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 6.3
 9:1 Pistons for 100.981, Oversize
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T.J. Woods

Australia
258 Posts

Posted - 08/22/2017 :  17:42:39  Show Profile  Reply with Quote
Hi All,

Just hoping to confirm if anyone has had any luck obtaining any oversize 9:1 pistons, or if they ever existed? According to the EPC, it looks as though they were only available as Std., with oversize being the lower compression version. Maybe this is due to the head gasket limitations?

Regards,
Tim

1976 450SEL 6.9 #1432
1979 450SEL 6.9 #5866
1969 300SEL 6.3 #1394
1985 W126 280SE

Art Love

Australia
6138 Posts

Posted - 08/22/2017 :  18:49:22  Show Profile  Reply with Quote
Tim,
#765 has first repair size 9:1 pistons made by Mahle.





I have also, in the past, asked Tom Hanson regarding the suitability of standard head gaskets to maximum oversize pistons, because one or two of the blocks that Justin had rebored [including the block from #771 which had water damage to one bore] were at maximum dimensions and Tom said that the standard gasket sets were applicable to all factory approved repair sizes.
Art
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T.J. Woods

Australia
258 Posts

Posted - 08/23/2017 :  10:30:06  Show Profile  Reply with Quote
Thanks,

That's good to know. The engine in my car has suffered water ingress in 7 and 8, and there's a fair amount of deep pitting, which might be more than 0.5mm. It remains to be seen though just how bad it is.

I see two listings in Mahle's online catalogue, but they have a shallow dish according to the drawings, however the CR is stated as 9.

Anyhow, at least there's a few options available. It will be a while before the block goes in for machining etc.

Tim

1976 450SEL 6.9 #1432
1979 450SEL 6.9 #5866
1969 300SEL 6.3 #1394
1985 W126 280SE
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AgSilver

USA
207 Posts

Posted - 08/23/2017 :  13:47:24  Show Profile  Visit AgSilver's Homepage  Reply with Quote
I have 104.5mm Mahle flat tops with matching molybdenum rings bringing the displacement up to 6.5L. I had the pistons Sanford Hardcoated to Mil-A-8625 spec which significantly reduces friction and scuffing. The block was refaced and the heads milled, and with a 3 angle cut raising the valves on the seats, the static compression ratio was increased to over 11.5:1. However, the camshafts' increased valve overlap and duration result in a lower dynamic compression ratio.

Palm Beach Gardens, FL
Niederheimbach, Germany
300SEL 6.3
E55K AMG
CLK63 AMG Gone
Ferrari 400GTC4 Gone
ML400CDI BiTurbo
ML350 CDI BT
9146GT
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T.J. Woods

Australia
258 Posts

Posted - 08/24/2017 :  00:26:32  Show Profile  Reply with Quote
AgSilver,

That sounds like a nice improvement, were you able to retain the stock head gaskets, or was it a case of going with a custom option?

Tim

1976 450SEL 6.9 #1432
1979 450SEL 6.9 #5866
1969 300SEL 6.3 #1394
1985 W126 280SE
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AgSilver

USA
207 Posts

Posted - 08/24/2017 :  12:11:36  Show Profile  Visit AgSilver's Homepage  Reply with Quote
Tim - - -

No problem with the stock head gaskets as they are fabricated to accommodate the factory oversize pistons. The only modification to the gaskets was to apply 4 thick coats of aluminum paint to both sides and allow them to dry thoroughly (at least 3 days) prior to installation. Over the years I have had a few race engine failures, but never a head gasket failure.

Steve

Palm Beach Gardens, FL
Niederheimbach, Germany
300SEL 6.3
E55K AMG
CLK63 AMG Gone
Ferrari 400GTC4 Gone
ML400CDI BiTurbo
ML350 CDI BT
9146GT
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tjryan

USA
25 Posts

Posted - 09/06/2017 :  22:32:06  Show Profile  Reply with Quote
Steve,

Where did you get those Mahle 104.5s?

I just finished taking down a spare m100, and it looks like these 9:1 std size are now of historical interest only.


Best,
Tim




TimRyan
71 300sel6.3
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AgSilver

USA
207 Posts

Posted - 09/07/2017 :  07:35:33  Show Profile  Visit AgSilver's Homepage  Reply with Quote
I obtained the 104.5 Mahle pistons more than 25 years ago. My understanding is that today they are made out of "unobtainium." Not to worry, JE Pistons will make them for you. Just supply JE with a sample dish-top piston and rings and they will make a flat-top piston. Be sure to follow JE's installation requirements regarding clearances.

Palm Beach Gardens, FL
Niederheimbach, Germany
300SEL 6.3
E55K AMG
CLK63 AMG Gone
Ferrari 400GTC4 Gone
ML400CDI BiTurbo
ML350 CDI BT
9146GT
Go to Top of Page
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