MAC .67 leaning out

[James Schmidt]

I Have a Mac .67 that leans out. its in a 36" sprint cat. running octura 455 and 457. and a 250 prather for props. it has a 67 CMB pipe. running 6 turns on a bobby Violette remote needle valve. standard size brass tubbing that comes with Sullivan tanks. I was thinking my bearings are leaking and need replacing. I have a 2 ounce hopper as well. its getting plenty of fuel, because I can barely get a hole heat in before running out of fuel. the primary tank is a flat 16 ounce Sullivan. the kind you would find in a sprint cat. so the total fuel is 18 ounces. I have looked for leaks in fuel system by doing a drop test. no leaks. so is it a leaking case/ bearing? thats where I'm going. give me you thoughts.

Thanks

Jim

 

[Duck899]

Bad bearings

 

[James Schmidt]

Runs good and fat on the first 1/2 lap then gets thin. motor not hot. about normal temp.

 

[Don Ferrette]

Standard brass in Sullivan tanks kits is 1/8" which is too small to feed a fuel hungry MAC67. I would recommend changing to 5/32" brass and see how it does.

 

[James Schmidt]

Thanks Rob, I'll tell you this Don that is one nice hard hitting motor you sold me. it sure woke up my cat, its a bullet! I will be changing the tubing too. if going to 5/32 tubing, should I increase the size of pressure fitting on pipe as well?

 

[Andy Brown]

Yep, what Don said. 5/32" brass in BOTH tanks and LARGE fuel line everywhere.

 

[James Schmidt]

Thanks a bunch guys. I really like this engine. she got good power.

 

[anthony_marquart]

If you think you might need bearings.. change them immediately. Seriously,.. I have left them too long before and engine never ran well again..