C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

Semi Serious C4 Fuel System upgrades

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Old Feb 17, 2018 | 03:12 AM
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Default Semi Serious C4 Fuel System upgrades

Hi all. I thought I'd chime in on my latest fuel system upgrades since it's been a bit quiet on this front.

Here's what I did:

-walbro 465 e85 compatible pump
-aeromotive reg to work with the 465 (stock one was too small)
-racetronix hotwire kit
-racetronix bulkhead upgrade (the wiring inside the tank and the bulkhead that connects the intank with the outside of the tank)

I'm currently running 60lb injectors. I have a gauge on the rail. Stock lines.

If I recall this puts out about 110 gallons per hour at 40psi. I"m running a 1 to 1 boost referenced regulator, so I'm trying to get good fuel volume at about 60psi.

if this isn't enough down the road(if I upgrade to bigger injectors), I'll add a boost a pump since I bought that racetronix harness as well. At 17 volts the pump will flow quite a bit more.

The bulkhead is pretty important since the stock pin that carries the fuel pump current is so small. I torched mine with a walbro 255 and a boost a pump. The racetronix unit uses larger pins and 2 instead of 1. The stock ZR 1 uses 2 pins but they're smaller. I was previously using one of those.

Anyhow, pretty simple but able to support some pretty big power demands.
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Old May 19, 2018 | 01:23 AM
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Did you ever get there bulkhead to work? And what about the bulkhead harness?
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Old May 19, 2018 | 09:39 AM
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I did get it to work. My problem was that I had the part inside the tank clocked 180’ wrong. There are letters on the outside the tank part and also on the inside the tank part. Make sure that you have the corresponding ones hooked up. I believe I grounded the black wire to a better ground. I’ll verify
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Old May 19, 2018 | 11:11 AM
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Thanks a lot! Since that ground wire isn't like your typical screw/bolt ground, I have no clue how or where to ground it. Racetronix was of no help.
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Old May 19, 2018 | 11:13 AM
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Originally Posted by 1993C4LT1
Thanks a lot! Since that ground wire isn't like your typical screw/bolt ground, I have no clue how or where to ground it. Racetronix was of no help.
Ring terminal with the appropriate sized male spade. What size is the female spade on the harness?

***On some tank units (fuel pump tree) the ground is actually 'sweat soldered' to the flange. That could be done with yours also.

Last edited by WVZR-1; May 19, 2018 at 11:18 AM.
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Old May 19, 2018 | 11:27 AM
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Really sorry to hi jack thread op. The metal tab that locks the bulkhead into place, it seems there is no place for it to go in? Here is what they sent me. This is the in-tank harness with the bulkhead locking tab.


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Old May 19, 2018 | 11:36 AM
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Originally Posted by 1993C4LT1
Really sorry to hi jack thread op. The metal tab that locks the bulkhead into place, it seems there is no place for it to go in? Here is what they sent me. This is the in-tank harness with the bulkhead locking tab.


Not that - a separate ring terminal with spade that would be secured with one of the flange bolts. I have a couple tank units here that are actually 'sweat soldered' like I mentioned.
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Old Sep 10, 2022 | 09:11 AM
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What kind of power does this setup support, is it for forced induction or NA. I need a pump upgrade as I do not think my walbro 255 will keep up with my new engine and turbo setup, I need a setup that can support 700-800ish rwhp depending on how far I can turn the wick up and this seems like it may fit the bill.
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Old Sep 10, 2022 | 02:50 PM
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Originally Posted by Impala Balko
What kind of power does this setup support, is it for forced induction or NA. I need a pump upgrade as I do not think my walbro 255 will keep up with my new engine and turbo setup, I need a setup that can support 700-800ish rwhp depending on how far I can turn the wick up and this seems like it may fit the bill.
Not sure if the OP will get back to you being that this thread is 4 years old. But you are right that a 255 pump probably won't support that kind of power. Especially with a power adder. I went with a Walbro in tank 450 LPH. I also have a flex sensor and run E85 with Holley 76 lb injectors. So far the only issue I have had is I drop fuel pressure with ethanol. It seems to run fine without going lean at all. It might be my regulator however.

They also have an in tank 525 I believe that would work well. That's probably the pump I should have went with.
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Old Sep 10, 2022 | 05:08 PM
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Originally Posted by Phobos84
Not sure if the OP will get back to you being that this thread is 4 years old. But you are right that a 255 pump probably won't support that kind of power. Especially with a power adder. I went with a Walbro in tank 450 LPH. I also have a flex sensor and run E85 with Holley 76 lb injectors. So far the only issue I have had is I drop fuel pressure with ethanol. It seems to run fine without going lean at all. It might be my regulator however.

They also have an in tank 525 I believe that would work well. That's probably the pump I should have went with.
I've been looking at the walbro hellcat 525... will it fit in the stock basket I wonder?
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Old Sep 10, 2022 | 05:31 PM
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Originally Posted by Impala Balko
I've been looking at the walbro hellcat 525... will it fit in the stock basket I wonder?
This would be a great question for Racetronix. But I made the 450 fit my hanger and basket but I had to fabricate a new hanger. I took pictures of how I did mine and posted them on my build thread HERE. The pictures of the hanger start on post #80.

Another option is to use 2 255 pumps. I remember seeing a thread about that a while ago but I can't remember who did it.
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Old Sep 11, 2022 | 08:42 PM
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Quick dumb question, what is the maximum amount of power can you support with the factory fuel lines
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Old Sep 11, 2022 | 09:40 PM
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Originally Posted by Impala Balko
Quick dumb question, what is the maximum amount of power can you support with the factory fuel lines
It's really tough to give you a power number and say "This is the limit of a factory fuel line". There are just too many variables. But the reality is that if you're after 700 to 800 hp in a street car you're probably going to be doing that with E85. If you are then just pull out every piece of fuel line and replace it with PTFE -8an feed and -6an return at a minimum and be done with it. I did this with mine and it wasn't that expensive. Even if you're going to try and get that much power on 93 I would still replace the fuel lines with better (and bigger) braided line but you wouldn't need PTFE.
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