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Old 02-23-2015, 07:26 PM   #1
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Default Engine Swap, custom pan vs custom subframe

Hypothetical question of the week time.

Say you were going to buy an engine swap kit would you rather have a custom cast oil pan and use the stock subframe and have the kit mostly consist of engine mounts. Or would you rather a tubular subframe that uses all NB geometry, use an OEM oil pan and stock style mounts from the motor in question?

Pan pros
$400 cheaper

Pan cons
Ships from europe

Subframe pros
lighter
stiffer

Subframe cons
$400 more expensive
Might not be legal in your racing class

The 3rd option is throw money to the wind, spend an extra $400 over the subframe option to combine it with the custom pan and mount the motor an extra inch lower.
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Old 02-23-2015, 07:35 PM   #2
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Pan cons seem less.
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Old 02-23-2015, 07:40 PM   #3
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It all depends on budget. Assuming the fitment and quality of both options are adequate.
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Old 02-23-2015, 07:48 PM   #4
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Why cast pan? Why not sheet metal? There are a bunch of people that make pans in the US (Milodon, Moroso, Canton, etc) and I would assume all of them can do a short run of custom pans.

As long as the pan doesn't have a compromise that we're not seeing cheaper is better.
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Old 02-23-2015, 07:58 PM   #5
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Pan is a structural member of this particular engine. I'd rather not have a thin sheet steel pan doing that job. The only compromise I can see for the pan option is that doing the subframe option you gain a stiffer and lighter by ~10lbs subframe. And $4/lb is worth it to a lot of people. But if you go with the oil pan option then it would still work with an off the shelf tubular subframe.
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Old 02-23-2015, 08:00 PM   #6
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No reason to redesign the wheel on the subframe part. If I did a swap and I had the option to keep OEM everything besides the engine it would be a no brainer. One of the FE3 guys actually swapped in a 1.6 in a day when he blew his FE in california.
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Old 02-23-2015, 08:51 PM   #7
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Assuming you're starting with a street car engine, probably a custom oil pan. The ability to improve oil control, probably better QC, and simpler assembly makes a solid argument. Now if using the stock subframe requires a less optimized oil pan, that would be bad. Also, if it's really designed for track work options for a dry sump (and maybe the new subframe to go with it) would be a vote towards a new pan(s).
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Old 02-24-2015, 10:24 AM   #8
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Does this imaginary tubular subframe have stock Miata engine mount points? That would permit the "return to stock".
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Old 02-24-2015, 10:28 AM   #9
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It could. It seems like the most sensical thing to do would be to just offer 2-3 height mounts or mount adapter that all work with the stock miata subframe mounts. 1 is stock subframe and low pro pan and also tubular subframe and OEM pan, low pro pan + tubular subframe, drysump pan + tubular subframe.
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Old 02-24-2015, 12:28 PM   #10
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It would make sense to produce the subframe with stock mount locations and the ability to accommodate a variety of engines. Then produce mounts to adapt each engine to the subframe. That's win for the buyer and builder. Otherwise you have a custom oil pan that fits one engine.
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