Newbie question - fuel tank drain plug, and engine compression

[Vespanation]

Hello to the Group,

 

My name is Paul and I'm a total American car newbie. I'm a British and Italian car mechanic by trade.  Last year, my mom passed, so, I've been going through TONS of old papers and such. I found a envelope of photos from when my parents were dating, so around 1948-49.  In there was a photo of my mom posing by a car in her 1940's one piece swimsuit.  Geez!  Mom!  Our parents are not people, they are parents, so yeah, kind of a shocker.  Behind her I could see the rear half, side view, of a car.  I assumed it was my Dad's car, which it was.  But what IS it?  I have a vague memory of my folks mentioning "the old Dodge", and, "the '46 Dodge".  So, 10 minutes with Google and photos and I can see that that is in fact what it is, it's that '46 Dodge they talked about.  1946 Dodge Custom.  Cool.  Fast forward 9 months - I'm in a huge old barn fixing a 1959 Triumph TR3A for an older woman.  There is another car in the barn under a cover.  I asked her what it was and she just rolled her eyes and said, "That..is my sons'.  It was his father's and I gave it to him after his father's passing, but that was 10 years ago and he hasn't done a thing with it."  "But what IS it", I asked.  "It's a 1946 Dodge Custom" she says.  I was stunned!  Of all the cars, of all the years, it's the same model and year my parents car was.  I asked look at it.  Wonderful shape, but it has sat that 10 years.  So, I'm thinking of buying it.  But, I got permission to go over it a bit to make sure I'm not getting into a HUGE project.  I got a new battery, new spark plugs, good spark, cleaned out the carburetor, engine spins  easily, (if slowly, 6 volts!), checked the brakes, changed the fluid, etc.  I'll give it a proper service if I buy it.  I want to run it first, so I was going to drain all the old gas out of it, but when I looked at the gas tank drain plug, well, I wasn't sure what I was seeing.  A female fitting with lots of notches inside it, almost looks like a Torx fitting, but I don't know.  So, first question, what tool is used to remove the gas tank drain plug?  Second, I'd like to do a compression check on each cylinder.  What would be good numbers to see there?  And that would be it for now,  There will be more questions no doubt.  Compared to what I work on everyday, this thing is HUGE.

- Paul

[Curt Lee]

Got no answers for you, but I share your interest in little British and Italian cars. I recommend reading through the Technical threads  and the Tips above us on the header of this forum. I re-read them constantly in search of tidbits of knowledge that don't necessarily apply to more modern cars. I think you'll find that 46 Dodge actually a lot more modern in design than you might imagine. With British cars as experience, you already know the quirks of six volts and positive grounds..... Lockheed brakes... Trunnions and kingpins... lever shocks.... see? Not as different as you thought. 

[DonaldSmith]

The drain plug needs some sort of square driver to get it out.  Think 1940's tool box.  No torx bolts and screws back then.  

 

These drain plugs are special, since the tank does not have a deep pipe-threaded hole, so the usual pipe plug will not work.  (There are holes around the base of the threads,  to drain the last drop from the tank.)  But there are workarounds. 

 

For a workaeround, I had a close-coupled nipple and a pipe cap.  The nipple screwed into the tank,and the pipe cap held a gasket against the tank.   It woked for 20 years, until I had the tank recoated, and the recoater came up with something, I don't know what.  But that should last another 20 years.   

[plymouthcranbrook]

On my 52 Plymouth to drain the tank I believe I used a half inch drive socket extension.  Been a long time but if it was something fancy that I had to buy I would have remembered it.  Same as on the differential.

Edited August 8, 2023 by plymouthcranbrook

[Sniper]

Make sure you have a new gasket on hand for that plug.

 

Odds are some of the valves are stuck open.

[Ivan_B]

Just "disconnect" the fuel line under the hood and dip it into a can with some gas. This will allow you to quickly test-run the car. No idea about the compression, I would just check all the cylinders to make sure the numbers are more or less the same.

 

Welcome to the club (you are getting the car, right? ) and we are certainly waiting for plenty of pictures.

[Curt Lee]

Gosh doggit he BETTER be getting that car

[soth122003]

When you do your compression check, do a dry first, then a wet check. As far as the numbers, about 100psi is normal for a good engine. Since this one has been sitting for 10 years anything above 50 psi should get it started and once running the piston rings will start working better and the compression should increase. 

 

As far as the gas plug, back in the day they used to have square bits (think a 4 sided allen plug) ranging from 1/4" to 5/8". I think the tank was either 7/16 or 1/2" in size, but like some one else suggested, disconnect the line at the carb and use a boat tank or the like and just use that to see if the car runs.  Since the engine spins, and has spark it should start fairly easily. It will probably run rough if some of the lifters are stuck, but that is easily fixed later.

 

Joe Lee

[Los_Control]

As earlier stated, just to hear it run would be easiest to just disconnect the rubber fuel line from the fuel pump.

Use a 2 gallon gas can & a length of 5/16" fuel line to connect the two together. ..... I tie my 2 gallon can onto the bumper so can move it around.

 

1 hour ago, Vespanation said:

I'd like to do a compression check on each cylinder.  What would be good numbers to see there?

Sitting for 10 years in a barn covered up .... should not be to bad on the engine.

The old cast iron rings like to stick to the aluminum pistons .... whatever they are made of ... dissimilar metals.

Adding a little marvel mystery oil in the cylinders to soak the rings will help loosen them up. Running the engine through a couple heat cycles will also help loosen them up.

 

Just saying if the rings are stuck to the pistons, you will have low compression. As the rings loosen up & begin to spin on the pistons as designed and seal against the bores, the compression will come back.

 

So don't be disappointed with a low compression number at first .... totally normal.

My truck sat for about 20 years outdoors in a field. I had 2 cylinders @100-110 psi, 2 @80-90 psi And 2 more at 20 & 60 psi. .... All over the place.

Last time I checked the lowest cylinder at 20 psi was up to 95 psi .... I have never driven it on the road, still painting. A nice long drive would help it out a lot.

[Sniper]

1 hour ago, soth122003 said:

anything above 50 psi should get it started and once running the piston rings will start working better and the compression should increase. 

 

You'd think.  When I got my 51 it's compression number were all around 50 psi per hole.

 

Two years later, they are still there.

 

Not an issue to me, it runs fine and I am building a 230 for it anyway.

[Los_Control]

2 hours ago, Los_Control said:

So don't be disappointed with a low compression number at first .... totally normal.

 

58 minutes ago, Sniper said:

Two years later, they are still there.

Now is time to be disappointed  

 

Like you say, you are building a engine anyways ..... I suspect it might not take much to freshen up the 218 you are running now. 

[Sniper]

Pretty sure a good valve adjustment will get some of it back.

Edited August 8, 2023 by Sniper

[D35 Torpedo]

Tank plug is 1/2" square. I used an o-ring on mine to seal it. I hope the price is right, because you need this car. 

[soth122003]

7 hours ago, Sniper said:

ou'd think.  When I got my 51 it's compression number were all around 50 psi per hole.

 

Two years later, they are still there.

Hey Sniper, If you taunt those english kinigit piston rings a second time it  might just work for you. LOL

 

Joe Lee

[Merle Coggins]

What you're seeing on the drain plug is actually a double square with 8 points. As stated you can use a 1/2" drive ratchet. 

[Vespanation]

Thank you all very much for all the information!  It's VERY helpful.  I guess my journey is beginning... 

 

- Paul

[Ivan_B]

Paul,

Did you get the car? Where are the pictures? You have to share all the good things

Edited August 10, 2023 by Ivan_B

[1952 Fargo]

Use a 1/2 inch drive ratchet WITHOUT the socket, the square end of the ratchet will fit into the drain plug. 

Brian