cylinder head surface finish

General engine tech -- Drag Racing to Circle Track

Moderator: Team

Dan Timberlake
Guru
Guru
Posts: 1388
Joined: Tue Jan 15, 2013 8:10 pm

Re: cylinder head surface finish

Post by Dan Timberlake » Sat Sep 22, 2018 11:55 am

Hi Arlancam509,

Do you have some means of measuring the actual surface finish? Ra, Rz etc.

Descriptions like "smooth"and "rough" or "coarse" don't work well for cylinder finishing, and visually evaluating a machined surface with an optical pattern can be downright deceiving.

arlancam509
New Member
New Member
Posts: 21
Joined: Thu Nov 07, 2013 8:23 am

Re: cylinder head surface finish

Post by arlancam509 » Mon Sep 24, 2018 9:52 am

we sure do have the means for measuring surface finish. without going into too much detail (not sure if i could get in trouble at work), but i work for a very large machine tool builder. we did 500 million in machine sales for the 2017 fiscal year. it isn't lost on me how lucky i am to work here. 8)
i am the only 'gearhead' here at this particular facility, that i am aware of, so this project has my obvious interest.

Frankshaft
Guru
Guru
Posts: 1037
Joined: Sun Jul 05, 2015 6:01 pm

Re: cylinder head surface finish

Post by Frankshaft » Mon Sep 24, 2018 12:25 pm

arlancam509 wrote:
Mon Sep 24, 2018 9:52 am
we sure do have the means for measuring surface finish. without going into too much detail (not sure if i could get in trouble at work), but i work for a very large machine tool builder. we did 500 million in machine sales for the 2017 fiscal year. it isn't lost on me how lucky i am to work here. 8)
i am the only 'gearhead' here at this particular facility, that i am aware of, so this project has my obvious interest.
So, if I get this straight, you created that finish to mimic the factory, to hide the fact you actually milled a whole bunch off, so as to get thru tech.

MotionMachine
Guru
Guru
Posts: 1183
Joined: Thu Sep 16, 2010 10:01 am
Contact:

Re: cylinder head surface finish

Post by MotionMachine » Mon Sep 24, 2018 12:28 pm

Maybe you should reconsider posting pictures of proprietary projects if you want to keep that job.

arlancam509
New Member
New Member
Posts: 21
Joined: Thu Nov 07, 2013 8:23 am

Re: cylinder head surface finish

Post by arlancam509 » Mon Sep 24, 2018 1:32 pm

MotionMachine wrote:
Mon Sep 24, 2018 12:28 pm
Maybe you should reconsider posting pictures of proprietary projects if you want to keep that job.
that is excellent advice that i will take. my only excuse is that it is a belly button common small block chevy head and if they come from the factory looking this way, we are good... well, because they all look the same.

arlancam509
New Member
New Member
Posts: 21
Joined: Thu Nov 07, 2013 8:23 am

Re: cylinder head surface finish

Post by arlancam509 » Mon Sep 24, 2018 1:38 pm

Frankshaft wrote:
Mon Sep 24, 2018 12:25 pm
arlancam509 wrote:
Mon Sep 24, 2018 9:52 am
we sure do have the means for measuring surface finish. without going into too much detail (not sure if i could get in trouble at work), but i work for a very large machine tool builder. we did 500 million in machine sales for the 2017 fiscal year. it isn't lost on me how lucky i am to work here. 8)
i am the only 'gearhead' here at this particular facility, that i am aware of, so this project has my obvious interest.
So, if I get this straight, you created that finish to mimic the factory, to hide the fact you actually milled a whole bunch off, so as to get thru tech.
we were told by our customer to create this finish because this is how it looks coming from GM. i have been in the machining business for 28 years now and somehow i had never heard of this trick to create the finish shown here. (probably because i am on the other side of the wall flying a desk 90% of the time.) when it was explained to me how it was being done, i wanted to get the experts opinion, so i posted here. it creates a surface that isn't flat. flat enough for the head bolts (screws?) to pull it flat? probably.

i literally have no pull on how the part gets machine. i can offer my 2 cents, but that is it.

MotionMachine
Guru
Guru
Posts: 1183
Joined: Thu Sep 16, 2010 10:01 am
Contact:

Re: cylinder head surface finish

Post by MotionMachine » Mon Sep 24, 2018 2:57 pm

I'm guessing it's a boatload of lines of G91 X.125 Z-.0015, Z0.0, X.125 Z-.0015, Z0.0, etc.etc. You could probably get the same result with a whipped out 570 broach with misaligned cutters.

David Redszus
Guru
Guru
Posts: 6644
Joined: Tue Nov 27, 2007 9:27 am
Location: Chicago
Contact:

Re: cylinder head surface finish

Post by David Redszus » Mon Sep 24, 2018 4:03 pm

SchmidtMotorWorks wrote:
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/
Jon nailed it.

A call to the head gasket mfg should provide you with their recommendation with regard to surface finish for the
gasket material being used. Generally, a smooth finish is preferred, but not always. The gasket mfg knows.

pdq67
Guru
Guru
Posts: 8169
Joined: Thu Mar 04, 2010 8:05 pm

Re: cylinder head surface finish

Post by pdq67 » Mon Sep 24, 2018 7:52 pm

Gee, stupid me!

I thought they, "broached', both the heads and the block decks??

Now when I put together old used stuff, I use a small 6" to 8" long triangle fine straight cut file and go from head-bolt to head-bolt while spraying WD-40 to smooth and clean any high spots and crap off all deck surfaces! Now this is one of my, "feelie", deals so go easy...

You can see the results so again, go easy!!

pdq67

pdq67
Guru
Guru
Posts: 8169
Joined: Thu Mar 04, 2010 8:05 pm

Re: cylinder head surface finish

Post by pdq67 » Mon Sep 24, 2018 9:47 pm

Well, did GM, "broach", their heads and blocks decks??

pdq67

pdq67
Guru
Guru
Posts: 8169
Joined: Thu Mar 04, 2010 8:05 pm

Re: cylinder head surface finish

Post by pdq67 » Tue Sep 25, 2018 12:30 pm

pdq67 wrote:
Mon Sep 24, 2018 9:47 pm
Well, did GM, "broach", their heads and blocks decks??

pdq67
Please just asking again is all..

pdq67

arlancam509
New Member
New Member
Posts: 21
Joined: Thu Nov 07, 2013 8:23 am

Re: cylinder head surface finish

Post by arlancam509 » Tue Sep 25, 2018 12:53 pm

i don't think anyone broaches cylinder heads unless they are putting in keyways

Frankshaft
Guru
Guru
Posts: 1037
Joined: Sun Jul 05, 2015 6:01 pm

Re: cylinder head surface finish

Post by Frankshaft » Tue Sep 25, 2018 1:02 pm

arlancam509 wrote:
Tue Sep 25, 2018 12:53 pm
i don't think anyone broaches cylinder heads unless they are putting in keyways
570 Van Norman rotary broach. Very popular back in the day.

arlancam509
New Member
New Member
Posts: 21
Joined: Thu Nov 07, 2013 8:23 am

Re: cylinder head surface finish

Post by arlancam509 » Tue Sep 25, 2018 3:18 pm

Frankshaft wrote:
Tue Sep 25, 2018 1:02 pm
arlancam509 wrote:
Tue Sep 25, 2018 12:53 pm
i don't think anyone broaches cylinder heads unless they are putting in keyways
570 Van Norman rotary broach. Very popular back in the day.
thank you for the info. that is something i have never heard of before. looks more like a blanchard grinder than a broach - at least to me. machines evolve so who i am i to decided what they can or can't be! :P

Post Reply