Petcocks Leak - '46 Chief

[rmmccon]

Both petcocks leak. I would think that in the 9 or 3 o'clock postion they would be closed. But I have to set them in the 8 or 4 o'clock position and even then they might leak out the backside of the petcock. The petcocks are from Greer. Are the bronze ones from Starklite any better?

[sirhrmechanic]

You can try lapping them in. Get some 400 grit compound (not rough valve grinding paste...) and see if that helps. A lot of the industrial supply places sell 'sets' of small tins of compound 180 - 600. And it's a must-have 'tool.' We use Clover brand, but any good lapping compound will do.

You will know right off if the petcocks are lapped together well as the compound will show up where contact is being made. You can check it yourself before lapping if you have some machinist blue.

Just don't lap too much or you will open up the tapers and then the holes will mis-align. But most common reason for leaking is small burr on the holes or tiny (often invisible) machine marks that will come out with lapping. Also, keep the petcock lubed! If the pieces gall and create the tiniest imperfection on the mating surfaces... instant leak.

We have to deal with these all the time for pressurized fuel tanks on early cars (no fuel pump... put 2 - 4 pounds of air in tank to push fuel to carb. Great system, unless you have an accident or a stuck float, then you dump all your gas out. Autovacs were a wonderful invention. But trying to get petcocks working right against 4 pounds of air pressure takes lots of time and PITA factor.

Cheers,

Sirhr

[PRG]

Howdy sir,

Lapping tapered brass petcocks can be a dodgy proposition as you are essential creating the unavoidable, ie, small grooves where the grit has carved arcs on both the valve bore and valve cone that overlap each other. Better to avoid taper damage in the first place.

Most of the brass valves on the market were not likely intended to be duty cycled in use as frequently as we do using them as fuel petcocks. The spring pressure is way to high and they essentially try to lap/potentially damage themselves with every activation. The better quality ones can actually seal without the spring fitted just by pressing the components together as the valve handle is turned. If yours don't leak when new, now's the time to make them last for years. Remove the spring and cut half to 3/4's of the spring coil off and refit. Not only will the effort be less to open/close them, they'll last for longer, I have had the same set on my 46 for 20 years.

[sirhrmechanic]

Peter:

Agree with you to some degree. Lapping can do damage, especially with low number compounds or if you use valve granding compounds. We use 400 grit or 600 grit and use it VERY lightly and add extra oil. If you go to fast, or get the pieces hot you do exactly what what just described... big radial grooves that essentially ruin the petcock. Gentle is the key.

For the OP, Peter's point about spring pressure is a very good one. Too much pressure, and you get galling and issues. And lubrication is important, as with anything metal on metal. Fuel will ultimately wash the lube off... but that's a maintenance item. Lubricate that petcock every now and again. And pushing the handle in after you finish turning it as Peter mentions, just lightly, works wonders.

Thanks, Peter. Great comments! OP: Hope this helps!

Cheers,

Sirhr

[indian301]

If you pull out slightly on the petcock when you open and close them they will last longer. I have also cut the springs to reduce the pressure. My aftermarket ones have been on my 48 Chief for almost 20 years as well.


Dave

[346INDIAN]

We had the brass petcocks for some of our earlier fire equipment years ago. They were used with water, but after a short while, the "like" metals would try to weld together. When I built my Indian, I didn't want to fight this problem. I I bought the hard chromed ones from Starklite in the late '80's, and I haven't had a problem. I have another Chief I bought about 8-10 years ago with the all brass ones. I have to use a wrench to turn them off and on. When I get tired of this, I'll buy another set of hard chromed ones from Starklite.