4 Piece trunk pan install?

[Lowhound]

Im just lookin for any tips on installin my 4 piece trunk pan in my 70 Bee. I will also be adding lower quarter patch panels also. I just replaced the entire front pan & I was planning on plug welding the trunk the same as I did it. Since its a multiple piece pan,I need to make double sure I do it rite.

 

[MoparBill]

I'm assuming you are installing a 2 pc trunk pan and both extensions. I would fit everything up before any welding- trunk pans, extensions, and lower quarter patches. use clamps to hold the extensions to the trunk pan and to the patches. Then use sheet metal screws to hold the trunk to the framerails. Once everything is fit up properly, remove one screw at a time and plug weld it. A bullitt drill bit works well for this- pull the screw and use the bullitt bit to enlarge the hole in the trunk but not the frame.

 

[Propwash]

Bill's got good advice...Once you have everything lined up, either take a paint marker or a spray can and mark the edges where the pans sit on top of everything. That way you can take the 2pc pan and extensions backout and drill your holes for the plug welds adjacent to the paint marks (not drilling into frame rails or shackle mounts), as well as when she goes back in, line up the paint lines to the previous lined up position for a good fit. Remeber 5/16" holes for a solid plug weld when possible.

Good luck!

 

[Pistol Pete]

....and if you're really **** about appearing factory-ish, after you knock down the plug welds and while the first coat of primer is still wet, take a pencil and spin the eraser end in the the substrate to replicate the now missing spot welds. Do this in the same places with every coat of primer and the first few coats of paint. Does this look exactly like spot welds ? Of course not, but it does look more like stock than a completely smooth floor.

 

[snakeoil24]

The eraser idea is insane. Get a life

 

[b-body-bob]

The eraser idea is insane. Get a life

I hope you feel better now that you got that off your chest.

I've heard of people using a round burr to make the divot in the weld ... I think it was a 1/2" burr to make the right sized divot.

 

[hunt2elk]

I hope you feel better now that you got that off your chest.

I've heard of people using a round burr to make the divot in the weld ... I think it was a 1/2" burr to make the right sized divot.

I've also heard of guys using the head of a 16 penny nail in the primer.

 

[wannadrag]

Trunk mat and its never seen.

 

[snakeoil24]

If you grind a plug weld flat you loose all the strength. Using one of those Harbor freight spot welders will not give you fast enough heat to duplicate the 500 amp spot welders used in the Auto plants. Just easier to live with the plug welds and not have them crack.

 

[MarPar]

The eraser idea is insane. Get a life

and you're a douche. so it's even now...

 

[Propwash]

If you grind a plug weld flat you loose all the strength. Using one of those Harbor freight spot welders will not give you fast enough heat to duplicate the 500 amp spot welders used in the Auto plants. Just easier to live with the plug welds and not have them crack.

Spot welds are flat and have no reinforcement, so what's the difference?
A typical factory spot weld on these cars has 50-75% of the 1/4-5/16" diameter weld bonding below.

A plug weld filling in a 5/16" hole not only has penetration further out horizontally from that, but deeper into the adjacent panel as well.

So if you grind it flush, it's still stronger than a factory spot weld. If you grind it out more shallow than the surrrounding base metal, then yes..it will be weaker.

As far as duplicating spot welds...what's wrong with that? Not my cup of tea, but if you got a fella that's wants to remember the car exactly how it was back in the day or has a car worth more than some of our houses, and a eraser mark in the primer makes or breaks thousands of dollars...well dabing the primer in certain spots for three minutes is peanuts..