intake manifold

[weblefty]

Quick question......is it normal for the intake manifold to be loose enough to be manipulated with your hand? I replaced the gaskets and torqued it down to 17 lbs and I can, with moderate force, move the manifold in a circular fashion, as if I'm rotating it like a throttle. The flanges dont move, just the manifold. Thanks. 2000 FXDX.

 

[RibEye]

Quick question......is it normal for the intake manifold to be loose enough to be manipulated with your hand? I replaced the gaskets and torqued it down to 17 lbs and I can, with moderate force, move the manifold in a circular fashion, as if I'm rotating it like a throttle. The flanges dont move, just the manifold. Thanks. 2000 FXDX.

If yours is like mine, the flanges do not lock the manifold to the heads (like the exhaust has retaining rings). Rather, they cause the rubber seals to compress against the manifold and heads, to make a seal. They will allow relative motion, but I would not move them more than a slight amount, as the angles will vary and you will get leakage. Solid locking down is done via breather bolts and intake backing plate screws.

Actually, to install, you put on the seals, flanges and connect the manifold to the heads, just starting the flange bolts. Then you install the alignment plate, or intake backing plate (works just as well), to line things up. Tighten up the backing or alignment plate, THEN, tighten up the flange bolts to spec, according to sequence instructions. If you take the backing plate off, after tightening the flange bolts, do your best not to allow the manifold to move on you. The flange/seal interface should provide enough resistance that the induction module or carb and manifold does not sag under its own weight. If not, your seals are worn or have shrunk or lost compliance, and should be replaced.

Note: I have noticed that aftermarket rubber seals tend to be bigger than stock, so you will not be able to tighten the flanges down completely against the heads. They may seal fine, but the flange bolts will not be locked to a torque (just tightened to the rubber seal's compliance) and can pretty easily work loose. I recomment OEM seals.

Enjoy,
Rich P

 

[weblefty]

Thanks, Ribeye. This is the third time I have replaced these things in the last two weeks and I still get the same leak in the same place and I cannot figure out what the heck is wrong with the way Im doing it. The left side front cylinder just does not properly seal. Everything is spotlessly cleaned. I've tried it dry, tried it with RTV and this time with dielectric grease on the gaskets so that it would seat properly. No change. Always used OEM gaskets, too and with proper torque. Maybe it's time to let a mechanic at it. Kills me that I cant figure this out. Thanks for taking the time to reply. I very much appreciate it.

 

[Jack Klarich]

Check the flanges to see they are not bent, lay them on a piece of glass can you rock them?

 

[weblefty]

I have not checked to see if they are bent, but it would seem an obvious cause. No one ever accused me of being smart. Ill check that in the morning. Thanks for the suggestions. BTW does anyone know the tightening sequence?