From: ryan@netnews.smithkline.com (Dominic Ryan)
Subject: Carburation Wizard needed, please.
Organization: SmithKline Beecham Pharmaceuticals
X-Newsreader: Tin 1.1 PL5
Date: Mon, 23 Nov 1992 16:40:57 GMT

This is a longish post, just to warn ppl, but I really need some input on 
this problem that has me *VERY* frustrated.  First the particulars of the
car:

'78 Mercury Colony Park wagon, 400cid old standard Motorcraft 2150 two
barrel.  Heads/cam/lifters recently redone and now in good shape, bottom
end tight, compression good and even.  Timing on (13oBTDC), advance seems
to be working ok -checked with advance timing light.  Distributor not sticking,
vacuum advance holds a good vacuum.  Egr system all fine, valve is new and
there are no leaks.  Spark is hot enough, registring around 18Kv at the
plug.  Carburator spark and egr vacuum taps are clear and draw fine.
Float is set to spec and seat looks good.  Fuel pressure is ok at around
8psi (I don't remember just what it was now but that it was ok when I
checked).  I have gone over every bit of vacuum hose that I can find and I
cannot find any leaks.  I know, this is hard to find sometimes, but for now
assume that there are no leaks, I have reduced the vacuum load down to the
minimum required and the problem does not go away. 

Problem:  It seems to be missing or bucking gently at cruise and is using a
lot of gas (I get around 11 mpg at best) and this engine should give me 17
or even 18 on the highway.  Pickup  is not too bad but could be a little 
better.  Idle is very smooth but there is one problem.  I get lower vacuum
at idle than I should.  This engine should give me 19-21 inches at idle and
I am getting only about 14-15" at idle in drive.  Slightly higher rpm in
neutral gives me 20".  The low vaccuum correlates in my mind with low power
at well.  In addition, although the idle is very smooth mostly, it will very
slightly miss at times, when that happens I get a shift in timing that seems
to be vacuum related, i.e. it will not happen if I block the advance line.
So, what is happening is that the vacuum drops off a tad and that shift the
timimg for that pulse.  Therefore I think this is a carburation problem.  
I am also convinced of this because I rebuilt the carb a while back when I
was having other troubles with this.  at the time I used a 'generic' carb
kit that was supposed to cover the apparently three kits that would
otherwise be available for this engine.  My problem is that the carburator
tag was *gone* from this engine when I bought the car.  I have even called
the Ford customer assistance line to see if they could look up the old part
number from the VIN data.  They were very helpful once before but I have not
heard from them in a long time now. 

I suspect that I have the wrong power valve in the base of this carb.  I
think that it is running too rich at off idle but I don't think it is the
jets since I am pretty sure that all the carbs used the same jet sizes.  The
accelerator pump diaphram is ok and not dripping through.  

I don't think *idle* mixture has anything to do with this though.  I have not
used an exhaust analyzer to check the mixture but it is pretty carefully
balanced and slightly on the lean drop idle side which should be good enough
to not give me this problem.

So.  If there is a carburation wizard out there, or a might-be-wizard,
please offer some suggestions. This is my haul-my-wife-and-5-kids-around-car  
and I cannot afford to replace this for another year or so.  

Does anyone have any clues about how to go about checking the carb out, 
tweaking it etc?   My news feed is several days late so e-mail please if you
have any ideas at all.  I gotta get this thing behaving better. 

Thanks for reading this far, and thank you for any help you might be able to
offer.