Same here...10mm studs and helicoiled all the holes. I did use ARP 10mm 12 point nuts though :naughty:
7/16" exhaust stud upgrade?
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Wait till you build a few more engines and have a couple 10mm helicoils (or Recoils) pull right out of the head before you even hit 15 ft/lbs, then you guys will understand why it is an upgrade. :icon_wink
The problem from what I can tell is that the head on a 7m doesn't have any coolant passages near the exhaust manifold studs, and the aluminum softens around the studs because of the extreme heat over a long period of time. If the stock studs come out without stripping the holes, then you probably could get away with 10mm helicoils. The whole reason I came up with the kit was because a customer had a machine shop helicoil his head and the helicoil pulled out before he hit the correct torque. 7/16" is the next size up that still fits the manifold without drilling. Then a few weeks later it happened to me, and know the helicoil was installed correctly, so I figured other people may have the same issue.
If the factory Toyota gasket doesn't fit over the studs, I don't think spending $6 or whatever the gaskets costs from Fel Pro is such a huge inconvienence or expense. The proper fix would be buying a new cylinder head, but I think a $60 helicoil kit is a lot better deal for most people. Honestly, I make so little money on the kits that the only reason I still have them is to help people out. It costs me more money in my time to round up all the parts from 4 different places then I make on it.
The problem from what I can tell is that the head on a 7m doesn't have any coolant passages near the exhaust manifold studs, and the aluminum softens around the studs because of the extreme heat over a long period of time. If the stock studs come out without stripping the holes, then you probably could get away with 10mm helicoils. The whole reason I came up with the kit was because a customer had a machine shop helicoil his head and the helicoil pulled out before he hit the correct torque. 7/16" is the next size up that still fits the manifold without drilling. Then a few weeks later it happened to me, and know the helicoil was installed correctly, so I figured other people may have the same issue.
If the factory Toyota gasket doesn't fit over the studs, I don't think spending $6 or whatever the gaskets costs from Fel Pro is such a huge inconvienence or expense. The proper fix would be buying a new cylinder head, but I think a $60 helicoil kit is a lot better deal for most people. Honestly, I make so little money on the kits that the only reason I still have them is to help people out. It costs me more money in my time to round up all the parts from 4 different places then I make on it.
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bigaaron said:
this is the reason why i went this way..heavier mani. turbo etc.
i heard nothing but great things about this upgrade.
just to clarify, the machine shop didn't do the studs, the mechanic that put the motor together did:icon_evil
i talked to the machinist and he couldn't understand why this guy didn't just let him do it while he was at it.
When you drop a head and block off at a machine shop, it is devoid of all studs and components like it. It is unproffessional of a tech to think the machinist needs to do his job.
Yeah...my original studs came out with NP. I used 10 x 1.25mm Screw-Lock Helicoils...they are holding very well at 40 ft/lbs of torque.
I do know what you're talking about Aaron...friend of mine had FUBAR'ed stud holes and even the 7/16" studs did not hold. We had to get 1/2" to 7/16" step down studs and install with the 1/2" side on the head. Worked really well and saved a head with over $1K in machine work/porting in it already.
I do know what you're talking about Aaron...friend of mine had FUBAR'ed stud holes and even the 7/16" studs did not hold. We had to get 1/2" to 7/16" step down studs and install with the 1/2" side on the head. Worked really well and saved a head with over $1K in machine work/porting in it already.
Usually you know you're in trouble when the stud comes out and you can't even see any threads because it's just covered in aluminum. 10mm helicoils use a 13/32 drill bit, but 7/16" uses a 29/64, and the larger diameter hole gets your new threads tapped into more solid aluminum.
If I ever do mine I'll helicoil to stock. No need though because I doubt I'll ever be taking it off again. The ones I did came out hard though, real hard. Had to use a pipe wrench on one. There are also ways around annealing of the head if that is indeed the cause of this problem.
The upgrade is good enough I suppose and will work for most users, just that my standards for quality and engineering are higher. For example the use of a coarse thread on the head side is a mistake. I also dislike having SAE fasteners on the car. As for the Toyota gasket it wasn't difficult to make it work so no harm no foul.
The upgrade is good enough I suppose and will work for most users, just that my standards for quality and engineering are higher. For example the use of a coarse thread on the head side is a mistake. I also dislike having SAE fasteners on the car. As for the Toyota gasket it wasn't difficult to make it work so no harm no foul.
And if you wanted to be really clever you'd use a thread roll instead of a tap and get forged threads! 
Tis true. Try and find coarse pitched cut thread fasteners on aircraft or other aerospace applications. You won't. There's a reason for that
Aerospace and aircraft are assembled by professional skilled workers with expensive equipment and almost unlimited resources, not people who can barely drill a hole without it being crooked. Coarse taps have taller threads which gets more into better aluminum in the head. I know fine threads are considered to be stronger, but you also have less tolerance in size of the hole. Since most people are using hand tools, I figured corse would work out better for those reasons.
BTW, if you can find 11mm x 1.25 x 50 studs, 11mm x 1.25 lock nuts, and 11mm x 1.25 helicoil kits at a local hardware store then I would be totally amazed. Then finding them for a reasonable price is the next step. See, that's where engineering meets real world pricing and availability.
BTW, if you can find 11mm x 1.25 x 50 studs, 11mm x 1.25 lock nuts, and 11mm x 1.25 helicoil kits at a local hardware store then I would be totally amazed. Then finding them for a reasonable price is the next step. See, that's where engineering meets real world pricing and availability.
Yes of course. Not my intention to knock the product Aaron. Let me rephrase: You came up with an affordable solution to a problem that could be employed by the majority of a community who lack the know-how to do it better. That's it's not something everyone would use doesn't reflect badly on it. That it works is good. It just not good enough for some of us
Or if you were really hardcore you would make your own custom exhaust studs from scratch like Ron!