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Old 08-19-2017, 11:31 PM   #1
amadioranch
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Pitting in block/combustion chamber

Pulled the head on my old 235 today due to a blown head gasket between #4 and #5. Was cleaning things up and noticed this pitting only on #5. What caused it and is it a issue?
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Old 08-20-2017, 06:35 AM   #2
truckdude239
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Re: Pitting in block/combustion chamber

Cuased by a blown head gasket beeing run for a long time its time for the block to be re decked or replaced if the pits are too deep a new head gasket will never seal properly with the pitting tbere
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Old 08-20-2017, 08:45 AM   #3
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Re: Pitting in block/combustion chamber

it's been a long time but if i remember correctly the head gasket does not follow the cylinder - as in it's not a round opening. lay the gasket on the block and if it fits around that area you are good to go.
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Old 08-20-2017, 09:16 AM   #4
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Re: Pitting in block/combustion chamber

Quote:
What caused it
Detonation from running hot.
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Old 08-20-2017, 09:43 AM   #5
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Re: Pitting in block/combustion chamber

Head gasket does not cover that area.....deck and align bore the block to see where you are...good luck.
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Old 08-20-2017, 10:04 AM   #6
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Re: Pitting in block/combustion chamber

you can see the same pattern on adjacent cylinders but I'd deck it for good measure but it may be ok as is....here's 235 head gasket..
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Old 08-20-2017, 10:32 AM   #7
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Re: Pitting in block/combustion chamber

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.deck and align bore the block to see where you are...good luck.
and we are line boring it because??????????
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Old 08-20-2017, 10:37 AM   #8
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Re: Pitting in block/combustion chamber

Thanks for the input guys! The pitting is directly below where to combustion chamber in the head is, not on any head gasket sealing area.

Think im going to slap a new head gasket on it and see what it does. If it blows out the gasket again im only out a little labor and $25 in a gasket. Id prefer not to pull the motor at the moment. If it blows again then ill pull it and do the whole shootin match. Its in a old 1949 2 ton that im only going to put a couple hundred miles on a year. Like to not put alot of money into it. Another factor is that I believe that this motor was rebuilt not long before I purchased it. It has strong compression (155lbs) and I can still see crosshatching on cylinders.

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Old 08-20-2017, 01:12 PM   #9
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Re: Pitting in block/combustion chamber

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and we are line boring it because??????????
so you ask me why ? I deck and align check all engines....dont you ??
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Old 08-20-2017, 07:09 PM   #10
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Re: Pitting in block/combustion chamber

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so you ask me why ? I deck and align check all engines....dont you ??
no... especially if i'm only replacing a head gasket. i don't machine anything that is not necessary
bty i think you said "Head gasket does not cover that area.....deck and align bore the block to see where you are...good luck."
did i miss something?
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Old 08-20-2017, 09:10 PM   #11
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Re: Pitting in block/combustion chamber

Sorry was thinking about small block v8 if the gasket seals on a smooth part id let it ride
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Old 08-20-2017, 09:21 PM   #12
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Re: Pitting in block/combustion chamber

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Originally Posted by cg285 View Post
no... especially if i'm only replacing a head gasket. i don't machine anything that is not necessary
bty i think you said "Head gasket does not cover that area.....deck and align bore the block to see where you are...good luck."
did i miss something?
are you challenging me on this or you just want to show you are the expert here ? not here to argue any thing.....just the way folks do things because I do not do things twice....so go ahead and do things your way, I could care less....

I dont miss anything...you can....
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Old 08-21-2017, 07:59 AM   #13
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Re: Pitting in block/combustion chamber

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Originally Posted by YoungPup1977 View Post
are you challenging me on this or you just want to show you are the expert here ? not here to argue any thing.....just the way folks do things because I do not do things twice....so go ahead and do things your way, I could care less....

I dont miss anything...you can....
point is some people here don't have much of a clue so now some may think they can't replace a head gasket without line boring the block.
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Old 08-21-2017, 05:22 PM   #14
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Re: Pitting in block/combustion chamber

LOL!!!! OK...maybe I get a call from several machinist thanking me for the work....LOL!!!!!
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Old 08-21-2017, 07:39 PM   #15
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Re: Pitting in block/combustion chamber

Back on topic..... just saw 155 on the compression test. Is that in all cylinders? Might be worth throwing a head gasket at it. Then just keep an eye open for a cheap 235 to replace this one when/if the time comes and you can build it at your leisure.
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Old 08-22-2017, 10:29 AM   #16
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Re: Pitting in block/combustion chamber

Yep. Obvious blown head gasket. That pitting is actually caused by 'cavitation' from compressed coolant I would say.

Not to scare you. Be sure to check radius of head combustion chamber for cracks too. Probably more than half the 235 heads I magnafluxed had one there. If not to water yet they can be in future.
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Old 09-03-2017, 12:55 AM   #17
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Re: Pitting in block/combustion chamber

So would it be a good practice to have the head checked before replacing the head gasket ? most likely the answer would be YES.....
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