Would you reinstall this cylinder head? (Pics)

[Launchpad McQ]

Well in a feat of immense stupidity I may have inadvertently damaged my cylinder head beyond repair. After removing the head to access the valves for my ongoing "in-boat" overhaul (un-seizing, valve cleaning, new valve springs, new gaskets, etc) I vinegar bathed, pressure washed, stripped, and painted the head. After which I placed it in a large "Tupperware" container for temporary storage and left it on the boat while I turned my attention to other matters. This afternoon I pulled the head out from under the pile of parts awaiting reinstallation only to discover that the face has seemingly corroded (substantially IMO) in a matter of weeks...ok maybe its been months but nonetheless I can't believe the corrosion especially in the area of the cooling passages:

What the head looked like when I pulled it off the motor...


and now...
(Sorry for the 'reflection in the pics.' In my panicked attempt to close the barn door after the horses left I coated the face with a copious amount of MMO to stave off further corrosion while I determine the best course of action)




In the forum members' opinion, would this head still be a candidate for reinstallation, or now in need of resurfacing, or replacing? If resurfacing is what the Doctor orders does anyone have a favorite SF Bay Area machine shop?

at least the top looks good now ...

[hanleyclifford]

I would reinstall that head. First give it a scrape with a large flat bastard file.

[Al Schober]

The corrosion isn't that bad - those head gaskets fill a lot of sins.
I would check how flat the head is from end to end (as well as the block). Straight edge and some feelers should do it.
If you really want to take it to a shop for work, ask your local favorite mechanic who does their cylinder head work and then take it there. Last place I took a head for flattening had a big belt sander. Put the head on it, turned it on, added a barbell weight, and went for coffee. Checked it after 5 minutes and took it off after another 5. $20 changed hands and we were both happy.

[lat 64]

With much respect, I disagree with both reinstalling that head as-is, and using the belt sander style resurfacing.
If you are experienced at evaluating engines for machine service, then disregard my advice.
If you are logging in to this forum because you are not, and need an evaluation, then a photo is helpful but does not tell absolute truths and measurements.
Take it to a good custom machine shop to be inspected.
If they recommend surfacing, specify a broach-cutter machine to do this.

You will get lots of pushback on this advice I'm sure. The belt sanders sell well to shops that don't want to spend twenty grand on a real head machine. The main difference is the direction the machine marks line up across the gasket surface.
The broach cutter makes rows of good "tooth" between the combustion chambers. On the other hand, the belt sander makes grooves straight from one combustion chamber to the next. Sometimes when a new belt is used, not properly broken in, it makes an especially deep groove.
Flathead-engine cylinder heads are the easiest to set up on a milling machine. You will most likely pay a flat rate for the work. It used to be $20 back in the '90s in Alaska.
Must be $50 now.

Belt sanders and files are carving tools not machines.

My wild-a$$ guess, it will clean up at .020"

Full disclosure: I did this for a living, so it is the way I respond to uncertainties. Make it flat. Then it's flat.
R.

[ndutton]

I agree, let the pro's assess the condition and recommend a suitable repair if any. One thing's for sure, if any material is removed from the surface be sure to reinstall using two head gaskets.

[Dromo]

Also It looks like you got 4 blocked water passages
You might want to address that first
Rick

[thatch]

I would certainly go along with Russ's input concerning what to do with this head. Having said that, there is one area that should be looked at carefully, and that is the inside of the thermostat hole. Depending on how much internal corrosion this head has seen, it could be quite thin limiting the "skim cut" that can be taken.
Tom

[hanleyclifford]

Spoken like a true professional, Russ and I can see why the appearance of that head disturbs you. But Thatch makes a good point about the thin metal under the thermostat. Will .020" do it? We don't know. Has this head ever been cut? We don't know. If we do know that this head came off a running engine and that it had good compression, and was not subjected to an overheating event, and we can see that the essential material between the cylinders is largely unaffected by the "acid" event, IMO it is worth investing a pair of gaskets to find out if the thing will otherwise seal where required. In the automotive (and especially hot rod) world of real compression and horsepower we would not even be having this discussion. If the head is reinstalled and tests OK for cooling system pressure and compression the pitting is likely to slumber unknown for many years. If it should fail the test, the financial exposure is a pair of gaskets and a measure of exasperation.

[romantic comedy]

Hanley, good point. I also worry about pulled studs in the casting when doing head work.
How much of a worry is this? This is probably the reason that I have not rebuilt my engine yet. (No, it is not broke, just smokes with great compression)

[hanleyclifford]

Originally Posted by romantic comedy

Hanley, good point. I also worry about pulled studs in the casting when doing head work.
How much of a worry is this? This is probably the reason that I have not rebuilt my engine yet. (No, it is not broke, just smokes with great compression)

Well, that is another question. I believe Don has the standard that 3 full threads must exist in the block for the stud to be reliable. Whether to rebuild or tolerate is a question related to how you use the engine.

[Dave Neptune]

McQ, I agree a bit with Russ and Thatch on this to a point. There are not a lot of shops around that even understand the flathead engine anymore. First check the head to see if it has been surfaced before. If it has I'd take an approach like Hanley. If you are not skilled at the "flat draw filing" methods there are other ways and it is really not that difficult. The trouble with most shops is they are going to probably try a single pass to surface (time is money) and remove far more material than necessary. This raises the compression and reduces the ability to breath at the same time.
Keep in mind that these flatheads can be far more warped and still draw down to seal just fine, a thin head like these is not as fussy as an overhead head for cracking.
My main concerns at this point would be inspecting the studs and threads and being sure they are properly sealed. The number of good threads in the block is the big question.
If the surfaces are not perfect I suggest that you do use aviation grade on he gasket(s). It really helps seal and does so very well, the down side is just the clean up if you have to R&R the head again.
I also recommend (just my choice personally) that if you are a direct drive you use a single gasket and if you have a reduction of any sort use 2 gaskets.

Dave Neptune

[lat 64]

Originally Posted by hanleyclifford

... But Thatch makes a good point about the thin metal under the thermostat. Will .020" do it? We don't know. Has this head ever been cut? We don't know. ….

This is why I use the term "respectfully". I've cut lots heads. But for this particular engine, our A-4s, I only have one rebuild to my experience and there are so many little unique points of concern to watch out for. Sage advice from Hanley. First do no harm.

Originally Posted by Dave Neptune

...The trouble with most shops is they are going to probably try a single pass to surface (time is money) and remove far more material than necessary….

Dave,
Do you have a recommendation for a good custom shop that would understand these concerns?

Another concern is time. If a new head is $412, then at what point does all the experimentation become too expensive?
Myself, I would keep experimenting because I'm budgeted(read poor).
If Launch has a other priorities(sailing, wife, job,) then the nuclear option could be favored.

Good thread,
Russ

[hanleyclifford]

If this operation were being done by a professional there is no doubt but that Russ is dead right. The head goes to the machine shop and maybe for more than a little "slice". What if those "wormholes" don't clean up at .020", or .030", or ever? What if the casting is compromised internally which we certainly cannot see? Would I drive 1000 miles from home with that head on my engine? Well, yes - but I carry a spare and have no reservations about doing the job swinging on a hook. These kind of subjective decisions almost always come down to how is the boat to be used and what is the skill/tolerance level of the operator?

[Dave Neptune]

Russ, I'd go to one of the Hi Perf shops in the area and start talking. If they say they are able to do a "kiss pass" of between .005 & .010, I'd give them a try. Any shop that can do decking and line boring should be able to do a simple flat clean-up pass. Perhaps even surface grinding at a grinding shop.

A flat draw filing and or some emery and a flat plate will work wonders on a head. I did mine with a "Block" and emery some 30 years ago when it was bought and at that time it was seized. I think my head looked far worse as far as pits. Using the Permatex with the pits really gives some grabbing area for the sealer.

I still would be more concerned with the studs, there threads and sealing them.

Dave Neptune

[romantic comedy]

Back in the late 90s, Don talked about a rough finish to the head mating surface. I think #125 was mentioned. This area I dont know about.

Anyone know about this?

[Dave Neptune]

romantic, yes indeed I do. If the surfaces are to slick or smooth there is nothing to grab for the gasket or sealer. Often on flat surface sealing areas for the gasket we would work with a hammer and a "center point" and put little dents all over the place, gives the gasket and the sealers something to bite into, aluminium is usually more problematic for this.

Dave Neptune :cool

[lat 64]

Originally Posted by hanleyclifford

If this operation were being done by a professional there is no doubt but that Russ is dead right. The head goes to the machine shop and maybe for more than a little "slice". What if those "wormholes" don't clean up at .020", or .030", or ever? What if the casting is compromised internally which we certainly cannot see? Would I drive 1000 miles from home with that head on my engine? Well, yes - but I carry a spare and have no reservations about doing the job swinging on a hook. These kind of subjective decisions almost always come down to how is the boat to be used and what is the skill/tolerance level of the operator?

Yea, We're really on the same page with this.
Guys like you, me, Dave, and all the other experienced engine builders can patch something together and live with the consequences ie. carrying a spare to do repairs in a remote place.

Not knowing another's skills, budget, or risk-aversity, I always err to sending them to the pros.

Launch,
Dave's recommendations of shops carry some weight with me. He makes the tooling that some of these shops use.
Call around and don't be afraid to tell them you are an amateur that is "restoring" an old engine. A good shop will have fun with the project.
If they blow you off as a know-nothing, go to a different shop.

Russ

[lat 64]

Originally Posted by romantic comedy

Back in the late 90s, Don talked about a rough finish to the head mating surface. I think #125 was mentioned. This area I dont know about.

Anyone know about this?

Yes, that is in line with my tirade about broach-cutter milling machines(that is, I like them best). They make grooves in the right direction more or less.