The FM manifold woes
 

About 4-5 months ago I sent my manifold back to FM because two of the studs broke off inside of it. This was after less than 6-7 months of driving. short story short I sent it back, paid $100 for a new manifold and hardware.
A couple days ago I took the heat shield off the turbo to fix the rattle coming from my wastegate actuator.
That's when I noticed that my manifold was missing two bolts, I figured that they just backed out, and there's no way they could have broken off again. So I call up FM and order the stage 8 hardware. I get the turbo and manifold off, Just my luck, I find that the studs didn't just back out, they of course broke off yet again. :vash:

Has this happened to anyone else? Did I over tighten the bolts?? Is it because there's no flex pipe in the exhaust?? Seriously WTF?!

To prevent this from happening again I suppose I have no other option than to upgrade to the M10 hardware.

If I add a section of flex pipe to my exhaust is it going to help?

So you're saying that shit rattled loose, you didn't tighten it, and then the weight of the turbo broke it? I've drilled so many studs out of my manifold I can't even count anymore. You can either drill the studs out and re-tap, or upgrade to M10 and safety wire it.

What kind of nuts are you using?

Just backoff on the preload. If your snapping the middle ones off, and the outer ones are fine, then your flange isn't being loaded the same anyways. Maybe try 50% the torque on the center bolts compared to the outers. The metal has to have room to "breath" when it gets hot. It doesn't matter if you put the unobtanium alloy bolt on there its still gunna snap under thermal stress.

Another thing, the thermal cycling kills all the heat treat those bolts get anyways. It forms whats called martensite when it cools. Really hard, and really brittle great for snapping, and not flexing like they should.

As far as I know they never came loose, they just snapped. I actually heard one fall off but didn't realize what it was. Both times it's been with the hardware FM sends.

I'm tempted to drill them out and re tap them myself, I tried this last time.. It ended badly.

These are the four that hold the turbo to the manifold. More specifically the top left and bottom right. Last time I think it was the top two.

I thought you were talking about the flange... Thats really strange... I would go with less torque on all four. If they are getting bound enough to break, they are way too tight at that temperature. It would be interesting if you could get them out of there undamaged to see if they are necked or cracked. If they are cracked, thats a good sign that they are loosing their ideal fastening characteristics. What do the other 2 studs look like? Any necking? pulled up threads? Do the nuts go on easy or do they hit a rough spot just below their normal engagement area.

The two unbroken studs came out fine, I havent taken the nuts off them yet, I'll go snap some pics..

Here are some pics. The studs that didnt break look fine.. The nut screws on and off with a normal amount of effort.

With the close up shots it looks like it took a bite out of the manifold when it broke??

how do OEMs keep this shit from happening?

It might be worth trying an easy out on the broken stud. You can buy the kit from Sears.

The bit is reverse threaded, so you drill into the stud, and then back it out. I've had about a 50% hit rate with the easy outs. They either work or snap when you try to back it out...

They use real life engineers. :laugh: Use a gasket so that there is a little more flexibility in the joint, and use less torque. Everything is just too brittle because of the heat cycling. Preload is based on rod stretch, and things don't stretch willingly after a bunch of heat cycles.

If you stretch the rod bolt an inch maybe thats the perfect preload and its just right. After a few hundred heat cycles, and it is stretched at that same inch it will snap because its harder then it was before so it needs less stretch to hit the same preload number. So basically with every heat cycle your are tightening those studs. Those busted female threads only reinforce that line of thought. That takes ridiculous amounts of pressure to do.

It's kind of funny. I hadd read lots of threads about studs breaking and nuts coming loose when I was building my mani.

What I ended up using is a Holley carburetor mounting stud kit from Advance Auto in 5/16" (essentially 8mm) as my weirtech flanges were tapped 5/16"-18. I don't have a ton of miles on it, but a lot of heat cycles. No breaking and no loosening of nuts. For the studs, they were long enough to go through the flange so I screwed them in snug and then tighetened another nut on the back as a lock nut. For the turbo side, I'm just using the nuts and lock washers that came with the kit. That side is fine thread (5/16-24), though, and I think that contributes to my stuff staying tight.

Drill it out and tap it, then go down to a fastener store and order grade 12 or 14, its not horribly expensive. You wont be able to brake that, I use grade 12 on my turbo studs, and down pipe flange. Grade 12 is what CAT uses on most of their stuff the 14 is just a bit stronger, you wont be able to get it every where and some might say it doesn't exist but if you go to a good shop they can get if for you.

I actually have a gasket that goes between the turbo and manifold, I didnt use it again after the first time they broke.
I'm going to try backing the broken studs out.. Hopefully I wont screw it up like last time..

Will report back with results.

Cant tell, but is it a cast iron Manifold? If it is your in luck. You can place a nut over the hole and mig weld the nut to the broken stud. The steel weld wont stick to the cast iron and then just back it off with a box end wrench. it may take a few trys depending on your welding skills, but i have taken out hundreds of broken exhaust stud out of V8 where room was limited and getting a drill in there is impossiable even a right angle drill.

If it is a steel manifold then your better off drilling, use a drill press, centering punch and LH ( Left Twist) drills. This should do the job with 95% success rate.
On a side note i broke a bolt before and i installed a flex pipe in my DP.ihave a 3" by 10"long flex pipe in my DP now. Its been almost 2 years now and still no problems. So that may help with your problem. I have plan jane class 5 bolts in my exhaust btw.

Hopefully this helps

That happened to me as well. Turns out my motor mounts were shot and under boost the motor and driveline were being twisted and that put too much force on the mani. I'd check my motor mounts if I were you. Put in the Mazda Speed ones if they are bad.

I say take it to a local machine shop, have them drill and tap the manifold for M10 hardware as well as your turbine housing. I would do this myself but you said last time that ended badly for you. The M10 hardware is used by BEGI for a reason.

So say if you used 3/8" -16 stainless bolts, and put mild torque (16ft/lbs), and safety wire everything, you wouldn't have the shearing and everything would stay in place?

Something along the lines of McMaster-Carr #90121A626

Yeah, I would take it to a local machine shop - or you can even send it to me- and have the holes drilled out to 10 mm. We have done that to several FM Manifolds at no charge.
Stephanie

How long would it take you to get it back to me??
That would be insanely awesome..

Shipping time here and back. We can get it machined and send out the next day. We need the turbo too to enlarge the holes.
Stephanie