler -- on startup, the headlights on our car go up and down. Everything has been replaced in the headlight system, including the switch, canisters, and diverter valve. No idea why it does this. Last time I drove the car, the driver side headlight actually opened and closed twice when I started it.

**Myko** · 09-21-2013, 08:34 AM

Sounds like a leak. If they go up and down multiple times there must be a leak in at least one of the circuits. Do they work when you turn them on?
There are a million headlight threads on the Corvette forums for diagrams, etc.

**pajeff02** · 09-21-2013, 12:26 PM

I just downloaded a headlight diagnostic. They work just fine when the light switch is turned on and they go down when the switch is turned off. Not a clue why they cycle like that.

**Myko** · 10-02-2013, 03:54 AM

On to wiring... Scary.

The dual fans and fuel pump are my first big concerns. Yes, I know I can buy a $500-1000 wiring harness that will avoid most issues. I am planning to use some GTO gauges (speedo, tach, odo) and some original Corvette gauges. I am also unsure about A/C, cruise control, and security features at this time. So, I want to explore the option of using my OEM harness with an additional under hood fuse box for the additional components.

Does anyone have information about using my GTO ECU/PCM for the fans and fuel pump relays? Wiring diagrams are helpful but some additional instruction would be even more useful.

Thanks,
Mike

**pajeff02** · 10-02-2013, 05:54 PM

I would need a schematic to see how they accomplish it through the ECM. Maybe just keep it simple -- you need a fan temperature switch that comes on around 10 to 15 degrees hotter than your thermostat's rating and a relay (or two) to handle the high current draw for the fans. Assuming that your fan temp switch closes a ground, you will run fused power to the relay trigger that is hot with the ignition on, the ground trigger will be attached to the temp switch, heavy gauge fused wire will feed the input side of the relay and the fans will be attached to the other side.

**Myko** · 10-04-2013, 02:40 AM

Here is the schematic but it doesn't give any detail on how/where to plug into the PCM. I don't have any problem wiring the fans outside the ECU, and may get a Painless harness to make it simple. I am trying to figure out how to get the temp gauge to work.

I am more worried about the fuel pump and problems with the VATS. If it is wired independent of the ECU can you just program the car to "forget" about the pump?

**pajeff02** · 10-05-2013, 03:45 AM

C1 is connector 1 and C2 is connector 2 at the PCM. You would simply splice into that wire and connect it to your relay on the trigger side. I'd have to look to see if the PCM is sending voltage or a ground signal.

**Myko** · 10-05-2013, 04:57 AM

The outputs are grounds for the relays. I have 30/40 5 prong relays that I thought would be needed but I'm a little confused after looking at the fans. Each fan has only two wires. Why are there 3 fans in the diagram, each with a different relay? I thought the temp sender would make the connection to operate a trinary relay on fan 2, not to operate the relay on all 3. Is fan 1 always on, fan 2 on low, and fan 3 just higher speed?

**pajeff02** · 10-05-2013, 06:24 AM

That third relay is the ground for Fan 1. Not a clue why they wire it like that.

**Myko** · 10-08-2013, 06:27 PM

Could it be that the larger fan on the right is dual speed? I thought fan 1 was constant, fan 2 and 3 were low and high speed on the Cooling Fan - Right. Could this be done in an A/C car if the fans each only have a hot and a ground wire?

**pajeff02** · 10-09-2013, 02:57 AM

If you trace the schematic from each relay, you see power to each fan and then that third one controls a ground circuit. Not a clue what they are doing. I could check my manuals to see if there is an explanation of the fan circuit and then post it for you.