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Hi.
I have a blown head gasket on my 1968 gto. I need to know is when I take the head to the machine shop.to have the head fix? what would it consist of? what I mean by this! like: valve job, surfacing the head and complete inspection for crack or just surfacing it only??? Thanks
 

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Hi.
I have a blown head gasket on my 1968 gto. I need to know is when I take the head to the machine shop.to have the head fix? what would it consist of? what I mean by this! like: valve job, surfacing the head and complete inspection for crack or just surfacing it only??? Thanks
What makes you think the head was the problem that caused the blown head gasket and not a block issue?

Need much more info. Original engine? Rebuilt engine? Did it over heat? Pictures of the block surface? Pictures of the head surface?
 

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I bought the car, drove about 3 to 400 miles. Next thing I notice is that white steam coming from the exhaust, i took it to the mechanic he pressure checked it and said it's a blown head gasket, He also said the engine was rebuild. So I have another mechanic will do the work on it. i am just curious when I take this head to a machine shop what would the machine shop will do to the head? are they just going to just surface the head only or they will do the valve job and whatever it needs???
 

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Most Mashine shops do rebuild the whole head valves, springs etc and hardened seats for today’s crappy fuel.But I think what Jim is pointing at is it could be something else,cracked head or worse the block. Wish you luck Figi
 

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Any idea how long ago it was rebuilt? If it was recent maybe you'll get lucky and it's something as simple as they didn't torque the heads down. Keep us posted, and pictures while it's apart. The guys on here may see something that could help you out.
 

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Don't think that it will be the worst case scenario, as it may just be something real easy.

Take apart the head carefully and pay attention as you remove the head bolts, head, gasket. It may indeed be as simple as a head bolt was not torqued down correctly.

Check the head bolts and see if they are the factory bolts or aftermarket ARP head bolts. It is possible that the threads in the block were not properly cleaned with a "thread chaser", - NEVER use a tap to clean threads, only a "thread chaser." The holes the head bolts go into are called "blind holes" as they do not go into the water jacket like other makers do which requires a sealant on the threads. Look down into each head bolt hole in the block after you pull the head and make sure nothing has fallen into it, like gasket scrapings, metal shavings, a nut, clump of dirt, etc. which might not let the head bolt tighten all the way down.

Check for excessive oil in the bolt hole. When you insert head bolts, some will put a light coat of oil on the threads. You should wipe the threads of any excess oil. But if someone did not know what they were doing, they could have put too much oil and the excess will drip into the block bolt hole and fill up the hole, however slight. When the engine gets hot, that oil wants to expand and has no where to go. The pressure can be high enough to crack/split the bolt hole and now you have a water leak coming from that bad head bolt hole.

Sometimes the head bolts can be too long and will bottom out and not torque down. This can happen if the head was milled excessively, or the previous owner used ARP head bolts and ordered the RA IV head bolts which have a couple bolts too long - I did this myself and put hardened washers under the heads of the bolts that were too long and then was able to torque them down. So you want to pay attention to the head bolts and the length. You should be able to insert all the head bolts with the head off and they will all be even. Photo enclosed showing this.

Do not remove the head gasket until you examine it. It may stick to the block or stick to the head, it does not matter. The cylinder that had the water leak should have a lot less carbon on the top of the piston so that will give you a clue as to which cylinder(s) to focus on. Just take a look at it and you may see right away what the problem is. It could be burned between cylinder bores, water stained, or even hanging into the cylinder because the head gasket bore size selected was too small as head gaskets do come in different bore sizes. Then look at the opposite surface, either head or block, and take a look at where the bad area of the gasket sits. Damage, crack, burned, etc.? What you are doing is trying to determine the cause of the bad head gasket. Could be as simple as the previous owner sat on the head gasket, put a dimple/crimp in it and it did not seal because it was damaged before installing it.

Make sure the block has 2 dowel pins - one on each end to align the head on the block. Sometimes these can be pulled out or knocked down/in and don't get replaced. If they are not there, the head/gasket could shift and cause a gasket failure. The bolt holes in the head are not a perfect fit to the head bolt, so you have a little wiggle room and they cannot replace what the dowel pins are designed to do - so make sure they are there.

If nothing seems out of place, take the head to the shop. They may or may not disassemble it to level the surface. They will measure it first and check for warpage. It may be OK and nothing needed. It may be slightly warped and they can surface grind the head just enough to take out the warpage. They don't have to disassemble the head to do this, They will put it on the milling machine and run a pass over it, then wash it thoroughly. But, it would be their call as they also may prefer to disassemble as is their practice - you will have to ask them.

At that point, your machine shop should be able to advise you on what to do or what your options are. Just hope for the best and it might be simply a bad head gasket.(y)

Head bolts sticking out evenly.JPG
 
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