I spent today pulling the head oof my '84 245 due to a leaking head gasket. The job went smoothly with no surprises. I took the head in to a machine shop to have it check for warp and it is warped. The center of the head is the highest point with .004" to .006" of warp. The machinist inteneds to mill the head back to flat. He won't be able to get to it until the beginning of next week. My question is: Is this an acceptable practice on a aluminum head? Will this cause problems with the cam bearings? I was taught something different in my college auto tech class. What's the consensus?
Thanks,
Nick

Passing along info for what it's worth. I work for an engine manufacturer and we machine our own cylinder heads, although these are 6 cyl diesels.

Combusion face flatness is spec'd at .002" in any 2" area (50 microns / 50mm) in other words if you could put an indicator thru a hockey puck and tram it around the combustion face we allow a .002 deviation anywhere on the surface - high or low.

Overall flatness, different from local flatness, is spec'd at .010". A little harder to measure in the shop, but basically if you had a flat surface to lay the head (combustion face down) you could slide feeler gages between the head and the flat surface to determine overall flatness. If a .010" feeler gage didn't go the head meets spec.

So, .004 to .006 on a head I owned with no known overheating problems that caused the head gasket problem would not send me to the machine shop.

The machinist I took the head to is very experienced. He also did all the machining for my B30. My concern was addressed by "Kentucky". Thanks. I didn't know if the head could be machined with the cam assembled. The "cooking" procedure was what I was taught, but I was unsure what the limit was.
Two more questions: With the head off, what is the best way to prep the block surface? As of right now, I have all the HG residue scraped off using a gasket scraper and cleaned with brake cleaner. Is there anything else that should be done?
Also, I noticed today vertical scuff marks on all four cylinder walls, right hand side of the block. Is this something I should be concerned with? If it matters, I can still see the cross-hatch on all cylinders and as far as I know, this is the first time this engine has been opened.
Thanks again,
Nick

I usually like to prep the block mating surface with a whiz wheel (cookie cutter). The air powered thing that does about a million RPM and has the 2" abrasive disks. Just to make sure the block is dead clean.

NEXT:
Scrape off the carbon from the top of the cylinders. As for the scratches in the sidewall. It is a fact of life with the lower tolerance engines. Caused by the piston skirt sliding around at the bottom, known and piston slap.

I rebuilt a B230 block for my college auto class. Cost damn near 2k. I wouldn't get any further into this project than you need to.

If you can. See about getting a 5 or 6 angle valve job. I did that to my head. Talk about more power!! Can't get the motor to idle over 300 RPM, but even at 300 it is dead smooth.

Good luck, and remember to keep smiling!!

Andrew

Nick,

My head (B230FD) is in the shop of an experienced machinist now. It checked at 0.004 inch arched high in the center. It was my machinist' opinion that 0.004 was an acceptable amount to shave off of an over head cam head, though he did say he would check it for flatness on the top as well.

When they seriously warped, he straightens them by clamping/shimming to a heavy metal plate and cooking them in the shop oven.

Charley

Just like Walrus3 said, (more or less), don't sweat it, but I have different advice. Have the head milled if it is under 0.010", its relatively cheap to do so, won't adversely impact timing, and any small corrosion pits around the coolant ports will be eliminated. I call that another 500K mile insurance policy.

jorrell
--
92 245 278K miles, IPD'd to the hilt, 06 XC70, 00 Eclipse custom Turbo setup...currently taking names and kicking reputations!

If it is otherwise in good shape I don't believe I would mill it. Others may have different opinions.
If it was much more, I WOULD mill it, especially if the center were low rather than high.
--
George Downs, Bartlesville, Heart of the USA!

There is a tolerance specification and it may be within the allowance. Check the manual. Some is expected that's the reason for gaskets. Even for the freshly machined heads that have set on the shelf.

That is not very warped! Especially if it from end to end. .006 might be maximum. Only .003 from the end surfaces, each. I'm just guessing about max.

As long as the machine does not impart any stress from clamping of the head. All of the other stresses should be relieved by now from the repetitive heating. What is there now is all that there should be.

I have wondered, if they can do it with the cam and all in place. I believe they do it with the head face down and the cutter is under it. They call it a broaching mill table. I have never seen all the types of automotive machining equipment per say. They are usually special single purpose machines.

Like brake drum machines. Just hope you don't get a rookie kid that wants to bury the cutter so he can make it in one pass. I hate that on brake turning.

I want the same with my brake disc as long as I get rid of hard spots if I ever get them. Machining as little from it saving as much to keep it as thick as possible so they won't warp again and prolong the repurchase by staying above the minimum thickness.

If I did my own head I would use a regular milling machine I have. Of course its more labor on my part from the way I would have to clamp it lightly with shims. I would indicate it as flat as possible and take as little as possible. Actually leave a witness mark of the prior surface. 90%+ cleanup. That is just my preference.

Then again. Like Jorrell say's, if it has any corrosion pits that could get worse it has to be considered. If the head has a lot of miles. It was probably the gasket that gave up the ghost. It happens even if you keep good coolant but it's quicker if you don't!

Your there now. If its needed, then this is the time?

It would take both to push me harder since I would do it the hard way!

Phil