Welded piston domes

[smeg]

Many years ago, I remember seeing some honda pistons that had the top welded up to make more compression. Anybody ever done this?

[englertracing]

Sounds generally terrible....
Maybe something some wild men were doing knowing full well they were only going to make a few passes.

[Leftcoaster]

Decades ago we bored a 1970 Honda 750F to take 900F pistons, which needed approx 0.050 added to create the desired 10.5 : 1 compression
Placed the guinea pig piston in an ali saucepan with water up to the top ring land including under the dome, and tig welded the ~1/2 x 1" rectangular flat portion of the crown between valve cut outs
In spite of working rapidly with comparatively low amps, water was boiling around the top ring groove by the time we finished
When cool and miked the piston diameter had shrunk around 0.005" beneath the top ring groove, and no doubt the temper ruined also
I'd be surprised if someone developed a method which created a durable product

[hoodeng]

I have also seen it done,,, Junk, is probably the best word to describe it.

[modok]

You can weld almost anything. Should you? Probably not, but can you, yes

[englertracing]

You can weld almost anything. Should you? Probably not, but can you, yes

Reminds me of this

Ian: "Your scientists were so preoccupied with whether or not they could, they didn’t stop to think if they should."

Jurassic Park

[Momus]

In about 1975 when working at a motorcycle dealership we had a 2 stroke Yamaha 400 brought in after it holed a piston on the highway.

The Swedish traveller gave us the OK and the piston was cleaned up, oxy acetylene puddle welded, reinstalled and off it went apparently for thousands more kilometres.

I have seen the same type of 2 stroke holed piston temporarily and successfully repaired with a nut and bolt through the crown.

[Schurkey]

Smokey Yunick wrote about welding pistons because they'd burned a hole in 'em and there was no "Chevrolet" development money to buy new ones.

I haven't read the books since Fido was a pup. Seems to me that he not only had to weld them, but also "age" them to harden the aluminum again, the welding left 'em soft.

[Tuner]

In 1950-51 I saw a DOHC Hal hole a cast piston (it may have been a Jahns but ?) Friday night, the piston welded with oxy-acetylene Saturday morning, and it won the A Main that evening. To cool it, two quarts of water were added to five gallons of fuel which was mostly methanol, but could have had some other secret sauce. There was some nitro in it Friday night, which explains the hole in the piston. The driver controlled the spark advance with the lever at the steering wheel. 1930s - 40s era AAA "Big Car" with the DO Hal head on a '33-'34 Model B Ford 4 cyl. AKA "The Poor-Man's Offy"

[dannobee]

Not really the domed, but welded none the less. Mahle made some pistons for the Porsche 962C engines that were comprised of separate forgings that were then electron beam welded together to form a circular channel behind the ring land so that a piston squirter could squirt oil through a hole near the piston pin, subsequently cooling the ring land area with cool oil. Obviously this was early on in the piston manufacturing and all machining and heat treating was performed after the welding. These were for the IMSA and LeMans engines, so they fully expected at least 50 hours of race time on the pistons.