carb open on bottom?

[prkaye]

I just bolted my carb to the sump. The bottom of hte carb is open (see pic). Does it stay this way? There are four threaded holes around the big opening, suggesting something eventually gets bolted up to the bottom of the carb...

Also, is there a torque setting for the nuts that hold the carb to the bottom of the sump? Or just hand tighten to compress the gaskets?

[N941WR]

Phil,

This is where the FAB comes into play. Check out this picture:


As for the torque, yes, there is a set value for them but my book is at the hangar and I can't look it up. You also want to safety wire the bolts that hold the FAB plate to the bottom of the carb.

[Lycosaurus]

Originally Posted by prkaye

I just bolted my carb to the sump. The bottom of hte carb is open (see pic). Does it stay this way? There are four threaded holes around the big opening, suggesting something eventually gets bolted up to the bottom of the carb...

Phil,

Gasket and carb air box top-plate go there. Take a look at your FWFWD kit, you should find those items there, as well as instructions and a diagram.

You will need to modify the air filter to clear the bottom of the fuel enricher plunger (accelerator pump), as per the instructions.

[OneCharlieKilo]

You'll bolt the airbox to the bottom, allowing filtered air to be provided to the carb:




I used standard torque for that size bolt but don't have the book with me and don't remember what it is.

[alpinelakespilot2000]

Originally Posted by prkaye

Also, is there a torque setting for the nuts that hold the carb to the bottom of the sump? Or just hand tighten to compress the gaskets?

These are coarse thread studs on that hold the carb/engine control bracket on (at least mine from Aerosport are coarse), so make sure you used the proper torque for coarse thread bolts. It is way less than what is called for with the fine thread bolts we usually use.

[RV6_flyer]

Originally Posted by prkaye

Also, is there a torque setting for the nuts that hold the carb to the bottom of the sump? Or just hand tighten to compress the gaskets?

The torque spec is in the Lycoming Overhaul Manual 60294-7.

I do not remember the size. The manual has the following in Table 1.

From Table 1.
Bolts, Screws, and Nuts
Note: Lubricate Threads Unless Otherwise Specified.
Thread - In. Lb.
10 ------ 49
1/4 ------ 96
5/16 ----- 204
3/8 ------ 360
7/16 ----- 600
1/2 ------ 900

Remember that the above size is the diameter and not the size wrench that goes on the fastener. I do not remember if the carb is held to the engine with 1/4 or 5/16. I do remember that the FAB mounts to the screw holes in the bottom of the carb with 1/4" bolts. Van gives your locking tabs with the FAB. I did not use the locking tabs but used drilled head bolts instead. My guess is that the carb mounts to the studs on the engine with 5/16 nuts that use a 1/2" wrench. Remember to calculate the torque value for the use of a crowsfoot IAW AC 43.13.

[az_gila]

Originally Posted by RV6_flyer

The torque spec is in the Lycoming Overhaul Manual 60294-7.
.....
From Table 1.
Bolts, Screws, and Nuts
Note: Lubricate Threads Unless Otherwise Specified.
Thread - In. Lb.
10 ------ 49
1/4 ------ 96
5/16 ----- 204
3/8 ------ 360
7/16 ----- 600
1/2 ------ 900
.......

...specifies the torque values with lubricated threads, unlike the airfame specifications which assume dry threads.....

Gary's guess is also correct - they are 5/16 - 18 size nuts.

[alpinelakespilot2000]

Originally Posted by RV6_flyer

The torque spec is in the Lycoming Overhaul Manual 60294-7.

From Table 1.
Bolts, Screws, and Nuts
Note: Lubricate Threads Unless Otherwise Specified.
Thread - In. Lb.
10 ------ 49
1/4 ------ 96
5/16 ----- 204
3/8 ------ 360
7/16 ----- 600
1/2 ------ 900

Gary-
Thanks for the numbers from the Overhaul Manual. I'm always learning!

Can you confirm that there are no typos in the numbers above? I don't doubt them, except that they are WAY higher (almost double) than the numbers shown in all the charts I've used to date, all of which use the same basic numbers (Van's Section 5, Standard Aircraft Handbook, Cleaveland Tool catalog insert, etc.)

For example, my Cleaveland Tools chart shows the following for coarse threads (all in.#):
10 ---- 20-25
1/4 ---- 40-50
5/16 ---- 80-90 (This is the size, 5/16-18, that holds my carb on.)
3/8 ---- 160-185
7/16 ---- 235-255
1/2 ---- 400-480

Even the fine-thread table is showing numbers well below the numbers you're providing:
10 --- 20-25
1/4 --- 50-70
5/16 --- 100-140
3/8 --- 160-190
7/16 --- 450-500
1/2 --- 480-690

If your numbers are correct (which I assume they are), does this mean we should all have a copy of the Lycoming Overhaul Manual just to follow Van's FWF instructions? (I'm guessing that answer must be yes!)

Thanks Gary.

[az_gila]

204 inch-lbs for 5/16 from my engine manual....

[RV6_flyer]

Originally Posted by alpinelakespilot2000

Gary-

--- snip ---

Can you confirm that there are no typos in the numbers above? I don't doubt them, except that they are WAY higher (almost double) than the numbers shown in all the charts I've used to date, all of which use the same basic numbers (Van's Section 5, Standard Aircraft Handbook, Cleaveland Tool catalog insert, etc.)
-snip

If your numbers are correct (which I assume they are), does this mean we should all have a copy of the Lycoming Overhaul Manual just to follow Van's FWF instructions? (I'm guessing that answer must be yes!)

Thanks Gary.

Copied right out of the manual.