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Carburetor Stud Locknuts?

nippaero

nippaero

Well Known Member
I have a couple questions on securing my carb to the sump on my O320.

What type of locknut or washer should I be using? The Lycoming manual shows a plain washer, nut and STD-1763 locknut (palnut).

Second question is what torque should I use on the four carb nuts?

I found an old thread for an O360 using the following. Is this accurate?

AE9887-5 4 Nut, Hex, Lock, 5/16-18 UNC 204 in.-lbs.
AE51412-5 4 Washer, Plain, 5/16 ID
AE51413-5 4 Washer, Internal Star, 5/16 ID
 
Yes.

That's correct. Those are studs on the engine. If you use locknuts they may grip the studs too tight when you remove them. If you look at the rest of the engine many things are mounted the same way, such as the mags, exhaust, vacuum pump, and governor. Washer, lock washer, and nut.
I do put torque seal on them so I can quickly see if they have moved (except for the exhaust nuts).

Vic
 
Carb installation

I saw a carb installed on a Lycoming 0-320 yesterday with no gasket between the two. Is this correct or is a gasket required?
 
a gasket is specified and required between the carburetor and the oil pan/plenum. Look at enough installations and I am sure you'll find all sorts of thing done incorrectly.

Larry
 
Yes. I have a gasket between each one. You want a good seal. The bracket I bought from Vans included an extra bracket.

Thanks guys!
 
I like to use a little gasket dressing on each one...not a sealant per se but a product that softens them up a bit to help them conform.
 
I'm searching for the torque on installing my governor on an IO-390 and the studs are 5/16 - 18 UNC also with a flat washer and internal tooth lock washer. Will 204 in. /lbs. apply here also or does some other factor come into play here?
 
Ron B. said:
I'm searching for the torque on installing my governor on an IO-390 and the studs are 5/16 - 18 UNC also with a flat washer and internal tooth lock washer. Will 204 in. /lbs. apply here also or does some other factor come into play here?
Click to expand...

This table for standard Lycoming torques may help -

lycoming-torques_zpsd981c236.jpg
 
Perfect , exactly what I was looking for and could not locate. I will print this off and place in the hangar.
Thanks Ron
 
The Lycoming document states "lubricate threads unless otherwise specified." I know that anti-seize/lubricant is used on exhaust studs/nuts, but what about other studs/nuts, like the governor and fuel injection servo? If they *are* lubricated, what lube should I use?

Dave
 
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