Found a film about making the Chrysler Astron 2 and 2.6 litre engines at their South Australia plant in the 1970's (judging by the old style cotton Makita cap one guy is wearing and the lack of robots). They even mention adding extra bentonite each time the sand is prepared after the previous use. There were 4, 6 and 8 cylinder engines made there and after Mitsubishi bought all the Chrysler assets, they continued the same Astron engines and cars like the Sigma (Stigma ). I had an old Sigma and went through a couple of engines and a few alloy cylinder heads as the number three cylinder would crack between the valves (the wreckers pulled apart four engines to get one good head for me ). The local engine merchant said the Astron was his "Bread and butter engine" as "They would throw the timing chain every 60 000 Km". I had this happen when turning across the oncoming lane of the highway and the motor seized solid with a bus full of tourists bearing down on me: I stuck the automatic shifter in neutral and it just rolled down the road camber out of the way in time to avoid the oncoming bus: bum puckering moment indeed . The story goes that Mistubishi cast an alloy block of the same design without extra material and they would crack between the welch plugs. Towards the end of car manufacture in Australia the suppliers would pester small foundries to make castings like manifolds and take on high volume contracts with very low margins: one failed casting would need ten more good ones to make up for the loss. Quite a few guys were left hanging with huge loans when car factories closed with no warning. The bigger foundries were refusing to supply such low margin work that the car makers demanded.
That video's a real memory tickler for me. My Dad used to work in a GM engine plant that made small block Chevy V8s, one year, probably around the same time that video was made, the plant had a family night that invited family members of employees to take a fairly detailed tour of the plant. I remember well the tour of the foundry, I didn't see the engine block being cast, when I was there they were making cylinder heads, I remember handling one of the smaller cores, I was very impressed by the level of detail they were able render in sand, for the cylinder heads at least, green sand was not used, the molds were made entirely out of resin bonded sand. In retrospect, one of the things I find interesting is that they used different colour binders for the various cores, I think this may have been done to facilitate quick and easy visual inspection of the molds prior to casting. I also remember seeing the raw castings fresh out of the sand and remember wondering at the time why there was so much metal there that was not part of the finished head, now of course I know these were the risers but at the time I was too young to appreciate shrinkage and differential cooling.
The video has a 1980 end credits date so I wasn't too far out on my 1970's estimate. Some things I note on the second viewing: The castings spend three hours left in the sand while cooling with five hours total cooling time. This must be the minimum cooling time that will give a soft machinable grey iron. The guy drilling the vent holes has a pneumatic drill with a straight length of wire in the chuck, that's the same as I'm using in a battery drill to make long vent holes. The worker drilled from the outside into the mould and didn't worry about loose sand in the cavity, maybe the high drill speed and the machine compacted sand avoids loose lumps. The green sand ingredients are used green sand and about 1/10th bentonite, fireclay, sea coal etc. to make up for the losses I guess.
I was estimating the date of the video based on the hair styles of some of the people in it, my visit to the plant was around 1973 or 74.
Me too, Australia was always five or so years behind USA fashions: at that time everyone was skinny and kids all had long hair and a skateboard and the caps were more like cricket caps than baseball caps. That footage could have been shot earlier than the 1980 editing date too. The cars in the lot at the end of the video were 1973 vintage too.
