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Milling a 235 head
#1311603 Thu May 23 2019 09:46 AM
Joined: Feb 2001
Posts: 1,130
D
Dusty Offline OP
Shop Shark
I want to clean up a rusty 235 head , I would like to know how much can be milled off before valve clearance becomes an issue .

I also need to know what the original thickness was , so I have a datum to work from .

Any links appreciated .

Re: Milling a 235 head
Dusty #1311637 Thu May 23 2019 02:06 PM
Joined: Mar 2005
Posts: 1,437
C
Shop Shark
An untouched head will measure 4.000" thick. At the front corner on the manifold side there is a small step...I just checked an 848 casting head and found it to be .090" deep. That step can be seen clearly in this tech tip:


https://www.stovebolt.com/techtips/milledheads.htm


As for facing I would suggest only the minimum required for cleanup rather than inviting other issues.


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Re: Milling a 235 head
Dusty #1311653 Thu May 23 2019 02:53 PM
Joined: Feb 2004
Posts: 20,885
H
Boltergeist
A trick we used on race engines with radical camshafts was to install a head onto the block without a head gasket, adjust the valves on one cylinder to zero clearance, and turn the crankshaft. If we got no valve/piston contact, the thickness of the head gasket was the safety factor. The same test would apply to a stovebolt engine, and it would be simpler, even. The only valve you need to be concerned with is the intake- - - -there's no way an exhaust valve can get into trouble due to its angle and position in the head.
Jerry


The murder victim was drowned in a bathtub full of Rice Krispies and milk.
The coroner blamed the crime on a cereal killer!

Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
Re: Milling a 235 head
Dusty #1311666 Thu May 23 2019 05:17 PM
Joined: Mar 2010
Posts: 9,407
5
Master Gabster
I had a 216 head milled by an old timer 30 years ago. He took just enough off to make it flat. He warned against milling too much off, as even if you don't end up with intake valve contacting the piston, you can still cause poor airflow at the intake valve from lack of quench area from too much milling in that area.
He mentioned that when he was into racing these engines, he would mill them on an angle, taking nearly most of the metal from the exhaust side of the head, resulting in leaving the intake side of the head mostly unmolested. He said that the valve train still worked fine and the difference in the head height could be taken care of since there are enough threads on the rocker arm adjusters to set the valve clearance. I wish I would have asked him what angle he used. I would also like to know what he ended up with in terms of reduced cc's of the combustion chamber and the resulting change in compression.
Hmmm, if I only new a guy who had the machinery, knowledge and the time to experiment with a project like this...
Carl

Re: Milling a 235 head
Dusty #1311684 Thu May 23 2019 08:02 PM
Joined: Feb 2001
Posts: 1,130
D
Dusty Offline OP
Shop Shark
Thanks guys , I never thought to look in tech tips .. Perfect datum info . I will take the verniers , knock a bit of rust off and see what I am up for .

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Re: Milling a 235 head
Dusty #1311691 Thu May 23 2019 09:19 PM
Joined: Dec 2008
Posts: 1,473
P
Shop Shark
The angle mill is a triangle. The width is the gasket surface, the height is the maximum mill depth (.100" etc.) minus the minimum mill distance (just enough to make a clean pass, like .002").
This angle also mis-aligns the head bolts, and the piston-to-head & intake-valve-head-to-piston contact surfaces.

Re: Milling a 235 head
Dusty #1311701 Thu May 23 2019 10:09 PM
Joined: Feb 2004
Posts: 20,885
H
Boltergeist
Angle milling works- - - -I've won dozens of races with angle-milled heads on small block V8's and the same principle would apply to a stovebolt. It just takes a few active brain cells to make the procedure work right. The nice thing about building "claimer" race engines that way is being able to use heads with casting numbers that dumb tech inspectors will pass without a second glance. "What are ya- - - -stupid or sumpin'? those are low-compression SMOG heads!" He didn't know I was making more compression pressure than illegal-for-class "camel hump" heads- - - -and running the same size valves!
Jerry



The murder victim was drowned in a bathtub full of Rice Krispies and milk.
The coroner blamed the crime on a cereal killer!

Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
Re: Milling a 235 head
Dusty #1311766 Fri May 24 2019 10:11 AM
Joined: May 2006
Posts: 848
T
Shop Shark
Don't do this. This makes me cringe -

https://m.youtube.com/watch?v=UDPsEwXXbMg

Last edited by tom moore; Fri May 24 2019 10:12 AM.
Re: Milling a 235 head
Dusty #1311770 Fri May 24 2019 11:43 AM
Joined: Feb 2004
Posts: 20,885
H
Boltergeist
The shop where I ran the connecting rod reconditioning department had a BIG belt sander- - - -like 18" wide and 4 feet long, that we used occasionally for cleaning up minor pitting on flathead Ford and MOPAR cylinder heads. For any real milling, we used a Blockmaster mill with a 24" circular cutter head and about 40 carbide bits on it.
Jerry


The murder victim was drowned in a bathtub full of Rice Krispies and milk.
The coroner blamed the crime on a cereal killer!

Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!

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