Yes he talks about pistons alloys including doing what i did. Melting down old pistons. which superseeds the worry. He even goes on to say despite all his engineering he has actually never had one he made even if not to perfect spec, fail. He talks about chilling the mold with steel plates to get a tougher grain in the critical spots. He also mentions that pistons are often made in Steel molds. In all fairess though if you had to machine one of these casting I made you would put that worry to bed. They are TUFF with a capital T and so far from soft you wonder if it is aluminum. He sand casts his and had risers and gates and pours actually about double the volume for the piston to get a good casting. He also makes his pistons .375" at least oversize to make sure they machine well when the errors are cancelled. With a steel mold the errors are reduced greatly and the mold breathes easily out the joints . Of course to make a steel mold you need to be able to weld at least and a bit of machining too. Both pistons I cast had under .020" skirt runout when chucked in the lathe right from the mold. I may have been lucky and am hoping it continues. I think the investment casting you spoke of would be the most accurate but I have this mold and it is working well. All i need is 6 good cores and 2 for future needs. I have to remind myself I am not starting a piston factory I am just casting a set for this new engine. Trouble is this is so interesting i could get easily sidetracked. I watched The Wrdls Fstst Indian again this afternoon. just the piston casting part. Not any significant difference from what I did. I watched the movie pour then my pour (on Utube) back to back. I also joined a casting forum and took a 7 day E-course in one day and got two free Ebooks on metal casting as well. My dad the Engineer gave me his text book on strength and use of materials and I will poke through it as well. We must remember though I want to drive about 20 miles a year which is very very different from use in a daily driver. I really have no concerns about hardness or strength. I have machined enough experimental stuff to know these are far from weak. Tomorrow i will start putting the finess on my mold with the die grinder. Probably wont cast till end of the week again as I have some "honey do" stuff to take care of too. Don
Don, great thread. You are the embodiment of true hotrodding, for those who have to ask why, dont bother they will never understand and for those who say you cant well they will never try Illegitimi non carborundum,brother!
Ok heat treating. The quicker the aluminum is brought down from its molten state the better the heat treat. Or specifically if it is cooled from above 500C quickly (like it is when it comes out of my crucible into my steel mold the better the heat treat. I could improve it slightly further by plunging it in cold water immediately but it is probably unecessary. The thickness of the piston in all areas appears to be more than is required even at minimum strength and no heat treat. I know when I machine them they are very tough. It takes a very sharpe tool bit and you have to keep its nose clean of build up to machine them. I dont think you could break them with even a 2 lb hammer giving it your best shot. You cannot scratch them say with a knife for instance. That is what i learned about heat treating aluminum so far. Don That was a paper from the aircraft industry on making sure aluminum was properly heat treated i got this from.
I made a hinged core box for forming the baked sand core for inside the piston skirt. I made this device so they will all be the same. I tested it on my natural farm sand I spoke of earlier and it worked well. I cleaned it up and painted it (The core forming tool , not the core!). several coats so it wont absorb moisture and so it will release the cores easily without sticking. I then spent about an hour cleaning up my mold . Removing little imperfections, extra bits of weld and so on so it will do a cleaner job. I also polished the inside of it a bit. I would like to lube it so it is protected and releases well but I am not sure what to use. I know Mobil one Syn trns fluid is stable to 1600 F and wonder if a light wipe withh a rag dampened with that might help. Any ideas? Don
Just wondered. I did some casting of simple shapes and often used old pistons for my aluminum supply. Stock pistons worked fine but one day I tried to use some dead Aries racing pistons. Best I could do was kind of a plastic constancy. Couldn't pour it. Have you tried racing (High silicone?) pistons?
No I havent. My OEM supply is good so I havent been tempted. I dont have any dead forged pistons to use. I have a couple of forged TRW left over from a job several years ago but they are brand new and I hate to melt them. Don
Don in post #185 you stated that mobile 1 trans fluid is stable to 1600 F. I do not think this is correct as even dot 5 brake fluid boils around 550 F I believe.
i love the below quote and i beleive it applies to you! nice work! Impossible is just a big word thrown around by small men who find it easier to live in the world they've been given than to explore the power they have to change it. Impossible is not a fact. It’s an opinion. Impossible is not a declaration. It’s a dare. Impossible is potential. Impossible is temporary. Impossible is nothing.
That's a lot of work but I do understand why you want to try to make a set of good pistons ! It's just one of those things you want to achieve and make work . there is always that little thing inside that tell you , you know if you do thins and that you can make it and it will work . So why wouldn't it work ? You have researched and got all the specs down to where it should work so why not just do it ! It's our nature to do things like this and some people can and some can't make things no matter how much you show and teach them . Let us all know how it turns out and what happens after you put those pistons you made by hand in an engine for the first time . I am know you can do it . Good luck ! retro Jim
Go man, GO! Make your own pistons, and have someone there to take a lot of pictures while you're doing it. Love your attitude. Man after my own heart for sure. Besides, what's the worst that could happen? The motor blows up? Hell, I can do that with store bought pistons!
<HR style="COLOR: #e5e5e5; BACKGROUND-COLOR: #e5e5e5" SIZE=1> <!-- / icon and title --><!-- message --> "Don in post #185 you stated that mobile 1 trans fluid is stable to 1600 F. I do not think this is correct as even dot 5 brake fluid boils around 550 F I believe." Yes that is actually true. Many moons ago I was running a 440 (from which my 440 OR book sprung. ) The car with driver weighed 4150 lbs. If I drove 4250(I then weighed #306) We had a partial sponsorship with the local Esso (Exxon to you guys south) They were at the time joined with Mobil. One day my sponsor brought the pres of Mobil by to see me. His name was Mike Priest and he was also an engineer. In talking to him I also realized very quickly that he was a former drag racer and had mopar knowledge as well. He asked me if we had any problems with the trans in such a large car. I replied that we did and that we had to service the high clutch drum and its sealing rings about ever three major races. (I could tell when it was starting to fail as the mph would mysteriously fall suddenly about 2 mph) "The front sealling ring burns up the most" he told me. It was true. Often you could have shaved with it it was burnt so thin. "Why dont you try Mobil 1 synthetic trans fluid?" he asked. I went off in one of my tirads how I didnt believe in all that magic crap. I will never forget what he said. "Well Don, Mobil 1 is stable to 1600f degrees. Aluminum melts below 1300 f so unless your trans has melted and run out on the ground it will still be lubricated. That was all he said and he left a few minutes later. I thought a lot about it the next few days. It was then $80 for a trans fill back then of Mobil 1 trns fluid. Unfortunately (or fortunatley) the guy spoke my language and the shear logic of it would not go away. I swallowed hard and bit the bullet and tried it. As an aside . I never had to service the trans for 5 years. Even when i checked every spring for a band adjustment etc it never needed even a 1/4 turn . When i did have to service the trans it was for a broken sprag which occured during a hard wheels up 5100 RPM launch. I went through all the clutch packs then because I had to change the main case . Nothing and I do mean nothing was hurt. We raced this car in the points and did not ever miss a race so it saw heavy heavy use. Mike has since passed away I have been told but I remember what he said loud and clear. That is how I know that and why. If any are curious about that particular car here is some old scratchy video of my last weekend running it before I sold it. http://www.dropshots.com/Dolmetsch#date/2009-01-06/17:55:57 Don Thanks all for the encouragement. i am getting close to another pour. And now for the $64 question. Do i still use syn trans fluid in my race car? "Coytenly!" Yeth! I would have to be nuts not to. BTW I do all my own trans work and i hate working for no good reason.
Here is the hinged core box I made to make form the baked cores. I also label everything I make and in the language of my direct ancestor (which I can speak even though he left Germany in 1709) I tell my wife that way when I pass she will get more for my stuff at "THE SALE". The painting like staining raises some of the open grain in the wood so I will have to wait till it is hard dry and go in and sand a bit more then repaint. The more time spent with things like this the smoother the casting will be I think. Don
have someone there to take a lot of pictures while you're doing it. Vern took a lot of pictures but he is hiding most of them. I must not have combed my hair i guess. Don
Today we took the 170 apart and seperated the what we will use from what we will not. We also did a vintage junk yard crawl (Roblins and Minakers )looking for a crank (or an engine) A 198. So far no luck. Lots of 225s but not many 198s I guess. The 198 was made from 70 to 74. The 170 had a E8 Isky cam should anyone need one. I had built this 170 for a friend's son many years ago. He did nothing with it and it sat in his dad's shop for many years. The car was sold and the engine was left to die. We rescued it. Don
A little OT from the piston casting, but this was scouted out today during our "County Cruise" Gonna have to investigate some more on this one. Not too much left at either Roblin's or Minakers, but if it is parts/pieces you are looking for, both locations are still a bit of a gold mine. If only the walls of either location could talk.
Like Vern said not many complete cars left but parts? Lots. We saw NOS pistons at both spots. (I am gaining confidenceas I look at these. ) 2 Str Buick 8 cyl heads. Some Y block stuff. Several NOS torquflights in a bus there. A couple of straight axles i or more correctly I beam axles. I would never assume they dont have it. I would always ask at either place. I am often surprised at what is there and i have been going to both since 1968. Don
Go for it. When the big one drops we are going to need folks who can still do for themselves. One question I have regards cam grinding pistons. I expect that this is beyond the capability of a home shop, unless of course you knurl them to add some ovalness. Is cam grinding really not that important? If it is, can you knurl them oval?
Cam grinding and oval shape are for noise. When a half deaf stiff old guy like me is sitting ina rail with a helmut on and the jewels resting on a 40 year old diff the very last thing I am worried about is piston noise. Any object than is sliding or turning inside another in an engine needs .001" clearance per inch of diameter. That will always keep you out of trouble even in a hiperfomance situation. Because these are slipper skirt pistons I dont have to worry about the pin side expanding into the wall since it is almost 3/4 of an inch away. As long as there is sufficient clearnace for the skirts of the pistons. The section of the piston where the ring grooves are is always smaller. Always at least .020" smaller sometimes more. Also most important and often overlooked is the pin must not be tight in the pin bore. I am fanatical about making sure the pin when honed , cleaned and wet will fall slowly through the pin hole on its own when turned on its side. It is not a bad idea to relieve the corners of even the slipper skirt slightly. Sometimes some folks think that these clearances are too loose but they are never engine builders but usually "experts" meaning they read in hot rod or MA or some rag that it should be done this way or that and when and if they ever get to do it that is how they will do it the first time. When it pukes they will come around. Too loose which these specs arent but for arguments sake we will use that term will at worst make a bit of clatter cold . Too tight will die for sure everytime. I remember back in the late 60s taking a clinic from the TRW guys. The guy was talking for a 1/2 hour about folks who fit their product tighter then their specs. He said and i qoute, "Our spec we give you is THE MINUMUM clearance the piston can survive with." Piston grinding? They used to have such machines and I have run one but not for that purpose. Really you dont want a piston skirt too smooth.(Like polished) I finish mine on the lathe with my auto feed as used for general purpose cutting. Otherwise the oil ring and scraper if used have too much work to do and the oil film must survive the hole stroke. With a piston finshed as I described it carrys some with it but takes it back with it too. Some of it doesnt go into words well. I have done a lot of piston mods over the years and have to admit if truthful some of it is just instinct gained over the years. Hopefully that will transfer well to making them from scratch also. We shall see. The biggest trick in machining pistons is to know which surfaces to machine first. You must establish a register from which everyhing else is measured. I cut the bottom of the skirt or balance pads first while the piston crown is chucked . Then I do what else needs to be done. There are a lot of skirt designs including the old spit skirts . These I am making are basically just chunks of aluminum meant to fill the bore nicely, support the rings and stand up to some abuse. I am a firm believer in the KISS principal especially when venturing into something like this. I may get fancy later but i doubt it will be necessary. Don
OK Unk but be advised I have read it (several times)and I am not using his methods. ( nor will i be. ) So I wont be wanting to hear steve ch says so and so . I am true to my bloodline and heritage, single minded when on a project. Don
Don...love your logic, never thought mechanical noises were a problem in race engines. Back in '62 three of us crazy high school kids build a flathead for a '53 Ford gasser we had. So much piston slap you could hear it over the open headers. Don't know the exact clearances, but it was a high mileage engine and we just honed the bores and gave it new rings. never had any problems with it and it ran real strong.
A few shots from today's effort. Results were somewhat disappointing. I am sure that Don will chime in with his thoughts on issues run into today.
The Jalopy Journal
