Chamfering the bottom of cylinders.

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Berserk
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Chamfering the bottom of cylinders.

Post by Berserk » Tue Mar 06, 2018 2:24 pm

Is it a must to chamfer the bottom of the cylinders in a block that has been bored? The block is a std deck big block with 4.25 stroke, srp pistons and 6.385" rods. I already assembled the bottom end before i noticed that not all of the cylinders have a chamfer att the bottom.

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Re: Chamfering the bottom of cylinders.

Post by groberts101 » Tue Mar 06, 2018 2:28 pm

Where the gauge point for the piston is located @BDC and how much skirt protrusion is a big factor. But generally speaking you never want to start a knife fight between iron and aluminum, if you catch my drift.

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Re: Chamfering the bottom of cylinders.

Post by Berserk » Tue Mar 06, 2018 2:34 pm

I Belive the skirts protrude about 0.15"

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Re: Chamfering the bottom of cylinders.

Post by blykins » Tue Mar 06, 2018 4:11 pm

It will most likely roll the aluminum up on the pistons and then you'll get some nice scuff marks on your cylinder walls.
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Re: Chamfering the bottom of cylinders.

Post by Keith Morganstein » Tue Mar 06, 2018 5:08 pm

Berserk wrote:
Tue Mar 06, 2018 2:24 pm
Is it a must to chamfer the bottom of the cylinders in a block that has been bored? The block is a std deck big block with 4.25 stroke, srp pistons and 6.385" rods. I already assembled the bottom end before i noticed that not all of the cylinders have a chamfer att the bottom.
Does the edge feel sharp? If not sharp, it should be O.K.
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Re: Chamfering the bottom of cylinders.

Post by jsachs1 » Tue Mar 06, 2018 5:32 pm

Put a radius on the bottom.

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Re: Chamfering the bottom of cylinders.

Post by hoodeng » Tue Mar 06, 2018 6:55 pm

Breaking the edges of all machined sharp finishes is a good habit to get into. It makes handling a lot kinder on the fingers.
A buzz around the bottom of the bore with a die grinder and finish with a flap wheel will do the trick.

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Re: Chamfering the bottom of cylinders.

Post by MadBill » Tue Mar 06, 2018 6:58 pm

A de-burring tool perhaps followed by a little rub with say 80 grit would also work and might be possible without disassembly for access and with care would leave no grindings that would require disassembly. Only a slight chamfer is necessary.
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Re: Chamfering the bottom of cylinders.

Post by Walter R. Malik » Tue Mar 06, 2018 7:40 pm

Break the sharp edges so they don't FEEL sharp. That seems to be enough.
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Re: Chamfering the bottom of cylinders.

Post by gnicholson » Tue Mar 06, 2018 8:31 pm

I deburr and radius every machined surface especially bores with reciprocating motion going on like lifters and pistons. Sharp edges are also stress risers for cracks

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Re: Chamfering the bottom of cylinders.

Post by hoodeng » Tue Mar 06, 2018 9:01 pm

I have found Noga BS2010 deburring blades to be amongst the best on CI ,but you can get some pretty tough old aged blocks and heads that require a more aggressive approach with power tools.

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Re: Chamfering the bottom of cylinders.

Post by j-c-c » Tue Mar 06, 2018 10:22 pm

Does a sharper edge vs any radius wipe any splashed oil off skirts better and with a more favorable result?

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Re: Chamfering the bottom of cylinders.

Post by MadBill » Tue Mar 06, 2018 10:34 pm

I say we leave the task of oil control to the oil ring...
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Re: Chamfering the bottom of cylinders.

Post by cgarb » Tue Mar 06, 2018 10:58 pm

Yes, oil on the skirts is a good thing, just as long as it doesn't make it past the rings. Imagine what a dry piston skirt would look like after 8000rpms.

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Re: Chamfering the bottom of cylinders.

Post by MTENGINES » Wed Mar 07, 2018 6:05 am

j-c-c wrote:
Tue Mar 06, 2018 10:22 pm
Does a sharper edge vs any radius wipe any splashed oil off skirts better and with a more favorable result?
Yes the sharper edge does a better job at wiping oil, along with aluminum from the piston.

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