Will Wiseco 9 port pistons work in a MC 75

[dean kanocz]

Will Wiseco pistons with the 9 port cutout work in a stock MC 75?The box says MC75 9 port.Will this be a problem with the 3 port in a 75.What is the difference?Thanks for any help guys.

[Tom Smith]

Mc-75s come 9 ported new from the factory. The difference is they require their own special 9 port piston which has notches at the bottom of the skirt to clear the crankshaft counterweights and a scallop cut on the exhaust side at the bottom of the skirt to clear the large PTO bearing pocket at BDC. You need the 9 port piston for a stock Mc-75.

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[dean kanocz]

Tom,I am still confused on this.The stock pistons I removed have the 4 notches like yours and same boost port design but it looks to me that the skirt is shorter and has no scallop to clear bearing -crank.The Wiseco replacements are short like the ones removed from my engines with the 4 reliefs on the bottom of the skirt.The boost port on the wiseco's is different though.It is open to the bottom of the piston skirt.Is this a concern?

[Tom Smith]

Here's a couple styles of Mc-75 boost port pistons. Don't put the piston in backwards.

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Mc-75 pistons boost port

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[dean kanocz]

Thanks Tom.

[Tom Smith]

The piston on the right has a light weight wrist pin. Both of them could stand to have the pins shortened for better oil access to the bearings.