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Discussion Starter · #1 ·
Hello all,

I had to drill into the bell housing alignment dowel pins in order to tap them to pull them out so I can install adjustable ones to index the bell housing for my new Tremec.

In doing so, I drilled too far and went clear into an oil passage behind the right dowel pin. I've drilled into the passage between the oil pump and the oil filter. I was able to remove the filter assembly and clean out the metal shavings, but now I have a 5/16" hole in the oil passage.

I can't put a dowel pin back in and call it a day because the new pins have a screw through the center for tightening, and the oil would leak right past them. So I have to plug the hole somehow.

I would JB Weld but I'm not sure it would hold up to the oil pressure and thermal expansion.
I would tap for a pipe plug but I don't have the tools/skill to tap tapered threads.
I don't own a welder but even if I rented one, I understand that cast iron is very hard to weld correctly.

Would pressing a sleeve into the passage work? I'm open to other suggestions as well

Thanks,
Alex
 

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Not that I have been in your situation, but many engines have OEM oil passages that just have press-in plugs that seal them up just fine...just like a freeze plug but smaller. I agree, that drilling and tapping for a small pipe plug would be best given you have enough room to drill and tap for the smallest plug you can get. A press-in plug would work fine too so long as you can drill the hole to the precise diameter and keep the hole good and straight. I have seen 5/16" aluminum plugs for carburetors and steel 3/8" plugs can be purchased from many parts stores. If you go this route...I'd double up on the plugs (given your hole is deep enough) and give them a good coat of RTV before tapping them in.
 

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1964 Tempest - work in progress
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Drilling and tapping for a tapered plug is not that difficult. You just need a tapered tap and tap handle. Drill using the correct tap drill for the plug you are using. The critical thing is tapping to the correct depth but you can do that by backing out the tap and test fitting the plug until it is correct. Maybe someone else can comment, but I'm thinking teflon tape to seal, then tighten it down. Don't put any teflon tape past the end of the plug because it will just come loose later into the oil passage.
 

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Red Loctite is permanent and will not come free without heat. Ive used it on mass produced, press fit hydraulic pistons, at over 5000 psi. So simply clean it and press in a metal plug with red loctite. Use accelerator and let it dry.

I can't put a dowel pin back in and call it a day because the new pins have a screw through the center for tightening, and the oil would leak right past them. So I have to plug the hole somehow
Not if you put red loctite on the screws first. However, they wont come back out without heat, either. Im not clear as why the new pins have a screw. Can you post a pic?
 

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If you press a pin, don't you have to use a reamer in the hole? It's not my experience that a drilled hole has a good enough finish or tolerance for pressing a pin.
 

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It's done all the time, but I wouldn't use teflon tape near an oil gallery.
Thanks. That was one of my concerns too. I've used teflon tape in similar applications but had to be very careful in applying the tape to the threads. I think most people get tape past the end of the fitting threads and it comes off inside.
 

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I'd like to see a picture of the part in question, first.

Im about to do a Tremec conversion on my 67, so Im curious... but to the OP's original dilema, he states that a screw passes through the pin and is used for tightening. If that's the case, the screw can merely be red loctited and the part will not leak. However, it also will not come back apart without heat.

And while I agree with everyone that drilling and tapping is not that difficult, and it's what I'd do, the OP is admitting that he's not comfortable with the process, so I doubt that I'd be looking to break him in on an oil galley, under his car. If the tap ever snapped, his problem would go from gecko to Godzilla. Im a 35 year seasoned metal fabricator and Ive snapped more taps in my life than I wish to recall.

Ive used epoxy on pool heaters, and while it's not the best bet, a putty type on a well cleaned surface, followed up with loctite on the screw, would likely do it.

So... Search for a pal to drill and tap it for a 1/8 pipe plug... if not then feel safe using these other methods.

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I'm on the tap and thread using sealer team. One recommendation would be to do a couple quick oil changes after you repair this. Don't bother changing the filter until the last change, and you could probably just use really cheap oil as the flush, but I would start it up and shut it down quick. Then drain the oil, refill, and repeat. One more time if it makes you more comfortable.

This sounds like the type of mistake I am famous for. Good luck!
 

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Discussion Starter · #17 ·
Thanks for all of the great responses guys. I think I'm going to try to tap it for the screw-in plug.

I did a quick google about how to tap tapered threads before I wrote the first post, and I was under the impression that a reamer was required. I've never used a reamer and I figured tapered tapping would be much harder than it's now sounding like it is. So I didn't pursue the idea further.

I know nothing about pipe threads so help me understand - since my "pipe" has an I.D. of 5/16", I need to get a 1/8 NPT tap & a type R tap drill bit, and a 1/8 NPT plug (such as Dorman 090-046)?

I would also need to get some sort of sealant or epoxy. Sounds like Teflon tape is too risky.

I've attached some pictures to hopefully better illustrate what I'm looking at.
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Eye Automotive tire Bicycle part Rim Automotive wheel system
Black Flash photography Material property Gas Auto part
Eye Automotive tire Human body Eyelash Rim
Automotive tire Gear Bicycle part Crankset Motor vehicle
Hood Automotive lighting Automotive tire Headlamp Bumper
Automotive tire Vehicle brake Motor vehicle Rim Automotive design
Bicycle part Vehicle brake Rim Metal Nut
Rim Metal Nut Auto part Automotive wheel system


Red Loctite is permanent and will not come free without heat. Ive used it on mass produced, press fit hydraulic pistons, at over 5000 psi. So simply clean it and press in a metal plug with red loctite. Use accelerator and let it dry.


Not if you put red loctite on the screws first. However, they wont come back out without heat, either. Im not clear as why the new pins have a screw. Can you post a pic?
It looks like you found a pic of the exact pins I have. As you can see, the split at the back of the pins would allow oil to get past so loctite on the threads wouldn't help.

Just out of curiosity, how long are the dowel pins? I may be doing this soon and would like to know how deep the drill can safely go.
The pins are about 1.1 inches long, but I ended up using a helicoil tap because it's what I had and put in a helicoil, which is less than half an inch and I got them out fine. So really you would only need to drill about half way. I pulled it the same way Fast Monty's Garage on YouTube did it, except my motor is in the car.

Not that it's relevant, but if I had to remove dowel pins I'd weld a bolt to them and use a steering wheel puller.
If I owned a welder and had any experience welding I would definitely go that route first.

I'm on the tap and thread using sealer team. One recommendation would be to do a couple quick oil changes after you repair this. Don't bother changing the filter until the last change, and you could probably just use really cheap oil as the flush, but I would start it up and shut it down quick. Then drain the oil, refill, and repeat. One more time if it makes you more comfortable.

This sounds like the type of mistake I am famous for. Good luck!
Thank you for the well wishes. Wouldn't it make more sense to quickly use a couple filters, then do a full oil change? This way I could cut open each filter to inspect for metal shavings, and I wouldn't be using up 10-15 qts of oil in the span of a day. You can see in the pictures that the oil passage the debris would be in (I cleaned it best I could) is literally a couple inches before the filter inlet.
 

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I'm seeing something I didn't realize before. I thought you had drilled the same diameter as the dowel. You have a small hole at the bottom of a larger hole. Are you going to tap the large hole or the small hole?
The small hole looks like it may not have enough wall depth for a tapered thread. And the large hole doesn't seem to have enough depth for even a bottoming tap.
 

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Here is a diagram for oil flow. If I am correct, the oil at the point of the hole when oil is pumping will not go through the filter, but up into the lifter galley and through all your bearings.

I might leave the filter off as in the photo and flush some thin liquid a couple times, like transmission fluid, into the hole using the single quart oil pump that screws on top of the quart. You should be able to get one locally. Let the flush drain through the oil filter hole, use a clean catch pan and look for any particles - if any.

Put a light coating of some JB Weld on the plug threads you use. The dowel pin should also act as a wall and means to keep the plug secure. Make sure the plug is flush so the pin sits flat on it.

Nothing else you can do from there and just keep fingers crossed. You should be OK.

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Fortunately, I have my engine out and apart right now so I could go have a look.

The bottom hole on the oil filter adapter, the one that you drilled into, is the pressure side of the oil pump before it goes into the filter. You can see in the 5th picture you posted that shows the back side of the block, that passage makes a 90 degree turn and goes down to the oil pump. The upper passage across the back of the block is the one that comes out of the filter and goes across to the lifter gallery, "output" from the filter. So, that hole you drilled is going to "see" the maximum oil pressure that the pump puts out.

True, that's a small hole and very shallow to be able to cut a tapered thread into for a small pipe plug, but I think the good news is that I don't think it HAS to be a tapered pipe plug to work. That's because the dowel pin will be sitting on top of it, and that ought to keep whatever you put in there from backing out. If it were me, I'd consider cutting normal threads into that small hole and putting a regular hex socket plug into it, with JB weld packed into the threads to seal it. Once that dowel pin is sitting 'behind' and on top of it, you shouldn't have to worry about it backing out, and if you make sure to get both the threads on the hole and the threads on the plug nice and clean, that very thin layer of JB weld that will be left after you put the plug in ought to seal it nicely. Make sure the plug doesn't protrude into the oil passage so as not to introduce a flow restriction. If you go this route, coating your tap with heavy grease before you cut the threads will help trap the chips so they don't wind up in your oiling system. Also with the pan off and the pump removed, you can blow air into that passage from the oil pump mounting face and that will clear it out. If for some reason you don't get a good seal, it should be obvious because you'll be able to see oil leaking from around that dowel pin after it's all up and running. It wouldn't hurt to use some kind of sealant around the dowel pin, perhaps something like regular old pumber's "pipe dope" for insurance.

My .02 - from someone who's also made more than his share of mistakes and created additional problems for himself therefrom.

Bear
 
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