Can I drill a 2" hole in a 5" C Frame?

Need to drill a 2 inch hole in the center of the 5" C frame on my F100. I can weld in some reinforcement but do I need to? Truck is already built (in avatar) so avoiding reinforcement would be nice.

 

Yes..............and I would not think a reinforcement is necessary

 

If you do that, you'll only have an 1.5" on top & bottom of the hole (as I'm sure you figured out). I'd box it for sure and probably sleeve the hole between the two sides.

It probably depends on where on the frame exactly the hole will be if it'll crack or not, but I wouldn't risk it.

But...that's me.

 

Could you drill the hole in a smaller diameter, and flange the hole (increasing the dia to 2") ?
This would lessen the loss of strength in the C rail.

 

What is it that you are trying to do that you need to drill such a large hole in your frame? Maybe we can help you come up with some alternate ways of doing it.

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I need to run the fuel fill through the frame for an under bed tank

 

A 2" tube would be plenty big. Make it a 2 1/2" hole and you are safe.

 

Why would you need a 2" hole for a fuel line?,,better yet can't you find a different section of the frame to do this?

I have fuel lines on all my cars running down the inside of the frame. HRP

 

Fuel FILL...................

 

Fuel tank filler tube, Danny.

Where does the hole need to be in relation to your suspension pickup points? if there is little stress on the frame where you want to drill it, then there's no problem. But if it's a stressed member, I'd sleeve and box it to be safe.

 

My bad,,looks like the new specks ain't a bit better than the old ones. HRP

 

Roughly at rear axle.

 

And you're running leaf springs? If so, that's THE worst place to drill the hole. The bending moment there is at its greatest.

 

yes, leaf, tend to agree with you.

 

I suppose if we saw some pictures it would be easier to understand why you feeling going through the frame is your best option.

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Can you change the location of the fill tube to avoid this?

 

It has been through the bed since 2007 because I couldnt stomach drilling a hole in a brand new steel fender. Now I can.

 

You could do the hole, but weld a 3/16" plate on easiest-to-access side of the chassis. I'd think of using a 4" x 7" piece of steel with a few rosette welds for good measure.

Bob

 

Why not do a c-notch ... inverted if you have to? Just did this to a f-100 frame. Is the pumpkin going to clear you tank?

 

Sounds logical
...and I laughed out loud at your signature!

 

Tank is between cab and rear on drivers side.

 

How much space is between the bottom of the floor and the top of the frame? If its 1 1/2 inches, you could fab up a flat piece of metal with your two inch ends, sort of like a Nascar exhaust outlet. Make it fit available space. Add the overflow to the filler separately instead of inside.

 

The bending moment of the frame depends upon the distance between the top cord (the upper flange) and the bottom cord (the lower flange). The frame doesn't care if it's got a 2" hole in it or not!!!

 

I'm no engineer but I would tend to agree. Don't many hot rod frames have such holes up front for lightening/looks?

 

Dave, I'd sleeve it.. use welders leather to curtail any sparks from getting where they shouldn't. How's the Hudson coming?

 

Oval pipe so the hole is wider then it is tall. You retain the strength in the frame better this way. With enough oval, you may be able to snake it over top of the frame.

Joe

 

That would make me nervous

 

Chopt top is right. Put a 2" hole and move on.

 

Drilling the hole changes the section modulus and the radius of gyration , Modify the top and bottom flanges to compensate for the hole in the channel 36fordguy.

 

Why not neck down to a 1 1/2" filler tube? Then use a 1 3/4" hole saw.

Or you could use a 1 1/2" hole saw, and weld in that short section of 1 1/2" filler tube, (thick wall), then box and weld that tube in for reinforcement. Then connect it up with rubber hoses and hose clamps.