Guys no excuses but I am seventy with bad eye sight macular. I am attempting a valve cover broken bolt repair on my old Dodge 318. The PO broke a bolt and I drilled it out ran a tap in too far and broke the tap. Well the bolt hole is in back by the firewall not much room to try and get a broken tap out. My thought was to drill an additional hole close to the old one . Has anyone done that successfully before ? If my eyesight was better I would attempt to get the broken tap out but I do not think I could pull it off. Any ideas or advise that I could do on my own would be great. Alternative fastening methods ? Thanks everyone for your help and ideas...
While it is possible to drill and tap another hole close to the old one (and drill the cover to match), I would try to get the tap out. If it is a 4 flute tap and broke off flush, I have had luck sticking a pair of needle nose pliers down between the flutes and backing it out. Pictures would help.
I have good luck welding washers to the broken tap, then weld a nut to the washer. You get a lot better weld when using a washer first. The heat loosens them right up. Sorry for you eye sight, it ****s not being able see what you need to.
Have you got any mates with good eyesight that can help you out or a local machinist that would come to your place after work and do it. They've probably had experience with this sort of problem. The money spent this way could save you in the long run.
With a tap take a torch and run the flame down one of the flutes of the tap if the flame comes back out the other flutes keep the torch there until the tap is red hot cool and remove.
Have to be extremely careful with a torch, remember the engine is in the vehicle. Wires, fuel lines, old oil that leaked, many combustible and close to the firewall as well.
Thanks guys for the responses. It a cheap *** ride so not going to spend a lot fixing it. I was looking for a low budget solution. It is recessed and very tight so the needle nose trick will not work. I think I will try a shallow drill and tap close to the hole and see if that works.
If its a tungsten tap you can get them out with a center punch. Just keep punching the stub of the tap and it will break up to fragments. You can then get the parts out with long nose pliers. The punch will look prety beaten up afterwards but it does work.
The drilling next to the hole will probably make things worse, especially if you are having vision problems. Depending on how the tap broke......probably either flush or below the surface, will affect what you can do. The best thing to do is find someone who can point a plasma cutter into the hole and blow the tap away a little at a time. Then redrill oversize if needed, and retap the hole. When doing tapping with smaller taps it is often best to proceed slowly and only put a 1 or two threads in. Then back the tap and clear the chip. More oil and another thread or two. I also often use a drill bit that is a few thousandths larger than what the chart tells you to use. That helps a little on problem threads. Broken taps are a real pain and its easy to mess things up trying to remove them. Of course, you could pull the head and take it to a shop with a "disintegrator" machine that will make short work of the tap. Better than ruining a head and not being able to find a rare replacement.
If by "recessed" you mean the tap broke off IN the hole and not flush with the hole, you may have enough threads to glue in a stud.
I'm afraid you're not going to have much luck until you have good straight line sight and access. And you know what that means. You're going to have to at least pull the engine forward far enough so that you can do what you need to do. I know, an awful lot of work for such a small thing. But it's as important as anything else. Good luck.
If you have a jar of OLD cotter pins on a shelf somewhere, I have had luck one time inserting the legs of one that fits in the flutes best and turning it out with pliers or vise grips. New chinese ones are too soft and just twist off. Gary
rather than drilling a new hole & possibly making things a lot worse .I would try the right stuff gasket maker put the rest of the bolts in it probably wont leak.
I wouldn't try to drill another hole. You could make it worse like mentioned above. I would seal it up good and just use the remaining bolts it you are not looking to spend any money.
I’d have to look at my 318 (***ume an LA engine?) but think there’s only 4 bolts to hold the VC down….yes, been awhile since I’ve been on that project…you’d surely have to use a sealant/gasket maker that would “glue/bond” it pretty well I’d think. If it’s a “I don’t care, etc, engine, I just want to stop a leak” thing. I see no issues (***uming the OP can drill straight in) bolting the VC down, drill a small Pilot hole through it and the head within close proximity of the original, pull the VC, drill it out for a 1/4 inch hole to tap (#7 drill as I recall, chart not handy) then tap the head, open up the hole in the VC stick a bolt in it and a gasket and get it on the road. I have to kinda say it again since the engine is in the car. Plasma cutters, OA, not even on my list with a (I presume) older engine that has ignitable substances on it, around fuel lines maybe, wiring, etc. Maybe I’m just a *****, but the OP mentioned he’s 70 years old (I’m 61, I feel ya) and I don’t want to pull an intake then pull a head to get a tap out of a car that just needs to get down the road. Cast iron drills easily, keeping the hole straight is the tough part. What I’d do, is take the VC, find a small rod, heck, maybe a off the shelf bushing would work. Spot weld it in the VC next to the original hole, use the bushing as a drill guide. It’s easy for me to say use a rod, as I have a small lathe that I could take a piece of 3/8ths rod, say an inch long, bore a 1/6th hole in it, then use it as my guide for the Pilot hole. If there’s a recess for the original bolt, no problem, I’ll grind off the rod for some flats that will sit, or just bore a 1/4 in rod. In fact, @carguy4sp if you want to send me a VC, I’ll do it and weld it up for you and send it back, will only cost you shipping to me, I’ll send it back ready to use. If you have the ability to weld/spot weld the Pilot square, I’ll make you one up later today when I wake up, and mail it out tomorrow.
^^^^^ Sorry Mike ,,,,LA 318 Mopar has 5 cover bolts,,,,,,,3 outboard,,,,2 inboard . That’s pre Magnum . Tommy
I had something similar - my 260 Ford had one of the valve cover cap screws replaced with a sheet metal screw. On examination there was a broken piece of round file jammed in a bit of original valve cover bolt in the hole. This engine was out of the car, so much easier to work on. I used the smallest tip for my oxy-acetylene torch and adjusted the flame so that it was about as lean as it would go without popping out, and burnt out the piece of file. Surprisingly the flame had little effect on the cast iron threads, but quickly ate up the steel from the file and screw, blowing the debris out as I worked. Unfortunately the threaded hole on your 318 is most likely all messed up if it was drilled and tapped with poor access and without being able to clearly see what was going on. If it were a rare engine or head, I'd take it off and first do what it takes to get the bits out. Then I'd put it on a milling machine and using an end mill, make an oversize, but centered hole in the correct place, and finally tap it to accept a bushing to suit the original screw size.
That's a common fix in my shop. The OP is not alone. These things happen. My vertical mill runs about 4-hours every day.
57 fury440 is on the right track get every thing clean and dry and use 3M weather stripping adhesive on both sides of the gasket.
The basic problem with a broken tap is that its usually harder than anything you can use to remove it. They make professional tap extracters that have multiple "legs", but unless the tap is only loosely lodged in place, they usually bend. And the tap usually isn't loosely lodged.....thats why it broke. The simplest solution is the use of a "disintegrator machine", but that requires the head being removed. It is a very controllable process and works pretty much every time. Next is getting a friend or hiring someone to use their plasma cutter . Simply point it into the offending bolt hole, being particularly careful that its perpendicular. Squeeze the trigger for a moment and pick out the small debris. Do that several times and the tap will disappear. Keep a water hose nearby but doubtful you will need it. Probably about 10 minutes to get it out. Being a valve cover bolt, it should be pretty shallow.
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