Honda GX390 cylinder head dowel removal

[lee]

I've got a GX390 that blew the head gasket. The area on the head where it blew is rough so I want to tape some 600 sand paper to a granite counter top and polish the head. The problem is there is a hollow dowel in the head that I need to remove. Any ideas how to get this out without destroying it? I was thinking I could find a socket or something to fit inside the dowel so it wouldn't crush and then try a pair of vice grips on it. So far I haven't even been able to find anything that fits snug inside the dowel. Any ideas how to get this thing out?

[KE4AVB]

Considering it is under $2 to replace it do what you need to remove it without further damage to the head. Probably a good pair of vise grip type pliers to compress it.

[Fulltilt]

I've got a GX390 that blew the head gasket. The area on the head where it blew is rough so I want to tape some 600 sand paper to a granite counter top and polish the head. The problem is there is a hollow dowel in the head that I need to remove. Any ideas how to get this out without destroying it? I was thinking I could find a socket or something to fit inside the dowel so it wouldn't crush and then try a pair of vice grips on it. So far I haven't even been able to find anything that fits snug inside the dowel. Any ideas how to get this thing out?

You don't want to polish the surface! Personally I use 180 grit dry self stick DA ( orbital sander) paper. Done it many a time, with excellent results. I wouldn't use 600 grit, too fine. You want to leave the surface with a little tooth to it.
The main thing is to make sure the head is flat with no warpage.

[lee]

I grabbed the dowel with some pliers and got it out. The head is warped though. Would it be worth taking it to a machine shop to get it milled, or should I get an aftermarket head off Ebay for $50. I've got another head that came off an engine that the previous owner let sit outside and got water in it. The intake valve and seat were rusted so I cleaned them up with some fine sandpaper. It's not sealing though. I've never tried lapping a valve but if you all think it would work to get this intake valve seated again I'll give it a try. Maybe I should take both heads to the machine shop and see what they say? In summary I've got one head that the valves are good but the head is warped. I've got another head that the gasket surface is perfect and the ex valve is sealing well but the intake valve is leaking. What do I do now?

[KE4AVB]

Machine work isn't cheap.

Unless you have a machinist for a neighbor that is willing to trade out work then either buy new head (off Evilbay if you wish) or lap the valves on the other head. Lapping is fairly easy to do just make cleanup all the compound and other grit when done. I would go your gut feeling on this one as you're a lot closer to the current items. My all seeing eye is on the blink right now.

[Fulltilt]

If you have a small eng. shop in your area ( Craigslist) take the head to them and let them lap the valves in, not a big deal as long as the seat isn't pitted. Could probably use the valve/s from the warped head if needed.
As for the warped head, did you not read my post? I have rescued several Briggs heads ( pretty common on certain models), using sandpaper and my chunk of dead flat granite.
Start out coarse with like 60-80 grit dry paper and finish with 180 grit dry. You can probably get some self stick paper at hardware or auto parts joints.
I use self stick DA paper avail in rolls,from my painting days, but they may sell it in smaller quantities. I suppose you could also tape plain paper down.
Use a circular motion with as even a pressure as you can. You'd be surprised at how quickly you can get them reasonably flat.
I use my trusty Snap-On straight edge ( not avail at Harbor Freight ) to check for flatness, but I suppose you could hold the two heads together to check.

[KE4AVB]

Much easier done with a pane of flat glass and a thin liquid such as 3 in 1 oil or machinist's blue(red) when checking for flatness.

[lee]

i went to the only machine shop in town and they didn't want to fool with either of the heads. They said the heads were too small to fit on their equipment and they would have to make a jig to hold etc. So I stopped by Autozone and got a tube of valve grinding compound. I put some compound all around the valve head, then put some 30 wt oil on the stem and pushed it in the head. I attached a cordless drill to the valve stem and spun it with the drill while working it in and out to make contact with the seat. After a minute or so I took it all apart and wiped the compound. I could see a nice contact band all around the valve head. So I cleaned everything up and installed the head. I pressurized the head through the spark plug hole with the rocker arms off. A very small amount of air was leaking through the intake, nothing like what it was doing before. So I put the rockers on and adjusted the valve clearance. I put my compression tester on and it topped out at 80 psi. Before it topped out at around 50. So I put it all back together, pulled the rope and it started and ran perfect on the first pull. So the engine that had the blown head gasket is up and running again.
The other engine that got water in it turns over fine, the cylinder looks ok, and the oil looks fine (not milky) so I'm thinking it may have just gotten some condensation in it from sitting outside. So I think it will run if I can get a good head on it. So tonight I'm going to tape some 80 grit sand paper onto my granite counter top and and see if I can get this head flat. I've got nothing to lose as the head is warped and the machine shop doesn't want to mess with it so it's a paper weight right now.

[Fulltilt]

It will work. Just finish with something like 180 or so dry. I use both a circular motion and then a twisting motion while pressing straight down. Ideally you want to get it dead flat, but up to about .002 will be OK. Use your feeler guage on the granite. You can also use a sharpie to color in the warped area, then when you get pretty much done, mark a line all the way around the gasket surface and sand till it's pretty much gone.

[lee]

I think I got it pretty flat with the 80 grit tonight. The area where the head gasket blew on the exhaust valve side was low and had a scratch in it that took a long time to sand out. The areas around the head bolt holes were the high spots. I'll finish up with some 180 grit tomorrow. The head gasket the came on this engine is a thin metal shim maybe .010-.012 thick not a composite gasket. This engine was on a pressure washer. Question: Is this an OEM Honda head gasket? I'm used to seeing the thicker composite gaskets in stock engines and I'm just wondering if this thin shim gasket might have had something to do with the failure. It's getting replaced with an aftermarket composite gasket.