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Author Topic:   angle milling heads
Dirt Maniac

Total posts: 174
posted September 03, 2002 01:34 PM
I could use a little more compression with the pistons we have to run, so I'm considering angle milling the heads. I've heard different views on this. What problems can I expect to run into? How can they be overcome? How much shaving should be done? Thanks.

Dirt Forum Champ
Total posts: 620
posted September 03, 2002 02:12 PM
angle milling decreases the combustion chamber size and gives more compression. it also decreases the valve angle which makes the heads more efficient. potential problems are intake misalignment and getting the deck too thin which will cause sealing/cracking problems. the intake misalignment can be taken care of by milling the intake side of the head to match the angle mill. if you take too much off of the deck, they're junk. every head is different, so there's no way to tell you how much you can remove safely.

Dirt Freak

Total posts: 353
posted September 03, 2002 04:31 PM
It all sounds easy to just angle mill the block side, then make the intake side match it but you also have to go through and realign the bolt holes because they are no longer drilled 90degrees to the face of the head. And is is more that just reaming the holes out because the surface of the head under the bolt head will also have to be remachined to the new angle. I couldn't tell you for sure but I am guessing that all of this could get rather expensive especially if you are in a budget class, like hobby stocks or similar.

Dirt Maniac

Total posts: 135
posted September 03, 2002 05:36 PM
All good info. Angle milling is one of those things that the magazines pass off as no big deal, but it has been my experience that it is a whole system that requires a total rethink to prevent problems. Personally,I have never seen any cylinder head flow increases as a result of the angle milling alone. The back wall of the chamber, as well as the angle of the port to the back of the valve stay the same. More things to check: You gotta get the bolt holes straight and true.. any little bind or misalignment will give you fits with water leaks and gasket seal. Some heads have blind dowel pin holes that get shallower when you may have to shorten the dowel pins. The valve notches in the pistons get effectively much shallower, and the angle may not be right must check this extremely close. We have one set of heads that there is no 23 degree shelf piston made with deep enough notches, but we can get a true 13:1 with flattops in a 358. Costwise, if done right, a new set of pistons with a larger dome vs a severe angle mill(the only kind worth doing) is probably a push, and if you value your time, the new pistons win. But sometimes, ya gotta do what you gotta do.

Dirt Maniac

Total posts: 120
posted September 04, 2002 05:52 PM
You can flat mill the heads quite a bit and raise the compression without having to worry about the intake issues. We have done this to the tune of as much as 40 thousandths with success and not had to worry about intake issues. How much valve clearance do you currently have ? THis is something to consider, also how much are you hoping raise the compression ?

Dirt Freak

Total posts: 353
posted September 05, 2002 09:23 AM
Like the previous poster said you can flat mill and make quite a difference. Also what are you using for head gaskets. You could always got to a thinner head gasket and bump up your compression. Going from a replacement gasket to a steel shim gasket might do the trick for you with the least amount of cost and work.

Dirt Full Roller

Total posts: 67
posted September 23, 2002 09:25 PM
well my 2 cents i built a 355 and i decked my block 10 thousands and flat milled the heads 20 thousands i havent had any problems with it.i wish i would have gotten zero deck clearance.i have aproximately 11.2.1 compression buy the calculator in the tool box.

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