Hello. I will be having my engine rebuild soon and I wanted some opinions on these housings. There are some visible cracks on both housings. The cracks dont really catch my fingernails at all. There is also some wear along the housing. Its a jdm engine; i do not know the mileage.

Plans were to go single turbo (bw s362). Im not interested in tracking the car; just street use.

Are these good enought to reuse? One reputable shop said they would prefer other housings while a different, reputable shop said these are okay for my use.

Front housing
The crack to the right measures roughly 5mm. The one to the left is about 3mm.






Rear housing
about 7mm and about 4mm

 

They're within Mazda's 11mm spec.

 

I told you your housings are fine Rick!

 

They're not perfect but they're fine. I would have them resurfaced as they were ran hot and the liner will not allow a perfect seal. PM was sent...

 

how bad is it to run housings with small hairline cracks in the spark plug holes? especially for a goal range of 380-400 hp ?? and does Mazda really have a max tolerance for these cracks??? any info would be greatly appreciated

 

Cracking there is typically caused by running too much boost on too hot of a plug. On higher hp cars I've seen the cracks get larger really quick and the chrome lift away hitting the apex seals. Personally I will not use any housing in my shop with cracking on anything but a very low hp goal and then the customer is made aware that it is not ideal.

 

its in the shop manual

 

FD Ricky - Try talking to Dan at Garage Life in El Monte. He recently rebuilt my motor and we ran into the same issue. We ended up replacing both rotor housings.

 

Here's where the decision comes in. There are other things you can spend the money on besides replacement housings. If you don't have an ample budget already for say a fuel system, engine management, tuning, intercooler, etc you have the option of reusing the housings and shifting the money to other priorities.

You can destroy brand new housings pretty easily if all the other stuff isn't done right at the same time and the engine fails. So think long and hard about how much money you are planning to spend on this build and how best to allocate it. In your situation my personal opinion is that replacing those housings is a "nice to have" but not "necessity."

 

In my opinion its best to put the majority of your budget into the motor and be done with it. If it takes a bit longer to accumulate the funds for everything else, then wait or lower your power goals. The whole build will be for nothing if you don't have the right foundation, and that starts with the motor.

 

I would work on the root cause of the problem.
Port the water jacket at the #5 passage (or have Jonathan at Gorilla Racing do it for you If you are not comfortable doing it).
I think I would reuse the housings adding a shallow football shaped depression at the cracks.
(But new housings would be better but expensive... and with time will look exactly like these if you don't do the cooling mod.)
Barry

 

I could not have said this better myself. From build numerous cars in the past, this has always been the case!