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Cut and shut bellhousings opinions

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Hi guys, just curious on the pros and cons of a cut and shut bellhousing for a gearbox conversion for a dedicated track car. What are your thoughts?

I've heard a lot of people dont recommend it but i personally don't see any problems. In saying that, my car knowledge is very basic.

Cheers for your input,


I, personally, wouldn't use one unless there was no other option. There are many conversions available now for manual gearboxes and even for automatics (new bellhousing not just adaptor plates although they are a good option in themselves) that unless you have an oddball conversion I don't see the need for cut and shut bellhousings.

So im actually talking about removing a manual gearbox frommy sr20 and replacing it with a manual gearbox from a nissan skyline r33. I've heard alot of people not wanting to go this direction but can you tell me why you wouldnt? What risks are involved?

A couple of reasons.

1. As already explained there is a wide variety of adaptor plates and complete bell housings in the after market to do many swaps.

2. Taking 2 separate housings, cutting them, and welding 2 separate parts back together requires precision.

Have you checked the Castlemaine Rod Shop , or any other conversion specialists, to see if they do a conversion housing?

are those dealers NSW based?

The issue with any adaptor is ensuring the input shaft and crankshaft are 100% concentric. The tolerance you can get away with is remarkably tight so it needs to be done very precisely. A cut and shut on a bellhousing is a viable technique but it adds one more element of complexity where the alignment may end up off in another plane. Welding the bellhousing will also potentially result in distortion. If you're planning to go down this path I'd recommend having the finished product machined to ensure the block face and gearbox mounting flange are 100% parallel.

The adaptor plate is a probably a nicer approach but you also need to be careful you're using a quality adaptor plate - Just because you have a nice shiny cnc'd adaptor plate doesn't mean it's concentric either.

awesome, thanks for that!

awesome, thanks for that!

Castlemaine Rod Shop (CRS) is based in Castlemaine Victoria. http://www.rodshop.com.au/

There is also Dellow Automotive (I've read mixed reviews about Dellow). Their website seems to be offline atm so google them to see what's around. They are in NSW (Silverwater I think)

thanks Michael.

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