MAC Engine

[OuterMarker]

I have a stock Mac 90 on a stock Bensen frame. I want to get the engine running again. It has a single Slick mag designed for the Mac engine. The engine doesn't have any form of exhaust...no header, nothing, just the full cooling shroud around the cylinders. The fuel system consists of a pressurized OMC boat gas tank, dual fuel pumps, fuel regulator, single carb, some one way check valves and a fuel filter. The stock Bensen stuff.

So, here are my questions. Since the Mac was designed for 130 octane fuel back in its day:

What has to be done to de-tune the engine to burn auto gas?

What ratio of oil should I use to ensure there won't be an overheating issue?

Does anyone have any documents supporting de-tuning the Mac 90 for auto fuel?

thanks!
albert

[Ron Iaconis]

Originally Posted by OuterMarker

I have a stock Mac 90 on a stock Bensen frame. I want to get the engine running again. It has a single Slick mag designed for the Mac engine. The engine doesn't have any form of exhaust...no header, nothing, just the full cooling shroud around the cylinders. The fuel system consists of a pressurized OMC boat gas tank, dual fuel pumps, fuel regulator, single carb, some one way check valves and a fuel filter. The stock Bensen stuff.
Look at these links below,,,,good luck!!!!!

So, here are my questions. Since the Mac was designed for 130 octane fuel back in its day:

What has to be done to de-tune the engine to burn auto gas?

What ratio of oil should I use to ensure there won't be an overheating issue?

Does anyone have any documents supporting de-tuning the Mac 90 for auto fuel?

thanks!
albert

R&D out of Texas will start you on your journey,,,with the Mighty Mac!
Red Smith was the originator,,,now his son has the business,,
It's R&D engineering,,,or what ever,,,just Google it and order his parts list & manuals,,,the charge is very nominal,,, ,I have been dealing with mac's since 1984,,,
Do That First Then Get with someone near you to assist you.
Also,,,,we have a knowledgeable fellow,,,,Rick Wittridge,,,he's here on this forum,,,that supports Macs and stuff,,,,look here on the forum,,,my spelling of Rick's name may be incorrect but you will locate him,,,,
I hope you well on your journey

"Check out these Links"

http://www.rotaryforum.com/forum/pro...t=friend&u=299

Rick Wittridge
is his name

http://www.aviastar.org/helicopters_eng/bensen_b-8m.php

http://www.pra.org/supportfiles/ezin..._Mar_hires.pdf

[Gyro28866]

Rick is the man YOU need to speak to!!!
It sounds like this engine is an old setup.
I use 5 gallons 100LL (aviaition) mixed with 14oz Blue Marbles oil
when I used petro based oils, I mixed 16oz of Pennsoil, or Mercury QuickSilver to 5 gallons of 100LL.
My carb is a Holly 1940 with a .68 main jet.
Rick can tell you the timing setting, I would recomend using his CDI ignition, it cured all my mag problems.
Builder of the World Famous GOGO GADGET!
Gyro Parts supplier
Wheel & Brake Kits
CDI ign for the Mac
Mac parts,Props,Rings,Fuel Pumps,Ect.
Advanced Rotor Designs
937-878-2598

If he does not answer, leave a message. Rick will return your call!