Recent Posts

1

Fuel Systems and Drivability / Re: new 20 gallon tank

« Last post by bd on Today at 06:42:09 pm »

75 C/K chassis single tank fuel gauge wiring (circuit 30, tan wire) used the firewall bulkhead connector cavity outlined in red below.

Dual tank wiring is more complicated.

2

Fuel Systems and Drivability / Re: new 20 gallon tank

« Last post by Rough75C20 on Today at 04:49:34 pm »

Thanks guys. I’m sure the bed was swapped at some point with something else. This truck seems to be cobbled together. It does have an older style tailgate with the “CHEVROLET” in the center.

To confirm if the wire is correct what is the best method? Check continuity between the plug of the back of the dash and the wires coming out of the fuse box? Does the accessory power need to be on to check this?

3

Fuel Systems and Drivability / Re: new 20 gallon tank

« Last post by ehjorten on Today at 04:31:45 pm »

Curious...you mentioned getting the tank setup so it goes through the fuel door, but if your truck is a 1975 C20 like your tag, then you shouldn't have a fuel door, it should just be a fuel fill cap on the side of the bed. That is unless someone prior to you, swapped beds for a 1979+. I believe that 1979 was the first year for the fuel door.

4

Fuel Systems and Drivability / Re: new 20 gallon tank

« Last post by Captkaos on Today at 01:15:53 pm »

Most all of the wiring schematics are here: http://forum.73-87chevytrucks.com/smforum/index.php?topic=30115.0
And depending on the year truck it may or may not be in the same place especially if it has been tampered with.

5

Fuel Systems and Drivability / Re: new 20 gallon tank

« Last post by Rough75C20 on Today at 11:48:36 am »

Can someone please post a picture of the fuel sending unit wiring at the front of the fuse box on the engine side? I'm trying to figure out which tan wire needs the sending unit wire connected to it but a lot of the wires on my truck at the fuse box have just been cut off. want to make sure I'm hooking it up to the correct wire. If someone could post a picture of the wire coming out of the fuse box that would be awesome. there is one on the left side bottom corner when looking at it from the front of the truck that looks promising but want to be sure.

Thank you!

6

General Discussion / Re: Master Cylinder question

« Last post by VileZambonie on April 24, 2025, 07:46:00 pm »

Disc drum uses a combination valve so make sure you get the correct one. I would run the drum brake MC until you are ready to do you swap.

7

General Discussion / Re: Master Cylinder question

« Last post by zieg85 on April 24, 2025, 03:41:48 pm »

The question would be where are the residual pressure valves in your system? In a GM the residuals are in the master. If you go to a Disc/Drum master, you might not have the residual pressure valve in the primary circuit. This will mean that your front slave cylinders will not have the 10 psi or so to keep the lip seals in the slave pressed against the bore and they will leak. Usually the Disc/Drum master has a slightly larger bore to compensate for the larger piston area of the caliper. Larger master piston area will reduce the output pressure and shorten the stroke of the pedal. It will mean that you need to push harder on the brake pedal to generate the same stopping force. It won't be dramatic, but it will be different. Do you have power or manual brakes?

Currently 4 wheel manual drum.  Planning on going to manual front disc/rear drum and changing out the differential valve to a proportioning valve at the time of the swap once all the components are rebuilt/replaced
 

8

General Discussion / Re: Master Cylinder question

« Last post by ehjorten on April 24, 2025, 08:48:58 am »

The question would be where are the residual pressure valves in your system? In a GM the residuals are in the master. If you go to a Disc/Drum master, you might not have the residual pressure valve in the primary circuit. This will mean that your front slave cylinders will not have the 10 psi or so to keep the lip seals in the slave pressed against the bore and they will leak. Usually the Disc/Drum master has a slightly larger bore to compensate for the larger piston area of the caliper. Larger master piston area will reduce the output pressure and shorten the stroke of the pedal. It will mean that you need to push harder on the brake pedal to generate the same stopping force. It won't be dramatic, but it will be different. Do you have power or manual brakes?

9

General Discussion / Re: Master Cylinder question

« Last post by zieg85 on April 23, 2025, 09:11:42 pm »

The conversion kits are pretty inexpensive. Why not git r done? Drum Drum reservoirs are the same size unlike disc/drum.

I have a donor car for the spindles, rotors, calipers which are Kelsey Hayse 4 piston calipers which I have to redo.  I was going new master anyway, my question was would getting the correct master that I will be needing for now and continue using my 4 wheel drum brakes be a problem?  I would still like to enjoy the car before I tear it down for the upgrade.  Thanks Vile.

10

General Discussion / Re: Master Cylinder question

« Last post by VileZambonie on April 23, 2025, 05:50:07 pm »

The conversion kits are pretty inexpensive. Why not git r done? Drum Drum reservoirs are the same size unlike disc/drum.