What to modify in a Mac 32cc
 

ok, so my mac 32 is a bit underpowered stock for my 15.5 pound extra 330, so it's been apart for a while waiting for me to take the time to play with it...

so far I've removed most of the nub in the intake port, and I got some aviation seal to seal the jug to increase compression a bit, and while I have it apart I might as well get a bowman ring and pin it... my only other plan is to open up the transfer ports with the dremel and probably compensate for the lost gasket on the exhaust port. I'm going to go a bit oversize on the carb, just a couple 64ths though, I think it has a 20 or 24 now, I've also modified the stock muffler to have a single 1/2" exit and removed the baffle

I guess I'm looking for ideas on how much I should modify the ports and what the best things to do would be. I'm looking to keep this easy starting and reliable

if porting doesn't work, I'll go gas/glow as it's a bit nose heavy anyway, or I'll swap to the homie 30cc I have...

Thanks!

I have searched and have looked at the "don't forget about echo" thread, haven't found much specific to the mac 32 or 28, or anything mentioning easy starting or reliability... I don't have a degree wheel yet and don't really want to go that far, just get it breathing a bit better...

RE: What to modify in a Mac 32cc
 

Change your carb first. and get a new Ring.

RE: What to modify in a Mac 32cc
 

The original carb is a 24. About the biggest you can use is a 32 or 1/2" carb

RE: What to modify in a Mac 32cc
 

You can download the degree wheel and print it out. Do a search to find it and other good stuff. Capt,n

RE: What to modify in a Mac 32cc
 

You're on the right track. I would recommend two exhaust outlets however.

I'm a little worried about the "nub" you took out of the intake port. My Mac 32's aren't handy to look at right this moment to check, but many times there is a little nub in the intake port that prevents the piston ring from popping out into the intake port at bottom dead center. If that's the one you took out it could be a problem.

What prop and rpms were you getting before?

AV8TOR

RE: What to modify in a Mac 32cc
 

He did say that he was getting a Bowman ring and installing a pin. Make sure the pin keeps the ring ends away from any ports... thats the purpose of it.

RE: What to modify in a Mac 32cc
 

Yes, I know, and that will keep the ends of the ring from getting caught in the exhaust or transfer ports. However, if the ring travels below the top of the intake port at bottom dead center, it can bulge out into the port and damage itself. That's why there is often a "***" or "nub" in the top of the intake port; to prevent that from happening.

AV8TOR

RE: What to modify in a Mac 32cc
 

I didn't cut it all the way out, just most of it, if I screwed myself over, I'll chamfer it back to good...

I used some DOM 1/8" wall tubing that I had for the exhaust, 2 of them seemed heavy so I used one, but of course after I made it up I realized I had some 1/2" conduit... one 1/2" outlet had to be better than the single 1/4" outlet it had originally...

the rpm's are low, sounded in the 5000range but it's been about 3 months since it was flown and I didn't have my 9Z radio then (no tach until about 2 months ago). that was with a 18-8 master airscrew classic black composite, I just got a 18-6 classic so if what I've done doesn't help all that much I'll throw that on and see what it does. low selection of 18" props and I opted against zinger from what I've seen here, and it cost as much for a fragile wood prop as it did for the composite...

RE: What to modify in a Mac 32cc
 

I've had the best luck with the APC props, and run them almost exclusively on all my stuff.

AV8TOR