Oil petcock help!

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1923Touring
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Oil petcock help!

Post by 1923Touring » Fri Jul 03, 2020 11:22 am

Hi guys, I was changing the oil on my 1923 touring and I decided to fix a terrible lower oil petcock leak with a little thread tape. I began to run the petcock back into the oil pan and it began to tighten up just the way it should, but then it turned again. I DID NOT use any tool or pry bar to tighten it. The hole is stripped but I cannot unscrew it from the oil pan, it will only spin in place. What is my best option? Should I find a helicoil, epoxy it in place, or are there better options?

Thank you,
Joshua


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Re: Oil petcock help!

Post by Scott_Conger » Fri Jul 03, 2020 11:29 am

pull hard while unscrewing...it will come out
If it is not coming out easily, which it isn't, that means there are threads left in the pan to some extent.

Your choice in adhesives/epoxies once it's out, though you may find that a new petcock and fuel resistant teflon tape will work just fine.
Scott Conger

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Mark Gregush
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Re: Oil petcock help!

Post by Mark Gregush » Fri Jul 03, 2020 11:41 am

It's a tapered pipe thread. I would try pulling back on it and try to get remaining thread to engage so it can be turned out. The thread in the pan may be ok, just needing a little clean up. The brass valve is softer then the pan so the threads may have stripped on it. The petcock size is 1/8-27 pipe. Just clean the threads, don't try and cut new ones. If you do the valve might run out of thread before it is seated/sealed. I would use something like permatex thread sealer when installing the replacement valve. If you don't have a replacement valve, just use a brass plug for now.
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Steve Jelf
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Re: Oil petcock help!

Post by Steve Jelf » Fri Jul 03, 2020 3:29 pm

If the softer threads of the petcock are damaged and the pan threads are OK, you're in luck. A new petcock costs about $13.
The inevitable often happens.
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Re: Oil petcock help!

Post by John kuehn » Fri Jul 03, 2020 3:59 pm

Steve is right. Could be the threads on the petcock were worn and if they were the petcock was the issue and not the pan. Get a new petcock and try it before doing anything to the pan.

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RajoRacer
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Re: Oil petcock help!

Post by RajoRacer » Fri Jul 03, 2020 4:22 pm

As a part of general c.c. repair, I most often than not, slightly tap all around the inside of both petcock openings forcing the threads to compress ever so much then I seal the threads with oil resistant RTV. I find that the petcocks are turned more to align the "opener" to be outboard thus opening the tapered threads too much !


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Re: Oil petcock help!

Post by Norman Kling » Fri Jul 03, 2020 4:42 pm

When you install a new petcock, be sure the threads are good enough to hold it. Otherwise, I recommend either replacing the crankcase, or welding up the hole and re drill and tap with a pipe thread. If that petcock should fall out while you are driving, you might lose all your oil and cause a disaster!
Hope the problem is just the petcock itself.
Norm


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Re: Oil petcock help!

Post by Greg Griffin » Fri Jul 03, 2020 9:48 pm

If the threads are gone in the pan, time-sert makes a repair kit for 1/8" npt. I have no experience with it.


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Re: Oil petcock help!

Post by 1923Touring » Fri Jul 03, 2020 11:32 pm

Thanks for all the advice. I was able to remove the petcock that had stripped out, but upon closer inspection of the oil pan it appears that a portion of the internal flange is chipped away. About 20-30 percent on the bottom side, but the rest are in good condition. Using thread tape and thread dope I installed a spare petcock and it tightened up as it should. Then as insurance I applied some JB weld around the connection, I plan to test this repair tomorrow. Does this seem alright? I'm not sure if a helicoil would work in such a location and would hate to pull the pan but will if I need to. The engine only has 225 miles.

Thanks for all the replies and have a great Independence Day.

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Re: Oil petcock help!

Post by Flatee » Sat Jul 04, 2020 2:11 am

A few things not yet covered you might consider:

1) I wouldn't have used JB weld around the petcock after installing it. JB weld isn't a sealant in this way and only makes things messier looking and will likely chip off if you ever turn the petcock. Unless JB weld is sandwiched between two pieces (such as a crack or a repair splint), it doesn't play well for the long haul.

2) What I would have done before installing the replacement petcock is gauge how far in the petcock pipe threads go. If there is 1/8" minimum male thread sticking out after the fitting seats, I would have run an 1/8" NPT tap through the hole to cut the threads deeper/wider. The beauty of pipe thread is the taper to where so long as the fitting has enough thread, you can enlarge the female threads by burying the tap. For slightly rounded-over threads, this method usually does the trick with sometimes needing to peen the boss opening as RajoRacer describes in a previous post. To prevent metal shaving from entering the internals, dip the tap in bearing grease to capture the shavings.

3) Teflon pipe tape isn't the best sealant to use for suspect threads like yours. Oatey "Great White" pipe compound #31230 is excellent for these types of situations. I actually use it on all fittings that require a flexible sealan (oil, water, steam, gas, SBC cylinder head bolts, etc.). Just about the only time I use Teflon is on stubborn inverted flare or similar straight threads just for thread lubricant and not for sealing or on fuel pipe fittings. I don't use RTV on fittings. It's not the greatest at sealing oily surfaces and is a PITA to clean off in the future, especially without dropping pieces into the crank case. It's good for making gaskets on oddly shaped, very clean surfaces (like the main-cap corners of oil pans and intake manifolds corners), but that's about all the use it gets in my shop simply because there are superior sealants.

4) If the petcock is suspect to where you have to be very careful opening and closing it, I would not leave it as is. These cars vibrate and bounce around enough, as you know, to where there's a decent chance you'll run into an issue with the petcock backing out or stripping down the road if it isn't strongly secured, and you'll have to fuss with it every time you check the oil. If the female threads don't hold and you can't repair them by burying the tap as I describe in point #2, I'd drill out the hole and tap to 1/4" NPT. Yes, it isn't OEM, but unless it's a concours car, who cares. Either use a 1/4" pipe plug or a 1/4" MPT to 1/8" FPT brass adapter and the 1/8" MPT petcock. For drilling, use the same method of dipping the drill bit in bearing grease to capture the shavings. Go slow, wipe off the grease/shavings, and reapply grease as needed. Cast iron can be tricky to get the tap started, so a technique is to not grease/lube the tap until you have a solid full turn cut in before reversing the tap or lubing it. It will require good pressure to hold the tap against the iron and stop it from bucking off, so position your arm where you have good leverage with your body weight planted. Drilling out to 1/4" NPT will likely remove most of the thickened pad around the boss, but pipe threads don't need many threads to seal. I just had to do this exact same procedure on my '26 Roadster because the upper oil petcock female threads were completely destroyed. Someone had JB welded the petcock in place. One twist to open the petcock broke everything loose, and out fell the petcock. After drilling and tapping to 1/4", I had no issue getting the 1/4" NPT adapter to seal without the factory thickened pad.

Good luck.
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Art Wilson
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Re: Oil petcock help!

Post by Art Wilson » Sat Jul 04, 2020 4:57 pm

I found on our car when attempting to chase the petcock threads with a new 1/8 pipe tap, that the tap would bottom out against the flywheel before enlarging the threads in the pan. The tap length needed to be shortened to work.

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Flatee
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Re: Oil petcock help!

Post by Flatee » Sat Jul 04, 2020 5:12 pm

Art Wilson wrote:
Sat Jul 04, 2020 4:57 pm
I found on our car when attempting to chase the petcock threads with a new 1/8 pipe tap, that the tap would bottom out against the flywheel before enlarging the threads in the pan. The tap length needed to be shortened to work.
Good point. I've found MAC brand NPT taps to be stubbier than others, but I suppose one could use a cutoff wheel to shorten the tap. The heat will take out the hardness for cutting fresh threads in a new boss, but it should function fine as a chasing tap.
Drivin' down the road I'll get my kicks
A' poppin' the clutch and a' slippin' my slicks

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1940 Ford DeLuxe Coupe

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