hrw blowing

[station tug]

hi.one of my heads is blowing from the cylinder/head joint...iv had it to bits twice now..re shimmed done the bump clearences had a straight edge over it.its blowing at the exhaust manifold side of the engine at the head barrel joint...cant see and cracks in the head....its a hrw4....i knew i should of fitted a twin!!!!

[Sir Nibble]

Tried blueing it?

[Chris Pink]

hi.one of my heads is blowing from the cylinder/head joint...iv had it to bits twice now..re shimmed done the bump clearences had a straight edge over it.its blowing at the exhaust manifold side of the engine at the head barrel joint...cant see and cracks in the head....its a hrw4....i knew i should of fitted a twin!!!!

 

Can you see where it's blowing?

 

I had a situation recently where the manifold stud had got so thin through being in salt air that the metal of the stub had got so porous it was blowing and i only discovered this when i put a fingernail through it.

[station tug]

Can you see where it's blowing?

 

I had a situation recently where the manifold stud had got so thin through being in salt air that the metal of the stub had got so porous it was blowing and i only discovered this when i put a fingernail through it.

 

 

hi chris, its blowing between the head and barrell between the back two cyinder head studs...iv tried new gaskets and put extra in to try and take up and difference.....its the best its been at the moment but not rite......

[Timleech]

hi chris, its blowing between the head and barrell between the back two cyinder head studs...iv tried new gaskets and put extra in to try and take up and difference.....its the best its been at the moment but not rite......

 

Sounds as though head and or barrel need skimming.

 

Tim

[TimYoung]

I have a number of HRW heads and barrels, if needed.

 

Tim

[soldthehouse]

You may have a "pull" which is a raised area directly around a stud or bolt hole preventing the head from sitting down tight at the point of contact where the pull is.

A pull occurs when a stud or bolt bottoms out and then raises the threads resulting in a raised area around the point of entry on the surface.

Sorry if I,m telling you something that you already know but these are common in engineering and will hold the gasket up if the gasket is cut tight around the stud holes.

Edited September 19, 2011 by soldthehouse

[Timleech]

You may have a "pull" which is a raised area directly around a stud or bolt hole preventing the head from sitting down tight at the point of contact where the pull is.

A pull occurs when a stud or bolt bottoms out and then raises the threads resulting in a raised area around the point of entry on the surface.

Sorry if I,m telling you something that you already know but these are common and will hold the gasket up if the gasket is cut tight around the stud holes.

 

Stuart, that's not applicable to the HRW, they have studs running right through from the crankcase. Also the gasket is just a ring around the top of the barrel, doesn't go near the studs.

Useful info for others with the problem though

 

Tim

[soldthehouse]

Stuart, that's not applicable to the HRW, they have studs running right through from the crankcase. Also the gasket is just a ring around the top of the barrel, doesn't go near the studs.

Useful info for others with the problem though

 

Tim

Thanks for the heads up Tim, as usual I didnt have any specific knowledge and without seeing the set up assumed a few things. Us amateurs shouldnt get involved in these threads and leave it to you pro,s

[onthecut]

Don't want to sound rude, but have you made absolutely certain that there are no fragments of carbon or rust etc. trapped between any of the shims / gasket / head ? Also, did the head appear to go down square ? If any doubts, take it back off and check you haven't got a slightly misplaced shim pinched over the edge of the barrel lip. If you do take it off again, carefully check the top of the barrel for any tell tale blow marks -- check also the mating surface has no pits etc. Remember if you are adding shims to try and get a better seal, you are reducing the compression and will be moving away from the specified bump clearance. Are you using new gaskets / shims -- if not, well worth doing so & they're dirt cheap by most marine standards. Also worth checking if you have it apart again, the state of the water tube seals -- they tend not to like being disturbed too often and if any signs of hardness or cracking, I'd replace those, too.

Good luck with it.

 

Mike.

[station tug]

hi ,

iv taken the head off...scrapped the head and barrel clean with a stanley blade..used vasoline to hold the shims and gasket to the head iv used extra shims in an act of despiration really.it always blows in the same place..i also had a friend who is merticulas when rebuilding engines and box's come and have a look.my initial fear was that the head bolts had pulled out of the block and this was causing the problem but we cant see a thing wrong....i think im going to run it untill it wont go any more and replace it with a twin that to be honest i'd much prefer...many thanks or your replies chaps

[TimYoung]

Hi,

 

I have some barrels and some heads if you might want to try a substitution.

I have been building an HRW4 from an HRW4 and an HRW6, so I have a few spare!

 

Tim