# 74 GTO Exhaust Manifold Broken Bolt and Pulling Heads



## Red74Goat (Jul 31, 2015)

I have a '74 GTO and was removing the old headers (I had previously soaked all bolts for several days with PB) when the front bolt on the drivers side broke off flush with the head, all other bolts came out easy. I've been trying to mig weld a hex nut on top of the broken off stud, but the tightness of the work space makes getting a good angle for the weld just about impossible, so the hex nuts break off due to poor welds (I'm not a particularly good welder, so that doesn't help!) No room to get a punch and hammer or drill into the space either. 

After six days of laying under the car trying to get a good weld, I'm getting pretty close to resigning myself to pulling the head to get the broken stud out. 

The engine/car has less than 30,000 miles on it and is relatively stock, so I don't want to have the heads milled at this point. With an advertised 7.6:1 CR, I have considered putting thinner head gaskets on to raise the compression a bit and possibly install a Summit 2800 cam while I have things apart. 

Any other thoughts about other possible mods while I have the heads out and the top end torn apart a bit? I'm not looking for anything radical, more interested in dependable. I haven't quite given up yet on getting the broken off bolt out while head is still on the engine, but getting close.

Thanks


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## BearGFR (Aug 25, 2008)

7.6:1 is WAY low, if that's what it really is. You can't go TOO thin on head gaskets without come careful measuring of things like piston to deck clearance at TDC and piston to valve clearance. You'll want to make sure you have 0.032 to 0.035 (at least) piston to head clearance. Bad things tend to happen when a piston whacks the bottom of the cylinder head.

If you can't get at the bolt to drill it and work it with an EZ out, you may indeed be looking at pulling the head. Be sure to drain the cooling system first, including the drain plugs on the side of the block. Have you tried using an angle drill? (Like one of these...


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## Red74Goat (Jul 31, 2015)

BearGFR said:


> 7.6:1 is WAY low, if that's what it really is. You can't go TOO thin on head gaskets without come careful measuring of things like piston to deck clearance at TDC and piston to valve clearance. You'll want to make sure you have 0.032 to 0.035 (at least) piston to head clearance. Bad things tend to happen when a piston whacks the bottom of the cylinder head.
> 
> If you can't get at the bolt to drill it and work it with an EZ out, you may indeed be looking at pulling the head. Be sure to drain the cooling system first, including the drain plugs on the side of the block. Have you tried using an angle drill? (Like one of these...


Bear, thanks for the advice on thin head gaskets, yep I bet that pistons hitting valves thousands of times per minute probably changes the shapes of those things pretty quickly! :smile3:

I spent some more time last night removing more things, like the PS pump, to give me a little more room to work. Unfortunately, the shock tower and the sub-frame cross member for the motor mounts lines up very nicely with the 1st exhaust head bolt location. I will likely end up removing the front clip for better access to the head before I pull the head off. I have a 90 angle drill, but may see if I can get a smaller one to fit in the space better.

Thanks


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## Pinion head (Jan 3, 2015)

For over a decade, I pulled 6X-4's & included them with generic code 400 shortblocks selling them to a major Pontiac engine builder. In the yards, I always popped the original ex man bolts, good, with my mini sledge jarring the threads slightly before carefully removing the ex man bolts with a long ratcheting breakover. Never broke an ex manifold bolt this way. During this time, also picked up loose heads from storage racks in salvages and from two monster engine core businesses. Some of these heads did have broken ex bolts. Broken exhaust manifold bolts can be drilled out, but it's a ton easier, with perfect results, when the head is off and at a machine shop. My machinist had a quick asm fixture he used on his drill press to do this. In your shoes pull both heads, take them to a Pontiac savvy shop, have the 46's treated to a good valve job, consider milling the head's slightly, and have the bolt properly drilled out, this would easily save wallowing the hole out and having to mess with a helicoil.


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## Red74Goat (Jul 31, 2015)

BearGFR said:


> 7.6:1 is WAY low, if that's what it really is. You can't go TOO thin on head gaskets without come careful measuring of things like piston to deck clearance at TDC and piston to valve clearance. You'll want to make sure you have 0.032 to 0.035 (at least) piston to head clearance. Bad things tend to happen when a piston whacks the bottom of the cylinder head.
> 
> If you can't get at the bolt to drill it and work it with an EZ out, you may indeed be looking at pulling the head. Be sure to drain the cooling system first, including the drain plugs on the side of the block. Have you tried using an angle drill? (Like one of these...


Bear, I understand draining the cooling system, why also the drain plugs on the side of the block?
Thanks


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## BearGFR (Aug 25, 2008)

Red74Goat said:


> Bear, I understand draining the cooling system, why also the drain plugs on the side of the block?
> Thanks


Because just draining from the radiator petcock won't get all the coolant out of the heads and down below the deck surface. If you pull the heads with it like that, you're going to dump a bunch of coolant down into the cylinders.

Bear


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## Rukee (Feb 8, 2007)

BearGFR said:


> Because just draining from the radiator petcock won't get all the coolant out of the heads and down below the deck surface. If you pull the heads with it like that, you're going to dump a bunch of coolant down into the cylinders.
> 
> Bear


.....and the oil pan.


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## Red74Goat (Jul 31, 2015)

Rukee said:


> .....and the oil pan.


Bear and Rukee,
Got it. That explains it pretty well.
Thanks


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## Red74Goat (Jul 31, 2015)

Any suggestions for good head gasket brands?

Thanks


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## Red74Goat (Jul 31, 2015)

Will be pulling the heads soon. Just removed the coolant drain plugs from the sides of the block; that was interesting. 

They had never been removed before, but they did come out easily with a socket. Had to remove the starter to get to the driver's side plug. 

Last year I had a problem when I replaced an Edelbrock aluminum intake manifold with the original Pontiac cast iron intake -- I didn't get the bolts torqued tight enough when I swapped manifolds :banghead:, leading to oil in the cooling system. I used Simple Green to flushed the system, then flushed it with water 6x, finally refilling it with 50/50 distilled water and coolant.

When I removed the drain plugs today, nothing came out, so I thought, "hmmm, where's the coolant?" I looked and saw a "plug" of oily goo in the drain plug holes. I used a piece of wire to reach around and jiggle around through the holes until coolant started to come out; once it started coming out the coolant picked up speed and they both drain holes seemed to drain well with normal colored coolant. 

I have a total of 3.5 gallons of coolant out of the engine and radiator. The manual says the total coolant capacity is 5 gallons--any idea where the other 1.5 gallons are at? Does the 5 gallons total count the overflow reservoir content?

Thanks,
Dan


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