Head gasket failure on mazda bp engine

hi.

Need some help to diagnos this problem.

The gasket and head has blown between cyl 3-4 and can also see a beginning leak between cyl 1-2.

The engine had new headgasket and used arp studs( not sure about how many times they have been reused, but I suspect at least 4-6 times. )

The head and block has not been resurfaced, the gasket was change because it was running very low compression 8.0:1 and should be around 8.7:1 now.

The engine was running 2bars of boost/300kpa on the Dyno on e75 4000rpm, 13 degrees of timing, 11.3afr when this happened.

Has a timing map from 13 degrees at 4000rpm to 17 degrees 8000rpm at 300kpa.

The timing was slowly increased to MBT was reached, and no knock detected at any time.

My theory is that the head/block has not been completely flat or the head studs have been weak after many times reuse.

It is quite possible that the head and block surfaces aren't perfectly flat, however you are running a reasonable amount of boost and making good power so it's possible that you're still partially lifting the head. Are you just using an off the shelf ARP stud? You may need to step up to a larger diameter stud and use one of ARPs superior materials such as L19. While the normal ARP 8740 and ARP 2000 materials are more than adequate for mild boost levels, once you really start to push the boundaries you may need something better. Unfortunately I've had limited experience with the Mazda BP engine at this sort of power level so I'm not aware if there may be known problems around head gasket seal.

Had the exact same unfortunate experience with mine, between cyl 1~2 during a track day. My conclusion was lean mixture due to a unrestricted exhaust system.

I was lower on power and boost than you, and my head studs were reused OEM ones.The head gasket was the OEM paper style Mazda uses on their 1.6lt engines.

When you are chasing guys at the track only the time matters : )

We are pretty sure its the head studs we are getting new ARP 2000 studs instead of the 8740 and a Athena Cooper ring gasket. Hopefully then the problem goes away.

This was not running lean was at lamda 0.76 at the time so we're actually a bit on the rich side.

@Japac, that's quite a nice job you've done there! In general a blocked exhaust will actually result in a rich AFR as all things being equal it reduces the VE of the engine. That being said, a blocked exhaust can cause other nasty issues too so this could definitely still be your problem. Composite head gaskets are never a good mix for a performance turbo engine though, so I'd definitely recommend an MLS gasket for your rebuild.

ve is around 118 in the map so it dosn´t drop of in high rpm.

this gasket is a composit outer and cooper ring is inox steel with groves, around the cylinders, shold work alot better than mls

or are you thanking about @Rotrexmiata and his case of this ?

think this is one of the highest torque bp engine around at low rpm we are making 600nm at 4000pm, the efr7163 is a real spool monster, and is probely a part of the problem why the head liftet