cylinder head surface finish

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arlancam509
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cylinder head surface finish

Post by arlancam509 » Fri Sep 21, 2018 10:28 am

this cylinder head was cut on a machine with the spindle NOT square to the workpiece. you can see how the scallops are being created with the leading edge of the cutter. the trailing edge of the cutter is not touching or you would see the cross hatch. what is everyone's opinion of this? would you prefer to have the crosshatch to hold the gasket or does it even matter?
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Re: cylinder head surface finish

Post by MotionMachine » Fri Sep 21, 2018 10:49 am

All resurfacing machine spindles for our industry have a slight rake in the head so the cutter does not drag on the backside. A CNC machine is set up with the spindle dead square to the table so when a block or head is cut in them you will see the "crosshatch". That looks like the typical ugly OE finish that most heads have.

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Re: cylinder head surface finish

Post by Frankshaft » Fri Sep 21, 2018 11:39 am

Must be a new vortech head. Like said above, that's how they are from gm. It seems to work for 150-200,000 miles with the grey, graphoil style head gaskets. I personally would resurface them though.

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Re: cylinder head surface finish

Post by PRH » Fri Sep 21, 2018 11:54 am

Yup...... looks like the factory finish.
Somewhat handy with a die grinder.

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Re: cylinder head surface finish

Post by mag2555 » Fri Sep 21, 2018 12:22 pm

You can't stop the block or Heads from expanding and contracting so even if you had foot ball cleats on both deck surfaces you can't stop them from moving and in turn chewing up the gaskets eventually.

The only way to go in regards to these facts is to machine both deck surfaces as close to mirror smooth as you can get them .
If you can find a shop with a old stone type wet mill then other then a Domond cutter type that's as good as your gonna get!

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Re: cylinder head surface finish

Post by SchmidtMotorWorks » Fri Sep 21, 2018 12:58 pm

The surface roughness of the head needs to be correct for the gasket design/material.

A surface roughness that is too smooth for the type of gasket you are using will cause problems.

http://scegaskets.com/wp_super_faq/what ... materials/
http://www.schmidtmotorworks.com Aerospace Machine Work: Prototypes, Tooling, Molds.

arlancam509
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Re: cylinder head surface finish

Post by arlancam509 » Fri Sep 21, 2018 1:34 pm

i am probably not at liberty to give specifics on these heads. what we are doing is trying to mimic the 'factory finish' and the way we are doing it isn't exactly kosher in my mind. this machine is as perfect as you can expect from a brand-new machine in 2018, so we are feeding a 'Z' move while cutting the deck face. this part will meet all of the tolerances on the print. will it pass statistical control? not so sure. unfortunately, i am on the one side of the fence and i don't have any pull on the other side.

i really appreciate everyone's input. i have lurked here long enough and been inside enough engines to know what kind of answers i was going to get. most importantly though, i finally have something i could talk about on speedtalk! man, i love this forum. :D

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Re: cylinder head surface finish

Post by 427dart » Fri Sep 21, 2018 2:42 pm

slow the feed speed down!

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Re: cylinder head surface finish

Post by PRH » Fri Sep 21, 2018 2:50 pm

The way I take it, you’re trying to mimic the factory finish.

I’d say what you have there would pass.
Somewhat handy with a die grinder.

arlancam509
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Re: cylinder head surface finish

Post by arlancam509 » Fri Sep 21, 2018 3:24 pm

427dart wrote:
Fri Sep 21, 2018 2:42 pm
slow the feed speed down!
:D never going to happen! :lol:
we have to make rate or we can't sell the machine.

arlancam509
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Re: cylinder head surface finish

Post by arlancam509 » Fri Sep 21, 2018 3:37 pm

PRH wrote:
Fri Sep 21, 2018 2:50 pm
The way I take it, you’re trying to mimic the factory finish.

I’d say what you have there would pass.
we are trying to mimic the factory finish. since this machine is brand-new and the bearings aren't worn out, we have to move in 2 axes at once:
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Re: cylinder head surface finish

Post by PRH » Fri Sep 21, 2018 3:42 pm

Is the finish on the head in the pic the factory finish, or something you cut?
Somewhat handy with a die grinder.

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Re: cylinder head surface finish

Post by exhaustgases » Fri Sep 21, 2018 3:43 pm

arlancam509 wrote:
Fri Sep 21, 2018 1:34 pm
i am probably not at liberty to give specifics on these heads. what we are doing is trying to mimic the 'factory finish' and the way we are doing it isn't exactly kosher in my mind. this machine is as perfect as you can expect from a brand-new machine in 2018, so we are feeding a 'Z' move while cutting the deck face. this part will meet all of the tolerances on the print. will it pass statistical control? not so sure. unfortunately, i am on the one side of the fence and i don't have any pull on the other side.

i really appreciate everyone's input. i have lurked here long enough and been inside enough engines to know what kind of answers i was going to get. most importantly though, i finally have something i could talk about on speedtalk! man, i love this forum. :D
Not on engine parts but I have done that Z move deal a lot to stop heel drag and it does not need to be very much. And in the old manual milling days to get a clean flycut face we'd always dial a very small angle into the universal vertical head of the mill, and that was for very critical aircraft parts.
That .002 is too much, I bet .0005 would work.

arlancam509
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Re: cylinder head surface finish

Post by arlancam509 » Fri Sep 21, 2018 4:20 pm

PRH wrote:
Fri Sep 21, 2018 3:42 pm
Is the finish on the head in the pic the factory finish, or something you cut?
it is one we cut. very first part. they explained how we were doing it and i was surprised.

thinking back now, they .002" i show in my cartoon is probably not what they told me. i will have to ask monday.

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Re: cylinder head surface finish

Post by PRH » Sat Sep 22, 2018 9:00 am

I’m impressed........ that looks very much like the OE finish.
Somewhat handy with a die grinder.

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