Air cleaner stud broke, 2nd time in the last year

[yahrt]

Hi all, I have a BP347 with a Sniper EFI, opened up the hood this morning to check fluid levels and found my air cleaner lying on its side. The threaded stud is broken off right next to the nut used to secure to the EFI. Happened last year and replaced with one sourced from Mr. Gasket. Any tricks to avoid this happening in the future? Thanks, TY

[JMD]

Are you using a nylon or metal stud? I've never heard of this happening with a metal stud, but could see this happening with a nylon stud and heavy air cleaner assembly. Make sure you're not overtightening it. Just enough pressure to get snug, no need to put any kind of torque on the nut.

[Blitzboy54]

Is your hood contacting the air cleaner? Maybe under heavy throttle when the engine torques?

[yahrt]

The stud is metal, I hqve the oval cobra cleaner with a 3" filter, plenty of clearance under the hood, the wingnut on top has to be fairly tighten to prevent the cleaner from rotating.

[Mike.Bray]

Just convert to stacks and be done with the problem:p

[JMD]

You're sure the stud is actually breaking and not just backing itself out of the TB? Make sure the stud is at least 4 full turns in the TB and secure with a jamb nut (or a few). The jamb nut will give it some extra strength and make sure it's not vibrating loose.

[efnfast]

Just convert to stacks and be done with the problem:p

ah, the journey of ITBs

the happiest day of your life - when you unbox your ITBs and see them in their glory

the next happiest day of your life - when you re-box them and sell them to the next guy to let them be his misery after you learn about all the @#$#@ problems that come along w/ them

[rich grsc]

Another ridiculous statement. My car runs perfect with stack EFI, better than anything else I've used, doesn't stumble, hiccup, backfire, nothing except smooth power.

[yahrt]

JMD - "You're sure the stud is actually breaking and not just backing itself out of the TB? Make sure the stud is at least 4 full turns in the TB and secure with a jamb nut (or a few). The jamb nut will give it some extra strength and make sure it's not vibrating loose."

Yes it is actually breaking, the stud is almost bottomed out in the TB and secured with a jam nut. Both times the stud snapped at the top of the jam nut.

McMaster sells high strength zinc-yellow-chromate-plated steel all thread rod, thinking of ordering some of that to see if it holds up better

[Bob Cowan]

Studs and bolts break mostly due to lateral stress. The air cleaner is moving around, slightly bending the stud. Eventually, it breaks.

Make sure that the hole in the bottom of the air cleaner exactly fits the throttle body, with no moving around. Use the aluminum foil burrito method to absolutely make sure there is NO hood or cowl contact with hard driving.

Grade 5 bolts and studs can stand some lateral movement without breaking. But grade 8 cannot. Grade 8 is extremely strong in clamping strength, but can be brittle in lateral stress. I think changing to a high strength stud will only make your problem worse.

Think about this: Hundred (thousands?) of cars over the years have used that air cleaner with that stud, and those cars don't have this problem. It's not a materials problem, it's an installation problem.

[Mike.Bray]

ah, the journey of ITBs

the happiest day of your life - when you unbox your ITBs and see them in their glory

the next happiest day of your life - when you re-box them and sell them to the next guy to let them be his misery after you learn about all the @#$#@ problems that come along w/ them

This is my third or fourth car with EFI stacks and I couldn't be happier with them. Starts easy, idles, responsive, and runs well throughout the entire range. If you have stacks and it's not running correctly it's a tune issue/not knowing what you're doing, not the stacks.


https://youtu.be/Q_5fTdGFakQ

[yahrt]

"Think about this: Hundred (thousands?) of cars over the years have used that air cleaner with that stud, and those cars don't have this problem. It's not a materials problem, it's an installation problem."

Great point and well taken. If an installation problem, none of the explanations suggested are the cause, everything looks fine, air cleaner fits snugly at the base and there is no interference on the top... perhaps its the added height of the 3" air filter and requirement for a longer stud that is creating the weakpoint....

[David Williamson]

Most likely a fatigue failure from vibration. I would check the fit of the air cleaner, make sure it is not bent and and moving on the carb with the engine running. or you might have it too tight and the matierial is over stressed.
David W

[Shamilton289]

The stud is metal, I hqve the oval cobra cleaner with a 3" filter, plenty of clearance under the hood, the wingnut on top has to be fairly tighten to prevent the cleaner from rotating.
Add a locating pin to the base so it can’t rotate, and you won’t have to torque down the wingnut gorilla-tight