www.RX7fb.com

I'm sure Jesse will have far more to add, but this is actually a common failure point in turbo engines. As the engine produces torque, that torque is trying to twist the plates and housings from each other, and the tension bolts and dowels are holding them together. The area of the rear plate around that dowel is the weak spot and is first to go usually, and on later engines they added more material in the casting in that area. Also by mounting these engines in an FB with the front cover being the only engine mount, the whole length of the engine is trying to twist, whereas later FCs and FDs mounted on the centre plate, then the rear plate, which also reduces the torque being put through the engine "block" as the rear iron is constrained. Bit of a right of passage really, breaking irons, when running decent power on a turbo engine! A lot of people get bigger studs instead of factory tension bolts, solid dowels and run an external oil line to solve the issue as well.

I feel your pain mate... Hope you get it all sorted out and back in no time

Sorry to hear about this. Yes unfortunately it is a common failure point but moreso in series 4 blocks and i think perhaps early series 5. Mazda thickened the casting in that area in later engines. But if you up the boost, the rear plate in later engines can still crack.

Pretty much everything James said.

This is now a chance to come back better and stronger than before!

In addition to higher tensile strength studs, the block can also be stiffened using a sump baffle plate. This really needs to be at least 10mm thick to make any appreciable difference...most of the US ones are only 3mm.

I got a billet 10mm one with integrated o-ring from Green Brothers in NZ.

Sorry to see this mate

That's awful to hear after all the work you've put into this. Fingers crossed you can it rebuilt stronger and back on the road before too long.

KYPREO wrote: ↑Wed Nov 11, 2020 9:18 pm In addition to higher tensile strength studs, the block can also be stiffened using a sump baffle plate. This really needs to be at least 10mm thick to make any appreciable difference...most of the US ones are only 3mm.

I got a billet 10mm one with integrated o-ring from Green Brothers in NZ.

Very good information Greg. My first thought was the us baffle plate. The plate with integrated o-ring rocks the scene.

Bloody hell Jesse, sorry to read this

Yeah nah .. Stink as bro. I''ve heard about that failure point but have never actually seen it. At least plates are somewhat easier and cheaper to source than rotor housings, Still sux though man

Sorry to read this, these cars do test us.