BDC

Got the engine torn down. Yep, big nasty set of cracks on the dowel land of the rear iron housing. Turns out its an older S5 w/ the thinner casting, same with the front iron. Hopefully we can find a newer S5 rear w/ the thicker casting. The front rotor had one collaped corner seal only. Rear rotor had one apex seal that was smashed in the groove but otherwise the seal and the groove are fine. I suspect only the springs were flattened so those will have to be replaced. Both rotor housings fine and smelled like leaded race gas.



Here's the pictures, guys:















B

Comitatus

Overall, That is good news to hear, B. I was preparing myself for the worst!



Since we have to replace the springs...I think I'll go with the OEM Mazdas. I've heard a that the RA springs were subject to some debate when comparing to OEM.

So I'm thinking Replacing all Corner Seals with Solid Atkins, and going with Stock Springs...Hows that sound?



P.S. - Seeing these pics still makes me feel sick, and I want to cry i think

1Revvin7

Any more pixs of the rotor grooves/seals etc? Any data on oil/water/air/exhaust temps etc? I have some speculations, but some more data would help.



I would also like to add that we use MSD wires on a lot of cars in the shop, not prefabbed ones, but we've never seen them fail.

Comitatus

Ok, scratch that...I already have Solid Atkins Corner Seals... But, Mazda OEM seal springs for sure.

BDC

So, any new ideas? My gut still says there's something going on w/ the plug wires but a part of me doesn't sit well with that since they're a high-dollar, aftermarket brand...



B

BNA_ELLIS

I think a combination of timing & the plugs is the cause, but more the plugs.

I'm not sure about the wires. I was about to buy a set of those from summit racing last week, but couldn't get enough info on it and didn't know of anyone else running that wire on a fd so chickened out.

I mapped a car before that had similar issues and it ended up being the ht leads, funnily enough they were brand new ht leads. Put stock ones on and they were fine.



P.S

Post an update on your alky kit, is it all fitted? have you started tuning yet?

BDC

Hey BNA_ELLIS,



I still don't think it's either (timing or plugs) because I've got a good chunk of prior history that convinces me of the reliability of both under the same and heavier-load circumstances. Even though I like to think that every motor I build is "special" (taking pride in what I do kinda thing), as far as his porting scheme and build, it's not really different internally than many of the other half-bridgeports I've done that I've tuned that ran with the same plugs and timing. Infact, on one car, I was running 20* at 20psi of boost with a 5* split. Luke's I had parked at 17* at 18.5psi with a 6* split from what I recall; same plugs. Both running leaded race gas.



My gut still says it's something related to spark, either be it plugs, some weird grounding thing, or something else screwbally that I am unfamiliar with. I've seen this happen on a handful of Rx7's (all 2nd gens now that I think about it) but am not sure what's causing it. I've got a local buddy here w/ a motor and haltech that I built and installed and tuned to lower boost that's got the same intermittent hiccup; same as Luke's at high RPM, very randomly. His power level is still in the mid 300rwhp range and isn't at the point yet of challenging pump gas let alone being too hot for the all 9's he's got plug-wise. I talked to him yesterday about it and he told me that one time when he had his intercooler piping touching his throttle body (underneath the connecting coupler) that it was misfiring badly. He's got that GReddy front mount w/ the intercooler outlet piping that travels right next to the leading coil and leading wires so perhaps there's something there.



/shrug



B

t72fd

hey b, my ports look real good thanks! but anyways, i understand that there was most likely a problem with ignition. but besides that fact, could there have been a tension rod issues causing vibrations and rendering the iron to crack? i also know the fact that, usually a tension rod wich is thinner than cast iron side housings would snap before cracking iron. but its deffinatly a possiblilty to take into consideration.

j9fd3s

the 20b vert ive been working on did the same thing, the ic pipe was touching the #3 L wire, and was arcing, its not something you would have seen with only 1 person either, it took him cranking it and me looking for something else to see it

BDC

I've uploaded a few pictures of Luke's engine bay for reference for anyone who may be interested in playing detective. As it stands right now, I'm at a loss as I've got nothing concrete to blame this failure on.



After checking the pictures out, I noticed the alternator power harness is nearby the plugs and plug wires - Suspect?



B