Mac extra porting !!!

[mcbob]

Well fellas i viewed a CD of the Snowy Mountains Chainsaw Classic of 1995 and 1996 and was amazed at what i saw a Mac with a BDC in the normal position and another mounted on the opposite side of the cylinder block ......... i was told of this saw by another Chainsaw fanatic like myself only recently and didn't believe it till i seen the CD of the races this engine is owned by a fella called Chris Brown but i'm not sure where he built the engine or not.

But is this a good mod or not, as it would certainly lift the induction capabilities of the engine, i have modded an old crabbed SP125 Cylinder to replicate his mod but here's my questions

1. Is this mod worth the effort ?
2. If i get the coil mount moved to another part of the cylinder could i run a second exhaust port coming out of the cylinder where the coil would normally sit.
3. Would i be better off instead using this proposed area to add bigger and better boost ports i cannot run both ?









I have just a few moments ago tryied to call Chris Brown at the Forrestry of South Australia and was told Chris has passed on about twelve months ago ... Chris was the fella who gave me all his Mac bits .... little did i know why ........... so sad to hear ...........

Mc Bob.

Mc Bob.

[Michael Jackson]

You have the makings of the Mac 102 in your hands but just didn't know it!

[Rob Voska]

Exhaust ports behind the coil.....NO

What do you need? RPM? Torque?

I would think a inlet blockoff plate and two stuffer mounted carbs might be a better deal for you. You would have lots of room and could run HL or HR series carbs easy. Adjust the carb size to the reed area and RPM you are looking for.

[mcbob]

Exhaust ports behind the coil.....NO

What do you need? RPM? Torque?

Both if possible ..........

I would think a inlet blockoff plate and two stuffer mounted carbs might be a better deal for you. You would have lots of room and could run HL or HR series carbs easy. Adjust the carb size to the reed area and RPM you are looking for.

==================================================================

We can't run two stuffer mounted carby's as our engines bolt to the oiler tank and bar and chain mount so that rules that one out.

As regards the extra exhaust port i recall getting rid of the spent gasses helped in making more power but in the case of the engines with the boost ports then that area is already taken but in a SP125C they don't have boost ports only a blank wall.

Mc Bob.

[steveohara]

Bob,

Your motor set up with a manifold on each side will make a great conversation piece but not much more. Whatever you can accomplish with the extra manifold can be achieved from the bottom or the traditional side and the end result would be the same. In other words.... if your objective is to double the reed area and carb area you could achive the same result with both on the side where the standard intake sits. Putting one on each side has a nice symetrical appeal but it would not make the motor stronger. As for the opposing exhaust port idea, there have been a number of small two stroke motors built that way and you might produce a benefit from that kind of mod if you have a big budget and lots of time on your hands to go through the whole transfer port design process from the ground up. As they are presently designed, the Mac engines transfers direct the flow of incoming charge away from the exhaust. If you put another exhaust opposite the standard position you will have the transfers directing the fresh charge right out the exhaust.... not good.
Regards,
Steve O'Hara

[steveohara]

Bob,

If you really want to have some fun with your Mac engines and build something cool consider this idea..... make a pressurized induction system by capturing the air flow generated by the flywheel and route it to the intake. Heated air under pressure, even with the very modest boost you would get from the flywheel fan, combined with straight alky would make for a very interesting effect on your Mac.
Steve O'Hara

[ted johnson]

G'day, McBob! The pictures reminded me of my street racing B-Limited 101A/A back in my sidewinder days. The 101 was a Dan Lumello mod with square intakes. I cut a hole in the back of the block and welded on an old Reed manifold from an AH-58. I put the alky Burco Supercarb in the normal location on a V-12, and an HL-293A with a GEM reed on the back. This setup ran very competetivly against the K-99's and BM-130's on the long Florida street curcuits, but didn't have enough low end for sprint tracks. Thanks for the memories! Ted

[mcbob]

Bob,

If you really want to have some fun with your Mac engines and build something cool consider this idea..... make a pressurized induction system by capturing the air flow generated by the flywheel and route it to the intake. Heated air under pressure, even with the very modest boost you would get from the flywheel fan, combined with straight alky would make for a very interesting effect on your Mac.
Steve O'Hara

What something like this setup .......... !!!!!!!

[jmendoza]

There they are Bob, two prototype MC-102 engines on the back of that Kart I have the only MC-102 in exsistance

[mcbob]

There they are Bob, two prototype MC-102 engines on the back of that Kart I have the only MC-102 in exsistance

Well Jay you's better pop ne a piccy of it so i can see if it's truely what you say ol mate

ozflea@bigpond.com.au

plus i believe they were developing a Mac 94 gee the story just gets better especially since they were stillborn !!!

Mc Bob.