RH4 head question

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NickZ said:
I am including photos of the inlet guide tubes, which I think appear ok.
I want to thank everyone for not busting me for including photos of the exhaust guide tubes earlier when I was referring to inlets..lol
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Maybe it's my eyes or an effect of the camera, but the left guide hole looks appreciable larger than the right.
 
NickZ said:
I am including photos of the inlet guide tubes, which I think appear ok.
I want to thank everyone for not busting me for including photos of the exhaust guide tubes earlier when I was referring to inlets..lol
View attachment 20886
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There's no busting from me on this, as stated earlier an RH4 head is known to crack around the inlet port valve guides and the guides can come loose and let oil down between the guide and the head
The head can also leak oil through porosity
I would get the valve guides fitted by a Norton specialist if I were you
 
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baz said:
There's no busting from me on this, as stated earlier an RH10 head is known to crack around the inlet port valve guides and the guides can come loose and let oil down between the guide and the head
The head can also leak oil through porosity
I would get the valve guides fitted by a Norton specialist if I were you
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You mean RH4 right ?
 
gortnipper said:
Blast it again and then rinse with a pressure washer, and then try the dye?
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I think this might be the best approach. It was pretty much painted all over, except some spots inside the rocker area and between the rocker housings where the spray was blocked. I'm beginning to wonder about this painting. Why didn't they mask gasket mating surfaces (including head gasket)? Why would someone paint the combustion chamber area? Trying to hide defects? If that's the reason, it didn't hide the porosity. Other than that, it sure looks pretty.
 
cliffa said:
Maybe it's my eyes or an effect of the camera, but the left guide hole looks appreciable larger than the right.
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I haven't been able to measure precisely, but I think you may be right about that, meaning I think the left hole may actually be larger.
 
Torontonian said:
Any way you look at it , this RH 4 will end up in a competent shop to fit the new guides and cut/seat the new guides and will do the penetrate dye test first too. I'd get it skimmed flat too All of this from a good machine shop.
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I would appreciate any references for such a shop in southern California or central coast.
 
I thank everyone for the advice regarding checking for cracking around the intake guide holes, and I will do that. And about getting a competent shop to install guides etc. I plan to do that too.
But back to my original post: How concerned should I be about the porousness of the metal, particularly the left side combustion chamber?
Is this just cosmetic? or Will it cause operational or maintenance problems? Can it be repaired or mitigated?
 
NickZ said:
I thank everyone for the advice regarding checking for cracking around the intake guide holes, and I will do that. And about getting a competent shop to install guides etc. I plan to do that too.
But back to my original post: How concerned should I be about the porousness of the metal, particularly the left side combustion chamber?
Is this just cosmetic? or Will it cause operational or maintenance problems? Can it be repaired or mitigated?
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I would recommend you send it to Jim Comstock aka comnoz here on the forum. He is in Colorado but I believe the postage is worth it, to have someone with his expertise assess it before proceeding and wasting money. Perhaps the new or newish process of ceramic coating could help out with the porosity problem.

p.s. MichaelB beat me to it.
 
Don't sand blast it - it could get worse. Media blasting is probably what opened up the pitting in the 1st place (its happened to me).
Someone should be offering screw in guides (with sealant) for the RH4 heads to prevent cracking (its been done before).
 
jseng1 said:
Don't sand blast it - it could get worse. Media blasting is probably what opened up the pitting in the 1st place (its happened to me).
Someone should be offering screw in guides (with sealant) for the RH4 heads to prevent cracking (its been done before).
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Makes sense.
 
NickZ said:
On closer examination of the head, it appears that it was media blasted, then spray painted (including all gasket surfaces). Not sure what kind of paint was used. It didn't come up when I tested it with lacquer thinner or denatured alcohol. I sanded it off the center head steady bus and you can see it compared to the other bus and also compare the exhaust ports which appear to have been machined after the painting (pictured with initial post).
This is significant because I don't think my dye penetrant will be effective if applied over this paint. Any ideas on what kind of paint this might be?
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It is probably an epoxy or polyurethane based paint if lacquer thinner did not lift it. Aircraft paint stripper used to contain chloromethane [aka methylene chloride or methyl chloride]. That is the "super" ingredient in aircraft paint strippers. However, at least in the USA, this chemical has been banned for consumer products as of 2019. I have found that polyurethane paints can be ignited and burned. That doesn't totally remove them. However what is left is soft and easily removed with a putty knife [paint scraper] or the now less effective paint stripper.
Regarding the recommendation of using a spray dye penetrant for crack checking, be aware that these products can result in a false positive. I have personal experience with this on a Lycoming aircraft engine crankcase set. I asked a local shop to do an electro eddy current testing. In stead, they used the dye penatrant process. They claimed that the cases showed 3 cracks. I then took the cases to my local aircraft propeller repair facility, who actually had the equipment to do the eddy current testing. Turned out that the "alleged" cracks were simply artifacts of the casting process.
Only use crushed walnut shells or plastic media for media blasting. Sand or glass media will enbed into the aluminum. When installed and raised to normal [hot] temps, the pores of the aluminum will open. This will then deposit the abrasive media into either/both the engine oil/cylinder.
 
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