Fuel tank cap question

[Vladislav]

I worked out one of the fuel tanks of my R, had to make some repair including welding and followed with sanding and polishing. It was a real nightmare and I'm not satisfied with the result. Although it's not the matter of question.

So... There's a filling hole with a cap. The cap(s) are aftermarket and I want to to swap tham with some other nice stuff.

I looked over Mack accessories catalog (online) and found out:

4.95" O.D. Vented Fuel Tank Cap -

4.0 Thread with Thermal Relief, 12"

Chain and MACK® Logo

16MF312

and

4.95" O.D. Vented Fuel Tank Locking Cap -

4.0 Thread with Thermal Relief, 12" Chain

and MACK Logo

9538-2541L

Local dealer answered me he's ready to supply any of.

To be shure I looked for the size of my tank's hole and measured out 111mm of the thread OD.

I know what the most of you think about my 111 millimeters so I recount it and got about 4-3/8.

Mack tells 4.0 thread.

This way I'm in conclusion and looking for advice.

The truck is R688ST of 1988 and it is Canadian.

[mack mhe9]

I'm not a cap expert. You did some nice work with what you had to work with.

[smorse54]

Vlad,the 4" is 4 inch N.P.T. (National pipe thread) which is about 4 3/8" outside diameter. Tank looks great.Your work is always first class. Steve

[thomastractorsvc]

Vlad

Are you going to be around this weekend I will bring my B over and let you help me on my tanks

[1MACK1]

Looks like std large type mack cap fairly standard

[Vladislav]

Thank you for the fast help, guys.

I was thinking about some kind of N.P.T. or something like that but absolutely couldn't be shure having no SAE experience.

We here use to use the sort of pipe thread wich is for heating/water supply. The sizes called 1', 1-3/4 and so on but the actual measurements are away from real inches. SAE hardware is difficult to get here, especially taps and dies. Although when looking at all that with a hobby wiew that's a kind of an adventure again.

As for the polishing it was a story I'm still out of my mind about.

For the first when I took the tank off I found out the inside cross wall was laying on the bottom off it's welding.

It was a surprize just on a flat place.

Googled for a tank repair shop, brang it there. They wanted to cut off the end side. I stopped that nice idea and told them to make a cut-out on the back side. Couple of days later it was ready and I got it. By the word I had to transport it in my Mercedes - G.

Next I said to the guy at my shop to send it with a hand electric machine. He started and said "no luck, it's better to work by hand".

Next (next day) we resolved to buy sand paper disks and continue with a hand drill machine. And so on.

To make a long story short he spent about 20 working days to grind off most of the corrosion cavits (on the face areas) and send it up with all numbers of paper.

In the end I started to work with a paste I used for Alcoa wheels and got some strange result of black stains I could get off only by sanding.

Probably the tank was made of a different kind of alloy.

A friend of mine gave me a bit of 3M branded stuff for alu polishing and I finally came up with what you now see.

The tank doesn't shine perfect still and I hope (a bit) to polish it up more right before the instalation. In the spring, not yet.

Now all that is about 3 weeks back but I'm still under impression and trying to figure out what to do with the other one

[farmer52]

Vlad,

Tank looks nice. I have two (2) from my MH if you need more practice.

[Vladislav]

Ken,

It's very kind from you, thanks.

I will keep 'em in my prayers.