Alfa Romeo Repair: valve noise or exhaust noise?, exhaust leaks, resistant silicone


Question
I recently drove 234 miles round trip to have some minor service performed on my 1988 Spider Veloce.  A new exhaust bracket was installed in the center muffler. Also,the heat shield on the two pipes coming off the exhaust header was reinforced with some heat resistant silicone.  This repair was made because the heat shield has broken away slightly from the pipe causing a rattle at certain speeds. During the drive home I noticed an increase in valve noise.  Question-If there is a leak in the exhaust near the header will this amplify the valve sound?  I just checked valve clearance 4 weeks ago at it was .002" within specs. If it`s not exhaust noise could an exhaust valve be stretching?  Look forward to your comments.

Answer
Jim,

Exhaust leaks can amplify existing and create some pretty strange noises.  I'd look closely at that possibility before ripping off the cam cover.  

Although not impossible, it's unlikely that you're valves are out of spec in four weeks.  Valve stretch is rare in street driven cars with stock valve train.  We have problems on one of the race cars because of the very radical cam profile, the heavy springs and lots of operation over 7000rpm.  On a street driven car with stock components, it's not likely unless you have over 100K on the engine.  Valves can shrink too from running large clearances.  The stem gets battered as well as the bucket.  Plus, valve stretch, would close clearances not loosen them.

We are testing some this weekend at Sebring, so I will be Internet Challenged for a couple days.  On this forum, they want us to answer these questions within three days, so I wanted to shoot this off to you.  If you don't mind, answer some questions for me and when I get home Sunday pm, I should be able to help more.  It's so difficult to diagnose without putting my hands and ears on the problem.

Is your engine running cooler/warmer than normal?

How many miles are on the car/engine?

Has the head been off the engine, if so, when and what was done?

Is the fix on the heat shield still holding?

Do you HAVE an exhaust leak that you know of, and if so, where is it?

Have you changed motor oil brands or any other lubricant's recently?

When you checked valve clearances, you said they were within .002" of specs.  Do you remember or have written down, what the clearances were?

You said you noticed an "Increase" in valve noise.  Can you quantify that?  Is it really clattering or just more noticeable than before?  How much louder is it when cold vs. hot?

If you don't mind answering these questions... this weekend, I'll also speak to a friend, Russ Ruland, who worked for Alfa Romeo Distributors here in Orlando.  He was there for 12 years as a Field Technician.  I'm pretty knowledgeable but he has forgotten more than I know!  You seem to have some saavy too, so between the three of us, I'm sure we can come up with some ideas.
You can write me directly at <doc1590@yahoo.com> if you like.  I will leave Saturday morning, so if you get back to me before that, I can take more info with me.
Where are you located?  Are there any Alfa clubs nearby?

Sorry... too many questions, huh?

Dave Miller
Deltona, Florida
1986 Spider
1984 GTV6