Pitting in block/combustion chamber - The 1947 - Present Chevrolet & GMC Truck Message Board Network

amadioranch · 08-19-2017, 11:31 PM

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?

**truckdude239** · 08-20-2017, 06:35 AM

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

cg285 · 08-20-2017, 08:45 AM

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.

Bigdav160 · 08-20-2017, 09:16 AM

Quote:

What caused it

Detonation from running hot.

*YoungPup1977* · 08-20-2017, 09:43 AM

Head gasket does not cover that area.....deck and align bore the block to see where you are...good luck.

**mongocanfly** · 08-20-2017, 10:04 AM

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..

cg285 · 08-20-2017, 10:32 AM

Quote:

Originally Posted by YoungPup1977

.deck and align bore the block to see where you are...good luck.

and we are line boring it because??????????

amadioranch · 08-20-2017, 10:37 AM

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.

*YoungPup1977* · 08-20-2017, 01:12 PM

Quote:

Originally Posted by cg285

and we are line boring it because??????????

so you ask me why ? I deck and align check all engines....dont you ??

cg285 · 08-20-2017, 07:09 PM

Quote:

Originally Posted by YoungPup1977

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?

**truckdude239** · 08-20-2017, 09:10 PM

Sorry was thinking about small block v8 if the gasket seals on a smooth part id let it ride

*YoungPup1977* · 08-20-2017, 09:21 PM

Quote:

Originally Posted by cg285

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....

cg285 · 08-21-2017, 07:59 AM

Quote:

Originally Posted by YoungPup1977

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.

*YoungPup1977* · 08-21-2017, 05:22 PM

LOL!!!! OK...maybe I get a call from several machinist thanking me for the work....LOL!!!!!

nonstop · 08-21-2017, 07:39 PM

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.

GRX · 08-22-2017, 10:29 AM

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.

*YoungPup1977* · 09-03-2017, 12:55 AM

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

08-19-2017, 11:31 PM	#1
amadioranch Registered User Join Date: Aug 2016 Location: Laveen Arizona Posts: 27	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? Attached Images

08-20-2017, 06:35 AM	#2
truckdude239 Senior Member Join Date: Sep 2005 Location: Lewisville, Nc Posts: 10,217	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 __________________ David fuller Ase Certified Mechanic Click here to help support our board!! 1971 Chevy c-10 under going a 4.8l LSx swap Build Thread http://67-72chevytrucks.com/vboard/s...d.php?t=421305 2007 Honda Accord my daily 145kmiles 2002 Honda Accord 4 door With 330k(sisters car) 2005 toyota Avalon 228k( brothers car) 2002 Sububran 5.3 245k 2000 Tahoe 5.3l 378 General manager for Marco's Carwash & lube

08-20-2017, 08:45 AM	#3
cg285 Registered User Join Date: Aug 2013 Location: sumterville, florida Posts: 914	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.

08-20-2017, 10:04 AM	#6
mongocanfly Post Whore Join Date: May 2015 Location: Alabama Posts: 14,583	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.. Attached Images

08-20-2017, 10:37 AM	#8
amadioranch Registered User Join Date: Aug 2016 Location: Laveen Arizona Posts: 27	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. Last edited by amadioranch; 08-20-2017 at 03:56 PM.

08-20-2017, 09:43 AM	#5
YoungPup1977 Account Suspended Join Date: Jun 2015 Location: No longer here Posts: 1,000	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.

08-20-2017, 09:10 PM	#11
truckdude239 Senior Member Join Date: Sep 2005 Location: Lewisville, Nc Posts: 10,217	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 __________________ David fuller Ase Certified Mechanic Click here to help support our board!! 1971 Chevy c-10 under going a 4.8l LSx swap Build Thread http://67-72chevytrucks.com/vboard/s...d.php?t=421305 2007 Honda Accord my daily 145kmiles 2002 Honda Accord 4 door With 330k(sisters car) 2005 toyota Avalon 228k( brothers car) 2002 Sububran 5.3 245k 2000 Tahoe 5.3l 378 General manager for Marco's Carwash & lube

08-21-2017, 05:22 PM	#14
YoungPup1977 Account Suspended Join Date: Jun 2015 Location: No longer here Posts: 1,000	Re: Pitting in block/combustion chamber LOL!!!! OK...maybe I get a call from several machinist thanking me for the work....LOL!!!!!

08-21-2017, 07:39 PM	#15
nonstop Registered User Join Date: Dec 2014 Location: Northern California Posts: 422	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.

08-22-2017, 10:29 AM	#16
GRX Registered User Join Date: Jul 2010 Location: MD Posts: 1,937	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. __________________ 1969 c-10 Step Side Long Bed. I-6 250cid = = 1969 Pontiac GTO hard top. 400, 4-speed.

09-03-2017, 12:55 AM	#17
YoungPup1977 Account Suspended Join Date: Jun 2015 Location: No longer here Posts: 1,000	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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