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MG MGA - Bolts missing

I removed both front wings recently in order to prep them for a new paint job. While looking over the sections under the wings forward of the "A" post and nearer the wheel arch, I noticed the 4 bolts that typically bolt through the reinforcement channel were missing on both the left and right side.

I will install the proper bolts, but can someone tell me the purpose of the reinforcement channel? The missing bolts were likely missing for 25 years, because that's when the car was last painted. I have never noticed any issues while driving the car without the bolts.

Thanks,
Fran

PS: I posted a photo from MOSS to show the channel in question. It is number 24 on the diagram

F Valenzano

Those are body mount bolts.
Del Rawlins

Fran, it is to reinforce the flat sheet metal of the body , presumably from the forces that would exist if you lifted off the body and rested it on the floor. My opinion only.
Art Pearse

Parts drawing above: Item 24 (shallow channel) is spot welded to item 21 (inner fender). Four bolts pass through this assembly and screw into the side of the frame goalpost. See photo attached. Due to contour of the surrounding body panels, this channel is probably not required as a body panel stiffener, but has a different purpose.

This is a key structural point where the body attaches to the frame. The only other body to frame bolts in the vicinity are front of heater shelf (not structural, only to seal the cork gasket joint) and one vertical bolt at bottom inside just ahead of the A-post. Screwing this channel and inner fender to the frame effectively combines the body and frame as a single structural assembly for greater rigidity. This isn't to keep it from bending or breaking, but to increase stiffness to reduce shaking and vibration. Specifically it will go a long way toward reducing or eliminating scuttle shake on a rough road. Screwing the body tight to the frame reduces the need for additional body stiffener braces.

I think the real reason for the channel is to increase thickness of the sheet metal on the inner fender. Without the channel the local structural load on the sheet metal from the bolts and vibration might lead to stress cracks in the sheet metal and failure of the mechanical joint. The shallow flanges on the edges of the channel will keep it straight (in plane) during the spot welding process. Installing those bolts is highly recommended.


Barney Gaylord

Thank you all for the insight and input. I have located the proper bolts and will be installing same in advance of re-hanging the wings.
F Valenzano

I am looking at these same bolt holes on my car. I have mounted the fenders, but did not bolt those holes. What goes there, just a body bolt and washer in each one?
Thanks,
Harley
Harley Johansen

According to the SPL:
(10) HZS0508 5/16-24-UNFx1 Hex Head Screw, zinc
(10) LWZ205 5/16 Medium Spring Lock Washer, zinc
(10) PWZ205 5/16 Standard Flat Washer, zinc
* ("Screw" means full length thread)
The 5th one each side goes inside, vertical at bottom just ahead of the A-post.
Barney Gaylord

Barney -

Aren't the "screws" you listed 5/16-24 the same thread pattern as the fender mounting bolts "screws" sans the pointed end?
F Valenzano

Barney, Thanks for the advice. I got the bolts in. I almost sent a picture and question about the two deep-set threaded holes on the top and then I saw they line up with windshield mounts. Duh! So progress is being made:)
HJ
Harley Johansen

Fender bolts originally have pointed tips and a different part number. Original part number for the side bolts indicates no point. Not that it matters. Even for concours show no one will look inside the frame box to see if the bolt is pointed or not. Marking on the bolt head would be more important for concours originality (an interesting proposition in itself). See here: http://mgaguru.com/mgtech/restore/rt104.htm
Barney Gaylord

This thread was discussed between 18/07/2010 and 21/07/2010

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