cracked BMW head

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Customer said "it didn't get that hot" Yea right! It had 5 carcks.1: Cracks ran through valve seat counterbores. Had to be removed for repair.2: Used 3" cutoff wheel mounted in die grinder to grind thorugh seat, this reduces press fit for easy/fast seat removal.3: Cut crack out. Usually use die grinder for 1 or 2 cracks but on this one mounted in mill and used endmill for speedy removal. Cracks went quite a way down the ports. Cut enough room to get tig torch in for welding.4: Colse up of gouge.5: Welded.Put in oven and heat to 350, weld with Syncrowave 250, set amps 250, used foot feeder for fine adjustment, 3/32 gold tungsten, A356 1/8 filler, AC, balance set to 7, weld every other crack- did 2 in 5 mins put back into oven to bring back up to temp repeat till finished, post heat 30 min at 350, cut off oven for cool down. Attached Images
Reply:more picsHead after pressure testing, new seats installed, streightning, surfacing, only thing left was assy. Attached Images
Reply:Great job castweld,do you have an oven right in you're shop?Lincoln 225 ACLincoln Mig Pak 15Lincoln Mig Pak 10Purox Oxy-Acet Outfit20 Ton PressHonda Generator
Reply:after the 4th pic why didnt you show the welding done in the chamber beforethe machine work
Reply:Originally Posted by bensweldGreat job castweld,do you have an oven right in you're shop?
Reply:HOLY HEMI BATMAN!!!Obviously this would be a walk in the park for you.  3406 Cat.MM200 w/Spoolmatic 1Syncrowave 180SDBobcat 225G Plus - LP/NGMUTT Suitcase WirefeederWC-1S/Spoolmatic 1HF-251D-1PakMaster 100XL '68 Red Face Code #6633 projectStar Jet 21-110Save Second Base!
Reply:Castweld,Nice looking repairs.  I do have one question though.  If I read your original post correctly, the head is cast aluminum alloy A356.  I believe this is a heat treatable grade of aluminum.  Your preheat and post heat treatment of the weld would have solution (over)aged the part because it exceeded ~200F.My question is, do you know how the head was heat treated originally? If it was solution aged, did you fully anneal and re-heat treat the head to match the factory treatment?  Or do you advise your customer that the head may no longer have the strength of an original factory cylinder head?Respectfully,DaveBenson's Mobile Welding - Dayton, OH metro area - AWS Certified Welding Inspector
Reply:Whoops, just re-read your original post.  Looks like you used A356 filler metal.  Is this an intentional match to the head alloy?  Or just an educated guess(which I happen to agree with)?Still leaves my original question in need of an answer....-DaveBenson's Mobile Welding - Dayton, OH metro area - AWS Certified Welding Inspector
Reply:was this a rare head or something? wouldn't it have been cheaper/easier just to get a good used core and rebuild it rather than do all that work?
Reply:Five (5) cracks like that to a engine head!! Makes you wonder what other hidden damages there were??Unless that is one rare head on that engine I would have shown the results of the magnafluxing to the owner and at that point gave the owner a couple of options. Repair it with no firm warranty specified even after re- magnafluxing the repairs since the repairs may have altered the material characteristic. Or the best option would be to fine a good used head.Wow Duanne looks llike you took a ballpene hammer to that CAT HeadCo-Own CNC shop:Miller :1251 plasma cutter, MaxStar 700 TIG/Stick, & XMT 456 Multiprocess Welder.&  2 Hypertherm HPR260's Plasma CutterSorry I had a bad stroke but now I am back.
Reply:I had a similar experience I scrapped the head, maybe If I had known castweld at the time I would have gotten it fixed lol
Reply:Originally Posted by duaneb55HOLY HEMI BATMAN!!!Obviously this would be a walk in the park for you.  3406 Cat.
Reply:Peter,Thanks for the insightful reply.  I used to work for Honda in their engine plant in Anna, OH.  I was there for about 18 months.  Among many other things, I used to troubleshoot high and low pressure castings of aluminum cylinder blocks and heads.  I also did some work for Ford on low pressure die-cast cylinder heads for their V6 engines; about the same length of time  That's why I asked about the heat treat.  It's something I spent some time solving problems on in the past.Results speak for themselves, and I'll be the first to credit that your past experiences are more relevant, and greater in depth, than mine.Your comments on machining the head are consistent with grades of aluminum that age at room temperature.  I'd have to do a bunch of digging to match up what you know about the Mag content with a specific grade.  The welded areas start out fully annealed, and then harden over a period of time at room temperature.  The good news is that these alloys return to higher, perhaps even optimal strength, all by themselves.  So long as the customer doesn't overheat them, and artificially over-age them, they should be good to go.  My concerns were not so much with the effects of welding in the areas repaired, but with the overall effects of the pre-heat to 350F.  This would affect other areas of the casting, like bolt holes, bosses, gussets, or ribs that stiffen the head.  The over aging that comes with prolonged heating at temps over ~200F would tend to slightly soften these areas. It's all an academic question, as it seems like your customers are happy and they know that the repaired heads may not be as strong as new ones.  It's good to talk with someone who knows there stuff.  Even though you've got it down pat, maybe some other novice welder will read this before leaping into fixing heads for their buddy's car.  Not everybody uses alloys, or component designs, that are so forgiving of solution heat treatment changes. Originally Posted by castweldDave thats a bunch of answers you are in need of!Alloy? Only BMW uses this alloy it has a high percentage of magnesium, I seem to remember 4%. Yes its hard, solution treat. No I don't anneal and retreat. Lets look at the repair, the port is welded. I think it would flow ex gas ok not treated. The seat area, has an hardened seat in it, shouldn't be an issue. The face area that the gasket seals on- bingo! thats the only area that would cause a problem. Brinelling. If I machine the weld as soon as its cool enough it is "gummy" and soft, after a day I notice it seems to get harder/cut better. The weld seems to get harder far a few days then the effect seems to level off. I bond heat tabs on repairs, center of tab melts out at 260 degrees. On heads returned with tabs melted I have seen a few with brinelling problems. Other than that it has been a non issue. I have a few racing customers that abuse the heads race after race. I have experimented with using 5356 in gasket areas, this usually prevents brinelling in the future. I have been repairing heads since the 70's- only posting repairs that have been proven with time.To soften the head noticibily usually takes over 600 degrees on most heads.Yes I will tell customers that if they want a head as good as new to get one. On the other hand some customers bring new heads for welding to make them "better" - racing apps.A356 works on heads I see. Don't see every kind. 4043 works on most heads.Peter
Reply:Your right castweld.   Aluminum heads must either be pressure tested and/or sprayed with penetrating dye to find cracks and porosity leaks or you can use X-Ray and/or Ultrasonic Testing.Co-Own CNC shop:Miller :1251 plasma cutter, MaxStar 700 TIG/Stick, & XMT 456 Multiprocess Welder.&  2 Hypertherm HPR260's Plasma CutterSorry I had a bad stroke but now I am back.
Reply:Lucky for me I have never had to try to repair an aluminum head. All the inspections we do are on our new work or cast work. And used aircraft stuff we send out for certified testing.My hat is tipped to Castweld and others who can do such specialized work.Co-Own CNC shop:Miller :1251 plasma cutter, MaxStar 700 TIG/Stick, & XMT 456 Multiprocess Welder.&  2 Hypertherm HPR260's Plasma CutterSorry I had a bad stroke but now I am back.
Reply:very interesting info in here thanks for the response!In my case the keyway in the crank pulley sheared off at around 2000 rpm / hole in piston broken seat bent most of the valves, broke that one. The head was ported and the guides were ground flush with the port roof. I threw the head on the shelf and got a new good core for $50 vw 8v heads/motors are dirt cheap  flow like garbage too
Reply:Originally Posted by A_DAB_will_doPeter,Thanks for the insightful reply.  I used to work for Honda in their engine plant in Anna, OH.  I was there for about 18 months.  Among many other things, I used to troubleshoot high and low pressure castings of aluminum cylinder blocks and heads.  I also did some work for Ford on low pressure die-cast cylinder heads for their V6 engines; about the same length of time  That's why I asked about the heat treat.  It's something I spent some time solving problems on in the past.Results speak for themselves, and I'll be the first to credit that your past experiences are more relevant, and greater in depth, than mine.Your comments on machining the head are consistent with grades of aluminum that age at room temperature.  I'd have to do a bunch of digging to match up what you know about the Mag content with a specific grade.  The welded areas start out fully annealed, and then harden over a period of time at room temperature.  The good news is that these alloys return to higher, perhaps even optimal strength, all by themselves.  So long as the customer doesn't overheat them, and artificially over-age them, they should be good to go.  My concerns were not so much with the effects of welding in the areas repaired, but with the overall effects of the pre-heat to 350F.  This would affect other areas of the casting, like bolt holes, bosses, gussets, or ribs that stiffen the head.  The over aging that comes with prolonged heating at temps over ~200F would tend to slightly soften these areas. It's all an academic question, as it seems like your customers are happy and they know that the repaired heads may not be as strong as new ones.  It's good to talk with someone who knows there stuff.  Even though you've got it down pat, maybe some other novice welder will read this before leaping into fixing heads for their buddy's car.  Not everybody uses alloys, or component designs, that are so forgiving of solution heat treatment changes.
Reply:Castweld, I appreciate your contributions to the forum.I'm not smart enough to even engage in the conversation, but I'm sure as he!! listening.Thanks for posting.
Reply:Hi Peter,I worked for Ford from 1996 - 2001, and for Honda from 2004- to almost 2006.  Both companies have improved their casting processes dramaticly over the years.  I'm not too surprised at your comments about the honda castings.  They really do a great job of ensuring melt cleanliness in the casting operation.  Both companies use low pressure die casting to make cylinder heads, and the low pressure process helps to reduce turbulence in the mold, which in turn reduces the amount of porosity that forms from cavitation of the molten metal as it fills the mold.  That cleaner metal and reduction in porosity make the castings easier to weld.  Fewer places to trap residual oil/coolant, and less garbage that floats to the surface of the puddle.I'm certain the alloys and solution heat treatment processes have changed over the last 3-4 decades.  The automotive companies spend a lot of money optimizing the designs of castings; thinning walls to reduce weight, aluminum used, and improve heat transfer.Solution aging of the types of alloys used in heads and blocks can begin at about 200F.  But, at that temperature the changes progress very, very slowly.  Aging at that temperature might take years to fully transform the aluminum.  But, as the temperature rises, the rate of change speeds up.  The effects of temperature are not linear.  What might take years at ~200F can occur in hours at 400F, or in minutes at 600F.  Solution heat treatment for aluminum alloys that can be strengthened is alot like ripening fruit.  In fact, in textbooks they call the process 'Ostwald ripening'; named for the guy who discovered it, I suppose.  Anyway, heat treatable aluminum alloys get cast, quenched, and then re-heated.  Things start happening at the atomic level during the re-heat.  It's vaguely similar to the tempering process used to strengthen steel, although the exact mechanisms are different in aluminum.  The heat treatment process causes the strength of the aluminum to rise, as a function of time and temperature.  Increase either one, and the change progresses more rapidly.  Eventually, the alloy strength maxes out.  If the heat treatment continues past this point, the alloy actually starts to lose strength again.  They call this over-ripening, or over-aging.I guestimate that this is one of the reasons that engine cooling systems, particularly in aluminum blocks and heads, operate at low pressures.  This keeps the boiling point of the coolant in the temperature range that also doesn't promote changes in the block/head alloy mechanical properties(strength, ductility, etc.)  Safety is also a concern, but engines would be more efficient, if they ran at higher temperatures.  I'm starting to preach, probably to folks who know more than I do, so I'll get back on subject...You're right that temperatures inside the cylinder are much higher than 200F.  There are some curious physics that occur within the combustion chamber, and so the temperatures at the wall are not nearly as high as the temperature of the burning fuel charge.  The walls head that are part of the combustion chamber are going to be thicker to compensate for the fact that they will only have the strength of the annealled aluminum after a short time in service.  The bolt bosses, and 'structural parts of the head are well removed from this heat, and shielded by the cooling channels in the head.  So they stay relatively cool, and retain the strength that comes from the heat treatment applied when the head is made.Coming back to the original topic.  I was curious about the preheat to 350, and maintaining that temperature throughout the work.  My edg-a-macated guess was that you were near that temperature range, for a long enough time, to really restart the 'aging' process.  To my way of thinking, 350F for several hours, might be enough to jump start the solution treatment process again.  That's why I asked about whether or not you fully annealed the head and re-heat treated it when you were done with welding repair.  It sounds like, based on your years of experience, that I'm wrong, and that the aging, if any occurs during your repair work, is minor.  Sure, welding in the areas of the combustion chamber anneal the material there.  But the mechanical design is robust enough to ensure this isn't a problem.  Just running the engine under normal conditions makes the aluminum in the combustion chamber over-age and stabilize in mechanical properties.I would suggest that if you're working on new heads or trying to maximize the strength of a repair, that dialing back on the pre-heat temp and time would minimize any chances of reducing the strength of the aluminum.  Even 25F reduction in temp buys you hours of more time at that temp, with less likelihood of change in the aluminum properties.Just curiously, and to see if anybody is still awake when they get to this point,  Have you ever seen any distortion in aluminum heads after making repairs?  Bolt holes that won't line up any more, valve seats that need to be remachined, or gasket surfaces that must be machined back to flat in order to seal properly?  I ask because one of the other effects of solution heat treatment can be expansion of the aluminum.  Some of the changes that occur in some alloys can cause the material to swell, dramatically.  I know that Ford and Honda work hard to control the alloy chemistry to ensure this changes are minimal.  But I was wondering about other manufacturer's heads that you've worked on over the years?I hope I haven't put anyone to sleep by droning on for so long in this post.   Originally Posted by castweldWhat years did you work for Honda/Ford?  (if you don't mind) Honda castings weld better than the Fords!Back in 70's and early to mid 80's I saw a lot of alum castings fully annealed, they didn't seem to age harden. Annealing was from overheat problem on car. Saw the soft head bolt bosses yor refer too. Back then I tried repairs either welding or simply rebuilding without success. Learned quickly  to look at head bolt boss area and head gasket brinelling before taking heads in for work. Refused a lot of heads back then, only see a few problems with late model heads. Possibly a change in alloy or heat treat? If driver keeps going after boiling out coolant, and does't stop untill the motor quits running when pistons seize- head is probably trashed.I don't get the 200 degree statement,  first whats your definition of prolonged? Most late model cars thermostats are over 200 degrees, also with normal running the combustion side of cyl/head gets much hotter than 200 even though the water is cooler. To me it seems that if 200 degrees would be a problem then just about all aluminum heads and blocks would be failing? I do not understand, could you give an explanation.Thanks for your replyPeter
Reply:Originally Posted by duaneb55HOLY HEMI BATMAN!!!Obviously this would be a walk in the park for you.  3406 Cat.
Reply:Originally Posted by daddyCastweld, I appreciate your contributions to the forum.I'm not smart enough to even engage in the conversation, but I'm sure as he!! listening.Thanks for posting.
Reply:I hope I haven't put anyone to sleep by droning on for so long in this post.
Reply:We make all of our heads from A356-T6. 350 pre and post heat is correct. Dont get too hung up on that low pre heat temp. Typically engineers design for the material in the "0" condition. Combine that with the thermal and mechanical cycles that are ever work hardening areas of the casting. Also you will find that material temperatures are much much higher then coolant temperatures. Its not uncommon to have the material surrounding the exhaust ports at 400F spark plug basses at 350F etc. Our castings are welded in the exact manner castweld did, approved by engineering. Its just a matter of understanding EVERYTHING affecting a part, not just your little piece of it. Nice repair!!-Aaron
Reply:Originally Posted by A_DAB_will_doHi Peter,I worked for Ford from 1996 - 2001, and for Honda from 2004- to almost 2006.  Both companies have improved their casting processes dramaticly over the years.  I'm not too surprised at your comments about the honda castings.  They really do a great job of ensuring melt cleanliness in the casting operation.  Both companies use low pressure die casting to make cylinder heads, and the low pressure process helps to reduce turbulence in the mold, which in turn reduces the amount of porosity that forms from cavitation of the molten metal as it fills the mold.  That cleaner metal and reduction in porosity make the castings easier to weld.  Fewer places to trap residual oil/coolant, and less garbage that floats to the surface of the puddle.I'm certain the alloys and solution heat treatment processes have changed over the last 3-4 decades.  The automotive companies spend a lot of money optimizing the designs of castings; thinning walls to reduce weight, aluminum used, and improve heat transfer.Solution aging of the types of alloys used in heads and blocks can begin at about 200F.  But, at that temperature the changes progress very, very slowly.  Aging at that temperature might take years to fully transform the aluminum.  But, as the temperature rises, the rate of change speeds up.  The effects of temperature are not linear.  What might take years at ~200F can occur in hours at 400F, or in minutes at 600F.  Solution heat treatment for aluminum alloys that can be strengthened is alot like ripening fruit.  In fact, in textbooks they call the process 'Ostwald ripening'; named for the guy who discovered it, I suppose.  Anyway, heat treatable aluminum alloys get cast, quenched, and then re-heated.  Things start happening at the atomic level during the re-heat.  It's vaguely similar to the tempering process used to strengthen steel, although the exact mechanisms are different in aluminum.  The heat treatment process causes the strength of the aluminum to rise, as a function of time and temperature.  Increase either one, and the change progresses more rapidly.  Eventually, the alloy strength maxes out.  If the heat treatment continues past this point, the alloy actually starts to lose strength again.  They call this over-ripening, or over-aging.I guestimate that this is one of the reasons that engine cooling systems, particularly in aluminum blocks and heads, operate at low pressures.  This keeps the boiling point of the coolant in the temperature range that also doesn't promote changes in the block/head alloy mechanical properties(strength, ductility, etc.)  Safety is also a concern, but engines would be more efficient, if they ran at higher temperatures.  I'm starting to preach, probably to folks who know more than I do, so I'll get back on subject...You're right that temperatures inside the cylinder are much higher than 200F.  There are some curious physics that occur within the combustion chamber, and so the temperatures at the wall are not nearly as high as the temperature of the burning fuel charge.  The walls head that are part of the combustion chamber are going to be thicker to compensate for the fact that they will only have the strength of the annealled aluminum after a short time in service.  The bolt bosses, and 'structural parts of the head are well removed from this heat, and shielded by the cooling channels in the head.  So they stay relatively cool, and retain the strength that comes from the heat treatment applied when the head is made.Coming back to the original topic.  I was curious about the preheat to 350, and maintaining that temperature throughout the work.  My edg-a-macated guess was that you were near that temperature range, for a long enough time, to really restart the 'aging' process.  To my way of thinking, 350F for several hours, might be enough to jump start the solution treatment process again.  That's why I asked about whether or not you fully annealed the head and re-heat treated it when you were done with welding repair.  It sounds like, based on your years of experience, that I'm wrong, and that the aging, if any occurs during your repair work, is minor.  Sure, welding in the areas of the combustion chamber anneal the material there.  But the mechanical design is robust enough to ensure this isn't a problem.  Just running the engine under normal conditions makes the aluminum in the combustion chamber over-age and stabilize in mechanical properties.I would suggest that if you're working on new heads or trying to maximize the strength of a repair, that dialing back on the pre-heat temp and time would minimize any chances of reducing the strength of the aluminum.  Even 25F reduction in temp buys you hours of more time at that temp, with less likelihood of change in the aluminum properties.Just curiously, and to see if anybody is still awake when they get to this point,  Have you ever seen any distortion in aluminum heads after making repairs?  Bolt holes that won't line up any more, valve seats that need to be remachined, or gasket surfaces that must be machined back to flat in order to seal properly?  I ask because one of the other effects of solution heat treatment can be expansion of the aluminum.  Some of the changes that occur in some alloys can cause the material to swell, dramatically.  I know that Ford and Honda work hard to control the alloy chemistry to ensure this changes are minimal.  But I was wondering about other manufacturer's heads that you've worked on over the years?I hope I haven't put anyone to sleep by droning on for so long in this post.
Reply:Originally Posted by handtpipelineWhat series 3406 is this? (as in B, E...) Do they all have 4 valve heads?  I ask this, because I have 2 trucks with 3406's in them, and never knew that they may be 4 valves.  Hopefully won't have to see the internals on either of them for quite a while yet...Originally Posted by castweldAll 3406 Cats were 4 valve, even the rare 3406 natural gas, we rebuilt a few of them for oilfield offshore platforns. Owners did'nt have to fly/boat in diesel.PeterThanks AaronWhat kind of heads do you (we) make?peter
Reply:Originally Posted by handtpipelineWhat series 3406 is this? (as in B, E...) Do they all have 4 valve heads?  I ask this, because I have 2 trucks with 3406's in them, and never knew that they may be 4 valves.  Hopefully won't have to see the internals on either of them for quite a while yet...
Reply:Hi Aaron,I have to respectfully disagree with one thing you said.   If [all]engineers designed everything based on the mechanical properties of aluminum in the '0', or fully annealed condition, there wouldn't be any purpose in ever heat treating the parts.  Yet, clearly some castings, and some parts that are manufactured from wrought or 'billet' aluminum, are solution heat-treated to T6 or some other condition.  Follow the logic backwards.  If parts are heat treated, and this costs money and time, it must be necessary.Now perhaps the factor of safety in most designs, coupled with part use at modest stress levels, makes the extra strength provided by the heat treatment unnecessary.But at least in Peter's case, some of his customers are using their heads in racing applications; and probably demanding 100% or more of the strength they can get from the part.  If those parts were heat treated when new, then you have to pay attention to that heat treat in making repairs.Granted, it seems like my original concerns are largely irrelevant for Peter's customers.  Either the heat treat alterations from the repair welding procedure don't make any real difference, or his customers are "compensating" for any loss in strength by not pushing repaired parts as hard as they might otherwise do with a brand new head.[/B] Originally Posted by makoman1860We make all of our heads from A356-T6. 350 pre and post heat is correct. Dont get too hung up on that low pre heat temp. Typically engineers design for the material in the "0" condition. -Aaron
Reply:I'm glad to share what I know.  Pardon if it seems like I sometimes gloss over some specifics.  I'm not sure how much of what I was exposed to was public knowledge, and how much is proprietary.  So I tend to err on the side of caution...It sounds like you've done your homework and have been given good information.  Excuse me for 'preaching at the choir', but in talking over the internet I've found it's tough to tell who is working from a solid foundation of knowledge, and who's wingin' it.  The pre and post heat you're applying to the whole part will (slowly) advance the aging or ripening of the casting.  The time involved in your repair is much shorter than I was imagining.  Looks like in this case the total time at temperature is about 2 hours.  I haven't looked at the heat treat charts, but at the temperature you're using, I guess you'd need 12-24 hours to really have an impact on the solution heat treatment of the head.  double the temperatureto 500F and you'd cut that time from maybe 16 hours down to 3-4 hours.  As your source said, raise it to 600F, and your aging time is measured in minutes.The nice thing is, with your furnace and a good temperature probe, you can restore the original heat treament.  Heat the head up, quench in still air to room temp.  Re-heat at a lower temp for the required time, and allow the heat to cool in still air again, and you've restored the solution heat treatment.  The exact times and temperatures required for this will depend on the alloy.  That you'd need to know for certain.  You'll have to deal with the distortion that arrises from the re-heat treatment.  But it sounds like you're well equipped to do so.  As you noted earlier, the annealed aluminum can be messy to machine, but the harder, heat treated aluminum isn't as bad to work on.The distortion comes from the atomic level changes that are going on.  My boss at ford spent a lot of time looking at aluminum chemistry and microstructure, trying to find an alloy chemistry that minimized these distortions.  To oversimplify a bit, when you heat the aluminum up, the atoms in the part do some serious reorganizing.  The additives like silicon, magnesium, and copper dissolve in the aluminum; like sugar does in hot water.  When the alloy cools, some of these alloying additives come back out of the aluminum.  If you've ever seen the experiment where you grow salt or sugar crystals from hot water, it's the same basic phenomena.  As these other atoms come back out of the aluminum and form microscopic structures within the aluminum matrix, they don't fit neatly.  As a result they cause pressure within the part.  Like jamming a square peg in a round hole; or more closely, too large a round peg in a round hole.  The aluminum and mixture of these other alloying ingredients look a bit like concrete, but at a very small scale.  Islands of stuff, like aggregate in concrete, surrounded by a matrix of aluminum, like the cement and sand in concrete.The solution heat treating process, allows more of the stuff dissolved in the aluminum to precipitate, or come out of solution.  More islands, or inclusions, or however you want to imagine them, start to grow, and the existing ones grow larger.  Just like the stones in concrete, these islands are harder than the surrounding aluminum, and they arrest the spread of defects or cracks.  Up to a point, the more of these islands you have, the stronger the aluminum gets.  But, just like concrete, if you add too much aggregate, there isn't enough cement to bind it all together.  So it goes with the heat treated aluminum.  If you allow the aging process to go too far, these islands get to large and too numerous, and they actually start to promot the formation and growth of defects or cracks.I didn't mention the resin used in castings as that was one of those things I wasn't sure how widespread the information on it was.  Besides all the oil and coolant, there are other things that can contaminate the surface of the casting.  Ford and Honda use special sands to form mold inserts to make the water channels in cylinder heads.  These sand molds are held together with special binders.  The binders mostly vaporize when the hot aluminum hits the mold.  But sand and binder residue are left in the surface of the casting.  Machined surfaces are cleaned of this residue, but anywhere there's raw casting showing, you'll probably have troubles welding, unless you grind that surface contamination away.  Those residues survive the running of the engine, so unlike the oil and coolant, they won't just burn off.I'll guess and say that's why you have trouble with some of Toyota's or GM's castings.  You mentioned the lost foam process.  Ford uses this too, or at least they used to in the past.  Maybe they use a different foam, or a different surface coating that leaves the casting cleaner, and that's why Ford heads are easier to repair.  I'm not sure, but it seems like a good guess to me.I don't know what Toyota's doing.  Could be mold binders, release agents, or melt cleanliness that make some of their castings a pain to weld on.Some engine castings, and perhaps some head castings are also repaired at the factory, rather than being scrapped.  The die casting process always produces some porosity in the casting.  It's virtually impossible to eliminate 100% of the porosity in a casting as complex as the average block or cylinder head.  What manufacturers do is adjust the casting process (time, temp, pressure, mold gate design) to move porosity into non-vital areas of the casting.  This is all confirmed by accelerated life testing, so no need to worry about porosity causing your engine to fail.In some cases, it's just impossible to fix porosity, but it is possible to repair it afterwards.  So at least some aluminum engine castings are TIG welded to close up specific areas of porosity, or the pores are filled with an epoxy resin; like J-B weld.  Again, all of these repairs are only applied to specific areas of the part where porosity consistently appears.  All the repair processes are confirmed by accelerated life testing, so the manufacturer knows that the engine will still deliver the life and performance the customer expects.  (under typical driving conditions)  They also do a mountain of destructive and non-destructive testing to confirm all of this.  I've seen engine blocks sliced in 1" or 0.5" slices, like a loaf of bread to inspect porosity issues.  I used to to film radiography and 3D X-ray CT scans of cast parts to find and quantify porosity and dimensional values for the interior of castings.This is another reason guys who are repairing aluminum engine blocks and heads need to do their research.  These repairs aren't easy to spot on a new engine, let alone one that's been in service.  Use too much preheat, weld overtop one of these patches, and you could punch a hole in the cooling jacket of the engine block or head.  May the weld looks bad, and the welder gives it up as an impossible repair.  And then again, maybe he burns up a hidden area of factory repair, and the engine fails later on, and nobody can figure out why.  Sounds like you know what I'm referring to.  You're welcome Peter.  I don't mind sharing what I know, or think I know.    It's been valuable for me to hear about your real world experiences.  Even if I don't ever weld on a cylinder head or block myself.  Maybe somebody else who is will find this info and avoid a mess of trouble.  I believe that knowledge is never wasted, but is often lost or overlooked...   Originally Posted by castweldI am WIDE AWAKE! Your experiences are very interesting to me.In my oven which has a large vent and large flue (high air flow through) aluminum heads are heated to 350 in 40 mins. I check with IR inside ports and large water outlets. I am guessing that some of the thicker areas of casting have not heat soaked in 40 mins. I remove head from oven for welding and only weld for 5 mins before re heat. In 5 mins i have usually lost 100 degrees (250) and it takes about 20 mins in oven to recover the 100 degrees (350) .  This head was taken out of oven 3 times to complete the 5 welds. Post heat is 20 min then oven off to cool. Was told by the equipment manufacturer to preheat heads to 525 and then blast for cleaning. Was told (and I have tested/proved) that mineral based engine oils burn to ash at 350 to 400 degrees, and synthetic oils burn at 450 to 500 degrees. Burning the oils, antifreeze and cleaning helps reduce porosity in welds. Same man told me that I could keep alu heads at 525 for up to 2 hours without damage. I have never tried this. He also said that heads would be annealed at 600 almost instantly. Distortion- I check heads when they come in and when alu heads get hot they warp.. And yes the valve seats and guides move around and need remachining to align them. And you did not mention but on over head cam heads, the camshaft bores get out of alignment. When most heads warp the gasket face will distort more than the valve cover surface, and the exhaust port side of the head warps more than the intake side. For instance on a gasket face that is warped .025 inch, the top of the head can be off between .010 to .020, or much less than the bottom. When I weld on bottom (chamber side) of heads it can cause more warp. When warp is above specs it has to be delt with, streighten it. There are several methods to do this. Usually I get the cam bores streight, then cut the warp out of the gasket surface.Ford has a casting I will not weld on, after trying and having too many porosity problems. GM has a 'lost foam" head that I had problems and do not weld on. You probably know which head.One of the Toyota castings will weld- but are dirty, the rest weld very good.Honda, Nissan, Mercedes, Jaguar, Bmw, weld very well.The rest will weld.The couple exotics I welded on were excellent to weld on.I weld a lot of powersports heads and they range from excellent to good.I have been waiting for you to mention the plastic resin used in castings. I do not have a vacuum imprgnator like the manufacturers use, so I have to make air/water tight welds. I  noticed what seems to be plastic resin impregnation on motorcycle castings.  Had porosity problems especially on engine covers. They are casted very thin, and the crap bubles in the puddle. A real PITA.Its been a pleasure communicating with youPeter
Reply:Originally Posted by A_DAB_will_doHi Aaron,I have to respectfully disagree with one thing you said.   If [all]engineers designed everything based on the mechanical properties of aluminum in the '0', or fully annealed condition, there wouldn't be any purpose in ever heat treating the parts.  Yet, clearly some castings, and some parts that are manufactured from wrought or 'billet' aluminum, are solution heat-treated to T6 or some other condition.  Follow the logic backwards.  If parts are heat treated, and this costs money and time, it must be necessary.Now perhaps the factor of safety in most designs, coupled with part use at modest stress levels, makes the extra strength provided by the heat treatment unnecessary.But at least in Peter's case, some of his customers are using their heads in racing applications; and probably demanding 100% or more of the strength they can get from the part.  If those parts were heat treated when new, then you have to pay attention to that heat treat in making repairs.Granted, it seems like my original concerns are largely irrelevant for Peter's customers.  Either the heat treat alterations from the repair welding procedure don't make any real difference, or his customers are "compensating" for any loss in strength by not pushing repaired parts as hard as they might otherwise do with a brand new head.[/B]
Reply:Originally Posted by BrinkIt's a series C and it was used to power a fire pump.  I'm sure Duaneb55 can get a pic of the valve train once he gets back from PA if you're curious to see the guts without having to rip one of yours apart Almost forgot . . . amazing work Castweld. You're an inspiration.
Reply:your work looks good
Reply:I just wish Castweld lived in Ohio! I know it will cost me more to go to Louisiana and get him to repair an engine for me. You work is art Castweld, and I for one am very impressed! Keep posting.Miller Thunderbolt 225Millermatic 130 XPLincoln HD 100 Forney C-5bt Arc welderPlasma Cutter Gianteach Cut40ACent Machinery Bandsaw Cent Machinery 16Speed Drill PressChicago Electric 130amp tig/90 ArcHobart 190 Mig spoolgun ready
Reply:Originally Posted by compyour work looks good
Reply:Hello Castweld and A_DAB_will_do I wish to thank you both for a excellent thread. I am currently enrolled in a metallurgy class for my welding certificate and found your conversation both informative and enjoyable to read thanks for the amazing read and information.Beavertrapper24Ps. great repair Castweld
Reply:ThanksPeter