So you are saying that the correct caps are air tight? And that all 1971-73 gas caps sold by FMC for mustangs are airtight and do not allow air to pass thru?
Ok, i will call scott drake and look to exchange the one i have. They said it is the right cap but must be for a 1970.
Sorry, scott drake D1ZZ-9030A is correct cap for 71-73. It is a vented cap......D1ZZ-9030B is same cap with the wire. It is for 71-73. It is a vented cap. Scott Drake DOES sell a non-vented cap....for 1970 california cars.
OMS, i believe the cap has a diaphram relief valve that allows air into the tank to compensate for low pressure created when vapors and fuel are sucked out of the tank, as i described above. The diaphram vent does not allow air/fumes to exit the tank thru the cap. Simple.
This was on the 429 mustang cougar site. "The D1Z pop open gas cap above was used on all 1971 Mach 1s. It incorporated a built in seal as shown by the red arrow at center. We believe the similar D2Z Pop Open cap, rear view shown below left (identical to D1Z, but no seal), was released to be used in conjunction with the screw on cap below right to help prevent fuel spillage during rear end collisions - this all in reaction to the Pinto gas tank issue."Ok, i will call scott drake and look to exchange the one i have. They said it is the right cap but must be for a 1970.
Sorry, scott drake D1ZZ-9030A is correct cap for 71-73. It is a vented cap......D1ZZ-9030B is same cap with the wire. It is for 71-73. It is a vented cap. Scott Drake DOES sell a non-vented cap....for 1970 california cars.
OMS, i believe the cap has a diaphram relief valve that allows air into the tank to compensate for low pressure created when vapors and fuel are sucked out of the tank, as i described above. The diaphram vent does not allow air/fumes to exit the tank thru the cap. Simple.
I asked them this question a long time ago - they couldn't answer it
If 70 Mustangs had to have a special sealed system for CA emmisions to be sold in CA
And all 71-3's are vented like drake says, that would mean Ford could not sell a 71-3 Mustang in CA
I'm going with EFI also and was told by Fitech not to use the vent line for a return. Was told it would be insufficient due to its size and I would need the vent. It was recommended that I use this from Summit for a return line.I know this is a very old thread but wanted to share my findings while taking down the tank and examining the whole fuel delivery system. This will hopefully help future readers of this thread. I was confused for some time.
wwhite72 is correct that the D1Z... cap has a vent, and like he states in the post above, the vent only allows air in, not out (http://www.7173mustangs.com/thread-vented-tank-for-mach?pid=116854#pid116854). You can read about it here, http://429mustangcougarinfo.50megs.com/fuel_system.htm
I have a early 1971 Mach 1 and I have a D1ZA-9A112-BB gas cap. This gas cap has a diaphragm in the cap, which I assume, its function is to allow air in one direction. However, when I tested it, mine is allowing air in and out, which is perfect for what I want. I will use the vent on top of the tank as a return for my EFI so I was wondering how I was going to vent the tank. The gas cap is enclosed so I can't see the diaphragm. I assume my diaphragm being so old is broken up so that's probably why it allows air in both directions. I guess that in this case, aging of the product is working in my favor.
I guess depending on your system. I am going the FiTech route as well, but I am using the PowerSurge pump from Robbmc. Since that's a sump pump system it only needs a 1/4" return line. Our vent line is 5/16" so it should work. Also, i am drilling the little hole in the vent nipple so there is no restriction. Otherwise, i can see it being an issue becausr that hole is really small.I'm going with EFI also and was told by Fitech not to use the vent line for a return. Was told it would be insufficient due to its size and I would need the vent. It was recommended that I use this from Summit for a return line.I know this is a very old thread but wanted to share my findings while taking down the tank and examining the whole fuel delivery system. This will hopefully help future readers of this thread. I was confused for some time.
wwhite72 is correct that the D1Z... cap has a vent, and like he states in the post above, the vent only allows air in, not out (http://www.7173mustangs.com/thread-vented-tank-for-mach?pid=116854#pid116854). You can read about it here, http://429mustangcougarinfo.50megs.com/fuel_system.htm
I have a early 1971 Mach 1 and I have a D1ZA-9A112-BB gas cap. This gas cap has a diaphragm in the cap, which I assume, its function is to allow air in one direction. However, when I tested it, mine is allowing air in and out, which is perfect for what I want. I will use the vent on top of the tank as a return for my EFI so I was wondering how I was going to vent the tank. The gas cap is enclosed so I can't see the diaphragm. I assume my diaphragm being so old is broken up so that's probably why it allows air in both directions. I guess that in this case, aging of the product is working in my favor.
https://www.summitracing.com/parts/mor-65385
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