Perhaps the pistons were incorrectly installed? It happened to me
once to my 1971 AC Beetle when a mechanic rebuilt my engine.
He had the pistons all in reversed direction. As a result the engine
lacked power and there was a not quite obvious knocking noise.
Another mechanic took the engine apart and confirmed the error.

Just my guess, a mistake very unlikely but possible. This is very
hard to diagnose without taking the cylinder heads off.

David

--- Michael Diehr <md03@XOCHI.COM> wrote:

> Stump the chumps:  I've got an 85 auto with a rebuilt engine with
> about 5000 miles on it.  It's running ok overall (mpg around 17-18 in
> fast california driving), but power seems a bit off (even for vanagon
> standards).
>
> The problem:  The engine makes a ticktick sound at around 3000 rpm
> that was definitely not there in the prior engine.
>
> It sounds a bit like ping, but the behavior is not always ping-like:
>   * only happens under 1/2 to full throttle under load
>     (consistent with ping)
>   * it's worse at altitude and cold
>     (backwards? ping is usually worse at sea level on hot days, right?)
>   * not obviously connected to the octane of fuel.
>     (inconsistent with ping)
>   * the frequency of the tick noise sounds like it may be happening on
> 1 cylinder only
>     (e.g. unlike ping, it doesn't seem to decrease in frequency when
> you add more
>      throttle, just the loudness increases.  When i've driven cars
> with ping,
>      usually the ping frequency is dependent on throttle/load too)
>
> It has rebuilt injectors that were flow tested at witchhunter.  The
> valves have never been adjusted, and I *think* the shop that installed
> the engine (to which i'm unable/unwilling to go back to them...a long
> story) may have replaced the distributor and messed with the mixture
> adjustment screw, as well as putting in a new (rebuilt) ECU.  I'm
> running mobil 1 15/50 w/mahle filter.
>
> Ideas?  I'm having a real mechanic look at it, and would like to make
> sensible suggestions...
>

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