Head/Intake swap and now a buzzing sound?

[cntchds]

I swapped from the stock intake and E7s to Cobra intake and GT40 heads, and now I'm getting a buzzing noise from the tranny tunnel. I can't really hear it from under the hood, but there seems to be a few more thuds and clunks coming from under there too at idle. I am almost positive that my motor mounts are shot (hit 220K miles this past weekend).

I was thinking it could be my throw out bearing or my pilot bearing, but then decided against it since it doesn't matter the orientation of the clutch (in out neutral etc.) It seems to be completely RPM dependent, but it doesn't happen all of the time, and it's driving me crazy. First thought was vacuum lines, but now that I've pinpointed all of those leaks it doesn't seem like any of them are where the sound comes from. I'm almost positive that it always starts under load, but that it continues after that regardless. The only other thing I've really noticed about it is that it gets much louder after 2k RPM.

Anybody else experience this?

[P63]

Is the buzz constant? How about when you're not moving?

[adamp]

Sounds like it might be something grounded out on the body.
Check to see if you bent or moved something when doing the Swap.
I'm guessing it didnt do it before the swap? Retrace your steps and your likely to find something overlooked that was tampered with during the install.

You may have to put it on jackstands and have someone load or rev it while your under there. Try loading it in reverse and in a forward gear. While your under the car inspect your engine mounts.

Good luck

[cntchds]

Originally Posted by P63

Is the buzz constant? How about when you're not moving?

After it starts it sometimes cuts out during a shift or under acceleration, but only for a moment(maybe half a second), then starts again. There is really no time that I've noticed it go away consistently though.

It's hard to hear at idle, but it is definitely there. It almost never occurs at start up, but soon after it does. My car warms up pretty quick though, and maybe it comes on when the car gets warm.

Originally Posted by adamp

Sounds like it might be something grounded out on the body.

Would that really make a noise? I know I have a ground doing something funky somewhere (temp gauge acts like a ground finder) so I cut the ends to the battery terminal and re stripped them so the contact was good. I checked all the grounds I could find and they all looked like they had good solid contact.

Originally Posted by adamp

Check to see if you bent or moved something when doing the Swap.
I'm guessing it didnt do it before the swap? Retrace your steps and your likely to find something overlooked that was tampered with during the install.

I'll have to try to do that, but I'm fairly sure everything found it's way back to its place. It was one of those jobs where I actually put back every bolt that I took out.

Originally Posted by adamp

You may have to put it on jackstands and have someone load or rev it while your under there. Try loading it in reverse and in a forward gear. While your under the car inspect your engine mounts.

Good luck

What's the safest way to do this? I have ramps that I can put up front, and jack stands to put under the rear, but where would be the best placement for the stands in the back?

I really can't imagine that it is something moving around that just stops and starts somewhat haphazardly. What systems physically change after start up?

EDIT: One more tidbit to add, when car is off rolling in gear the sound does not occur, which again leads me to believe that it has to do with some sort of system, rather than something moving around.

[adamp]

When I said grounded out I was referring to two parts touching, for example a line of some sort be it transmission line etc transferring engine vibrations into the body because it is touching "grounded" the body when it previously was not. Not an electrical ground lol.
Hopefully that clears that up.

As for duplicating. before putting it on stands. Put the vehicle in reverse and hold the brakes hard and torque up the engine steadily to see if you can duplicate the sound. If it doesn't do it with the car in reverse try in forwards. Basically your just trying to flex what you can and duplicate it on demand so when you do actually get under it you will know how to get the noise to come back.

If you can consistently duplicate it in vehicle have someone else bring the rpm's up to where it needs to be while you use a stethescope or long rubbber hose to try and narrow down the location from up top before you worry about getting under it.

And again check to see if your engine mounts have failed. I personally have never seen one bad enough to transmit enough vibration to cause an audible noise but I suppose it can happen.

[Ryno8705]

Is there any buzzing through the radio? Also, did you keep the stock cam?

[cntchds]

Originally Posted by adamp

When I said grounded out I was referring to two parts touching, for example a line of some sort be it transmission line etc transferring engine vibrations into the body because it is touching "grounded" the body when it previously was not. Not an electrical ground lol.
Hopefully that clears that up.

As for duplicating. before putting it on stands. Put the vehicle in reverse and hold the brakes hard and torque up the engine steadily to see if you can duplicate the sound. If it doesn't do it with the car in reverse try in forwards. Basically your just trying to flex what you can and duplicate it on demand so when you do actually get under it you will know how to get the noise to come back.

If you can consistently duplicate it in vehicle have someone else bring the rpm's up to where it needs to be while you use a stethescope or long rubbber hose to try and narrow down the location from up top before you worry about getting under it.

And again check to see if your engine mounts have failed. I personally have never seen one bad enough to transmit enough vibration to cause an audible noise but I suppose it can happen.

I'm still really doubting that it is something that is moving around since it so randomly disappears and comes on, but I guess there is no reason not to check it out.

Originally Posted by Ryno8705

Is there any buzzing through the radio? Also, did you keep the stock cam?

No buzzing through the radio, stock GT cam.

[Ryno8705]

I think this guy is having a similar problem to you: http://forums.corral.net/forums/show...43#post9329043

[adamp]

Did you ever fix this? Post up what it was if so incase others have a similar problem.