I believe I had mentioned that I had a completely ported slant head that I decided to go back and take another cut inside the intake bowls.

This head had new guides, seats ,,,,and I ended up breaking into the water jacket on one bowl.
I found a machine shop here in Indy that said they could weld it. ( Richards Cylinder Head Repair). I spoke directly with the shop owner, he said he was 99% confident that he could repair it.
They also said they would do a leak test to verify the repair.

The price of the weld repair was reasonable enough, $125.00
After the repair, I put the head on my leak test apparatus, at 10 psi in the water jacket there was one pin point at the weld repair where, when I sprayed soapy water bubbles would slowly form. You could stand there and watch the bubble slowly fill. Repeated the leak test a couple of times and convinced myself the leak was really tinny, but it was there.
I considered having the head welded again, but I did not want to send it back through the heat process so I looked into impregnation.

Found a shop in Fort Wayne IN that would do one off jobs. (Industrial Anodizing) It ended up being pricy, $300.00 however since this was a finished head and the leak appeared to be the size that impreg would resolve, it was done.

Got the head back and ran it across my leak test process, at 20 PSI in the water jacket, with soapy water sprayed into the port where the weld / leak was, the soapy water lays flat, no movement - no bubbles. I tested it a couple of times. The leak is repaired.

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Doo Ron Ron and the Duke of Earl are friends of mine.....
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Still not a bad price. Of course, the true cost of impregnation usually begins after 9 months lol.

But really....what is the process?

here is a link that discusses casting impregnation.

https://www.godfreywing.com/blog/how-im ... sure-tight

The impregnation process is real common in aluminum die casting. I would bet that many die cast automotive aluminum transmission cases and engine blocks are impregnated as part of the normal production process. It can also be used with cast iron, but is not as common as cast iron does not typically have the porosity issues that aluminum has.

basically with impregnation,
the clean part is put into a pressure vessel, the vessel is sealed and a vacuum is drawn, the impregnation fluid is flooded into the vessel, due to a vacuum being present the impregnation fluid will penetrate into the casting pores. The fluid is pumped out, atmosphere is re introduced into the vessel, the parts are removed.

the impregnation fluid is similar to Loctite, it flows and wicks easily,

_________________
Doo Ron Ron and the Duke of Earl are friends of mine.....
https://www.youtube.com/watch?v=uX8Nj8ABEI8

That is a good price. I was quoted it would start at $500, just to bake the head, then add cost of welding.
-Matt

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-MattMan
LEANED & MEAN

I learned something new!

I read the article in the link you posted, but I still couldn't tell what the material is that is used in impregnation. Will it stand up to heat and pressure in the head? I assume so, but what, exactly did they use to fill the pores? I researched this a bit more and it seems they use aluminium, magnesium, cast iron, steel, and carbon fiber composites. So, depending upon which material they use, it should stand up to the temperatures/pressures of the head.

I heard a story about a run of V8's on the Mercedes Benz production line. They made it through somehow, the blocks were cast aluminum I believe, and very porous. Customers were going to the dealers with bad oil leaks. It turns out the oil was literally seeping through the sides of the block. They had to replace a ton of engines due to that bad run and poor QC.

Brian

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That was really my question, too. I'm very familiar with VPI processes but a big question is always 'what is the material?'. You can use just about any liquid but it needs to be the 'right' one in order to do what you want - and to last.

The actual material used in the impregnation process is a combination of
beeswax and vasoline, mixed to a consistency of pancake syrup, it is most effective when applied to a warm part on a moonless night, in the presence of a Toad, either animal or vehicle.....

Just kidding, both the web site that I linked in the original post and the web site of the supplier that I used and named list the MIL standards that apply to the impregnation fluid.
In the case of the cylinder head that I just had impregnated the cost could have been as low as $100.00 to get the process ran on my part, however as they were
currently in a run of parts that required a different MIL standard fluid I had to pay a $200.00 change over fee to get my part processed.

Back in my working days I was involved in a project that oversaw the impregnation of thousands of fully machined diesel cylinder heads to fix leaks in: intake ports, exhaust ports, head stud bosses, injector ports,,, due to pososity in a very difficult to cast iron cylinder head. Was 100% of the leaky heads fixed with impregnation, no. As some of the defects were too large to be resolved via the impreg process. The fixed net averaged in the 70% range. But of the heads that were fixed, and by fixed, what I am saying is they were then passed by the same production leak decay test that had rejected the head initially, the heads went into use in the field with zero warranty claims for failure related to leaks. Prior to releasing the process for use, there were internal engine reliability and durability tests ran. When applied correctly to a void that is within the size range that the process can handle, impregnation is a casting industry standard method to repair parts that have porosity.

If you are looking for something that you can try in your own garage, use Loctite 290. That is the green wicking Loctite that can be applied to a threaded bolt and will wick up and around bolt threads.
here is a Technical Data Sheet for the Loctite 290

https://tdsna.henkel.com/americas/na/ad ... 290-EN.pdf

The TDS mentions that the Loctite 290 is suitable for sealing porosity in castings, welds,,,
Although no defect size is listed, the porosity would need to be pretty fine, but so is the space between a threads of a threaded nut and bolt and it wicks through those.
I would consider the vacuum impregnation process to be superior in sealing and strength to the bench application of Loctite 290. But certainly Loctite 290 is intended for bench application.

_________________
Doo Ron Ron and the Duke of Earl are friends of mine.....
https://www.youtube.com/watch?v=uX8Nj8ABEI8

Thanks a bunch for the info, John, and everyone for the discussion. I have an old head that leaks in an exh port and tried to get it fixed but it failed. I might try this. The head flowed really well and made several drag passes and a roundtrip to Mopar Nats, but popped and leaked in a thin spot after some abuse.

Lou

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Home of Slant6-powered fun machines since 1988

On a repair like this, is it worth it before the repair to have it sonic checked for thickness, so see what you are working with?

Not a bad idea, when necessary.
The head that I had repaired, an error in my technique allowed the burr to set in one spot too long, there was a definite depression that I could feel with my finger where the wall break through occurred. I could judge the wall thickness around the void.

If you have a head with a visible hole in a port wall, where there is not a tactile depression at the wall hole, it would be appropriate to probe around the hole very lightly with a small diameter drift to attempt to gauge the thinned area size, to see if a weld repair is feasible. When welded the extremely thin areas at the edge of the hole will be blown away anyway. If the hole keeps spreading as weld heat is applied because the wall is thinned out over too big an area, it will not be weld repairable.

And how thin is too thin for a port wall? With all the over bored slant sixes running around and large over bores on some of the drag racing slant sixes, a guess is there are cylinder walls in use that may be around a hundred thousands thick. Those cylinder bore walls will see a lot more pressure and many more shock waves than a water jacket to port wall will ever see.

The wall thickness that we see in head cut ups is due more to make the part castable than it is for strength. If the head internal walls were designed on the thin side, it makes the part much more difficult to cast. The poured metal cools significantly as it flows around the cores and mold walls. When two fronts of liquid metal meet they must be hot enough and liquid enough to fully intermix prior to solidification. If the two fronts of liquid metal do not intermix, but touch and solidify separately there will be a linear defect, typically called a 'misrun'. A thicker wall takes more metal to fill, more metal means more retained heat, more retained heat means the separate fronts of liquid metal are more likely to intermix prior to solidification.

_________________
Doo Ron Ron and the Duke of Earl are friends of mine.....
https://www.youtube.com/watch?v=uX8Nj8ABEI8

Had lunch today with Jonathan, the guy that does the valve seats for me. I told him of the head that I had welded and impregnated.

He said that he has had good luck with Z Spar Marine Epoxy in intake ports to fix small water jacket break throughs.
He also used it to change internal port shapes. He said he would not use it in an exhaust port .
Also mentioned that it smooths off best after cure with a sanding roll.

here is a link
https://www.go2marine.com/Z-Spar-Splash ... poxy-Putty

Note: at the link it is stated that the product is used by "race engine builders".

_________________
Doo Ron Ron and the Duke of Earl are friends of mine.....
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