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Discussion Starter #1 (Edited)
Hello knowledgable and experienced ones,

I recently posted about a cracked 1-4 exhaust manifold and a noise coming from the engine that I thought was caused by that faulty part. the sound has been present in my '91 Spider since I bought it last September but has gotten more prominent over the past 4 months. Though I have read on these pages that a cracked manifold CAN produce a flickering metallic sound, I'm really thinking that something else is causing it.

At first I thought it was a valve shim problem but as I listened today, it sounded as though it was coming from the front of the engine - near the pulleys. It does sound metallic but also "brassy" and "tinky." When the engine idles there's just a hint of the sound but as I rev up the engine it increases with the speed of the acceleration. As I listen again to the attached video, it almost sounds like a belt noise. When I'm crusing it is intermittently constant - that is, it rings for a few seconds, quiets of a few seconds and then starts up again, over and over again in that kind of series, all in a steady rhythm. It is quite noticeable standing outside the car and when sitting in the cabin. Oil pressure, engine temp, power and acceleration don't seem to be affected. It's mainly annoying and must be signifying that something isn't right.

Anybody have ideas? Water pump? - documentation says it was replaced in 2014. Belt? - also replaced then. Actually, it sounds even more metallic in person.

This video I uploaded to Youtube will take you there. www.youtube.com/watch?v=aVUzGu_QCTg
 

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Have you replaced the cracked manifold?
 

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No, unfortunately the one I ordered from Centerline didn't fit so we had to reinstall the old one but with new gaskets and bolts. I'm on the trail for another but they're hard to find.
 

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that engine wobbles too much for my liking...so, possibly the crank pulley rubbing intermittently on sway bar as you rev and the engine wobbles and contacts....bad mounts I'm guessing?

Photo shows mine was just starting to rub (a feeler gauge might have fitted in there, just!) when I noticed the shot engine mounts.
New engine mounts and now my fingers fit between the gap!:)

PS: old photo so that gungy oil is gone, and the slightly frayed belt is changed;)
 

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I used to have a late 70's spider that had a sheet metal heat shield tack welded to the downpipe below the exhaust manifold. I don't know if your '91 has something similar. A few of the tack welds fatigued over time, allowing the shield to vibrate at certain RPM's. The sound would be like what you describe: a metallic ringing.

My loose heat shield caused no harm, other than driving me nuts. I eventually used a chisel to break the other tack welds, and lived without the shield. Of course, a new part would have been a better solution.
 

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Discussion Starter #8
Thank you all for your input. I'll check out that possible crank pulley rubbing as well as the heat shield. My stethoscope arrives tomorrow; that may help locate the sound. I'm also thinking about taking the car over to the Nick Falcone shop near Philly to have a few things checked out.
 

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I think your going to find that its the exhaust leak.

FYI. The 91 and later exhaust manifolds are slightly different from the standard 2 pc factory headers. Alfa had to curve them a little differently to clear the power steering.
 

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A mechanics stethoscope is some of the best ten bucks or so that I've ever spent.
 

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Discussion Starter #13
The sound is gone! Vince Votto, the Master Mechanic at Nick Falcone in Bala Cynwyd, PA replaced the belt that ran the A/C and the alternator and it was no more. What a difference. The air conditioning is not working for a different reason but we'll take care of that later. It turned out to have nothing to do with the manifold. By the way, I did bid and win the '92 manifold on eBay. It includes the entire set of 1-4, 2-3 and two heat shields. Hoping for the best. Thanks, Jim G. for pointing me in that direction.
 
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