What kind of #@%*!# hack?

[Chainsaw Jim]

Does this crap?


Lol. 394 piston hacked up to fit a 660 big bore without freeporting.


How long until it goes "kaboom!"?

 

[bryanr2]

I have nothing to contribute so I’ll just sit over here and eat .

 

[Marshy]

Dat thing has a chubby!

 

[huskihl]

Does this crap?
View attachment 152582 View attachment 152583

Lol. 394 piston hacked up to fit a 660 big bore without freeporting.


How long until it goes "kaboom!"?

Wonder how thick the crown is at the edge of the popup

 

[Wolverine]

I have nothing to contribute so I’ll just sit over here and eat .

Mmm. Popcorn.

 

[Dub11]

You got one that will fit my wild thing?

 

[Deets066]

Run that mfer.

 

[Bigmac]

Does this crap?
View attachment 152582 View attachment 152583

Lol. 394 piston hacked up to fit a 660 big bore without freeporting.


How long until it goes "kaboom!"?

Neve know until you try it!

 

[Bigmac]

Dat thing has a chubby!

Looks more like a c cup!

 

[Chainsaw Jim]

Wonder how thick the crown is at the edge of the popup

The sides and back are still pretty decent, but it's the front that has me concerned. I marked the spot where it is 2mm thick. It's a pretty small spot so maybe it'll fly.

 

[huskihl]

The sides and back are still pretty decent, but it's the front that has me concerned. I marked the spot where it is 2mm thick. It's a pretty small spot so maybe it'll fly. View attachment 152620 View attachment 152621

Seems like enough. I hope it works for ya.

 

[Bigmac]

The sides and back are still pretty decent, but it's the front that has me concerned. I marked the spot where it is 2mm thick. It's a pretty small spot so maybe it'll fly. View attachment 152620 View attachment 152621[/QUOTE
2mm is pretty thick, i have ran a pop up that had ,.070 at the ring land, it’s held up!

 

[Chainsaw Jim]

Seems like enough. I hope it works for ya.

I wish the cylinder had better plating. It needs some big fingers and whatnot, but it may not take it. I suppose if it runs well enough it'll be worth sending off to us chrome.
I need to get a few saws done before I can get back to this one.

 

[huskihl]

I wish the cylinder had better plating. It needs some big fingers and whatnot, but it may not take it. I suppose if it runs well enough it'll be worth sending off to us chrome.
I need to get a few saws done before I can get back to this one.

How do you account for different wrist pin diameters?

 

[drf256]

How do you account for different wrist pin diameters?

A 395 bearing allows the 13mm pin to fit into a 660. It’s thinner.

 

[drf256]

Looks good Jimbo.

Thickness should be fine, I think. My 026 pistons get pretty thin with cutting off the dome and I’ve never had an issue, but you are on the edge of an area that weighs a lot. I’d polish the top to remove any stress risers.

It just looks heavy. Also looks like compression will be in the 280 range.

You always seem to pull the impossible off with few tools and lots of talent and skill.

Can’t wait to see it run. I used a spacer plate when I did one with a 395 piston. The pin location allowed fingers. It was 180psi and a total beach to start.

Do you need a custom metal badge for it?

 

[Chainsaw Jim]

How do you account for different wrist pin diameters?

The rod ends are the same diameter on both saws. 13mm thin bearing, 12mm thick bearing. 395 piston on the 660 is plug and play, the 660 piston on the 395 would require clearancing to fit the wider rod end. There's no need for spacers with the 395 on the 660 because the cylinder holds everything centered.

 

[Deets066]

The rod ends are the same diameter on both saws. 13mm thin bearing, 12mm thick bearing. 395 piston on the 660 is plug and play, the 660 piston on the 395 would require clearancing to fit the wider rod end. There's no need for spacers with the 395 on the 660 because the cylinder holds everything centered.

Spacers are used to hold the rod straight, not center the piston. Once that wrist pin bearing wears a little the rod gets more lateral movement

 

[Chainsaw Jim]

Spacers are used to hold the rod straight, not center the piston. Once that wrist pin bearing wears a little the rod gets more lateral movement

Dammit Billy! You made me get up to go back out in the shop to take a look.
I thought the weights held it tighter centered than that. It doesn't shift side to side far enough to expose a lower bearing roller, but if the top and bottom goes in the opposite direction then it'll definitely chew hard and probably eat the lower bearing cage.
I guess I'll use the ends off a couple cages with bad bearings for spacers, unless they're too sloppy on the pin. Or a junk piston pin boss, hacked and milled.

 

[Chainsaw Jim]

Well how about that... no kaboom yet. It seems to be a little on the intense side... even with a bar & chain.