The exhaust pop is usually caused by an exhaust leak or loose/unsealed
heads.  perform a compression and leak-down  test and check for exhaust
leaks by blocking the tail pipe at idle with a bunch of thick rags.  You
should be able to stall the engine.

Dennis

-----Original Message-----
From: Harmon Seaver <hseaver@HARMON.BML.USOUTHAL.EDU>
To: Vanagon@VANAGON.COM <Vanagon@VANAGON.COM>
Date: Wednesday, August 26, 1998 7:25 PM
Subject: Exhaust popping??

>OK, got my '81 engine back in my '73, with new heads, new seals, and
>it starts and runs really good. Much better than before, because besides
>the new heads (and the engine only had about 10K on it), I found a
>cracked rubber elbow on the air regulator (?? -- is that the right name,
>it controls the cold start valve -- a bad vacuum leak that I never could
>see before) and also figured out that since I don't have the EGR hooked
>up (extractor exhaust w/no EGR port) I should disconnect the
>EGR/throttle connection, right? Otherwise that's just another vacuum
>leak at high speed.
>   Anyway, this morning I re-did the valve adjustment, just to make sure
>that it was right after the lifters got pumped up. One, the intake on
>#3, which I noticed when I put the engine back together made a weird
>clicking noise when I turned the engine over by hand, still seems a
>little weird. Like it isn't as solid as the rest, but it doesn't make
>that rattling noise that lifters sometimes make after the engine has sat
>for awhile.
>    So, I wouldn't worry about it, except that I've got this constant
>exhaust pop whenever I let off the gas. Sounds great otherwise. Could be
>a slight exhaust leak, I guess, since I couldn't get the right side top
>bolt to tighten all the way -- the support bracket that comes down from
>the fan housing on that side seems too short and won't pull in all the
>way. I could  get the bolt thru it and get a nut on it, but not really
>snug it up.
>    So should I worry about the exhaust pop or not -- I'm about to take
>a 1120 mile cruise with this?
>   Also, I should mention, my timing light died, so I just set the
>timing statically at 0 TDC to be on the safe side. Sure starts nice, and
>great throttle response, power, etc. So far the oil temp hasn't gone
>over 210 with 95 ambient temp.
>    Hey, another thing -- you volks should be proud of me -- I got rear
>tin! A bit crude, probably never get a real seal on it, but at least
>it's a heat shield between the exhaust and the fan.
>
>--
>Harmon Seaver hseaver@harmon.bml.usouthal.edu
>http://harmon.bml.usouthal.edu
>=======================================================================
>All is impermanent, but this too shall pass away, and the way of the
>Samurai is death -- so speak your mind now, or forever hold your peace.
>=======================================================================
>Copyright, Harmon F. Seaver, 1998. License to distribute this post is
>available to Microsoft for US$1,000 per instance, or local equivalent.
>=======================================================================