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Old 07-16-2012, 04:19 PM
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What does this look like?

Hey I was wondering if you guys could help me out here. My buddy sent me a picture of this head he was given (I think I know why). Its a B16 honda head and is loaded with all the aftermarket goodies. Can you explain what the pitting is around the edge of the chamber? Also looks like there may be a crack forming on the edge too but I will have to check it to be sure. He is planning on having the combustion chamber welded up to a clover design for more compression but just curious as to what causes this. Thanks!
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Old 07-16-2012, 04:22 PM
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Quote:
Originally Posted by zildjian4life218 View Post
Hey I was wondering if you guys could help me out here. My buddy sent me a picture of this head he was given (I think I know why). Its a B16 honda head and is loaded with all the aftermarket goodies. Can you explain what the pitting is around the edge of the chamber? Also looks like there may be a crack forming on the edge too but I will have to check it to be sure. He is planning on having the combustion chamber welded up to a clover design for more compression but just curious as to what causes this. Thanks!
Not real sure looks like it's coming apart to me.JMO what does the block look like ?



Cole
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Old 07-16-2012, 05:00 PM
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Quote:
Originally Posted by zildjian4life218 View Post
Hey I was wondering if you guys could help me out here. My buddy sent me a picture of this head he was given (I think I know why). Its a B16 honda head and is loaded with all the aftermarket goodies. Can you explain what the pitting is around the edge of the chamber? Also looks like there may be a crack forming on the edge too but I will have to check it to be sure. He is planning on having the combustion chamber welded up to a clover design for more compression but just curious as to what causes this. Thanks!
That's not unlike "fretting" (sometimes called brinelling but I'm unsure if that's a correct term for this or if it's false brinelling or neither), where the fire ring of the head gasket erodes away some of the material of the head caused by small movement of the head in relation to the head gasket. It can be from using a HG w/the wrong type fire ring (not pre flattened, for example), or from insufficient fastener torque or the fasteners are unable to contain the compression (see this when spraying w/nitrous).

That may be a mar and not a crack but I'd definitely do a dyeglo test on it to be sure. The damage looks to be shallow enough that milling the head should remove most if not all of it, and if he's looking to raise the CR anyway (as long as it won't make the deck too thin) that shouldn't be a problem.
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Old 07-16-2012, 05:11 PM
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Pitting is on chamber side of the fire ring. Probably from moisture (water) or possibly a small bit of something got loose in the cylinder.. A mild cut (.002-.005") will remove it if you are concerned. Most Honda heads can't be cut more than .008"
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Old 07-16-2012, 05:32 PM
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Pitting is on chamber side of the fire ring. Probably from moisture (water) or possibly a small bit of something got loose in the cylinder.. A mild cut (.002-.005") will remove it if you are concerned. Most Honda heads can't be cut more than .008"
fire ring being the piece of metal imbedded into the head gasket that goes around the chamber?
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Old 07-16-2012, 07:02 PM
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Correct............
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Old 07-17-2012, 07:06 AM
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So this isn't a sign of like detonation or something like that?
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Old 07-17-2012, 07:27 AM
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We (machinists) call them "diggers". It IS from detonation most of the time. It "rattles" the gasket and the fire ring "digs in". It's VERY common in Japanese engines, both on the head AND the block. Isuzu is perhaps the worst. Honda is right up there... Resurfacing the head will "fix" it. Inspect the deck surface of the block, too. It probably will "mirror" the damage in the head.

I've read the "limit" on milling Hondas before. I've even seen it in Honda service books. I've also seen a shop that builds a lot of Hondas, take .040" without a second thought... Valve-to-piston clearance is crucial, and MUST be checked/modified. My point here is, don't take EVERYTHING literally. Sometimes, there are reasons for these "rules" and other times, these "rules" appear to serve no logical function.

Jim
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Old 07-17-2012, 07:35 AM
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We (machinists) call them "diggers". It IS from detonation most of the time. It "rattles" the gasket and the fire ring "digs in". It's VERY common in Japanese engines, both on the head AND the block. Isuzu is perhaps the worst. Honda is right up there... Resurfacing the head will "fix" it. Inspect the deck surface of the block, too. It probably will "mirror" the damage in the head.

I've read the "limit" on milling Hondas before. I've even seen it in Honda service books. I've also seen a shop that builds a lot of Hondas, take .040" without a second thought... Valve-to-piston clearance is crucial, and MUST be checked/modified. My point here is, don't take EVERYTHING literally. Sometimes, there are reasons for these "rules" and other times, these "rules" appear to serve no logical function.

Jim
Awesome response. thanks for the reply! Why is it so common on japanese engines? I never understood how so many of my friends slap on turbo kits and take a tune off the internet and go drive. This must be what happens when you don't put the correct tune on the engine or understand whats really going on.
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Old 07-17-2012, 11:16 AM
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Originally Posted by zildjian4life218 View Post
Awesome response. thanks for the reply! Why is it so common on japanese engines? I never understood how so many of my friends slap on turbo kits and take a tune off the internet and go drive. This must be what happens when you don't put the correct tune on the engine or understand whats really going on.
Is the history of this engine known, as in has it seen nitrous or turbocharging?

My take on it would be that the limits of how much boost or nitrous/compression was found and almost exceeded. Looks to me as though he got away w/it- but barely. The cause could be excessive boost or nitrous use even w/a good tune on the engine, too much timing for the conditions (this can occur naturally aspirated as well as boosted), insufficient fuel octane, overheating, lean air/fuel ratio, to name just a few.

Also my opinion, the head fasteners weren't originally designed to hold the kinds of pressures seen under heavy boost/nitrous use. There are studs and such to help keep the head and block together w/o a failure of the head gasket seal, but even then there are limits. Considering how much power these small import engines make under boost, I believe their durability is exceptional.

Under the extreme conditions seen when running a lot of boost or nitrous, the small amount of damage seen is almost routine, especially during the dialing in phase where the limits are being found. On the other hand, if the engine was NA I'd be very concerned about the tune because it would need to be far from ideal to see that happen unless boost/N2O was involved.

I'd be curious to know the history of it, though.
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Old 07-17-2012, 12:09 PM
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We've seen it mostly on high-miles smaller 4 cyls. that are "high output". A lot of those "little" engines are built to a higher level of tune than others. That's how they get enough power out of them to "satisfy" American drivers. Even with modern engine management, detonation occurs. "Inaudible" detonation is the culprit here, as one can't "hear" the pinging.

SBI and others supply "head saver" shims to raise the head and lower the compression, usually around .020" thick. This little bit makes all the difference.

BTW, we see a significant amount of this type of damage in diesel engiens, as well.

FWIW

Jim
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Old 07-21-2012, 04:37 AM
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It was on a turbo charged engine.
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