1957 gas cap under high pressure | Ford Thunderbird club group 1955-2005 T-Bird models

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1957 gas cap under high pressure

PeteC

PeteC

Gold Member
Reaction score
2
Thunderbird Year
1957
As a new ‘57 owner I need guidance on this issue. I’ve owned the vehicle about 2 months and never experienced this before. My tank was just under half full. When I got to the pump and opened the cap, the LITERALLY BLEW OUTBOF MY HANDS and smashed into the gas pump. I was very thankful no one was hurt or another vehicle damage by this “rocket”. The tank took 11 gallons to fill (out of the 20 it would hold).

Why would this happen?

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I agree, when it heats up the gas fumes expand and with no vent in the system it would be a violent event. Just get a vented gas cap or if you have one make sure it is working (doesn’t sound like it is).
Glad nobody lost anything they may need later…….
 
Yeah...agreed. Replace the cap but....if you buy an aftermarket cap, drill a small hole in it. The newer caps vent at a higher pressure than the OEM caps. Too much pressure/not venting soon enough the '57 might vapor lock
 
Modern "vented caps" will allow outside air in with no problem. Whether they allow inside pressure out at some point I don't know. I bought a new modern vented cap and experienced the same thing you did with high pressure buildup that resulted in a very large whoosh when the cap was removed. It may be that at some level of pressure they will vent out but I did not like how much was building up and was afraid it would force fuel past the fuel pump(s) and needle and seat and flood the carb. So I drilled a small hole in the new cap.
 
PeteC said:
Is there a part number from one of the catalogs to get the proper cap?????? I’m very worried now
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I would guess most vendors have them. Here's the listing from NPD

GAS CAP, REPRO - #T-9030-5 - National Parts Depot

Buy part #T-9030-5 GAS CAP, REPRO for your classic 1957 Tbird from National Parts Depot. Free shipping on orders over $300, fast delivery & everyday low pricing! Order now!
www.npdlink.com www.npdlink.com
 
I have a 55 TBird. Pressure build up would make starting an issue. Take cap off, it starts up. So how should I drill a vent hole?
 
Tom Alpers said:
I would guess most vendors have them. Here's the listing from NPD

GAS CAP, REPRO - #T-9030-5 - National Parts Depot

Buy part #T-9030-5 GAS CAP, REPRO for your classic 1957 Tbird from National Parts Depot. Free shipping on orders over $300, fast delivery & everyday low pricing! Order now!
www.npdlink.com www.npdlink.com
Click to expand...
I purchased a new one when I got the car from TeeBird Products: 9030C. That was listed for a ‘57. I’m confused.
 
PeteC said:
I purchased a new one when I got the car from TeeBird Products: 9030C. That was listed for a ‘57. I’m confused.
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Sounds like it's not a vented cap or perhaps is a new style that only vents in. You can drill a very tiny hole thru it and make it vented. When they are made properly the vent sort of is hidden under the center rivet.
 
mmusgrovetn said:
I have a 55 TBird. Pressure build up would make starting an issue. Take cap off, it starts up. So how should I drill a vent hole?
Click to expand...
The gas cap on your T-Bird must be vented to allow air to enter the tank. If air cannot get into the tank a vacuum will be created which can stop the flow of fuel to your engine. To vent the fuel tank, the 1955 and 1956 gas caps have a rib stamped into the surface which allows air to enter from the outside edge of the cap to the center.

Fuel Cap 1.jpg

The problem with the gas cap is that sometimes the inside diameter of the gasket was so small that it prevents the venting process. The problem can be easily repaired by removing the gasket from the gas cap and increasing the inside diameter of the gasket by cutting it with a razor blade.

Fuel Cap 2.jpg

doug7740
1955 Thunderbird Blue
 
Ford made 2 caps for the 57 Bird. The early models had a vent but in first part of year1957 Ford went to unvented cap. If you go to NPD scroll down to find the vented cap. The non-vented cap shows up first. I found that out the hard way!!
 
Here's another variation of the vented gas cap. Unlike my other new one, this one seems to vent properly both ways.
gas cap mine vented anti surge tbird 1957 1.jpggas cap mine vented anti surge tbird 1957 2.jpg
 
When I took my cap off (unvented) you could hear the air trying to equalize the negative pressure in tank. That is why I went on NPD and found out there were 2 variations.
 
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