carb offset question

carguy614 · #1 11-02-2007, 09:47 AM

Hi all...

9A with superior XP 0-320. Getting ready to do up the airbox, and have discovered that there is a great deal of left hand offset with the carb in relationship to the cowl. About 2 inches. Centering it all up will not clear the cowl, and I barely have enough room below the airbox, so it looks like I won't be able to fit the filter bypass, if it clears at all. Looks like I will have to offset the upper filter plate on the square bore carb to fit vans airbox. The carb is a lot longer than all other -4 carbs that I have seen, so a lot of upward crank on the airbox neck will obviously be in order. I am wondering how other builders have solved this issue. Bump out the cowl??? I hope not...

Thanks in advance...Chris

Mel · #2 11-02-2007, 09:57 AM

The offset in the carb is to enable the prop to be centered on the aircraft with the right thrust of the engine. To accomplish this the rear of the engine had to be shifted to the left.
Make the cowling fit the engine.

mahlon_r · #3 11-02-2007, 02:03 PM

All O-320 carbs are the same length. Are you sure you haven't got an O-360 carb by accident? If O-360 carb, the M/N is MA4-5 and P/N 10-3878 or 10-4164-1 instead of an O-320 Carb that is a model number MA4-SPA. The O-360 carb is a few inches longer then the O-320 carb. The offset of the mounting flange, for the carb, on the bottom of the sump, is normal and exists on all vertical Lycoming sumps.
Good Luck,
Mahlon
"The opinions and information provided in this and all of my posts are hopefully helpful to you. Please use the information provided responsibly and at your own risk."

N941WR · #4 11-02-2007, 05:20 PM

Quote:

Originally Posted by carguy614

...so a lot of upward crank on the airbox neck will obviously be in order. I am wondering how other builders have solved this issue. Bump out the cowl??? I hope not...

Thanks in advance...Chris

Chris,

This is normal. The one O-320 powered -9A in the area had to turn the snout to the right and bend it upward to line up with the inlet.

FWIW, on my O-290, this was about the only thing that worked in my favor. Other than canting the FAB towards the opening, it was a straight run. Of course, my MA3 carb is a good bit smaller than your MA4.

BTW, this should go fairly fast. It sounds like you are really moving along!

joeboisselle · #5 11-02-2007, 07:46 PM

Quote:

Originally Posted by Mel

The offset in the carb is to enable the prop to be centered on the aircraft with the right thrust of the engine. To accomplish this the rear of the engine had to be shifted to the left.
Make the cowling fit the engine.

I just discovered this on my -4 this evening...(i had to buy a new cowl

) if the lower cowl isn't level it will offset the air intake significantly. On my first cowl (

) I attempted to cut and re-fiberglass the air intake on the cowl to the air intake/filter thing... that don't work! Mel's got it, make the cowling fit the engine. And, if you can, six hands work better than two on the lower cowl.

carguy614 · #6 11-03-2007, 04:29 AM

Quote:

Originally Posted by mahlon_r

All O-320 carbs are the same length. Are you sure you haven't got an O-360 carb by accident? If O-360 carb, the M/N is MA4-5 and P/N 10-3878 or 10-4164-1 instead of an O-320 Carb that is a model number MA4-SPA. The O-360 carb is a few inches longer then the O-320 carb. The offset of the mounting flange, for the carb, on the bottom of the sump, is normal and exists on all vertical Lycoming sumps.
Good Luck,
Mahlon
"The opinions and information provided in this and all of my posts are hopefully helpful to you. Please use the information provided responsibly and at your own risk."

Hi Mahlon.. Indeed my carb is marked MA4-5 PN 10-3878 so it may be the wrong one. Are you sure about these numbers?? If so, I guess a call to Superior will be in order.

Thanks a million...Chris