Joined: Thu Mar 22 2007, 08:13AM
Location: In the workshop
Posts: 1063
Thats great info, Mike. Its answered a couple of questions. I'll start collecting the material I need to fit the tank I have, then do an update on here.
Dont hold your breath though guys, things take time here....
Joined: Thu Mar 22 2007, 08:13AM
Location: In the workshop
Posts: 1063
Making good on my promise to let you all know about fitting a '67-on tank to a '65/'66.
Its really a simple job, nothing more than lining up the rear of the tank to enable the filler pipe to be fitted, and mounting it very slightly askew to give enough space for the left hand tailpipe to pass. Thanks to Mike '66, I was able to make up the twin vent pipes. These fitted no problem either, even if the '65 originally onnly has one.
The biggest problem with the tank, (Spectra CR20B) was a little corrosion. That was despite the fact that it was new, and had been covered with a little grease before shipping. Here it is in place on the car:
Glad this is being discussed this popped into my head the other day.... I have a 2 vent tank with a non vented (i think) gas cap and I plugged one of the vents up, so I only have one. is this a big deal, should I use both vents? a 65 polara 383.
Joined: Tue Oct 11 2005, 01:33AM
Location: Calgary, Alberta
Posts: 5893
I think you need both vents. As I understand it, one vent is at the front of the tank and the other at the rear. When you drive on flat road, both vents are above the fuel and allow air to enter the tank as fuel is used. Now climbing a long hill will shift the fuel to the rear, down hill end of the tank. This will submerge the rear vent, but air can still enter at the other end. Going down a long hill, the front vent gets submerged and the tank gets air from the rear vent.
I'm nogt sure which of your vents is plugged, but say its the front one. That would mean climbing a long hill would submerge your only working vent and create a vacuum inside the tank as fuel is used. The tank could deform or more likely the vacuum would over power your fuel pump causing your engine to starve and loose power.
I should qualify all this to say it would most likely only happen when the tank is near full, or the hill is near vertical.
Joined: Thu Mar 22 2007, 08:13AM
Location: In the workshop
Posts: 1063
Assuming the Polara to be the same as my Chrysler. In '65, they used a single vented tank (confirmed in the parts book) and a vented gas cap. They moved over to 2-vents for 1966, with a non-vented gas cap. So yes, both are needed. I've even seen warnings somewhere (for mine) to check the vents for being blocked, and unblock them if they are.
Its no big deal to fit the two vent pipes. Make your own, or get a kit for a '66 from somewhere like Inline Tube.
Joined: Sat Apr 25 2009, 03:08AM
Location: Out West
Posts: 626
On the topic of tank vents, a pitfall for guys that have not done work on those parts, is clogged or rusted vents. It took me a long time to figure that one out on my '71. It would randomly starve for fuel and bog out under throttle when vacuum in the tank overcame the fuel pump's ability to pull fuel. Finally got around to the vent lines one day and found they were all basically rusted shut from the inside.
never thought one would run all the way back to the other side. I poked a paper clip down both mine and ran one of the lines and put a vacuum plug on the other. guess ill run both, and for good measure ill blow some compressed air down both of them to make sure they breathe. my tanks almost empty right now, probably a good time to do it.