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I need a definite answer on machining heads

13K views 23 replies 8 participants last post by  protraxrptr17 
#1 ·
Can you machine the heads? If so, how much? Do you grind the valves an seats to make up for what you took off? Is the surface finish something that an old school local head shop can do?

I had my local head shop surface these heads and now I have valve/piston contact. Luckily I rotated the engine by hand after I torqued the heads down. They cut very little. You can still see stains where the combustion chambers were. They have the old machine with stones. Can it make a good enough surface finish? Would it be safe to reuse the gaskets and bolts?
 
#2 ·
Absolutely no more than 8 thousandths off a 6 liter head. If it was ever machined before toss it.

If it takes more than 8 thousandths to make it flat toss it
 
#7 ·
The correct answer is C, 3.74".

So we measured one of the heads that happened to be laying around. The head measured 3.7038".

Next question: Should this head be milled?

Again, multiple choice.....

A) Yes

B) No
 
#8 ·
If it measured 3.7038, how in the name of jesus did the valves not punch thru the piston? Dont see how thickness is relevant to valve/piston interference.

Please measure the valve recession for me. I NEED that measurement. My heads measure 3.7338 after machining, so I'm in the mood to gamble if I can get the recession right. I'm guessing that all the heads will measure under the 3.74 cutoff. I dont see why that is so critical. Unless they think that the thinner head will crack or warp. The head could measure 4" thick and if the valves were out too far the will hit the piston. I have an 06 model engine out back that I can dismantle if I have to. Would hate to tear down an engine just to get a measurement. The head gaskets were leaking on it too or I would just use those heads.
 
#11 ·
Nope, you're right. It was a long day yesterday and I wasn't thinking clearly. The head we measured was 3.738.

Reading about your situation raises another question for me: if you can get the valves to clear the piston, what are you doing about the pushrods?
 
#9 ·
Not sure if this will work for you but I had the same problem with my 6 leaker. If you use the black onyx gaskets you may be in the clear. The factory OEM ford gaskets are .035 to .045 thick and the black onyx gaskets are .070 to .080 thick. I had to take .016 off my heads and I didnt have any problems with the valves hitting yet. i did how ever not tighting the injectors down tight enough and had the orings blow out and wasted the injectors. But before that happened i ran the truck to 4400rpm and still had no problems on a motor with 114k on it.
 
#10 ·
Thanks for the info. I'll call them in the morning. Meantime, anybody else with experience or suggestions, please chime in. This is a customers truck and I have already put him off for a very long time and then promised I would have it ready for him this week. (which isn't gonna happen) :mad:
 
#12 ·
3.7338 is under the minimum head thickness, so the head is scrap no?
 
#13 ·
Depends on who you talk to. At 3.7338 -- this means .0062 has been shaved off the heads. Which is the obvious part of the situation. Some people say that you can shave this much off and the valves will still clear the pistons. However, a lot of people don't know how thick their heads are and think they can still go .008 out.

The rest of the stuff that comes along with decking the heads gets more complicated. Valve to piston clearance, push rod legth, etc, etc....

By the time you figure everything out and have everything machined its usually less expensive to just buy new heads.

To the OP -- give Doug at Direct Injection Performance a call about the numbers you need. I'd bet my house he has that info. His website is Direct Injection Performance - GoGoDiesel.Com, Your Source For All Things Diesel!

But if you're already having valve to piston contact, my recommendation would be to buy new heads and start over. If you recess the valves, you're going to need new pushrods. Or deck your pistons. Waaaaay too many variables there for my taste....
 
#14 ·
I thought the spec of 3.74" was a MINIMUM thickness... meaning it could be higher, but not below that right? I thought that's how it was called out as a tolerance. 3.74" -.000" + .xxx ?Where X can be whatever Ford calls out, and .000 meaning it can't go under? Follow? Just trying to learn here...

and yes, Doug knows his stuff.
 
#15 ·
I spent all day with him this past Friday (9:00 am - 1:00 am). He's definitely one smart mofo. And you're right: 3.74" is the MIN spec for 6.0 head thickness. Some will argue that you can go a little past that (3.738 for example) and there are those who have. If it were my truck and the heads measured 3.738" and weren't flat, I'd replace them. Hell, if they were 3.74" and only needed .002" to be flat I'd still replace them. LOL But I'm real particular about my stuff...

And I would definitely scrap them if they measured 3.7338". Screw trying to recess the valves, shortening the pushrods, or decking the pistons.
 
#16 ·
Definitely a lot of extra work involved if you go past for sure. Thanks for clarifying that up. I'm trying to sign up on GoGo's forum now actually.

Any idea what a new head measures in at from Ford?
 
#17 ·
WHy would you need to shorten the pushrods? These have hydraulic lifters dont they? Not disputing, just asking. I have heads milled every day. Never had to do anything to the pushrods. We're not talking about hogging .100" off. Maybe .0005", VERY small amount. These heads were under the minimum when ford put 'em on.
 
#18 ·
Milled .0005 from what original thickness though?

The 6.0's do have hydraulic lifters. But when the valve is recessed and the pushrods are the same length, the hydraulic lifter pumps up and opens the valve when its not supposed to.
 
#20 ·
Yes, they machine the stem to compensate for grinding the seat.

These heads have never been machined before now, so navistar should have canned 'em before they installed 'em.

Tried again this morning and still have interference. Where do i go to get some heads? Ford qouted me $1400 eachLOL
 
#21 ·
Yes, they machine the stem to compensate for grinding the seat.
+1

Kind of where I was going with that. You can mill the head down but can run into valve / piston clearance problems. To compensate, you have to machine the valve stem down or shorten the push rods. Even then, you may have to deck the pistons depending on how much the heads were milled.

The only place I know of to get heads is from Ford, but if you have someone on the inside, you might be able to get them for less than $1400/ea.
 
#22 ·
Liberator performance (they sell EGR delete kits) sells heads. I've heard they have pretty reasonable prices.
 
#23 ·
And the more I think about it, the more I believe that when the heads are milled you're going to run into issues with pushrod length, even if you machine the valve stem. If you don't, the rocker arms won't be centered (short valve stem and long pushrod).
 
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