Bad Mileage and Fouled Plugs

Looking for advice. Having problems with 1970 Coougar w/351c. It is hard
to start and uses lots of gas (<9.something mpg in city, used to 12 or so).
When strarting cold, it appears to flood easy as you can smell gas at tail
pipe. Recently put kit in carb trying to fix this and found float orings
pretty much gone (crumbled when removing) but can't say much improved.

Changing the plugs helps with the starting for a while but not long. Pulled
plugs and the front 4 (1, 2, 5 and 6) are black with soot but other 4 are
ok. This is after about 500 miles on new plugs. The motor was rebuilt
about 10 years ago with a used alum edlebrock dual plane intake and 600 cmf
Holley 4bbl. There are no vacuum leaks to the outside along the intake to
head seams. Don't think there are any other vacuum leaks.

What would cause the front 4 plugs to run rich but the back 4 be OK? I'm
99% sure cylinders 1,2,5 and 6 are not on the same side of the dual plane
intake so does that elimnate the carb having a problem left to right? I'm
tempted to get a new carb but would like some confidence that will solve the
problem. Since the carb rebuild, there is a flat spot in the throttle when
you accelerate hard. Probably just the accel pump not set right but maybe
another symptom.

Any advice appreciated. I will try to post pictures of the 8 plugs later.
thanks, bobby
bbusselmanCoyote at hotmail dot com (remove the dog to send email)

"bob" > wrote in message
...
>
> "bob" > wrote in message
> ...
> > Looking for advice. Having problems with 1970 Coougar w/351c. It is
hard
> > to start and uses lots of gas (<9.something mpg in city, used to 12 or
> so).
> > When strarting cold, it appears to flood easy as you can smell gas at
tail
> > pipe. Recently put kit in carb trying to fix this and found float
orings
> > pretty much gone (crumbled when removing) but can't say much improved.
> >
> > Changing the plugs helps with the starting for a while but not long.
> Pulled
> > plugs and the front 4 (1, 2, 5 and 6) are black with soot but other 4
are
> > ok. This is after about 500 miles on new plugs. The motor was rebuilt
> > about 10 years ago with a used alum edlebrock dual plane intake and 600
> cmf
> > Holley 4bbl. There are no vacuum leaks to the outside along the intake
to
> > head seams. Don't think there are any other vacuum leaks.
> >
> > What would cause the front 4 plugs to run rich but the back 4 be OK?
I'm
> > 99% sure cylinders 1,2,5 and 6 are not on the same side of the dual
plane
> > intake so does that elimnate the carb having a problem left to right?
I'm
> > tempted to get a new carb but would like some confidence that will solve
> the
> > problem. Since the carb rebuild, there is a flat spot in the throttle
> when
> > you accelerate hard. Probably just the accel pump not set right but
maybe
> > another symptom.
> >
> > Any advice appreciated. I will try to post pictures of the 8 plugs
later.
> > thanks, bobby
> > bbusselmanCoyote at hotmail dot com (remove the dog to send email)
> >
> Forgot to add that I have opened the choke wide open a month or so ago and
> still floods easy.

Did this just happen all the sudden or did it get gradually worse?

Check the timing. But, Hollys are known for blowing power valves. If it
was
me I would go buy an Edlebrock carburetor (ie: a Carter carb) and use that.
Much better design than the Holly, far more bullet proof.

Ted

It seems so intuitive that this is a carburetor problem that I am afraid I
am missing something.

When you rebuilt the carburetor, did you reset the floats? And did you
check to be sure that the floats were still bouyant (not full of gasoline?)

I am trying to remember how the power valve function worked on this
carburetor, and I just can't picture it right now. If this is leaking, it
can dump
fuel into the manifold and you will get some of the same symptoms.

"HLS" > wrote in message
...
> It seems so intuitive that this is a carburetor problem that I am afraid I
> am missing something.
>
> When you rebuilt the carburetor, did you reset the floats? And did you
> check to be sure that the floats were still bouyant (not full of
gasoline?)
>
> I am trying to remember how the power valve function worked on this
> carburetor, and I just can't picture it right now. If this is leaking, it
> can dump
> fuel into the manifold and you will get some of the same symptoms.
>
>
Thanks for the message. I did reset the floats and they are OK. I also
changed the Power valve. The old one was OK but had a new one in the kit so
installed it. I would assume this would foul all plugs euqually though.

"Ted Mittelstaedt" > wrote in message
...
>
> "bob" > wrote in message
> ...
> >
> > "bob" > wrote in message
> > ...
> > > Looking for advice. Having problems with 1970 Coougar w/351c. It is
> hard
> > > to start and uses lots of gas (<9.something mpg in city, used to 12 or
> > so).
> > > When strarting cold, it appears to flood easy as you can smell gas at
> tail
> > > pipe. Recently put kit in carb trying to fix this and found float
> orings
> > > pretty much gone (crumbled when removing) but can't say much improved.
> > >
> > > Changing the plugs helps with the starting for a while but not long.
> > Pulled
> > > plugs and the front 4 (1, 2, 5 and 6) are black with soot but other 4
> are
> > > ok. This is after about 500 miles on new plugs. The motor was
rebuilt
> > > about 10 years ago with a used alum edlebrock dual plane intake and
600
> > cmf
> > > Holley 4bbl. There are no vacuum leaks to the outside along the
intake
> to
> > > head seams. Don't think there are any other vacuum leaks.
> > >
> > > What would cause the front 4 plugs to run rich but the back 4 be OK?
> I'm
> > > 99% sure cylinders 1,2,5 and 6 are not on the same side of the dual
> plane
> > > intake so does that elimnate the carb having a problem left to right?
> I'm
> > > tempted to get a new carb but would like some confidence that will
solve
> > the
> > > problem. Since the carb rebuild, there is a flat spot in the
throttle
> > when
> > > you accelerate hard. Probably just the accel pump not set right but
> maybe
> > > another symptom.
> > >
> > > Any advice appreciated. I will try to post pictures of the 8 plugs
> later.
> > > thanks, bobby
> > > bbusselmanCoyote at hotmail dot com (remove the dog to send email)
> > >
> > Forgot to add that I have opened the choke wide open a month or so ago
and
> > still floods easy.
>
> Did this just happen all the sudden or did it get gradually worse?
>
> Check the timing. But, Hollys are known for blowing power valves. If it
> was
> me I would go buy an Edlebrock carburetor (ie: a Carter carb) and use
that.
> Much better design than the Holly, far more bullet proof.
>
> Ted

It happened gradually and I checked float levels and found the primary high
but it wouldn't adjust. I pulled the valve out of the top of the carb and
found the crumbling oring so thought I had the answer. I put the kit in and
thought I had blown carb cleaner through all ports to verify none were
plugged with oring chunk.

I'll try to double check timing but I need a new balancer. This one has
slipped so timed by ear right now. Also get a backfire when starting
(through carb) occasionally so maybe a little too advanced but if I already
have it backed down from where it used to be and power is noticably lower.

I am very close to getting a new carb and leaning towards Edlebrock. The
reason I don't just do that is because of the way the plugs look. Don't
understand how a carb could cause the front half of the motor to run rich
and not the back with the dual plane intake. If one jet is plugged or there
is a leak on one side, I can see every other plug in the firing order go
lean but not front to back. Wondering if the intake is leaking from
underneath

Ted Mittelstaedt wrote:

> Hollys are known for blowing power valves.


Change the floats if they are foam and not brass. But even the brass
ones can get a pinhole.
I'd bet your power valve(s) is/are bad. One backfire will destroy them.
Use only Holley brand valves, they are available separately.
If your carb has a thick (1/2") plate between rear bowl and body, then
it has 2 power valves. Change them both. You can re-use the bowl
gaskets. I bet that will solve your problem.

BTW, if your carb is one of the universal units they came from the
factory jetted rich (but not that rich). Once you get the "way-rich"
problem solved, you can get better economy and smoother acceleration by
dropping the primary jet size a few steps at a time.
--
- -
Rex Burkheimer
WM Automotive
Fort Worth TX

bob wrote:
> "Ted Mittelstaedt" > wrote in message
> ...
>
>>"bob" > wrote in message
...
>>
>>>"bob" > wrote in message
...
>>>
>>>>Looking for advice. Having problems with 1970 Coougar w/351c. It is
>>
>>hard
>>
>>>>to start and uses lots of gas (<9.something mpg in city, used to 12 or
>>>
>>>so).
>>>
>>>>When strarting cold, it appears to flood easy as you can smell gas at
>>
>>tail
>>
>>>>pipe. Recently put kit in carb trying to fix this and found float
>>
>>orings
>>
>>>>pretty much gone (crumbled when removing) but can't say much improved.
>>>>
>>>>Changing the plugs helps with the starting for a while but not long.
>>>
>>>Pulled
>>>
>>>>plugs and the front 4 (1, 2, 5 and 6) are black with soot but other 4
>>
>>are
>>
>>>>ok. This is after about 500 miles on new plugs. The motor was
>
> rebuilt
>
>>>>about 10 years ago with a used alum edlebrock dual plane intake and
>
> 600
>
>>>cmf
>>>
>>>>Holley 4bbl. There are no vacuum leaks to the outside along the
>
> intake
>
>>to
>>
>>>>head seams. Don't think there are any other vacuum leaks.
>>>>
>>>>What would cause the front 4 plugs to run rich but the back 4 be OK?
>>
>>I'm
>>
>>>>99% sure cylinders 1,2,5 and 6 are not on the same side of the dual
>>
>>plane
>>
>>>>intake so does that elimnate the carb having a problem left to right?
>>
>>I'm
>>
>>>>tempted to get a new carb but would like some confidence that will
>
> solve
>
>>>the
>>>
>>>>problem. Since the carb rebuild, there is a flat spot in the
>
> throttle
>
>>>when
>>>
>>>>you accelerate hard. Probably just the accel pump not set right but
>>
>>maybe
>>
>>>>another symptom.
>>>>
>>>>Any advice appreciated. I will try to post pictures of the 8 plugs
>>
>>later.
>>
>>>>thanks, bobby
>>>>bbusselmanCoyote at hotmail dot com (remove the dog to send email)
>>>>
>>>
>>>Forgot to add that I have opened the choke wide open a month or so ago
>
> and
>
>>>still floods easy.
>>
>>Did this just happen all the sudden or did it get gradually worse?
>>
>>Check the timing. But, Hollys are known for blowing power valves. If it
>>was
>>me I would go buy an Edlebrock carburetor (ie: a Carter carb) and use
>
> that.
>
>>Much better design than the Holly, far more bullet proof.
>>
>>Ted
>
>
> It happened gradually and I checked float levels and found the primary high
> but it wouldn't adjust. I pulled the valve out of the top of the carb and
> found the crumbling oring so thought I had the answer.

That's the needle and seat. Would not affect mixture to the extent you
are seeing. And a bad o-ring would only make it leak, not upset mixture.
>
> I'll try to double check timing but I need a new balancer. This one has
> slipped so timed by ear right now. Also get a backfire when starting
> (through carb) occasionally so maybe a little too advanced but if I already
> have it backed down from where it used to be and power is noticably lower.

Timing won't have any effect on the mixture, or the plugs fuel-fouling.
Timing by ear is pretty iffy with today's gas.

> I am very close to getting a new carb and leaning towards Edlebrock. The
> reason I don't just do that is because of the way the plugs look. Don't
> understand how a carb could cause the front half of the motor to run rich
> and not the back with the dual plane intake.

Some dual-plane manifolds have a plenum area right under the carb (which
defeats the purpose). This design could allow the front to run richer.

Edelbrock is a good choice for a dependable street carb.
It's basically a Carter AVS/AFB with updates.

--
- -
Rex Burkheimer
WM Automotive
Fort Worth TX

"Rex B" > wrote in message
...
> Ted Mittelstaedt wrote:
>
> > Hollys are known for blowing power valves.
>
>
> Change the floats if they are foam and not brass. But even the brass
> ones can get a pinhole.
> I'd bet your power valve(s) is/are bad. One backfire will destroy them.
> Use only Holley brand valves, they are available separately.
> If your carb has a thick (1/2") plate between rear bowl and body, then
> it has 2 power valves. Change them both. You can re-use the bowl
> gaskets. I bet that will solve your problem.
>
> BTW, if your carb is one of the universal units they came from the
> factory jetted rich (but not that rich). Once you get the "way-rich"
> problem solved, you can get better economy and smoother acceleration by
> dropping the primary jet size a few steps at a time.
> --
> - -
> Rex Burkheimer
> WM Automotive
> Fort Worth TX

Thanks for the advice. The floats are plastic and hollow so no leaks (no
fuel inside the float). The bad oring was in the stem of the float
adjustment. It was allowing fuel to leak past the needle and seat. The
carb only has 1 powervalve (I had both bowls off when putting the kit in)
and the plenum is seperate all the way up to the carb.

The comments I get are still pointing to carb but still trying to figure out
why the front plugs foul first. I will try and post pictures tonight of
the 8 plugs.

bob wrote:
>
> "Rex B" > wrote in message
> ...
> > Ted Mittelstaedt wrote:
> >
> > > Hollys are known for blowing power valves.
> >
> >
> > Change the floats if they are foam and not brass. But even the brass
> > ones can get a pinhole.
> > I'd bet your power valve(s) is/are bad. One backfire will destroy them.
> > Use only Holley brand valves, they are available separately.
> > If your carb has a thick (1/2") plate between rear bowl and body, then
> > it has 2 power valves. Change them both. You can re-use the bowl
> > gaskets. I bet that will solve your problem.
> >
> > BTW, if your carb is one of the universal units they came from the
> > factory jetted rich (but not that rich). Once you get the "way-rich"
> > problem solved, you can get better economy and smoother acceleration by
> > dropping the primary jet size a few steps at a time.
> > --
> > - -
> > Rex Burkheimer
> > WM Automotive
> > Fort Worth TX
>
> Thanks for the advice. The floats are plastic and hollow so no leaks (no
> fuel inside the float). The bad oring was in the stem of the float
> adjustment. It was allowing fuel to leak past the needle and seat. The
> carb only has 1 powervalve (I had both bowls off when putting the kit in)
> and the plenum is seperate all the way up to the carb.
>
> The comments I get are still pointing to carb but still trying to figure out
> why the front plugs foul first. I will try and post pictures tonight of
> the 8 plugs.

That usually means one barrel of the carb has the troubles in it. Try
carefully looking down the throat of the carb while it's running and
give it an easy shot of throttle to see if one side has a strange gas
stream or something.

It is strange, the barrels are side by side up top, but they seem to
affect the front and rear of the engine.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's

> Looking for advice. Having problems with 1970 Coougar w/351c. It is hard
> to start and uses lots of gas (<9.something mpg in city, used to 12 or
so).
> When strarting cold, it appears to flood easy as you can smell gas at tail
> pipe. Recently put kit in carb trying to fix this and found float orings
> pretty much gone (crumbled when removing) but can't say much improved.
>
> Changing the plugs helps with the starting for a while but not long.
Pulled
> plugs and the front 4 (1, 2, 5 and 6) are black with soot but other 4 are
> ok. This is after about 500 miles on new plugs. The motor was rebuilt
> about 10 years ago with a used alum edlebrock dual plane intake and 600
cmf
> Holley 4bbl. There are no vacuum leaks to the outside along the intake to
> head seams. Don't think there are any other vacuum leaks.
>
> What would cause the front 4 plugs to run rich but the back 4 be OK? I'm
> 99% sure cylinders 1,2,5 and 6 are not on the same side of the dual plane
> intake so does that elimnate the carb having a problem left to right? I'm
> tempted to get a new carb but would like some confidence that will solve
the
> problem. Since the carb rebuild, there is a flat spot in the throttle
when
> you accelerate hard. Probably just the accel pump not set right but maybe
> another symptom.
>
> Any advice appreciated. I will try to post pictures of the 8 plugs later.
> thanks, bobby
> bbusselmanCoyote at hotmail dot com (remove the dog to send email)
>
Finally got some pictures posted. Per all of the posts, Carb is being
blamed. Still not sure how the carb can make the front 4 cylinders richer
than the back but that is what is happening. The pictures are at
http://mysite.verizon.net/blondechick/sparkplugs.htm . I wire brushed #1 to
see if it would clean up but it originally had black fluffy soot on it.

Bobby