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New pistons too high?

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michaelb

Post subject: New pistons too high?

Posted: Tue Feb 12, 2013 9:24 pm

1275cc

Joined: Sun Jan 21, 2007 9:16 pm
Posts: 3166
Location: North of the Harbour planning my next mini project

I have just assembled my 1100 engine with new GR 80+ flat top pistons and they are sticking out above the deck by about 20thou

I'm thinking this is too much as the old dished pistons from memory were either level or slightly below the deck?
With the old pistons I think the engine was about 9.5:1 compression as the head is a modified 202 with approx 60thou shaved off the face.

_________________
1969 Cooper "S"
1967 Mini Deluxe
1973 Clubman Van (the fleet spare)
1978 ex 1275 LS ("Wizard" Eaton Supercharged)

2015 HSV GenF GTS(occasional drive & tow car)
2019 MINI F55 Cooper S

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Harley

Post subject:

Posted: Tue Feb 12, 2013 9:27 pm

1360cc

Joined: Mon Aug 23, 2004 10:07 pm
Posts: 10654
Location: SE Melbourne

Do you know for sure if the block was ever not machined on top to raise compression with smaller pistons?

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drmini in aust

Post subject:

Posted: Tue Feb 12, 2013 9:34 pm

religious status

Joined: Fri Mar 19, 2004 6:19 pm
Posts: 39764
Location: near Baulkham Hills, NSW

Block has been decked.
Take the pistons back to GR and he can face them off for you.
Or, I can do them here. :wink:

_________________
DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R. :mrgreen:

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michaelb

Post subject:

Posted: Tue Feb 12, 2013 9:41 pm

1275cc

Joined: Sun Jan 21, 2007 9:16 pm
Posts: 3166
Location: North of the Harbour planning my next mini project

Yes block has been decked but not sure by how much?
Engine number is still visible, although last skim avoided the engine number area.

Yes I would be happier with 25thou skimmed from the top of each piston.

_________________
1969 Cooper "S"
1967 Mini Deluxe
1973 Clubman Van (the fleet spare)
1978 ex 1275 LS ("Wizard" Eaton Supercharged)

2015 HSV GenF GTS(occasional drive & tow car)
2019 MINI F55 Cooper S

Top

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