Topic: Think this head needs to be decked?

[kidrcth]

So while cleaning the surface of my head i found a rather odd condition near one of the cylinders. Every other cylinder the entire way around is perfectly flat. this one has a slightly eroded area or something.

Looking back at a picture from 3 years ago when i took the head off, it is obvious there is a lot of carbon buildup in the area. Is this the cause or the effect?

[chewbacca5000]

Not sure what you are talking about here.  Are you referring to the black gasket material on the head?  All that needs to be removed before you can check for flatness.

[kidrcth]

my appologies, ill outline it.

i know its not gasket material, because if i spray it, and then go over it with a blase, the edges come clean, and the center stays the same.

[chewbacca5000]

For a high spot in the combustion chamber smooth it out.  Other wise put a head gasket on it and use black marker and trace around the inside.  Chances are it won't matter.

[kidrcth]

thats why i posted a picture with the head gasket on. Head gasket metals lay exactly where the imperfection is.

guess ill goto the store and get some feeler gauges and see how bad the head is overall.

Straight and a flashlight trick shows its pretty flat, but i need to know.

[chewbacca5000]

thats why i posted a picture with the head gasket on. Head gasket metals lay exactly where the imperfection is.

guess ill goto the store and get some feeler gauges and see how bad the head is overall.

Straight and a flashlight trick shows its pretty flat, but i need to know.

I normally put a piece of flat aluminium angle on the head and check it that way.  I can't tell from the photo if that is a high spot or a low spot.  I'd clean it up and make sure there are no sharp edges and bolt it back up.

[bwaller]

The area you marked is a result of a chemical reaction with carbon/air/moisture and don't ask me more.  It sure doesn't hurt to get the surfaces machined but it isn't necessary to remove much.

[kidrcth]

So i went to the store and got a straight and super small feeler gauge set.

Came home my mechanic neighbor was outside, brought it to him and turns out, he used to be a machinist so he got the same tools i just bought out, and we measured. The impression is .003" deep because a .004" will not fit. Which is way below the spec that manufacturer says needs resurfaced. The manual says anything over .009 will not pass.

Feeling much better about it now.

[mystic_1]

BTW that 0.009" figure is more "maximum warpage across the whole face of the head" as measured with a long straight edge.

That said, I'm sure you'll be fine with those marks.  I've seen worse, and as you point out they're under the fire ring, which is the thickest part of the gasket, and that is probably what cause them in the first place 

As long as everything else is in good shape you should be GTG

mystic_1

[kidrcth]

BTW that 0.009" figure is more "maximum warpage across the whole face of the head" as measured with a long straight edge.

That said, I'm sure you'll be fine with those marks.  I've seen worse, and as you point out they're under the fire ring, which is the thickest part of the gasket, and that is probably what cause them in the first place 

As long as everything else is in good shape you should be GTG

mystic_1

yeah i mean i understand the idea of serviceable limit. However, the area just next to the imperfection has a gap of only .002. that area i was worried about is only .003. So i'm not so worried about it.

I am not a perfectionist my any means, but i work on helicopters daily. Specifications are out lifeline, things are checked constantly. they are followed like your life depends on it.

[strynboen]

looks like the sqvis band effekt goes to far aut..and make" calvaision".(.dont got the english vord  )vho remove material..by vaccum/ pressure kollapsing make small explosions
the best is to get the gasket to fit the head perfekt..evt machine 1 mm of the head..to make perfekt fit of the gasket..eventuell veld some matrile inn..to make it easyer

are all gaskets same desein..i have seen variasions on other brands of engines..hvere not all gaskets set fits all years engines

[mystic_1]

yeah i mean i understand the idea of serviceable limit. However, the area just next to the imperfection has a gap of only .002. that area i was worried about is only .003. So i'm not so worried about it.

I am not a perfectionist my any means, but i work on helicopters daily. Specifications are out lifeline, things are checked constantly. they are followed like your life depends on it.

Excellent, I'm sure you're on top of it, then.  Didn't want to just assume  

looks like the sqvis band effekt goes to far aut..and make" calvaision".(.dont got the english vord  )vho remove material..by vaccum/ pressure kollapsing make small explosions
the best is to get the gasket to fit the head perfekt..evt machine 1 mm of the head..to make perfekt fit of the gasket..eventuell veld some matrile inn..to make it easyer

are all gaskets same desein..i have seen variasions on other brands of engines..hvere not all gaskets set fits all years engines

strynboen I suspect the word you may be looking for is "cavitation"?  http://en.wikipedia.org/wiki/Cavitation

In other words, the fire ring of the gasket is larger than the bore, so when you assemble, a gap or cavity is formed there between the top of the cylinders, the underside of the head, and the metal fire ring?  And then when combustion occurs, a pressure wave hits this cavity at high speed and does Bad Things to the metal over time, cumulatively?  This would seem to make a lot of sense to me.

mystic_1

[kidrcth]

Sorry for my misspellings throughout this post and thank you for your help.

I'm sure the head will be fine

[alacrity]

imho you wanna weigh the (POTENTIAL) value of your time and the cost of another head gasket and o-rings vs the cost of taking that head to a machine shop to have it surfaced before assembly.
It MIGHT be perfectly fine for the next 50,000 miles.  It might not.  I would think of it as relatively inexpensive way to buy some piece of mind.

[kidrcth]

imho you wanna weigh the (POTENTIAL) value of your time and the cost of another head gasket and o-rings vs the cost of taking that head to a machine shop to have it surfaced before assembly.
It MIGHT be perfectly fine for the next 50,000 miles.  It might not.  I would think of it as relatively inexpensive way to buy some piece of mind.

i agree, and normally i do that. Normally i am ok with piece of mind. But the measurements checked out fine, and a machinist looked at it the same way i did and told me it would be fine. Either way, the pieces are just not being painted, they wont be installed for at least 2 weeks prolly. My engine build is rather slow and mythological.