mc-7
Moderator: Rob Voska
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steve miller
- Posts: 249
- Joined: Wed Jan 27, 2010 1:20 pm
- Vintage Karting items owned: simplex,rupps,fox,putt nik,go kart 1600,alley cat ,hellcat,mcculloch,hornett,moss..
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mc-7
merry x-mas all ...i was wondereing if you can put a 91 piston in a mc7 ..i have brand new 5 over wisco ..its got blind pin ..stepped skirt ..i think its for a 91.
Last edited by steve miller on Sat Dec 25, 2010 9:47 pm, edited 1 time in total.
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ted johnson
- Posts: 1685
- Joined: Fri Jun 15, 2007 7:59 am
Re: mc-7
If your Mc7 is 9-ported, it can work. If you're running the original third port configuration, don't use a 9-port piston. TJ
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steveohara
- Posts: 411
- Joined: Thu Jul 19, 2007 2:29 am
- Vintage Karting items owned: 1969 Bug Sprint Mc 91B1
1965 Dart Gran Prix twin Mc100s
1963 Bug Scorpion ESll Mc45
Re: mc-7
Steve,
The 9 port style piston will fit your motor and run fine if block off the back side passage that bypasses the reeds. It can be done easily with a home made gasket or you can make a new reed plate using the standard plate as a pattern... just don't cut out the slot that feeds the back passage.
Another option is to use any of the manifolds that route all air intake through the reeds. The Mc 45/75 version looks just like the original 7 except it takes a pyramid reed cage.
Steve O'Hara
The 9 port style piston will fit your motor and run fine if block off the back side passage that bypasses the reeds. It can be done easily with a home made gasket or you can make a new reed plate using the standard plate as a pattern... just don't cut out the slot that feeds the back passage.
Another option is to use any of the manifolds that route all air intake through the reeds. The Mc 45/75 version looks just like the original 7 except it takes a pyramid reed cage.
Steve O'Hara
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steve miller
- Posts: 249
- Joined: Wed Jan 27, 2010 1:20 pm
- Vintage Karting items owned: simplex,rupps,fox,putt nik,go kart 1600,alley cat ,hellcat,mcculloch,hornett,moss..
- User Agreement: Yes
Re: mc-7
thanks steve ,that sounds good to me.. since someone alredy hogged out stock reed plate and put in pyramid reed cage .thanks again .looks like i have couple choices for what i can do ..
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steveohara
- Posts: 411
- Joined: Thu Jul 19, 2007 2:29 am
- Vintage Karting items owned: 1969 Bug Sprint Mc 91B1
1965 Dart Gran Prix twin Mc100s
1963 Bug Scorpion ESll Mc45
Re: mc-7
Steve,
Great, you already have a Mc 45/75 intake. That is all that they did at the factory... took the early manifold and bored a bigger hole in it so the Go Power cage would drop in and then added longer studs to allow for the extra material of the reed cage.
With that intake manifold the "piston valve" portion of the intake tract in your Mc 7 is effectively eliminated and so you could gain a bit of performance by filling in the back side passage with epoxy to "stuff" the motor a little bit more. The next step would be to elongate the three holes that are no longer used to charge the case into "9 ports" as they have been called over the years.
The change in performance would be modest and reliability might even be improved as the "9 port" layout can provide some cooling and lubrication benefits to the piston and wrist pin bearings.
If you choose to create the "9 ports" make the top of the ports the same height as the transfers.
Or, you can just leave it all as is and run either type of piston with no worries.
Regards,
Steve O'Hara
Great, you already have a Mc 45/75 intake. That is all that they did at the factory... took the early manifold and bored a bigger hole in it so the Go Power cage would drop in and then added longer studs to allow for the extra material of the reed cage.
With that intake manifold the "piston valve" portion of the intake tract in your Mc 7 is effectively eliminated and so you could gain a bit of performance by filling in the back side passage with epoxy to "stuff" the motor a little bit more. The next step would be to elongate the three holes that are no longer used to charge the case into "9 ports" as they have been called over the years.
The change in performance would be modest and reliability might even be improved as the "9 port" layout can provide some cooling and lubrication benefits to the piston and wrist pin bearings.
If you choose to create the "9 ports" make the top of the ports the same height as the transfers.
Or, you can just leave it all as is and run either type of piston with no worries.
Regards,
Steve O'Hara