sump screws

[jimgreen]

I have a box of AN4 bolts but not much selection in the coarse thread screws used on the sump.
Can the AN4 bolts be substituted, using all metal locknuts instead of the star washers? It would make it easier to get the right length fastener when including a hose clamp. My sump screws are too short to add a clamp.

What is the relative strength of the two bolts, and would I use the normal published torque value for AN4s?

Thanks for the help.

[mahlon_r]

If you are putting a nut on it and it is for experimental use, I don't see why using a fine threaded bolt should make any real difference. Yes, the fine threaded bolt should offer a little bit more squeeze to the gasket but not enough to worry about. I think if you torque the bolt nut combo to 90-100 inch pounds you should be fine.
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."

[jimgreen]

Originally Posted by mahlon_r

If you are putting a nut on it and it is for experimental use, I don't see why using a fine threaded bolt should make any real difference. Yes, the fine threaded bolt should offer a little bit more squeeze to the gasket but not enough to worry about. I think if you torque the bolt nut combo to 90-100 inch pounds you should be fine.
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."

Thanks Mahlon, and to Kyle for the pm.
Why does the sump need such a high clamping force? It seems it would only need to be snug enough to make a good seal. Is it "structural" adding rigidity to the crankcase?
Also, if I crank an AN4 bolt to 90-100 inch pounds isn't that over torqued? The max on my chart is 70.

[mahlon_r]

In the certified engine world, Lycoming engines use course threatened fasteners in most cases and TCM engines use fine threaded fasteners in most applications that use a nut. Lycoming torques their 1/4-20 course general purpose bolts to 96 inch lbs. and TCM torques their fine threaded 1/4-28 fine threaded general purpose bolts to 90-100 inch pounds. So if you are using a quality aircraft grade bolt with 1/4-28 threads like the AN bolts you have, they should take a 100 inch pound torque fine. I have always torqued 1/4-28 bolts to the same 96 inch pounds that Lycoming uses for 1/4-20..... makes it easy to remember the torque value.
Merry Christmas,
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."