this is from my friend who wanted me to post this up to see if anyone has any ideas.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by my friend from email &raquo;</TD></TR><TR><TD CLASS="quote">
I just finished rebuilding the head of a 1991 prelude si with a
B21A1, which my uncle gave me after he broke the timing belt. I
replaced 5 valves in total – all four valves from #2 cylinder and one
exhaust valve from #3 cylinder. The car is all back together now and
running, but I'm having a few problems. Most importantly, between
3250 rpm and 3500 rpm, I'm noticing a very distinct and disgusting
metallic buzzing sound. It sounded like some kind of exhaust system
heat shield vibration, so I went along the exhaust pipe and cleaned
out a bunch of rocks, and tightened up the heat shielding. Then I
disconnected the exhaust from the exit side of the catalytic
converter, to remove more heat shield that was completely mangled,
thinking that may be buzzing against the exhaust pipe. When I did
this, I noticed a huge chunk of the interior of my catalytic converter
blocking the exit port. So, I removed the cat and "replaced it" – no
more chunk. . . I put the exhaust together figuring that all my work
would pay off with no nasty buzzing, but I was wrong.

I'm starting to think that it may be an internal buzz, possibly from
worn cam lobes or something similar, but I don't know for sure. I've
adjusted the valve clearances twice, just to make sure, and they are
perfect.


Summarization – sickening buzz sound between 3250 and 3500 rpm.
Thought it would be exhaust / heat shield related, but apparently not.

I haven't checked the muffler itself yet, but I'll do that next.
</TD></TR></TABLE>

 

i have no idea but i ll tell my engine teach in school tomorrow if he knows what it could be

he one smart ****

 

thank you. anyone else have any ideas?

 

just check the stupidest stuff first. you can drive yourself insane with this kinda ****. good luck, noises are always fun.

 

yeah thats a good point. my money is on the muffler..

 

from 9 years as a bicycle mechanic, i've learned to always check the stupidest possible explanation first. not the simplest, but the stupidest, there is a marked difference.

 

this is really really old, but muffler heat shield FTW..