I have a plan. Could do with a bit of feedback though to make sure it doesn't end in tears. The plan is to shorten a Ford 2.9 V6 EFI intake manifold and plenum so they fit a Cologne V4 engine for one of my Saabs. I've done my homework, all relevant ports and channels line up and I'm convinced I can make it fit. I need to hack a 12 cm piece out of the plenum and the manifold (that's how much the V6 is longer than the V4), and then the remaining pieces need to be welded back together. The cooling channels need to be modified too. I'm set up for MIG welding aluminium, but I've never had much luck with it despite having a decent welder, gas and wire, so it must be lack of skill. I don't have a TIG welder myself, nor do I have any experience with TIG welding aluminium, but fortunately a mate is happy to do it for me. I've read a few threads on this forum on welding cast aluminium manifolds, but I still have two questions. Comparison between a V6 manifold and a V4 one, it's clear it isn't a bolt on conversion! So this is the idea, V6 manifold/ plenum in the first pic, rough Photoshops of the envisioned end result in the following two. After cutting out the middle, I can bolt the pieces to a jig (e.g. a thick piece of flat material, or maybe safer, an engine block) and align them, and then tack them with the MIG so my mate can fully weld the manifold in his workshop. My first question is, how much warping should I expect after TIG welding the halves together? I will have the contact surfaces machined after welding, but there's not that much leeway because the manifold can't sit too low between the heads. Then onto the cooling situation; the V4 has a coolant channel under the inlet that the V6 doesn't have. Fortunately there's empty space there and blind ports have been cast in and machined, so it looks like I can modify it to do what I want it to. Before cutting out the middle of the manifold, I'll remove the remaining cross web with a die grinder, and mill down the ones that run along the length a few mm so they're flat. I don't have a mill, but a jig and a router has worked very well for me before on aluminium (decent router bit or carbide burr and plenty WD40 as lubricant). The idea is then that a "lid" (approx. 60mm wide) can be welded on when the two halves have been welded together, as per the following pic (the piece that isn't filled in will go). My second question is what grade aluminium I should use for the infill piece. It probably doesn't matter much for strength, but it might do for bonding to the cast aluminium? Can't do with cracking welds as it need to be fluid tight. Not sure if corrosion resistance matters because there will be coolant flowing through it? I think I'll just look for a short piece of flat stock on eBay, 3-4mm max thickness should be OK I'd think? Maybe I'm overthinking this (or quite the opposite!), I just completely lack experience in this domain. Thanks in advance for your feedback!