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L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

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Old 03-30-2002, 10:43 AM   #1
VetteDrmr
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Default HELP!! I've got 2 exhaust bolts broken off in my LT-1 head

I know, it's not C4 specific, but it's an LT-1 engine, and I'm in trouble! I've got two exhaust manifold bolts broken off, both on the #7 exhaust. Looks like one has been broken for quite some time (maybe before I bought the car 2 1/2 years ago), while the head of the other one popped off this week.

As tight as the other bolts have been coming out, there's no way I see other than pulling the head to get these babies out. But, once I have the head off, how do I go about getting them out? My Helms manual was of NO help (first time it's totally let me down). The customary answer is that you use heat to loosen up a joint, but that advice has always been for steel on steel joints. What about aluminum on steel? What about warping the head?

I do virtually all the work on my car, but I'm not sure I'm up to this one.

Thanks for any help,
Mike
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Old 03-30-2002, 10:48 AM   #2
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Default Re: HELP!! I've got 2 exhaust bolts broken off in my LT-1 head (VetteDrmr)

you re gonna have to tap them. you may need to pull the heads. I wish I could offer some help on this one
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Old 03-30-2002, 11:15 AM   #3
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Default Re: HELP!! I've got 2 exhaust bolts broken off in my LT-1 head (My 95)

Yep, pulling the (driver's side) head is already on the list of things to do. The only thing I've thought of is putting in a heli-coil insert, since the bolts are only torqued down to 26 ft-lbs.

Others have suggested a machine shop, but I don't know what they'd be able to do, other than drilling it out.

Thanks for the speedy reply (even if it's confirming my worst case scenario),
Mike
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Old 03-30-2002, 11:19 AM   #4
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Default Re: HELP!! I've got 2 exhaust bolts broken off in my LT-1 head (VetteDrmr)

A machine shop would drill them and retap...they should also retap the others while they have the head...use anti seeze when you put it back togther.
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Old 03-30-2002, 11:24 AM   #5
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Default Re: HELP!! I've got 2 exhaust bolts broken off in my LT-1 head (JonM)

If you drill them, then use an easy-out, why would you need to tap and install a heli-coil? I would recommend a stakeing style easy out. It has 4 sharp edges that cut into the hole you drill in the broken bolts.

Make sure you drill a large enough hole in the broken bolt that you take out a lot of material, but small enough that you don't cut the threads that are in the head. Drilling the bolt removes pressure on the bolt threads, and add heat to the bolt due to friction. Easy outs are sized for specific size bolts. You can buy a whole set for ~$15.
:seeya Purp
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Old 03-30-2002, 11:29 AM   #6
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Default Re: HELP!! I've got 2 exhaust bolts broken off in my LT-1 head (PurpleC4)

Hmm. The other bolts were so tight coming out in one piece that I didn't think an easy-out would have a chance. I didn't think about reducing the strength of the existing bolt to the point that it'll come out, but it's worth a shot.

Any other ideas, these are fantastic help (regardless of which way I go).

Thanks, and have a good one,
Mike
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Old 03-30-2002, 11:44 AM   #7
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Default Re: HELP!! I've got 2 exhaust bolts broken off in my LT-1 head (VetteDrmr)

The problem I see with using the easy out method is getting the bolt center punched and drilling it out using a hand drill. Unless you have a drill press you can clamp it to. Lets see...give the machine shop a few bucks to do it and take the reasonability, or do it yourself and take a chance you do it right. You only get one shot...How much does an Aluminum head cost?
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Old 03-30-2002, 12:16 PM   #8
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Default Re: HELP!! I've got 2 exhaust bolts broken off in my LT-1 head (VetteDrmr)

Is the bolt broken off flush with with the cylinder head or is did the head of the bolt seperate from the body? If first, a machine shop is probably your best bet as they can spot face the top of the bolt and then center drill it, followed bydrilling to tap size and retapping or extracting the remainder. Have to do this often in my field of work. Kind of a PIA but best way if the part has to be saved. If latter remove all other bolts and take off exhaust manifold, soak bolt with PB Blaster and remove with Vise Grip. Dave
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Old 03-30-2002, 12:42 PM   #9
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Default Re: HELP!! I've got 2 exhaust bolts broken off in my LT-1 head (GS583)

When this happened to us (it was in the cylinder head but from intake manifold bolts) we welded a bolt to the 1/4" of marred metal that was sticking out from the head. When we got good enough penetration on the weld the bolt turned it all out! This could be an option if any metal is above the surface of the cylinder head.
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Old 03-30-2002, 04:42 PM   #10
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Default Re: HELP!! I've got 2 exhaust bolts broken off in my LT-1 head (GS583)

Dave,

Actually, I've got one of each kind. The stud that's protuding has been soaking since last night; I'm hoping it'll come out via Vise Grips. Of course, that doesn't solve the problem of the one broken off flush.

JonM,

I'll be using either a drill press or mill to hold the head while (if) I drill this out myself. Of course, I've got to get the head off first. ;)

Thanks so much for the suggestions,
Mike
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Old 03-30-2002, 06:55 PM   #11
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Default Re: HELP!! I've got 2 exhaust bolts broken off in my LT-1 head (VetteDrmr)

TO: Lucky Guy
Well this might not have been your best day but, perhaps I can make a suggestion to prevent a repeat. You have been using the term "Bolts" to describe what I call a "Cap Screw" That is, one end is threaded and screws into the aluminium head and the other end has a hex "cap" for a wrench or socket. This, of course, causes a mismatch of materials when the threads are tightened and the result is called "galling", meaning that the steel threads have pulled some of the aluminium material into the steel and this almost bonds the two metals together. This is why they are difficult to get out. I would bet that someone used common oil to assemble the parts. Oil actualy promotes the galling process. If you have nothing else to use, try kerosene, but never oil. Everyone elese has made excellent suggestions on how to get the broken off piece out, now here is what I do to prevent the problem from happening again.

1) Run a "bottoming tap" of the correct size into the threaded hole, using lots of kerosene or WD-40 to rinse out any chips that break loose.
2) Blow out the hole with air.
3) Buy some exhaust manifold "Studs" of the appropriate length and thread size.
4) Get a tube of "Anti-seize" lubricant and apply it to the end of the stud that goes into the head. Now install the studs to about 5 lb torque more than specified for the original cap screws. You can "jam" two nuts on the other end of the stud to give you a hex head to torque with.
5) Install your gaskets and manifold using new matching nuts and torque to the specified value. Be sure you have all the nuts started before you tighten any, sometimes you will find it difficult to position a nut after the manifold is tight against the head.
Sorry this was so long, I had to learn it the hard way :crazy: :yesnod:
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Old 03-30-2002, 07:04 PM   #12
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Default Re: HELP!! I've got 2 exhaust bolts broken off in my LT-1 head (Vette9d1)

vette9d1 has a very good suggestion.

If that does not work, I have drilled out a broken accessory mount bolt from one of my my Brodix Al heads a few years back. I drilled the entire bolt out and then inserted helicoils to replace the threads.

Brodix is pretty good, they came with helicoils in every header bolt hole...but just the tapped holes for the accessory bolts.
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Old 03-30-2002, 11:41 PM   #13
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Default Re: HELP!! I've got 2 exhaust bolts broken off in my LT-1 head (myblack864+3)

Quote:
3) Buy some exhaust manifold "Studs" of the appropriate length and thread size.
Unfortunately, the LT-1 in an f-body is so tight that studs can't be used as there isn't enough room to get the manifolds off. In fact, one of the broken bolts failed at the head, and I had to spend the better part of an hour with a hacksaw nibbling part of the remainder off so I could get the manifold off.
Quote:
4) Get a tube of "Anti-seize" lubricant and apply it to the end of the stud that goes into the head.
Believe me, I use anti-sieze on EVERYTHING that bolts into this engine.

Have a good one,
Mike
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Old 03-31-2002, 12:00 AM   #14
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Default Re: HELP!! I've got 2 exhaust bolts broken off in my LT-1 head (VetteDrmr)

No matter what, you have to drop the exhaust manifold. When that's out of the way, check to see if you have a stud protruding from the heads. If you do, you're in luck. Saturate the stud in PB Blaster penetrating oil and let it sit over night. Give the stud a few firm taps with a metal hammer. The shock from the hammer blow will losen the treads. Get yourself a stud installer/remover tool. Slip it over the stud with a T-handled wrench and apply even torque to the tool. You won't have to drill anything so long as you have a stud that sticks out from the head. I would say that's you best hope. If the stud is even with the heads, get yourself a set of cobalt drill bits and Snap-On or Mac extractors. Don't mess around with any other tool brands. You only get one shot at making a clean stud extraction and Snap-On and Mac are worth the money they charge. Then again, you could yank off the heads and drop them off at a machine shop. Just make sure they can EDM (electro discharge milling) the studs. EDM is the best way to extract a bolt/stud. It won't matter what grade bolt it is, EDM will eat right through it.
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Old 03-31-2002, 09:32 AM   #15
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Default Re: HELP!! I've got 2 exhaust bolts broken off in my LT-1 head (M2001)

Quote:
Just make sure they can EDM (electro discharge milling) the studs. EDM is the best way to extract a bolt/stud. It won't matter what grade bolt it is, EDM will eat right through it.
Never heard of EDM. How does it extract the steel bolt without harming the aluminum threads?

Thanks for the advice, I do have one stud sticking out about 3/8ths (actually had to hacksaw a bit off just to get the manifold off), but it's partner is broken off flush (and has been for a long, long time).

Have a good one,
Mike
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Old 03-31-2002, 12:26 PM   #16
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Default Re: HELP!! I've got 2 exhaust bolts broken off in my LT-1 head (VetteDrmr)

I
Quote:
Hmm. The other bolts were so tight coming out in one piece that I didn't think an easy-out would have a chance. I didn't think about reducing the strength of the existing bolt to the point that it'll come out, but it's worth a shot.

Any other ideas, these are fantastic help (regardless of which way I go).

Thanks, and have a good one,
Mike
I've broken easy outs before.
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Old 03-31-2002, 01:16 PM   #17
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Default Re: HELP!! I've got 2 exhaust bolts broken off in my LT-1 head (VetteDrmr)

EDM is an electrical method of removing metal. When a stud is EDM'd, the only thing that will be left in the heads will be the studs threads that will be picked out. What you have left in the head will look like a heli-coil.

Although you can certainly use the old fashion way off drilling out the old studs and use an EZ-Out extractor, I just want to make sure to avoid the use of heil coils. Even machine shops make mistakes while drilling out old broken studs. It seems the EDM method is more accurate way of removing a stud. There's nothing wrong with using a heli-coil if you mess up the process of extracting a broken stud. I just don't want to use heli-coils on my car, even though all the threads on my cars head have heli-coils for the rocker arm studs. I guess GM had to do something with all those old press in rocker arm stud style heads. Imagine, 16 heli-coils between a pair of heads.... :cuss


[Modified by M2001, 11:24 AM 3/31/2002]
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Old 04-01-2002, 12:56 AM   #18
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Default Re: HELP!! I've got 2 exhaust bolts broken off in my LT-1 head (VetteDrmr)

An Update: First off, thanks so much for your on-going suggestions. I've finally got the head off, and am going to take it to a shop to have the bolt remnants removed. I had all the tools I thought I'd need (penetrant, heli-coil kit, drill bits, etc.) except I couldn't find a drill press/milling machine available (I live at an airport) that could securely hold the head while drilling. As they say in the beer commercials, "not so good." ;)

Anyway, the hardest part so far has been getting the stupid banjo bolt out of the coolant cross-over tube in the back of the head. F-bodies are so cramped for room that it took me almost an hour to get that sucker removed, and at that the head is rounded enough (no way to get a straight pull on it) that I'm going to replace it.

On a positive note, the valve train, combustion chambers, and pistons look to be in excellent condition (not that I had any symptoms of any problems), so it looks like I've just got to get these bolts out and start putting things back together. Also, my intake valve leak fix was clean and dry for the last 50,000 miles.

Have a good one,
Mike
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Old 04-02-2002, 10:54 AM   #19
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Default Re: HELP!! I've got 2 exhaust bolts broken off in my LT-1 head (VetteDrmr)

An update: I was able to get the "stud" out of the block with a pair of vise grips. Then I took it to a shop to get the one out that's broken off flush. Plan A was to get a good centered hole drilled and try an easy out. No luck, it was in way too tight. So, on to Plan B, which was to drill out the metal out to the threads and then remove the remaining material with a tap. Plan B worked well until the tap got jammed and ended up breaking. So, now they're on to Plan C, which is to heli-coil it (which is what I figured we'd have to do once the easy out didn't work).

This experience once again shows the value of this forum. The $30 I'm going to spend to have a machine shop deal with this is WAY less than the heartburn I'd have gone through trying to do it myself.

Thanks again for all the suggestions, and have a good one,
Mike
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Old 04-02-2002, 11:12 AM   #20
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Default Re: HELP!! I've got 2 exhaust bolts broken off in my LT-1 head (VetteDrmr)

I've broken an ez-out before, talking about getting pissed :cuss

The last time I broke one off in my TB, I just center tapped it and started with a very small drill bit and worked my way up until I was close to the threads and used an ez-out, then re-tapped just to make sure it was clean. Seems to be hit or miss with those things and ez-taps will not drill out, they are hard as hell.
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Old 04-02-2002, 11:12 AM
 
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