Go Back   The Ford Barn > General Discussion > Early V8 (1932-53)

Sponsored Links (Register now to hide all advertisements)

Reply
 
Thread Tools Display Modes
Old 09-10-2020, 02:02 PM   #1
Mart
Senior Member
 
Mart's Avatar
 
Join Date: May 2010
Location: Solihull, England.
Posts: 8,732
Default Head skimming: Any tips?

I just did a test and I can just about get a head on my small milling machine. no overlap at either end or side but I can just about cover the surface.

I tried with parallels under the ends and middle (Under the head nut bosses) and bolts down through the end spark plug holes.

I was hardly touching the ends but taking quite a bit off the middle.

So a couple of questions.

Are the head nut bosses a reliable surface to mount the head on?

Is it better to mount the head face down and level the nut bosses first? Too late on my test head.

Is it better to use just 3 mounting points so the head isn't pulled into a bind?

Any hints and tips gratefully received.

Mart.
Mart is offline   Reply With Quote
Old 09-10-2020, 02:24 PM   #2
Kube
Senior Member
 
Kube's Avatar
 
Join Date: May 2010
Location: Wisconsin, USA
Posts: 8,937
Default Re: Head skimming: Any tips?

Quote:
Originally Posted by Mart View Post
I just did a test and I can just about get a head on my small milling machine. no overlap at either end or side but I can just about cover the surface.

I tried with parallels under the ends and middle (Under the head nut bosses) and bolts down through the end spark plug holes.

I was hardly touching the ends but taking quite a bit off the middle.

So a couple of questions.

Are the head nut bosses a reliable surface to mount the head on?

Is it better to mount the head face down and level the nut bosses first? Too late on my test head.

Is it better to use just 3 mounting points so the head isn't pulled into a bind?

Any hints and tips gratefully received.

Mart.
Mart, When I used to do these, I'd mount the head on a number of adjustable supports, usually six. The difficult (time consuming) issue was leveling the head as best I could.
I clamped it in many places (usually six) and would mill as much as possible around the clamps. Remove one clamp at a time - mill. Replace that clamp and move to the next.
The bosses are close but in my opinion, not nearly close enough to solely utilize.
__________________
"I can explain it for you. However, I can't understand it for you".
Kube is offline   Reply With Quote
Sponsored Links (Register now to hide all advertisements)
Old 09-10-2020, 03:44 PM   #3
supereal
Senior Member
 
supereal's Avatar
 
Join Date: Jul 2014
Location: Iowa
Posts: 1,634
Default Re: Head skimming: Any tips?

Take the heads to a shop that has a surface grinder. Using a milling machine can quickly damage the surface. If you don't know whether the heads have been surfaced before, you can check valve head clearance by placing modeling clay in the valve area, then placing the head on the block, and turning the crankshaft. Then observe the clay to see if there is sufficient clearance.
supereal is offline   Reply With Quote
Old 09-10-2020, 03:46 PM   #4
Lawson Cox
Senior Member
 
Lawson Cox's Avatar
 
Join Date: May 2010
Location: Above the gnat line in Georgia
Posts: 7,009
Default Re: Head skimming: Any tips?

Take it to a good reliable machine shop and 'splain what you want done. Couldn't be all that much trouble or money. Some things are better paid for than experimenting with yourself. My 2¢.
__________________
Life is like a roll of toilet paper. The closer to the end, the faster it goes.

It is better to be seen, than viewed.

"We sleep safe in our beds because rough men stand ready in the night to visit violence on those who would do us harm".
Lawson Cox is offline   Reply With Quote
Old 09-10-2020, 04:26 PM   #5
Lawrie
Senior Member
 
Lawrie's Avatar
 
Join Date: May 2010
Location: Qld, Australia
Posts: 4,195
Default Re: Head skimming: Any tips?

Mart ,can you spin it it that lathe of yours
Lawrie
Lawrie is offline   Reply With Quote
Old 09-10-2020, 04:27 PM   #6
jimalabam
Senior Member
 
jimalabam's Avatar
 
Join Date: May 2010
Location: Lee County Alabama
Posts: 828
Default Re: Head skimming: Any tips?

Sponsored Links (Register now to hide all advertisements)
I agree with Lawson...
jimalabam is offline   Reply With Quote
Old 09-10-2020, 10:36 PM   #7
Newc
Senior Member
 
Newc's Avatar
 
Join Date: May 2010
Posts: 2,460
Default Re: Head skimming: Any tips?

Every time the heads are surfaced the dome diameter gets smaller-easy to measure. Newc
Newc is offline   Reply With Quote
Old 09-10-2020, 10:48 PM   #8
Brian
Senior Member
 
Brian's Avatar
 
Join Date: May 2010
Location: Masterton, New Zealand
Posts: 3,816
Default Re: Head skimming: Any tips?

When a local machine shop surfaced a pair of finned heads I had, they tapped the stud holes in the four corners. [Probably 1/2 unf?] Screwed in bolts and clamped the bolt heads. Having this setup allowed them to jack up/lower each end of head[s] to set up.
__________________
Unfortunately, two half wits don't make a whole wit!
Brian is offline   Reply With Quote
Old 09-10-2020, 11:29 PM   #9
Wat-0
Junior Member
 
Wat-0's Avatar
 
Join Date: Apr 2019
Location: Keizer, Oregon
Posts: 29
Default Re: Head skimming: Any tips?

https://youtu.be/YPe4ddzlr-k
Wat-0 is offline   Reply With Quote
Old 09-11-2020, 04:13 AM   #10
Mart
Senior Member
 
Mart's Avatar
 
Join Date: May 2010
Location: Solihull, England.
Posts: 8,732
Default Re: Head skimming: Any tips?

Thanks for all the advice, fellas. I did a test on an otherwise scrap head last night and it came out ok. I'm just playing about with this, with the aim of being able to fine tune the over the piston clearance somewhere in the future.

I was just pleased to find I could actually get one on there and physically cover the whole surface. I always assumed that my machine wasn't big enough.

Once I get it working as I would like I'll no doubt show it in a video.

Mart.
Mart is offline   Reply With Quote
Old 09-11-2020, 05:48 AM   #11
JWL
Member Emeritus
 
Join Date: May 2010
Location: Fitzgerald, Georgia
Posts: 2,204
Default Re: Head skimming: Any tips?

The head should be completely relaxed when being leveled/positioned on the milling machine. If the head is warped excessively it should be straightened or completely machined at the gasket face and in the chambers. Too, it must be supported so as not to deflect when cutting pressure is applied. I have a special fixture which locates the head at the 4 corner holes on adjustable, hollow, dowels and 4 more , adjustable, supports at the sparkplug faces. After the tedious job of finding the best position, with all four corners touching, bolts are used at the 4 corners to clamp. Then the supports at the sparkplugs are applied while observing a Test Indicator, resting on the gasket face, to avoid changing the position or flexing the head. Finally, clamping can be accomplished through the sparkplug holes with the rest pads supporting. You will find it impressive to see how easily the head can be flexed. When work is done in the chamber the supports at the sparkplugs are not clamped/bolted. When cutting at the gasket face the sparkplug clamps are used. Finding the best condition at which to set the head can take some patience and time. I use a Platten surfacing machine after milling cuts to achieve the finish I desire.


I found a picture which partially shows the fixture I made for head work on pages 58 and 62 of my book.
JWL is offline   Reply With Quote
Old 09-11-2020, 09:59 AM   #12
flatrod
Senior Member
 
flatrod's Avatar
 
Join Date: Dec 2012
Location: Anchorage Alaska
Posts: 290
Default Re: Head skimming: Any tips?

Mart, I found that on my Bridgeport 9x42, I can get a head on there but have to use all of the table with the Bridgeport head all the way to the right. So having done that I use all of the table. But my machine has wear in it and will cut things into a banana. Its because of wear. With the table all the way to one side the weight of the table is pulling that end down, then when in the middle it levels off and goes to the other end and it hangs from the weight again, therefor cutting the head into a banana high in the middle. Never found a way to get it out of it.
flatrod is offline   Reply With Quote
Old 09-11-2020, 10:21 AM   #13
cadillac512
Senior Member
 
cadillac512's Avatar
 
Join Date: Apr 2019
Location: Kansas
Posts: 897
Default Re: Head skimming: Any tips?

Quote:
Originally Posted by Lawson Cox View Post
Take it to a good reliable machine shop and 'splain what you want done. Couldn't be all that much trouble or money. Some things are better paid for than experimenting with yourself. My 2¢.

This is why we do stuff ourselves...
Attached Images
File Type: jpg red green.jpg (37.0 KB, 36 views)
__________________
"It don't take but country smarts to solve the problem" (Smokey Yunick)


'41 Merc Town Sedan / 260" 8CM engine
'66 Fairlane four door / "warmed up" 302

Last edited by cadillac512; 09-12-2020 at 07:42 AM.
cadillac512 is offline   Reply With Quote
Old 09-11-2020, 05:56 PM   #14
42merc
Senior Member
 
42merc's Avatar
 
Join Date: Feb 2011
Location: Buchanan, MI
Posts: 675
Default Re: Head skimming: Any tips?

Anything can be bought.
Some folks enjoy being creative and learning.
I'm with Mart.
42merc is offline   Reply With Quote
Old 09-14-2020, 12:08 PM   #15
rotorwrench
Senior Member
 
rotorwrench's Avatar
 
Join Date: Jun 2010
Location: San Antonio, Texas
Posts: 16,369
Default Re: Head skimming: Any tips?

Flatrod has a good point. Knee mills are good for a lot of different milling jobs but the table can be a problem if things aren't in a good tight condition with it. Most machines that are designed to deck things with accuracy have full support underneath to make certain there can be no deflection under cutting load. A regular knee mill would be fine for small stuff like motorcycle heads but may not have the support it needs for the longer stuff.

If it works for you then that's great. A good surface cut should be very smooth. If a person has what I refer to as a grave stone or surface plate, it's easy to check the job. Lapping machines are another way but those things can get expensive. They can get the surface better than a gnat's ahrs by far.
rotorwrench is offline   Reply With Quote
Old 09-14-2020, 02:37 PM   #16
Mart
Senior Member
 
Mart's Avatar
 
Join Date: May 2010
Location: Solihull, England.
Posts: 8,732
Default Re: Head skimming: Any tips?

Thanks for all the input guys. I did a test and it is ok-ish. I think as my mill is so lightly used it is ok re sag, but just holding the head is the difficult part. I'm working on something else now, but will revisit this subject in the future.

Mart.
Mart is offline   Reply With Quote
Old 09-14-2020, 04:52 PM   #17
vincent
Senior Member
 
Join Date: Jun 2020
Location: Germany
Posts: 201
Default Re: Head skimming: Any tips?

Put your head with the chambers down on the mills table and underlay the banana with shims as best as you can before tightening down thus holding the warped head in its true warped stage on the table. Do a small fly cut on every bolthole surface, of course all to the same depth. When finished you have 24 points to lay the head on, all of them in the same plane and level. When head is mounted on these points and tightened down on the table you can skim the gasket surface and get a straight and flat head again.
vincent is offline   Reply With Quote
Old 09-14-2020, 05:43 PM   #18
cdan34
Senior Member
 
cdan34's Avatar
 
Join Date: May 2010
Location: Mill Valley, Calif.
Posts: 120
Smile Re: Head skimming: Any tips?

When I milled the heads using my bridgeport, I balanced the head with five 1/2 threaded rod on flat bar plates bolted to table. Using nuts and adjusting the head. The nuts were resting on bolt hole bosses. The head was secured by clamping down with 3/8 bolts through spark plug holes. The important thing is to indicate at the bottom of combustion chambers on each end of head lengthwise and your set to go.

cdan34
cdan34 is offline   Reply With Quote
Old 09-15-2020, 08:14 AM   #19
flatrod
Senior Member
 
flatrod's Avatar
 
Join Date: Dec 2012
Location: Anchorage Alaska
Posts: 290
Default Re: Head skimming: Any tips?

Same here, I use 5 small jack stands. 4 at the outer corners and one in the middle. pull the head down with bolts through the spark plug holes. Adjustable or shim able as you need. Also made t slots in 3/8 to fit the slots in my table.
flatrod is offline   Reply With Quote
Old 09-15-2020, 01:07 PM   #20
john in illinois
Senior Member
 
john in illinois's Avatar
 
Join Date: May 2010
Location: Illinois
Posts: 2,181
Default Re: Head skimming: Any tips?

The machine shop that I use has a dedicated head mill. They thread the holes and attach it to a fixture that tilts to perfectly index the head. they told me that clamping the head down distorts the head and when removed it is not flat.

They do a lot of race engines so they are kind of out of my league and my home shop Bridgeport. I think Mart could do one and have acceptable accuracy.

John
__________________
Welcome each day
john in illinois is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Sponsored Links (Register now to hide all advertisements)


All times are GMT -5. The time now is 05:59 PM.