I ran into a guy who was telling me about his small block Mopar. He said he had the tops of the pistons chrome plated. Has anyone ever heard of doing this? Is this BS or a misunderstanding from the engine builder?
I've seen ceramic coated piston tops. Chrome isn't out of the realm of possibility either. I know of a guy who specializes in the ceramic treatment. They need to be redone frequently. I can't remember the advantages gained offhand. My son would.
There have been coatings for pistons or piston tops around for years. Not chrome either decorative or hard chrome though. This is the Ross racing page on their coatings Ross Racing Pistons Piston Coatings For High Performance Racing (rosspistons.com) Chrome plating internal engine parts has been around for a long time but it is hard chroming that can be machined to tollerance. 53 years ago I worked across the tracks from a shop in Waco Tx that hard chromed crankshafts for locomotives and ships. They would haul crankshafts in on flatbed rail cars that took up the whole length of the rail car. I never got to see the inside of that place but it looked interesting from our loading dock.
Ceramic coats will help to isolate heat into the chamber and let the piston and head run a little cooler, thus generating a better inlet charge and more heat in the compression chamber. Chrome will not do this - maybe the guy got some misleading info and now tells that his stuff is chromed. Of course you can chrome a big end or mainshaft to repair undersized stuff or in a case of bad wear characteristics the harder chrome layer will wear slower than the parent material. On the other hand you might run into more problems as the soft material below might deform under load and thus the chrome layer will break and flake off - destroying the engine on its way into the oil pan. As chrome is very hard it was widely used by japanese motorcycle engines for sliding cam followers on cast material. It did work up to the point where we ground more radical cams and needed stronger springs - within 5 minutes on the dyno the noise began and the followers were worn through the chrome coating. So chrome has its limits as well.
I grew up with a neighbor who used to tell us little kids stories like that. The guys name wasn't Dick by any chance, was it?
I worked as a machinist in a hard chrome shop for several years. Nasty, nasty stuff. Hard chrome is "applied" directly to the base metal unlike decorative chrome. In all the years I worked there, the shop never put hard chrome on aluminum. The owner, who had been in the business since WW2, never talked about the possibility of it either. So, I'm not buying the chrome piston thing at all. My response to such a claim might be something along the lines of "Is that a fact?" Then leave it at that, being unwilling to engage such a story teller. It is difficult enough to get a bond onto bare steel, even more difficult on alloys such as stainless steel, and a downright bitch to get it bond to cast iron. New cast iron, yes. Feasible. Oil impregnated cast iron such as cast cranks and cylinder liners....nearly impossible. It's been done, but the bond is sketchy at best.
Yeah, thats why I asked. I took it with a grain of salt when he told me. But not being a professional racer or machinist ........inquiring minds want to know.
The expansion rates of chrome and alum. are very dissimilar. In my drag racing days, people would chrome their bugcatchers. If it was a real race car, the chrome started to come off after several heat cycles.
It can be, and is done: https://www.vanwest-holland.com/piston-crowns/ Usually only an option on very large pistons where replacement cost would be high. I don't think it would be economically viable for a car engine. Unless he is running a ship diesel engine..............
At the aircraft salvage and engine shop I worked at fresh out of high school, I can remember crating up radial engine cylinders and sending them out for hard chrome. Something to do with wear, I'm sure. Never pistons, though.
Reading down, they are talking about steel pistons, and shows a repair on one being welded up by submerged arc.
Hard Chrome on Aluminum is a practice that has been used. Moto Guzzi for one hard chromed the aluminum bores before Nikasil was developed. So the "is it possible" part to the question should be answered with a yes. If someone has a friend in the trade I would not be surprised if someone experimented. I have seen people try crazy things to get a bit more performance out of a motor. Therefore in my opinion it is likely someone has done this. I would be surprised if they achieved any meaningful gains.
Apparently, it is a thing. My employer at that time, who started in the aircraft industry during WW2, working at the process until the 90s said he wouldn't do it. Our shop specialized in industrial applications though. Oil field tooling, pump shafts, hydraulics, etc. Every shop has their specialty. Stuff they can make money at.
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