Variation in Squish?

[P.M.P.]

Are you talking about the new bobblehead pistons?

I used to have a a Joe Dumars which ones are new?

 

[paragonbuilder]

Are you talking about the new bobblehead pistons?

Perhaps... [emoji57]


Sent from my iPhone using Tapatalk

 

[drf256]

My bet is that the chamber in an 028S is VERY offset. Like Mike is saying above, you’re compressing less solder at the three places other than the ex side of the band, which is the thickest IIRC.

If you’re using thick solder, the difference will be magnified.

Being it just the Ex side, bolt the jug on and check with solder through the plug hole. Turn the saw over numerous times, and use the thinnest solder you can (closest to squish-I use .024 solder). My bet is that if you mash it like 50x, you’re gonna see a squish similar to the sides and back.

Pretty sure I got a jug on my bench. I’ll get a chamber pic.

Also, check your piston side clearance with a feeler gauge.

 

[drf256]

Rings bells:
with ones that were hand cut on a mandrel .......... The cutter digs in more on the thin side
Thanks Mike !

I used to cut with a mandrel. Still do on occasion if the saw needs very little out of its band, and I’m only doing one jug. It’s just faster. I avoid it on saws with assymetric bands because, as you said, it digs in more on the thinner side. But that will give one a tighter squish on the thicker side which is opposite of what Jon is seeing.

Here’s an 028 Super Chamber:



Sorry for the dark pic, best I could do.

My bet here is that the wider band on thicker solder is just allowing more springback of the solder. I bet if he uses thinner solder, his ex reading will be similar to the other 3.

 

[Fruecrue]

Wondering if doubling the solder (side by side) on the thin side would yield a more even result.

 

[Mastermind]

Is the piston crown eroded on the exhaust side?

 

[drf256]

He can Rotate slug first as well. Good point.

 

[JonCraig]

You guys have given me some homework!

I don’t know exactly what thickness my solder is, but I know it’s significantly thinner than my other solder. So at least I’m not using the super fat stuff.

Will do these suggestions this afternoon.

 

[blsnelling]

Check both sides individually, letting the piston rock fully. That way you eliminate the difference caused by the wider squish band. This will give you an excessive reading, but will tell you if it's off or not.

 

[JonCraig]

Can’t put jug on backwards, there’s the part of the case that comes up to the av mount that interferes.

Trying Brad’s idea of individual measurements now.

 

[JonCraig]

Measured individually, exhaust side .001 larger, intake side .005 larger.

 

[blsnelling]

I would be more concerned if it was off along the axis of the wrist pin.

 

[JonCraig]

You mean I should measure again individually along the pin to see if it’s rocking on that axis?

 

[blsnelling]

I thought your measurements were close along the pin. No?

 

[JonCraig]

I thought your measurements were close along the pin. No?

.0025–two and a half thou.

 

[Al Smith]

2.5 thou is only the thickness of a piece of paper. I wouldn't worry about it .
It could be anything,piston pin hole off a tad ,rod off a little,piston machined off a bit .
Then look how it's being measured .Smashing lead solder works but it's not the most accurate method .It's close enough .

 

[JonCraig]

It's close enough .

That was my thought, but I learned long ago to learn from other people’s mistakes and always ask questions of people smarter than me (of whom there are a great many.)

Thanks guys!

—JC

 

[Moparmyway]

Yellow plastigauge will eliminate the solder playing any role

 

[Al Smith]

I didn't know plastigauge came that thick .I've only used it to measure bearing clearances on rods and mains in automotive type engines .

 

[Moparmyway]

I didn't know plastigauge came that thick .I've only used it to measure bearing clearances on rods and mains in automotive type engines .

https://mahle.partnumber.company/mpy-1-yellow-plastigage-plastiguage-plastigauge-clevite