Bore Sizes?????

[625fireman]

Working on my rebuild, found a cracked top piston ring. Does anyone know what the real set numbers are for standard bore, .020 over, .030 over .... seems to be discrepancy across manufactures!!!!!!!!!! My pistons are stamped 103.631. Did I get screwed??? Can match that number up with any manufacture????

 

[ak diesel driver]

where did you get those? got a side view pic?

 

[THEFERMANATOR]

I believe that is the millimeter sizing instead of inches, and if memory serves me correctly, +1 mm is .040 over. When all else fails, break out the micrometer.

 

[THEFERMANATOR]

Just looked it up, and if that number is the piston size, then it would be a .020 over. Stock bore is 4.06 inches or 103 mm, 103.631 comes out to 4.08 inches, so .020 over if it's correct, but I would double check with a micrometer to be safe.

 

[ak diesel driver]

I was wondering about the steel reenforcing for the rings. IIRC it's usually under the rings.

 

[3500GMC]

Looks like a MAHLE piston. Top keystone ring land should be steel integrated into the casting.

 

[625fireman]

Thanks kinda what I was thinking too. But what is throwing me was some state stock is 103.055 and other show the 103.06. I don't really want to get into gapping rings but might have to. The conversion mm to inches is too tight to guess. Manufactures need to pick one and stay with it across the board!!!!!!
103.631-103.000=.631mm=.0249"
103.631-103.055=.576mm=.0227"
103.631-103.060=.571mm=.0225"

103.000mm=4.0551"
103.055mm=4.0573"
103.631mm=4.0800"

Now that being said I know the piston is not a TIGHT fit to the bore, but ?!?!?!?!?!
I will mic them tomorrow to check, tough for me to do the bore, all I have are snap gauges. I just don't always trust them.
Next question, where is you alls best place to get rings????
@ak diesel driver those are what came out of it when I tore it done. Not sure what brand they are!

 

[625fireman]

Here is what the mic says. Measured in cyl #5.
Along with the service manual charts...
Looking like Im at .030" oversized.

 

[WarWagon]

Gapping rings is easy. Just push them in with a piston and measure. I recommend Total Seal direct for rings or send your favorite brand in for ~$90.00 to be made gapless. I have posted Total Seal Gapless results.

If I were you I would take the pistons and block to a machine shop to be measured. 0.30" over isn't "common" for a 6.5 as most are .5mm over: that is 0.20". Military manual says .5mm over than if it needs more scrap it. Taxpayer funded of course to get em out of harms way. Anything is possible so hire an expert to measure it.

 

[625fireman]

Ok after looking at my numbers they don't make sense. I will have to do something different. Probably follow what you said Warwagon....The shop that did this last time is supposedly a race engine shop. I'm wondering if the machined down the over sized pistons to fit. Bore mic'd closer to stock?!?!

 

[625fireman]

Rechecked and did more digging...... I have Mahle pistons .030" over sized. I have a call into Mahle to get new rings. I have found numerous kits with pistons. Hopefully I can get the ring kit. Pistons are good, don't want to spend the extra $$ on new ones.

 

[MrMarty51]

That 0270113 number stamed in the piston appears to be a GM number, have You tried crossing that number ?
About gapless rings ?
Can they be purchased from right off the shelf or do they have to be made from rings with gap ?

 

[ak diesel driver]

They're pretty much made, you can buy a set from total seal. I believe they just take an off the shelf set and machine them. Or you can send them your new set and they machine them for about $90

 

[625fireman]

Stock item from Mahle. Talked to tech support there he gave me a part number to look for cannot buy direct. Summit has them but doesn't have them tagged to 6.5s just says Chevy v8. They are supposed to fix it. FYI Mahle ring kit for 6.5's is part number 41718. This is factory bore. Over bores are 41718.0x0. Insert oversize for X. Ie. Mine Is 41718.030...

 

[denata]

[QUOTE = "625fireman, post: 548971, member: 2146"]
Вот что говорит микрофон. Измерено в цил № 5.
Наряду с диаграммами руководства по обслуживанию ...
Похоже, я на 0,030 "негабаритных.
[/ QUOTE]
interesting manual.
And there are detailed dimensions for the repair of cylinders sizes?

 

[denata]

Found in the manual for a Hummer another table

 

[denata]

On the site of Mahle it is said that this is a piston with a reduced compression ratio.
Part number of this piston is 224-3403.030

 

[MrMarty51]

On the site of Mahle it is said that this is a piston with a reduced compression ratio.
Part number of this piston is 224-3403.030

I wonder what compression ratio would be for them pistons. maybe I`ll do some research, see what I can find.
thank You for posting this.

 

[MrMarty51]

Could not find any info on compression ratio.

 

[Twisted Steel Performance]

18 - 1, they sit lower in the hole.