The long tube Hooker header flanges get real close to bottom edge of the deep 904 oil pan. I am working on re shaping the pan in one section to allow for proper clearance.

The cut out provides ample room, my welding skills are adequate, but to get this done the best way possible, I have a few questions.

1) the cardboard templates will be used to size the pieces to be welded in, is there an advantage to making the long sides on the rectangular piece
maybe 1/4 inch longer to do a lap seam,, or would a butt weld be fine? The cuts in the pan are pretty straight, there will be some small gaps, but I believe I can
cut the weld in pieces to just about snap in place.

2) If all butt welds I know that I can get all but one seam welded from inside the pan, the wing close to the end may be too tight to get the weld tip in...
If I have a choice, does it make a difference if the welds are inside or out side the pan for sealing? I plan to gravity leak test the welds prior to re installing.

_________________
Doo Ron Ron and the Duke of Earl are friends of mine.....
https://www.youtube.com/watch?v=uX8Nj8ABEI8

I don't think I'd limit myself to welding only on one side or the other. At each length I'd weld on whichever side was easiest.
Spend extra time on the filler pieces getting a real nice close fit.
The ideal thing would be to TIG weld it. With a great fit little or no filler would be needed.

When I've done similar mods in the past I usually coat the inside of the joint with gasket sealer as extra insurance against leakage.

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--> Check out my FI Turbo build <--
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When Robbie made my deep oil pan and Ryan's new one he welded both side. No sealer needed. I would be sure the pan is bolted down tight or go slow to avoid warping. He also blasted the inside of the pan also to get any slag off from the mig process.

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2 Mopars come with Spark plug tubes. One is a world class, racing machine. The other is a 426 CI. boat anchor!

12.70 @ 104.6

I have a MIG and have welded pieces thinner than this, but that job did not require being leak free.
Good tips on welding where the access was best and or both sides.
Thanks

_________________
Doo Ron Ron and the Duke of Earl are friends of mine.....
https://www.youtube.com/watch?v=uX8Nj8ABEI8

When I butt weld, the gap gets swiss-cheesy...........

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

A piece of copper plate held tightly to the back side of the joint can make it easier to get a good bead.

_________________
--> Check out my FI Turbo build <--
--> And the race truck build project <--
--> The Diesel Corvette <--

a finished part update

Welded the plates in on both sides as recommended,
then checked for leaks with water, there was very slight seepage that would wet a paper towel under the part after an hour +.

I then applied a coat of the Loctite 290 on both sides, that is the wicking Loctite that is intended for sealing welds or locking threads on parts already assembled.
Rechecked with water and there was no seepage.

https://www.henkel-adhesives.com/us/en/ ... e_290.html

For an an additional sealing I painted the welded areas with a coat of red Glyptal
Then sprayed the pan with black enamel

_________________
Doo Ron Ron and the Duke of Earl are friends of mine.....
https://www.youtube.com/watch?v=uX8Nj8ABEI8

Nice work!