What is angle milling, what does it do and how much does it cost?. I thought it was to raise compression. Am I partially correct?. Thanks as always!

Originally posted by 75c10:
What is angle milling, what does it do and how much does it cost?. I thought it was to raise compression. Am I partially correct?. Thanks as always! =
It is taking almost all of the material off of the outside of the head instead of flat across the whole surface.
Yes, it is to raise the compression & you can make the chamber smaller on especially on a small block without getting into the intake seat which is usually the limiting factor on how much you can flat mill the heads.
It is not real difficult but you need to bring the intake surface back to the original angle, spot face the tops of the bolt holes & in some cases ream the holes so the bolts will go through & check the pushrod holes for binding.
I have angle milled 23 deg heads about 120 thou which is almost 1deg.
It also causes a few other problems not normally considered like header fit.
If your headers are close to the engine now, 1deg will move them a lot more than you think. You can figure it by taking the sine of 1 deg (or whatever angle you cut them)times the length so if your headers are say 24" from flange down to collector in height you will move the collector in almost 7/16" !

As for cost, it depends :D

Yes, it's used to reduce chamber volume. Heads can be Angle milled, or flat milled. It trues up the surface of the heads and raises compression. Some times used to gain compression in lieu of a piston swap. The differnce between the two I'll leave for some one else............ :D Milling heads can cause other things to change, push rod length, manifold fit, and of course piston clearence. Whoops. EDIT, strated to post, went to supper, came back and hit send. Mike's the man, he know's!!!

What Wolf said....

It's a kind of last resort thing that you do when you are forced to run a particular casting (class rules or whatever), or the castings you already have offer some unique advantage, or there is no casting with a suitably small chamber.

It's not something you just casually do to old junk smogger castings that turns them into a hot setup. Although sometimes the magazines make it seem so.

It's also not something you just casually do to valuable, desirable castings either; after all, it's irreversible.

I assume this question wasn't asked in a vacuum... what do you have in mind?

The one article that comes to mind to me on flat milling is the 400hp+/305 motor buildup where they hunted around for quite some time until they came up with a pair of older, HEAVY castings with the chamber shape and intake ports they wanted and then planed heck outta them b/c the lightweight ones will more then likely crack b/c they are already thin.

The article said to check the water holes in the head flats for thickness comparison...

pdq67

Originally posted by pdq67:
The one article that comes to mind to me on flat milling is the 400hp+/305 motor buildup where they hunted around for quite some time until they came up with a pair of older, HEAVY castings with the chamber shape and intake ports they wanted and then planed heck outta them b/c the lightweight ones will more then likely crack b/c they are already thin.

The article said to check the water holes in the head flats for thickness comparison...

pdq67 =
Sometimes I hate magazine articles graemlins/angry.gif
They make it sound like a walk in the park.
Hell, you just throw the head on the mill & start wacking away until you get what you want right??
Never mind that pretty soon you have no intake seat left or that the bottom of the intake port has no place for a gasket to seal, it's only gotta run long enough for the magazine article to get a number assuming they even run the damn thing.
And RB is dead on, it ain't something you do as the trick of the week.
There are vary valid reasons to do it in some cases like a lot of circle track stuff when you have to run a stock casting but for street use there really isn't much reason to stick with a 30 year old head any more unless you just like a challenge :D

Now a disclamer before it starts :(
Most of this has to do with small blocks.
This don't apply to all you gotta have 781 oval guys,,, I ain't goin there :D :D

Mike,

The article was very up front about what they did to the heads and was a fine explanation to me!

I figure they REALLY wanted guy's that wanted to make a high hp 305 to be able to if they followed the article close enough b/c to me the whole story was there!!

But I see where you are coming from b/c most of the B/S articles are more into making somebody's stuff look better, thus worth more to sell then other stuff AND they end up making a darned "apple's to orange's" comparison that really pi--es me off too!!!

Ya, that extra 3/8th's of a point higher compression and the "SLIGHTLY" different shaped combustion chambers as well as ports ONLY being 5 or so cc's bigger DOES MAKE A DIFFERENCE to me!!! Sh-t, gimme a break!!!!!!!

pdq67

har! :D