Head bolt problem !!!!!!

[osborne looney]

I AM WORKING ON AN 1987 470 170HP. WATER IN OIL . REMOVED WHAT NEEDED TO REMOVE TO TAKE OFF HEAD . ALL BOLTS CAME OUT WITH 1/2" IMPACT EXCEPT 1 THE ONE ON OUTSIDE CLOSEST TO THERMOSTAT I HAVE TRIED BREAKER BAR EVEN WITH 2' PIPE OVER IT -- HEATED BLOCK JUST A LITTLE WITH MAP GAS (DID NOT WANT TO GET BLOCK THAT HOT ) BUT NOW I AM THREATENING TO GO TO OXY/ACY TORCH !! JUST HOW WARM CAN I GET THIS BLOCK BEFORE DOING ANY DAMAGE TO IT ? OR A TRICK THAT I AM NOT AWARE OF ? THANKS

 

[NetDoc]

Re: Head bolt problem !!!!!!

Hopefully you are already using the ultimate maxim: Righty tighty, lefty loosey. Using a breaker bar with a short socket, whack the crap out of the top of the breakerbar/socket with a heavy brass hammer while applying your max pressure. A sharp jolt with all that pressure can give you the extra pop you need to break it loose. A friend will really help out with the logistics here. An oxy-acetylene torch gives me the willies, but it might be needed. In any case, I would replace the one head bolt and possibly all of them (especially if they are torque to yield). I would also chase a tap down the block. It might even require a helicoil.

 

[Lyle29464]

Re: Head bolt problem !!!!!!

Do search on removing bolts. I think that head is iron. If so it will take some heat. Lots of tricks on removing bolts. a little heat is good to help draw oil to the area. Heat then oil repete. A sharp tap is ok. acetone mixed with transmission fluid is great. I use break fluid in a saltwater area. turn down the air on your impact and let it hammer. drill a small hole in the head bolt so the lubricant can get to the problem area. do all of the things. reverse the wrench. when it comes lose keep it wet and dont try to hammer it all the way out nonstop more oil etc.

 

[osborne looney]

Re: Head bolt problem !!!!!!

Once i get head off the darn thing i am going to chase threads--will replace all head bolts only for the stretch factor ( cheaper than head gasket kit !!!) i have tried the whack with brass hammer maybe i need bigger hammer !! Sorry just frustrated with one stinking bolt !!

 

[achris]

Re: Head bolt problem !!!!!!

As a last resort drill the head off the bolt, lift the cylinder head off over the 'stud' and then you can work with the head out of the way and no load on the remainder of the bolt. I would be reticent to use oxy. The block is ali and that will heat up nicely. The only problem is that the difference between the ali being warm and the ali being a pile of molten metal is about 1.2 seconds. The use of any heat is not recommended because the one thing you do not want to do is the heat the head and cause it to expand. That will just lock the bolt in even tighter.

Chris.......

 

[BaileysBoat]

Re: Head bolt problem !!!!!!

As a last resort drill the head off the bolt, lift the cylinder head off over the 'stud' and then you can work with the head out of the way and no load on the remainder of the bolt.

Chris.......

Important point being the seized bolt is easier to remove with no load, so re-install and torque the head, then start to remove the seized bolt. Impact wrench can sometimes snap a seized bolt free better than a breaker bar.

 

[Pete104]

Re: Head bolt problem !!!!!!

I'm leaning towards the bolt being rusted to the head. The head bolt is threaded into aluminum. The threads are already junk most likely.
Try heating with oxy/ace the head, not so much the bolt but you can't help it. Get it hot, the head & bolt, and quench it with ice. It's gotta be hot hot but not glowing, then dump the ice & keep it on it. I like impact (air) with torque turned down slightly and let it rap on it.

 

[osborne looney]

Re: Head bolt problem !!!!!!

I'm leaning towards the bolt being rusted to the head. The head bolt is threaded into aluminum. The threads are already junk most likely.
Try heating with oxy/ace the head, not so much the bolt but you can't help it. Get it hot, the head & bolt, and quench it with ice. It's gotta be hot hot but not glowing, then dump the ice & keep it on it. I like impact (air) with torque turned down slightly and let it rap on it.

i am leaning towards the heating head myself -- as i will try it this morning , heat has always worked in the past for me to free bolts & nuts that are stubborn . i tried map gas but that did not get hot enough or it would of popped so i really am left with no other choice. i will let you know the turn out thanks for the info.

 

[osborne looney]

Re: Head bolt problem !!!!!!

well tried a lil more heat this morning and beat the snot out of breaker bar with little pressure against it ,then hit it with impact with 200 psi on it and it popped loose but i see NO EVIDENCE of bad head gasket or visible cracks in head or block i am assuming the head gasket was bad or intake gasket ? just a little little rust built up at top of cylinder #4 ? problem bolt was #1 cyl next to t-stat -this thing overheated so i was told after replacing gasket i assume it would be a good idea to replace impeller pump in lower unit ?

also when i re-install head bolts should i use never seize or oil or hi-temp silicone ? or just plain clean and dry ?

 

[fmalott]

Re: Head bolt problem !!!!!!

when the 470 head gasket goes it's the #4 the goes first if you seen rust in #4 then head gasket blown. use a tap and die to clean threads and my opion keep dry. guys correct me if i'm worng there is a plug behind #4 that rust out that creats problems for #4

 

[osborne looney]

Re: Head bolt problem !!!!!!

when the 470 head gasket goes it's the #4 the goes first if you seen rust in #4 then head gasket blown. use a tap and die to clean threads and my opion keep dry. guys correct me if i'm worng there is a plug behind #4 that rust out that creats problems for #4

if you could define plug ? do you mean frost plug type plug ? i have not looked at yet but if this is what you mean i will look at it .

 

[stonyloam]

Re: Head bolt problem !!!!!!

If you don't have it, here is a link to the manual: http://www.4shared.com/document/zTbCbkDD/Service_Manual_08.html It doesn't have to look blown. Just look for a dark stain under the head gasket, will indicate a problem. While you have it apart it might be a good time to change the reservoir/exhaust gasket. Make sure you get the right one, either aluminum or cast iron manifold, whichever you have. Bolts go in dry, make sure there is no fluid in the bolt holes. A good substitute for perfect seal (for the instillation) is NAPA (Permitex) aviation sealant. Make sure you follow the torque sequence in the manual and retorque after bringing the engine up to operating temperature. It is recommended to use the OEM Mercruiser head gasket. That little plug is a casting plug, and can rust out. If it does it blows the exhaust from #4 directly out. You might want to check to make sure it is in good shape, is kind of a PITA to replace with the head on, no real problem, but the loud noise is a WTF moment LOL. Good luck.

 

[osborne looney]

Re: Head bolt problem !!!!!!

If you don't have it, here is a link to the manual: http://www.4shared.com/document/zTbCbkDD/Service_Manual_08.html It doesn't have to look blown. Just look for a dark stain under the head gasket, will indicate a problem. While you have it apart it might be a good time to change the reservoir/exhaust gasket. Make sure you get the right one, either aluminum or cast iron manifold, whichever you have. Bolts go in dry, make sure there is no fluid in the bolt holes. A good substitute for perfect seal (for the instillation) is NAPA (Permitex) aviation sealant. Make sure you follow the torque sequence in the manual and retorque after bringing the engine up to operating temperature. It is recommended to use the OEM Mercruiser head gasket. That little plug is a casting plug, and can rust out. If it does it blows the exhaust from #4 directly out. You might want to check to make sure it is in good shape, is kind of a PITA to replace with the head on, no real problem, but the loud noise is a WTF moment LOL. Good luck.

will do and thanks for the link !! although i probably wont to get to it till tue or wed of next week thanks again

 

[Lyle29464]

Re: Head bolt problem !!!!!!

Do a search on here "470" you will find other things to look for while your apart plus tons of info on that motor.