I have been contemplating putting a set of Edelbrock aluminum heads on my 360. I was sharing my plans with some fellows I work with and one of the guys tried to deter me from buying them. I asked him why and he said back in the mid 90s when he was drag racing he had used a set of aluminum heads on his tube chassis car and had issues of the metal going soft. He said he discovered this, I believe when he removed the heads to repair a crack or perform a port job on them, I'm not sure why they were removed from the engine in the first place. Either way the machinist told him the metal had gone soft the heads were junk. This is the first I have ever heard of this, and although I am not a racer or pro. engine builder I have been reading magazines and working on cars for about the last 20 yrs. Is this something that was a problem back in the 90s and its now not an issue or is this something that could happen now. Most new cars are running aluminum heads so I have a hard time believing this is a current problem. Thoughts?

I have ran many different aluminum heads, many. I ran aluminum chevy heads in the early 90s and no trouble ever. My 1985 3 wheel ATV has a aluminum head also and it still runs great.

First time I have ever heard of that. I have run aluminum heads on BBC, SBC, BBM, and SBM and Brad hemi heads and others I'm sure.

I have had a set of eddies on my 340 since 2007 and have driven the car almost 20K miles so far in some really hot and cold conditions. Like Vegas in July and Reno in Aug and pikes peak at 32 degrees. Plus ran the car wide open at Bonneville for miles at a time. I put my 340 eddie heads though extremes and they have held up great.

Can't believe what people say, just like the internet. We are all full of sh!t.

The only way to find out for sure is to get off the internet and just go do it yourself and become experienced.

Good thing my Brad heads didn't go "soft"!

I heard that they have a fix for that. Its called alumagra. You have to be careful as if you put too much on the heads they will not fit the engine anymore and you will have to seek the services of a machinist.

Well I would say you are right about the internet and "people" and usually I wouldn't even ask a question like this figuring it was bs anyway, but I have worked with the fellow that told me this for about 7 yrs. and he is one of those super sharp fellows, but it is good to know that this was probably just a fluke.

hey may have been old heads and needed a bit of Viagra or Cialis in the oil. I heard that will stiffen them right back UP

Maybe the "soft spot" was a porosity issue or core shift?

Unless it's a bad run of heads, about the only way to soften up the head is to much heat.

I guess it is possible if you overheat some of them.
I don't know how is too hot, depends on too many things, it sounds.
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It sounds like your buddys shop had a set of heads they wanted to sell I have had some of the original Mopar aluminum hemi heads seem soft when torquing the head bolts down with washers under them What motor was your buddy racing and which type of racing? Edlbrock wasn't makeing Mopar heads out of aluminum yet in the 1990

Well... One thing I can think of is that I have seen old coolant turn acidic and eat through aluminum intakes. Not so much a matter of the metal "going soft" as much as the metal getting eaten away because someone was too cheap or lazy to change the antifreeze once or twice a decade.

Maybe your buddy sniffed too many Nitro fumes!
Aluminum doesn't go soft. It does corrode if the proper coolant isn't used. Electrolysis occurs when straight water is used and left in the engine. After awhile, corrosion forms and can make the aluminum weaker and porous.

I have seen aluminum plate and bar that doesn't meet mechanical properties from the producing mill due to problems with the thermal ageing process. Perhaps the heads never met properties and somehow escaped the quality control checks and the billet was shipped to the machining house where the heads were machined and assembled.

I heard that Saturn 1 cam engines develop porosity in the aluminum block beyond 100k miles. Twin cam version does not have the same issue. Porosity is not the same as "soft" in my mind, but maybe that's what he was suggesting. Or straight bluffing.

Is your friend is a Chevy guy? Maybe they were dissolved by the coolant?

I had a guy tell me that POR-15 caused hydrogen embrittlement, making metal to brittle because it draws all of the water from the metal.

Typically cast aluminum heads and blocks receive a T6 heat treating process. If the process is not done correctly they can be "soft". I don't know what could cause them to go soft if they were ever done correctly in the first place. It would take a pretty high temperature exposure.