Cosmo Kramer

I have read that many machine shops will use high temperature epoxy based filler on aluminum heads that have pits in the areas where there isn't gasket sealing. It is less evasive then welding and holds up just fine. The epoxy is non porous and keeps the coolant out of the damaged area and causing further spreading.

Chris Lockhart

There are too many deep spots close to the fire rings. I definitely want to fix it right. I would prefer to NOT have to do this again. LOL.

Chris Lockhart

Here's another:

Cosmo Kramer

Agreed those are too close to the sealing area to leave. Some are already creeping under the gasket area. It has become a common repair with so many vehicles having aluminum heads and bad coolant, so you should be able to get it done locally.

Check your cylinder tops and make sure they are ok too. Also if the heads are pretty true get them to take the least amount of material possible to which will give you a buffer in case it needs work again.

Chris Lockhart

That's a big part of my problem. I can't seem to find a local automotive machine shop that I would trust to touch these heads. Been searching on and off for a year. I'm going to start a new thread on cleaning the bores/piston tops. Thanks for the help.

69gaugeman

The one spot where it looks like it is under the fire ring makes it a gamble to leave it. Likely it will be fine unless you are stressing the motor by putting on forced induction. Any shop that does quality work can machine these. It's not rocket science. Ask around at the car clubs in the area. They would have a good idea where to go.

linderpat

I would guess cavitation would continue to cause the imperfections to grow. Thus, unless repaired back to smooth, it won't matter about the quality of the coolant.

Jim Devine

Something to consider- the 1/2 off sale at 928 INT. starts soon. Don't know what it would cost to have your heads properly welded and machined vs getting a different pair, but might be an option.

Also- if you go that route- hang on to your heads, in the future when the supply of used ones dries up they will be worth having.

Chris Lockhart

Was thinking about that too. Need to talk to Mark Anderson and see how clean the mating surfaces on their offerings are.

69gaugeman

I'm not sure that the flow around there would be enough to cause cavitation. That's not what causes this in the first place.

GregBBRD

I realize what causes tooth decay. I was just trying to find an analogy.

Leaving even a tiny amount of old decay will cause new decay under the new filling. Same thing with the aluminum (obviously not from bacteria.)

I'm guessing that unless all of the bad aluminum is removed, the acidic material remains at a molecular level and eats at new aluminum.

Note that I'm not a scientist. I'm a simple dumb mechanic. I can only speculate on what I see and try to pass on any knowledge I might have gathered.

In my opinion, the heads the OP asked about need to be repaired.

terry gt

I think Greg offered you some very good advice . aluminum needs to be very clean to weld . Find out the alloy too , first thing my welder on staff asked me .

ptuomov

My personal opinion is that it's so expensive and time consuming to otherwise check and then install the heads that I would as a policy repair any damage that I see when the heads are already off. That's just a personal opinion, though.

Rob Edwards

Build a pair of boxes (or wrap them 3x in corrugated cardboard and 2 rolls of strapping tape) , ship 'em to Greg, fix 'em right, done. Mark might have a good set of R2 (or R3) heads on the shelf but it'll be cheaper to fix the originals and have them good as new.

Adk46

Corrosion is a very complicated topic - I've sat through several graduate level courses, and worked in labs that worried about corrosion. Still, I'm hesitant to say anything here, since I've never had any direct involvement in this specific sort of corrosion.

But here's the general deal: Corrosion involves differences in chemical potential, here versus there. We all know this from observing dissimilar metals, and yes, a chemical potential is the same thing as an electrical potential in this context. Even in a seemingly uniform bit of metal, there are differences from due to impurities, grain boundaries, casting segregation, etc. Then you have differences between an exposed surface and within a crevice, or a pit. If it leads to a reaction, you might get the reverse of anodic protection, where the large surface is safe, but the base of the pit is attacked. The pit evolves to have it's own mix of ingredients; the good stuff in the coolant doesn't get in, or is overwhelmed.

A tooth cavity is not such a bad analogy, since it gives a safe home for bacteria to concentrate and do their nasty business.