Stump Shot review's The Duke's new 2100CD piston

[Marshy]

Timing will not change running one of these pistons from running the original.

Because pin to crown is the same height and pin to skirt is the same length?

 

[huskihl]

Because pin to crown is the same height and pin to skirt is the same length?

I think what he’s saying is that, most pistons are within a few thousandths in height and skirt dimensions of the original. At roughly .015” per degree, it would have to be drastically different to change port timing enough to where it would be noticeable

 

[Stump Shot]

Because pin to crown is the same height and pin to skirt is the same length?

I think what he’s saying is that, most pistons are within a few thousandths in height and skirt dimensions of the original. At roughly .015” per degree, it would have to be drastically different to change port timing enough to where it would be noticeable

Yes

 

[Stump Shot]

I had both pistons pinned together at one point and I failed to get a picture of it. That's my bad, you have my word that this is a faithful reproduction of the original dimensionally speaking (I think they actually look better than the OEM)
If you want some changes to your timing I hear tell that 394 and 395 pistons can be made to use, but I have not done so myself to report on.

 

[srcarr52]

I had both pistons pinned together at one point and I failed to get a picture of it. That's my bad, you have my word that this is a faithful reproduction of the original dimensionally speaking (I think they actually look better than the OEM)
If you want some changes to your timing I hear tell that 394 and 395 pistons can be made to use, but I have not done so myself to report on.

I have, you have to cut the cylinder base a fair amount for the shorter crown height. Then the skirt height difference makes you gain a bit of intake duration.

 

[Stump Shot]

I have, you have to cut the cylinder base a fair amount for the shorter crown height. Then the skirt height difference makes you gain a bit of intake duration.

 

[Marshy]

I had both pistons pinned together at one point and I failed to get a picture of it. That's my bad, you have my word that this is a faithful reproduction of the original dimensionally speaking (I think they actually look better than the OEM)
If you want some changes to your timing I hear tell that 394 and 395 pistons can be made to use, but I have not done so myself to report on.

I guess I was just trying to ask if you made that comparison or not and if there was a negligible difference in skirt/crown or not. Thanks.

 

[Duke Thieroff]

I had both pistons pinned together at one point and I failed to get a picture of it. That's my bad, you have my word that this is a faithful reproduction of the original dimensionally speaking (I think they actually look better than the OEM)
If you want some changes to your timing I hear tell that 394 and 395 pistons can be made to use, but I have not done so myself to report on.

One of the interesting caveats that I have noticed is that when dealing with older parts, oftentimes if you get an older part reproduced the modern version may be as good or slightly better than the original. Like the Poulan 4000 cylinder we're having made. The machines/processes used for production on are more modern and potentially more accurate than the ones from 30-40 years ago.

Of course "better" in this situation depends on myriad factors including the manufacturer, materials used, the engineer doing the programming, QC etc...

 

[Stump Shot]

I guess I was just trying to ask if you made that comparison or not and if there was a negligible difference in skirt/crown or not. Thanks.

I just touched on that in my opening remarks, definitely could have done a better job for sure. With three projects going at the same time all swimming around my head, I suppose it's easy for something to lost in the translation. I will try and be more thorough next time...

 

[Stump Shot]

One of the interesting caveats that I have noticed is that when dealing with older parts, oftentimes if you get an older part reproduced the modern version may be as good or slightly better than the original. Like the Poulan 4000 cylinder we're having made. The machines/processes used for production on are more modern and potentially more accurate than the ones from 30-40 years ago.

Of course "better" in this situation depends on myriad factors including the manufacturer, materials used, the engineer doing the programming, QC etc...

And in all reality, better should be the norm here. Without good options the less than standard parts are not going anywhere. It's good to see some folks still give a dam and are working towards a higher goal.

 

[Duke Thieroff]

And in all reality, better should be the norm here. Without good options the less than standard parts are not going anywhere. It's good to see some folks still give a dam and are working towards a higher goal.

Generally that's what we're going for here. If we have a problem with a vendor on a certain part we usually move on. If we develop something we're usually looking for the best we can go within a reasonable price range.

 

[cuinrearview]

We could really use a solid aftermarket option for performance Dolmar 5100s and 5105s. The VECs are OK but the skirts are so narrow. Pretty much the only other reliable option is a $70 OEM. Unless something has been released in the last few months.

 

[Duke Thieroff]

We could really use a solid aftermarket option for performance Dolmar 5100s and 5105s. The VECs are OK but the skirts are so narrow. Pretty much the only other reliable option is a $70 OEM. Unless something has been released in the last few months.

Noted.

 

[huskihl]

We could really use a solid aftermarket option for performance Dolmar 5100s and 5105s. The VECs are OK but the skirts are so narrow. Pretty much the only other reliable option is a $70 OEM. Unless something has been released in the last few months.

Noted.

7900’s also. 3mm wider skirts on each. Single ring dead center on the intake

 

[Duke Thieroff]

7900’s also. 3mm wider skirts on each. Single ring dead center on the intake

Is this how they come standard?

 

[huskihl]

Is this how they come standard?

On the original 7900’s with windows (not needed), the ring pin was centered on the intake. On the newer 7910 slab pistons, it’s over on the right skirt edge.

 

[Lightning Performance]

On the original 7900’s with windows (not needed), the ring pin was centered on the intake. On the newer 7910 slab pistons, it’s over on the right skirt edge.

Is there any change in the 7910 jug besides the exhaust compared to the 7900? I'm still debating on what one to get.

Went through Chris's site the other night. Nice selection there. Good looking stuff!

 

[huskihl]

Is there any change in the 7910 jug besides the exhaust compared to the 7900? I'm still debating on what one to get.

Went through Chris's site the other night. Nice selection there. Good looking stuff!

Port numbers are similar. I like the 10 for porting. Extra metal

 

[raumati01]

Will this fit a double eagle 80?

https://www.sawsalvage.co/collectio...per-pro-81-replacement-piston-and-rings-92519

 

[ferris]

View attachment 219435 View attachment 219436Here's some comparison shots of the titanium nitride and the moly.

What are the pros and cons of these two coatings?