If there is still a trace of thread left, check the metric or BSF or BSW or whatever thread pitches if something comes close to your original thread pitch but is a bit bigger in diameter, i.e. your now existing bore is the core hole for the next thread. If the thread is completely gone you can use a different pitch. You would only need as much space as the your tap is long. If successful you could have someone with a lathe make you a stepped bolt. I don´t think there is any glue that will hold an exhaustbolt in the hot head.
No pics so I'm going out on a limb here ... any chance a cheap, air powered, 90 degree, right angle drill with a shortened drill bit would fit?
In my experience, if you don't do it right in the first place you'll be doing it again. And if you have a bigger hole that may prevent you from using the size insert you need to get back to stock thread size, so you may only get one chance.
I'd bet you could get it straight enough but if you're worried, build yourself a guide that bolts to other exhaust studs or stud holes. A piece of hardwood would be sufficient I would think.
Sometines studs are quite shallow fixing. There may be enough thread left to put in a longer stud or bolt
I would loosen off the motor mounts and whatever else prohibits the engine from side shifting for more room, allowing for a small, shortened drill and bit. Its only aluminum and should be easy to re-tap in place as well by hand once the drilling is done. A picture would help.
Just a thought...but in the long run to save the head wouldn't it be worth the day and a few gaskets that it takes to remove the intake and head and repair it properly? They're only fastened with bolts.
Take the head off and do it correctly, especially so for aluminum. Don't use epoxy, JB Weld, nor some mystery product. The HeliCoil style thread repairs work well, and will provide ample strength. You can buy an off-brand version at AutoZone, etc. that will work just fine, and they have the correct taps, too.
You can use a manual tap wrench to both drill & tap the hole . a piece of 3/4" flat stock bored appropriately will be a sufficient guide .
I agree! Pull the head do a proper Heli-Coil repair it’s done properly and you don’t have to worry about it anymore. If you damage the hole drilling or break a tap because you don’t have enough room the repair will only get more expensive and time consuming. Your mileage may vary!
I agree also with pulling the head or both for a repair and cleanup. The worst part of the job is draining and getting the anti-freeze out of everything.
Pull the head, just went thru this on a broke off Harley exhaust stud I got roped into fixing. Wasted hours trying to do it on the bike...not worth it.
I generally have lots of scrap meta;s around the shop. I would definitely make up a drilling/tapping block to keep everything straight. Aluminum is good, I have a general use tapping block I made years ago using phenolic.
With a right angle drill, bolt the manifold back on. Use the hole as a guide. Steady hands, kinda peck at then pressure on the drill. Then take the manifold off and tap for an insert. I’m guessing this head may be on and OT HAMB engine, and understand the 1/2 day it takes just to pull the intake off on many of them, then reinstall.
I'm spoiled having a Bridgeport to make jobs like this easier. Even a stout drill press will keep a hole straight and square. I do a lot of "fishing expeditions" for my buddy that owns a shop. Busted off bolts, stripped threads mostly. He brings me his shaggy-dog tales that he attempts first. I get exhaust and intake manifolds, timing case covers, water pumps that he can't get a replacement of.
I say try it with the head on. It's an exhaust manifold stud not a rocker stud or a bolt used to align a 427 SOHC timing chain. Heck, with the existing threads already pulled out, the hole may already be the perfect size for the heli-coil tap. I am assuming the existing hole is already square/true, just missing its original threads ... if you need to drill it slightly over what it is now, the present hole should basically guide you in anyways. Like Jerri Steinfold used to say "Git'er Done"
If you end up trying to do it on the car and it doesn't work the result may be a head screwed up where it has to be pulled, and may be very costly to fix. In my experience these things rarely work out well enough and often result in you having to do what you were trying to avoid doing, and much more!
Get the small drill, then you will always have it for other jobs. Look on a drill chart and see which drill sizes are slightly bigger than what you need, but not the full size for the next larger thread. A 5/16-18 thread means the outside diameter of the thread is 5/16 or .3125. So first use a 9/32 drill in the hole to clear any remaining thread. If its a 3/8 (.375) then use an 11/32 to clear the existing thread. Now you have less metal to deal with. Get a couple drill bits that you can clear the old threads out with., but NOT the size needed to tap it to the next size. Use these drill bits to gradually enlarge the hole, as they will be removing very little metal and tend to follow the existing hole. Then finally drill the hole to the correct size for tapping. You want a coarse thread for aluminum. It also helps if you get a "set" of taps. Taps come as "starter", "plug", and "bottom" types. Most people use a plug tap only. If going all the way thru some thing they are fine, and they will start a hole because they have some taper at the point. The best way is a "starter" because it has a long taper and tends to follow a hole better. Then the plug and finally followed by the bottom tap to get a thread all the way to the bottom of the hole. With a 5/16-18 it turns out that a 5/16 (3125) drill bit is the correct size for a 3/8 tap. So I would run a 9/32 (.281) and then a 19/64 (.2969) before going to a 5/16 .312 for tapping. I would spray WD 40 in the hole when you get ready to actually tap it and blow the hole out a couple times while doing so to clear the debris out so it doesn't clog the tap. If its already a 3/8 hole, then use an 11/32 (.3438) then a "U" (.3680) drill before enlarging to a 7/16-14 thd. I have used a slightly larger 3/8 (.375) drill with no problems if a "U" isn't available. Get the drill in a position where you aren't fighting the hose while drilling.............
What car and what motor? Can you remove an inner fender panel to get straight access to the bolt hole?
My dad always said “If you can’t find time to do it right the first time when are you going to find time to do it over” I heard that over and over and they are words of wisdom and experience. I find myself saying the same thing over and over. Your mileage may vary!
The threads are already pulled out of the original hole. In order for a lag to work, it will need to cut its own threads. Me no likey that idea. If you are going to use anything to cut new threads, it should be a tap. Tap the existing hole using whatever tap is able to leave threads in the present hole (metric or std/imp). Find a bolt that fits. Chop the head off the bolt and convert it to a stud then drill out the manifold to fit. If the manifold can't take a slight hole enlargement, then thread the new bolt into the head, mark how much sticks out. Now, the part that sticks out of the stud needs to be machined thinner so it can accept the original thread size. Thin out the bolt on either a metal lathe, a drill press and a file or grinder, of just a grinder. Cut the new threads. Done. The existing hole will help keep the tap straight, assuming you are doing your best to line it up in the first place. No helicoil, no right angle drill, no head removal, just a tap set, a bolt, and a grinder. Personally, I'd use the drill and helicoil method but this will work too.
Since it's aluminum and the threads are partially gone anyway, could you go at it by hand in a couple steps using a short reamer or two with a T-handle? Seems like it might be a simple way to keep the hole straight and prevent drilling into someplace you don't want drilled.
That's fine but , sometimes what your fixing only has to work for a short period of time , when you're done with it , you'll junk it . in that case however it gets done is good ! I have some junk that still works " fixed" like that ..Then again , I'm a fixer , not a " tech"
Like "Dirty Harry said".............."A man's got to know his limitations". The problem I have seen is that when things don't get fixed well, they usually manage to fail at absolutely the worst time for something to fail..........never happens in the driveway or 2 miles from home.
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