What is the max allowance for milling the heads on a 6.0L?

Would turning the engine over by hand after the head is torqued be a reliable way to check?

I got my heads back from the machine shop and they had to take off 0.008" to get them flat. The machinist said I should be OK but I don't know how much he knows about 6.0's. He said it appears that it's the first time the heads were milled as that he saw the factory machining marks. I saw other clues when disassembling the engine that the heads have never been off before so I'm confident they have not had additional milling by a prior owner.
I talked with a local diesel mechanic who works on 6.0s and he said I "should" be ok but seemed a bit nervous about it. He recommended I also call RCD and ask them.
I did call RCD and the guy on the line said I would be OK but I'm not real sure how much to trust a sales guy over the phone.
My local Ford service rep wouldn't say but seemed nervous about it also.
I really don't want to spend the $$$ for new heads if it's not needed.

What say you experts here on FTE?

 

.008 is ok but you really dont want anymore. I think some people have got by with .009 but its not recommended. Yes you want to turn it over by hand when you got it all together to make sure nothing binds up as in push rods and valves.

 

Theres a guy on here that did .014 and his truck runs. I would not go that far or recommend it. .008 is at the top end of comfortable in my book.

 

.008 was taken off my heads and my truck is running great! You might consider installing new push rods too. Our push rods were superseded with a shorter push rod, .050 shorter than our currently installed factory ones. If you go to the dealer and by new push rods for your 6.0. it'll be from the 6.4. All 6.0s will get the updated PR when ordered from the dealer now.

 

Would shorter push rods equal a bit more room for the heads to be milled?

 

Well that is a tricky question.
But yes. Here is the reason it is tricky.The roller linters are also hydraulic and will
set them selves so some extent. With the shorter pushrods they will have more
headroom so that they don't bottom out.

I would replace the pushrods with the new ones.

Sean

 

.014 is a BAD repair. I don't care how he spins it or tries to justify it it's a BAD repair. In the end it's all about the thickness of the head, valve train geometry, and how good the machine shop can do the work to get them right. Any tech that says .014 is "OK" isn't a tech in MY book. He's a used car salesman that's just trying to make a sale.

 

What Tim says is true because the original max, IIRC, was .005. Going more would greatly depend on all the other spec. in the equation.

 

I would like to say I was just trying to make the op feel ok with .008. I also agree .014 is too much and wouldnt personally do it.

 

When milling 6.0 heads the better question is how good is the machinists. How does one know what a machinist actually does to a head without independent measurements? You think you can see the difference between 8/1000 of an inch and 20/1000 of an inch?

I was told to absolutely not use heads that had been milled more than 8/1000 of an inch. I did not listen and used a head milled 14/1000 (almost twice the value recommend on this site and almost 3 times the 5/1000 recommend by some). Well, actually, I had the heads machined before being told not to use heads milled over 8/1000. So I was kind of stuck with using the heads or throwing them away and buying new heads.

Why? Because my mechanic said he used heads plenty of times milled more than 8/1000 with no problems and that the quality of the machinist's work and the machinist's knowledge of the Ford spec is more important than an arbitrary value such as 8/1000 of an inch. The machinist had done 100s of 6.0 heads and rejects them when his measurements indicate there will be a problem.

I hope to prove my mechanic right and, through experience, the 8/1000 limit wrong. So far so good. If I made the right decision, I saved myself at least $2,000. If I chose poorly, I cost my self an additional $2,000. It is a gamble. At the moment the truck runs great and gets 19-21 mpg highway.

If the valves are hitting the top of the piston I cannot tell it. But it could fail tomorrow. I am keeping a record.

What I suspect happens is those that have their heads milled 8/1000 and have problems used heads that were actually milled much more than 8/1000 or the heads were milled wrong. Thus one's heads fail and the problem is blamed on too much milling.

I also had the 0.050 shorter push rods installed. I am told they do not give more piston to valve clearance but they will extend the life of the rockers.

 

Ok, trying to reply from my phone while at work, please excuse any typos.

Thanks everyone for the awesome replies!

Are there any measurements that can be taken to verify?

I run a coordinate measuring machine at work so precision measurements are my thing. I probably could sneak it into work on the weekend if I know what measurements and tolerances to check.

 

Yes. Ford does have a head specification a machinists should use to make the decision on whether or not a head meets specifications.

I do not know the specs but many on here do. That said, a good machinists that has machined plenty of 6.0 heads should already have such specification.

By the way, I had both heads milled. One was milled 12/1000 and the other 14/1000. Thus, both were milled more than 8/1000 and both are still working.

That said, please do not go to some hack machinist who knows nothing about 6.0 heads and have him mill your heads "14/1000" (or whatever random value he picks) that fail and then blame me for the problem. If you go to a good machinists that has experience milling 6.0 heads and knows the Ford Spec an he mills "14/1000" off and the heads fail, then we have a problem.

 

I won't go that far and mill the head 14 thous,it's too risky,they crack before they are milled. With that said there are guys milling them farther and they do work.....for a while.It's cast iron and every pour is different,meaning 8 thou is the "safe" zone due to this inconsistency, I've been twisting wrenches for many a year,played with all the hi po heads and tried all sorts of different approaches,some work some don't.It's your money,your truck.I have a saying "you can pay me now,or pay me even MORE later".....my 2 cents

 

And you may prove to be correct. All I can do now is cross my fingers and hope for the best.

Also, I bet there are a lot of people out there that have their heads milled and ARP head studs installed and EGR Delete installed and think their truck is now bulletproof and rev the engine to 4000 or more. Then they float a valve, and spank, valve slaps piston and breaks or warps.

The rev limiter on my tuner is set tuner 3800.

 

Some people have milled FE blocks .080 and gotten away with it. Most haven't however.