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Bore scope shows burned piston
Date: October 26, 2017 04:49PM

Wouldn't you know it, I bought a borescope and almost immediately #5 cylinder started smoking badly. The new borescope says burned piston. My question is: can I replace the piston and cylinder without pulling the engine?



Edited 1 time(s). Last edit at 10/26/2017 08:17PM by MattNall.

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Re: Bore scope burned piston
Posted by: Wagon Master ()
Date: October 26, 2017 04:51PM

Yes. Easy peasy. GM supplied a piston with rings installed in a cyl. with rod attached together as an assy. just for this purpose.



Edited 2 time(s). Last edit at 10/26/2017 04:55PM by Wagon Master.

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Re: Bore scope burned piston
Date: October 26, 2017 04:55PM

Wagon Master Wrote:
-------------------------------------------------------
> Yes. Easy peasy. GM supplied a piston with
> installed in a cyl. with rod attached together as
> an assy. just for this purpose.


OK, where do I find such an assembly?

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Re: Bore scope burned piston
Posted by: Wagon Master ()
Date: October 26, 2017 05:10PM

GM supplied......as in used to. You'll have to make your own assy. now. Still no big deal. First off, what is the condition ​of the other 5 holes. Do a good hot compression check and report back.

'64 Monza Coupe 140 4 speed
'61 700 Lakewood 95 4 speed
'69 Monza Convert. 140 Auto.

Been aircooled since 1973
Northwest Ohio

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Re: Bore scope burned piston
Date: October 26, 2017 05:18PM

They are all 150 +/_ 10

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Re: Bore scope burned piston
Posted by: Wagon Master ()
Date: October 26, 2017 05:36PM

You can get everything you need from any of our supporting vendors. My compression question came from an attempt to find the smoking gun. Pistons usually don't just burn. Any clue as to if you the pistons you have now are stock cast? What form of racing is BorondaFarmRacing envolved in?

'64 Monza Coupe 140 4 speed
'61 700 Lakewood 95 4 speed
'69 Monza Convert. 140 Auto.

Been aircooled since 1973
Northwest Ohio

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Re: Bore scope burned piston
Posted by: American Mel ()
Date: October 26, 2017 06:03PM

"What form of racing is BorondaFarmRacing envolved in?"
Well, that is an easy one, they race FARMS ! grinning smiley

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sorry, just could not resist.

.
-----------------------------------------------
WA. state, 1 mile south of the Canadian border,
I am not at the end of the world, but you can see it from here.
'66 Monza Coupe - 4spd, 140 Daily driver beater
'67 Monza Vert. - PG, 140 Daily driver beater

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Re: Bore scope burned piston
Posted by: RobertC ()
Date: October 26, 2017 07:44PM

Yes, you can replace a piston / cylinder without pulling the engine.

It is easier if you remove the carb studs from the intake manifold - one side you have to; the other side there is enough room that you do not.

BUT, you probably should figure out what caused the problem - too lean; detonation; pre-ignition...

Because all the other pistons are at risk...

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Re: Bore scope burned piston
Date: October 26, 2017 07:57PM

The car has a central four-barrel carburetor and all of the spark plugs were sooty so I leaned out the idle, but did nothing to the main jets. I also discovered a few days ago that the intake runner between #4 and #6 was not secured and probably sucked air around the base. I corrected this. This whole fiasco is very strange. I have been tuning the car - plugs, points, dwell, timing, etc., and the last time I ran it, it was fine. Then, today when I started it up there was white smoke from the right bank and #5 plug was oily. Prior to this it was sooty like the others, rather than oily. I used my borescope for the first time, and it looks like the edge of #5 piston is burned. I looked at #3 piston for comparison and it looks OK. I'm just not sure what I'm seeing with the borescope.

Boronda Farm was the Lee family compound in Portola Valley where my late wife, Patty, grew up. We named our race team after the compound. Patty died in 1995 and I raced a bit after that, but lost interest.

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Re: Bore scope shows burned piston
Posted by: junkman ()
Date: October 26, 2017 09:07PM

I have some NOS pistons and cylinders, but will need more information to make sure that what I have is correct for your car. As for the connecting rod being attached to the piston from the factory, I have never seen one like that. That doesn't mean that it never existed, just that in all the clean outs of dealership parts rooms, where I found all these parts, I never found a piston cylinder with the connecting rod. If you need a replacement connecting rod, I can probably fix you up with a NOS one also. If you want it installed on the piston, I can arrange for that to be done also. Junk

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Re: Bore scope shows burned piston
Posted by: JimBrandberg ()
Date: October 27, 2017 04:17AM

#5 cylinder suffers when the Fresh Air hose is not good. The cooling air esacpes through the path of least resistance instead of going through the head like it should. Probably more of a valve seat type of thing but I have to wonder.
I would just do the one cylinder if the others seem okay. There's the whole fix it right thing but it's easy to spend $3000 when you start replacing the pistons and boring cylinders and head work and... where do you draw the line?
I have just replaced one cylinder with used stuff and motored on. How many miles are you really going to put on it these days anyway. Maybe a lot and doing it right is best. It's a philosophy that you need to decide on. If you get the head off and the head gasket surfaces are sunken, it may change the deciding factors a bit. If the rod bearing looks good, I would just put it back in it's home, changing all 6 is a different matter.
There was a picture here a while back with Patty and the Corvair racer which was pretty cool.
Jim Brandberg
Isanti, MN
CorvairRepair.com

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Re: Bore scope shows burned piston
Date: October 27, 2017 09:30AM

junkman Wrote:
-------------------------------------------------------
> I have some NOS pistons and cylinders, but will
> need more information to make sure that what I
> have is correct for your car. As for the
> connecting rod being attached to the piston from
> the factory, I have never seen one like that.
> That doesn't mean that it never existed, just that
> in all the clean outs of dealership parts rooms,
> where I found all these parts, I never found a
> piston cylinder with the connecting rod. If you
> need a replacement connecting rod, I can probably
> fix you up with a NOS one also. If you want it
> installed on the piston, I can arrange for that to
> be done also. Junk

Thanks so much for the offer. The engine has a YN code, which suggests it is a 1964 110HP engine with 140 heads. Could you supply a new piston with rings and connecting rod attached, fitted to a new cylinder; so that I could just pull the old one out and insert yours? If so, how many dollars do I need to send you? Thanks.

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Re: Bore scope shows burned piston
Date: October 27, 2017 09:55AM

junkman Wrote:
-------------------------------------------------------
> I have some NOS pistons and cylinders, but will
> need more information to make sure that what I
> have is correct for your car. As for the
> connecting rod being attached to the piston from
> the factory, I have never seen one like that.
> That doesn't mean that it never existed, just that
> in all the clean outs of dealership parts rooms,
> where I found all these parts, I never found a
> piston cylinder with the connecting rod. If you
> need a replacement connecting rod, I can probably
> fix you up with a NOS one also. If you want it
> installed on the piston, I can arrange for that to
> be done also. Junk

I should have said that although the engine is a 1964, the new cylinder barrel should be a 1965-69 because of the 140 heads.

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