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Alloy sump for strength? Similar to dowels?

Old 03-14-19, 10:48 PM
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Alloy sump for strength? Similar to dowels?

Hey guys,

Was hearing from my engine builder that engine sumps made from cast (10mm) can further strengthen the engine much like dowels and stud kits?

Was wondering if there was any benefit to help. Stop the engine from twisting. And potentially unlock some more boost or engine protection

Have found some sumps locally for a good price.

Can anyone think of any pros and cons?

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Old 03-15-19, 09:08 AM
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i'm sure it helps, not sure by how much.

the other data point is that this is what Mazda did, they run a thick sump plate with bigger bolts. then they added a top plate, which is a CF sandwich
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Old 03-19-19, 09:09 PM
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Without any data to back it up, I'm confident they have an effect, but it needs to be thick enough to prevent the engine from twisting/stretching.

There's quite a few threads on this on AusRotary, as in Australia we've tended to go down this road than the custom sump path. The consensus seems to be that the bracing should be 10mm or thicker to have an effect. The thin baffle plates made by Mazdatrix and Racing Beat will act as a baffle, but are probably not effective as a brace.

One of the first people I saw to release a 10mm+ thick baffle plate was Rohan Ambrose/Guru/Xtreme Rotaries - who also happened to be one of the first (if not the first) to experiment with high tensile strength studs (whereas before everyone else was playing around extra dowels). I trust what Rohan recommends on anything to do with building a reliable powerful engine. Rohan built my first 10mm baffle plate on my old engine setup - which I got in around 2005, and I'm pretty sure he was selling those plates in the very early 2000s.

However, it really depends on the engine we're discussing. The series 4 13B engines crack for a specific reason - due to the weak/insufficient material around the dowel below the oil filter. Bracing the engine at the bottom, probably won't act as much as a band-aid for the design flaw at the top of it. Series 5 and later blocks are much stronger by design but can still crack through general stretching and twisting - in those cases, the extra bracing from a sump plate might help more, noting that an FD 13B-REW can handle a lot of boost/torque without any form of dowels/studs/bracing so long as it is properly tuned and doesn't detonate.

You may have seen in my build log that I got a custom plate made by Green Bros Racing in NZ - 10mm billet aluminium with grooved o-ring for better sealing. How much it will help, I don't know, but I certainly don't think it can hurt - it will at least help as a sump baffle.
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