As a little introduction I don't own a Z28. I'm building a '48 Chevy street rod and bought a wrecked '95 Z28 to use as the powertrain. I did this 25 years ago and then got busy doing other things and now I'm getting back to the car. I took everything from the Z except for the front suspension. I had the rear narrowed and built mounts for the rear. I'm using the brake pedal, steering column and the complete wiring harness. I chopped the top 2 inches in the front, none in the back. I shortened the body 2-1/8 inch to make the windshield line up. Then I took doors from a coupe and cut out the B-pillars from it and welded them in place so the doors fit. It has many other minor body mods as well. It has a sunroof from a Ford Taurus and seats from a '02 Sebring convertible.


Here's my question. I'm working on the fuel tank now. I had a custom tank made so I could use the stock fuel pump. I plan on using all the OEM pollution control equipment. I have the EVAP canister mounted and will be mounting a stock fuel vent. I took the gas filler door from a Ford Taurus and mounted in my fender. It has a small diameter tube above the fuel filler line. It went to the tank and I assume worked as a vent. I think I can just cap that small line since I have the stock Z tank vents that originate from my pump. Does that sound OK? The ford fuel filler cap is not vented.

 

Appears the vent tube from the tank to the top of the fill pipe discharges into the fill pipe, almost at the top, but still inside the fill pipe when the non-vented cap is in place.

I think that vent tube allows the tank to vent the large quantity of air/fuel vapor displaced as you fill the tank. The fuel fill nozzle assembly used in most areas has a bellows seal over the fill tube that collects the vapors. Otherwise, the canister system can’t vent the volume of vapor generated while filling the tank, and it will take forever to fill the tank.

The stock 95 tank has one vent that flows to the canister, via a pressure control valve. The second vent connection is for the pressure/vacuum relief valve. The latter is not intended to operate except to relieve pressure or vacuum that could damage the tank.

https://www.camaroz28.com/g/picture/8176783

 

Thanks for the quick response. From what you are saying it seems like I could run this tube by my filler hose into a "T" at the line going to either the evap canister or the pressure relief valve. My preference would be the canister. Does that sound correct?

Walt

 

I'm not sure if the small diameter of either of the two vent pipes is adequate to vent the vapor displaced by the high flow of the fuel being pumped into the tank. The 1993-1998 cars had a pipe internal to the fill pipe. In 1999 they introduced the plastic tank and created a complex system of vents and pipes on top of the tank to force the displaced vapor through the carbon canister, which was also on top of the tank. I believe that was mandated by EPA.

A member here swapped a late model plastic tank into his 1997. He labored with figuring out how to vent the tank through his 97 canister in the rear fender well, and deleting the late model canister on the platic tank. We went back and forth on how to do that. When he got all done, appears the vent through the canister early worked OK, except when filling the tank. He could not get reasonable flow into the tank, the nozzle kept shutting off as fuel backed up in the fill pipe.

Eventually he had to drill a connection for the “funnel” at the top of the fill pipe. Then he ran a line from an existing vent opening in the plastic tank. That worked, but I suspect the vent opening on the plastic tank was much larger the those on the metal tank sending unit, because the opening on the plastic tank was designed to vent the larger volume of displaced vapor the occurs when filling the tank.

You could try a “T” into one or both of the two vent lines on your sending unit. Might work, but if it doesn’t you will only be able to pump ~1/2 gallon before the pump nozzle shuts down. The backup would be a new, larger vent connection on top of the metal tank, to match (or possibly larger than) the size of the existing fill pipe you picture above.

See this thread. It deals with slow filling starting at post #24.

Just for info, at the beginning of the thread is a photo of the top of the plastic tank, showing how complex the vent system is.

Please let us know how this turns out.

https://www.camaroz28.com/forums/lt1...-886314/page2/

 

Great information. From the last diagram on the linked thread it looks like I can just run that vent tube from the top of my filler neck and tie into the line going to the charcoal canister from the pressure relief valve. My canister is mounted up under my front fender so will have to run another line alongside the existing supply and return lines but I have to do that anyway. I may also put a bung of some type on the top of the tank so I can run from it to the filler neck in case the canister idea doesn't pan out.
It's -6 here at the moment and I can't get my garage warm enough to work if it's much below 20 so I may not get to this for a day or so. :-)
I'll let you know what I come up with but won't be putting gas in it for a while yet. Still have to get the wiring harness in and lots of other little things. The goal is to get this thing running in 2023.

Walt

 

The “T” ( or 2 “T”s) would be installed near the sending unit, and go to a single hose the same inside diameter as the pipe on the fill tube upper portion in your photo.

What is the purpose of running a new line to the canister in the front of the car?

 

Yes, that is where I would put the "T". The canister is in the front, and all I have going there now is my supply and return lines. From the canister I'll go to the EVAP canister purge solenoid.

 

OK …. that's clearer.

 

Finally getting back to the fuel system. Been concentrating on getting ready for paint and wiring.

Connected Taurus filler door section using some mandrel-bent tubing and a couple sections of rubber fuel line. Bought some AN fitting to connect the vent hoses. Do you know a good source for a new fuel pump?

I've tried to upload a couple pics but I keep getting an error that file format in incorrect. I'll keep trying

 

I assume you must have the stock sending unit, minus the pump? Does it include the pump bucket?

Is the engine basically stock, or modified to the extent it may require extra fuel?

 

I had a customer tank made with the stock baffle. I assume that is what you call the bucket? The engine is not modified at all. I have the complete stock sending unit and pump but the rubber (plastic?) hoses are badly cracked. Can they just be replaced?

 

The pump in the stock sending unit should have plastic “bucket” surrounding it. It's critical to extending the life of the pump. I have a fairly complete 1994 sending unit (missing float level sensor). I'll post a picture of it in the morning. 1995 may or may not be slightly different.

Racetronix sells replacement LT1 pumps, and kits with various replacement parks, or some parts separately. I know they have a higher capacity 255 LPH pump, not sure if they have a stock capacity pump, which I believe is less than 200 LPH.

They also have a good writeup on why you want to reuse the stock bucket when you replace the pump. See “Application-Specific Features” in this example of a high flow replacement pump kit:

https://www.racetronix.biz/k/flt1-fu...xp255/rfpk-003

 

Thanks. I hope to drop the tank in a couple weeks and then I'll send a pic of what I have. I do believe I have the "bucket" as you described it.

 

Ooooops….. forgot to post the photo.




As noted the level sensor is missing, and there is a missing short hose that goes from the metal return line to one of the nipples on the top of the bucket.

 

Finally got back to working on fuel system. Here's what I have. The rubber (plastic?) hoses are shot so I'll need to replace them but everything looks good other than that, I think.