[DeTomaso] No Idle Blues

[Will Kooiman]

I have a Proform center section, QFT baseplate, QFT metering blocks, and QFT
fuel bowls.

I'm not debating Mikie's experience.  I'm just offering mine.

I couldn't be happier with my carburetor.  I'm getting right at 20mpg, it
starts great once it warms up a little, and it runs great too.  2-3 years
ago it did 342HP at the wheels.  I've fixed some stuff since then, so it's
probably around 370HP by now.

My 4-corner idle screws are out 1/2 of one turn.  Any more than that and the
A/F gauge goes way rich all the way up to about 3000rpm.

It idles at 800rpm.  I believe the idle vacuum is around 17 or 18.

If you have to open your screws that much to get it to idle, you probably
have a vacuum leak somewhere.  The most common places are the intake
manifold and possibly missing ports on the carburetor.  Also - there's the
vacuum line to the brakes, but I imagine you would have noticed that if you
drove it.  Try plugging all vacuum lines (especially the PCV) and see if it
will idle.

It could maybe be the timing too, but it would have to be way retarded to
act like this.  You said you had 30BTDC at 1450rpm.  I'm not sure when the
advance starts kicking in, but I doubt it adds that much by 1450rpm - maybe
8-10 degrees.  If that's so, your initial is around 20BTDC.  We could debate
forever if that's "right", but it surely isn't retarded.

I don't know how retarding the cam affects all of this.  I've never done it,
so someone else will need to chime in.

If your fuel lines are too small, you'll see it under load or at high rpm -
not at idle.

I started with a 650 dbl pumper.  It ran fine.  The only problem I had was
the manual choke closing on its own once.  Not a big deal.  Oh yeah, I also
got junk in the needle/seat once.  The first change I made was the center
section.  Just for grins.  No problems there, but it didn't seem any better
either - maybe a little smoother, but not that big of a difference.  The
next step was QFT billet metering blocks.  They have changeable power valve
enrichment circuits, plus all the emulsion circuits can be changed.  I was
running 1.5 turns out on the idle screws with the Holley metering blocks.
With the QFT blocks, I had to go to .5 turns.  The last step was the billet
baseplate, plus the QFT fuel bowls.  The QFT fuel bowls have a site window
that is easy to see through.  The others are almost impossible for me.  It's
a lot easier to set the floats with these fuel bowls.

By the way, I have A3 heads, a Mallory (with pertronix) distributor, stock
pistons - so about 10.5-1, slightly smaller cam - Comp 282S, and straight up
timing.

To reiterate, what you're describing sounds like a big vacuum leak.  I had a
small one at cylinders 7 and 8.  That's where I attached the carburetor
return spring.  When I tightened the bolt, I didn't get it tight enough.  It
kept pinging, when it shouldn't.  I removed the intake and saw a black path
into the ports where it had been sucking oil.

What intake are you running?

Will.

-----Original Message-----
From: detomaso-bounces at realbig.com [mailto:detomaso-bounces at realbig.com] On
Behalf Of MikeLDrew at aol.com
Sent: Wednesday, July 04, 2007 1:08 AM
To: charlesbuthala at yahoo.com; detomaso at realbig.com
Subject: Re: [DeTomaso] No Idle Blues

Charles,

FWIW I had the same problem with my Cobra, which had a Holley 750 with a 
Proform center section.   It turns out the Proform center was a complete and
total 
POS.

It was virtually impossible to start the car without without pumping the gas

and holding the throttle wide open, and it didn't idle properly.   RIck 
Moseley came over to help troubleshoot it, and was horrified at the spray
pattern.   
At idle, the carburetor was literally POURING gas into the engine.   The 
'spray' boosters weren't spraying at all--it was just running like a water 
fountain.   There was no way to adjust it.

The solution was to throw the 'trick' Proform center section over the hedge 
and reinstall the stock Holley 750 center, which works flawlessly.

Be advised that efforts to start the car with the ProForm section often 
resulted in a fireball three feet high out the carburetor, something you can

ill-afford in a Pantera.   You might not have the same problem, but just in
case, be 
prepared.

Mike


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