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cast aluminum hardness

H

headrebuilder

Plastic
Joined
Nov 29, 2006
Location
Virginia
We are an aluminum cylinder head rebuilder and for years we have repaired heads that were overheate by the customer in actual running conditions. I now have a Ferrari cylinder head that has been overheated and the customer is asking us for a hardness check.
#1. Which method is used on cast aluminum, Rockwell or Brinnel.
#2. What numbers should we be looking for.
#3. At what temperature, engine operating temperature, would the head become too soft to be put back in service.
#4. Any recommendations on someone that could test
#5. Never had a problem with rebuilding heads that were overheated but have never been asked this question.

Regards,
 
I have used a Brinnel machine on aluminum, but I don't have any of my data with me now. Besides, this is a question for the engine/designer/manufacturer. Need to know what alloy is used in the casting. Most aluminums are heat soaked to solutionize the elements, then age hardened either natually or with low heat. We don't really know enough. You could test a similar head then see how it compares with the overheated one that you have.
 
...I think such things as cracks, loose valve seats or guides, or distorsion as measured across the gasket surfaces would be more relevant than a hardness test. If all the above check out okay...I would say it didn't get too hot...you might check on the website below though...there are some technicians and plain old mechanics on their forum there that may be able to help...

http://www.ferrarichat.com/forum/forumdisplay.php?f=4


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pmjk120.jpg
 
I would use Rockwell B or F scale. That is done with the same machine as C scale, but with a 1/16" round ball penetrator instead of the Brale penetrator.
 
Brinnell machines make a very large dent in the sample, and require a large flat surface with a flat base to run the test. It uses a 10 mm ball and a load of 1500 kg. I cannot imagine trying to Brinnel test a cylinder head.

A Rockwell tester would be more appropriate because of the smaller ball and lower load. But you still need the two parallel flat surfaces. And you will have a little indentation in the surface where you test.

If you want to check for localized differences in hardness due to uneven heating, you would need several parallel flat surfaces. If you are comparing two heads, run the test in the same location on each.

I suppose the highest temperatures occur near the exhaust valves. The factory engineers would cut up the head and run hardness checks on many little pieces from different places in the head.

Larry
 
Rockwell would not normally be a first choice for checking casting hardness. Brinell would be the common method. For a source, try a local foundry that pours aluminum. That being said, Brinell testing uses sufficiently heavy loads as it could compromise structural integrity of the head. Rockwell B uses much smaller loads, but fixturing the head will be a problem, as will deflection internal to the casting due to the loading.

Due to probable localized overheating (and localized annealing), I'm not sure how meaningful a hardness test will be. My concern would be sufficient hardness to prevent the head gasket fire ring from brinelling into the head surface.
 
headrebuilder
Unless the customer is a rocket scientist,ha,ha,ha. Surface/rebuild it and send him down the road.
I repair Brodix heads,Donovan,Rodeck,Arias blocks as in welding the ports,valve seat areas and burn thru between cylinders all the time never had a come back yet, been doing it thirty plus years.
Forget the hardness crap.
 
There are portable hardness testers that overcome the problem of needing flat parallel surfaces for testing in the traditional Rockwell or Brinell machines. One fairly flat smooth surface on a fairly heavy part is all that is required.

The catch is the cost. But if you ask a local heat treating company, maybe they can help for less than the cost of buying your own tester.

Flexbar portable hardness tester $2150.00

You can buy a set of Chinese hardness testing files pretty cheap, but they are too hard for your cast aluminum.

Larry
 
johnoder
Donovan blocks by todays standard are mediocre at best,repaired a 528 CU.IN. Indy/Mopar block last week nice casting by the way, both pan rails were cracked vertical up towards the water jackets about two inches between cyls. 5-7 and 6-8.for a quick
local bracket racer, 70 Challenger super/pro class runs 8.46@166MPH. I also give a lifetime guarantee on all my work,dropped valves,kicked rods,broken cranks not included :D
 
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