Carburetor EGR port question

Simpson wrote:.
>
> The way I see it I have three main ways to lower HCs:
>

One more way, a fresh oil change using conventional oil.

High HC's can come from oil getting past the rings also so a really thin
oil or old oil that goes 'thin' can bump them up.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
'New' frame in the works for '08. Some Canadian Bush Trip and Build
Photos: http://mikeromainjeeptrips.shutterfly.com

Mike Romain wrote:
> Simpson wrote:.
>> The way I see it I have three main ways to lower HCs:
>>
>
> One more way, a fresh oil change using conventional oil.
>
> High HC's can come from oil getting past the rings also so a really thin
> oil or old oil that goes 'thin' can bump them up.

Oil is fresh and the rings seem to be in good shape. I can go all the
way between oil changes at 3,000 miles without having to add a quart. I
bought it new and changed oil and filter fairly regularly.

>
> Mike
> 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
> 'New' frame in the works for '08. Some Canadian Bush Trip and Build
> Photos: http://mikeromainjeeptrips.shutterfly.com

aarcuda69062 wrote:
> In article >,
> Simpson > wrote:
>
>>> Hi Jack,
>>> Does this truck have an air pump?
>> Yes it does. It injects air directly into the cat.
>
> I suspected so. The only way to make meaningful determination of
> the gas readings is to take the gas readings again with the air
> pump disabled.
>
>>> The reason I ask is because
>>> there is an awful lot of O2 in the exhaust sample.
>> That's what I thought.
>
> At this point, it's nether good or bad until you attempt to use
> the gas readings as a diagnostic aid.
>
> There's a thing called the Brettschneider equation which allows
> with the input of 4 or 5 gas reading to accurately calculate the
> air fuel ratio. The equation works whether or not there is a
> catalytic converter ahead of where the sample is taken.
> What the Brettschneider equation can not compensate for however
> is false air introduced either by leaks in the exhaust pipes or
> joints or an auxiliary air system such as is on your truck.
>
>>> If the truck has an air pump, that would account for it, but
>>> unfortunately the dilution from the air pump makes analyzing the
>>> gas samples difficult.
>>> If there is NO air pump, here;s what I think; too much O2, too
>>> much HC, not enough CO2 and not enough CO. That is a lean
>>> mixture. Richening it up a bit will drop the HCs, lower the O2
>>> and increase the CO2.
>> I'm confused. If there is excess O2 and excess HC, what prevents them
>> from combining in a burn to produce more CO2?
>
> Low catalytic converter efficiency.
> The excess gases are in the wrong ratio.
>
> Ever use a cutting torch?
> If you set the flame as oxidizing, you won't get the results you
> need. If you set the flame as carburizing, you won't get the
> results you need.
> One size fits all replacement parts...
> I've seen vehicles fail emissions tests because the air pump was
> too small, I've seen vehicles fail emissions test because the air
> pump was too big. (the OEMs rate/size them by CFM)
>
>>> A richer mixture doesn't contribute to more
>>> NOx typically as long as the other NOx treatments are functioning
>>> as they should.
>> That's seems to be in line what what I have read concerning the
>> formation of NOx, which is mainly a factor of a too hot combustion chamber.
>>
>>> Advancing ignition timing hurts NOx, it tends to hurt HC and CO
>>> also, the exception being if the ignition system is marginal and
>>> HCs are caused by an ignition misfire, this is because it takes
>>> less voltage to ionize the plug gap the farther the piston is
>>> away from TDC (advanced).
>> I can't quite follow you on this. Did you mean that "it takes *more*
>> voltage to ionize the plug gap the farther the piston is away from TDC
>> (advanced)."?
>
> No, opposite that. If you have a weak ignition system, chances
> are it will present itself or be more problematic with less
> ignition advance.
> if I see low firing voltage on a secondary waveform on a scope
> and no indication of plug fouling, I first grab my timing light
> and check ignition timing.
> You can search for my posts in either of the Chevy truck groups,
> you want to focus on exchanges between myself and a poster named
> "snoman" for my attempts to get him to understand why his truck
> runs better with the ignition timing jacked sky high contrary to
> the hundreds of identical trucks I've worked on in the last 20
> years that would just ping, rattle and set ESC codes when set the
> same or similar.
>
>>> Late ignition timing tends to help HC
>>> and CO for the exact reasons given in my first post, hotter
>>> combustion chamber wall, hotter exhaust valve and port, but late
>>> timing can reveal marginal ignition components.
>> Plugs, cap and rotor are all very healthy looking, but the resistance of
>> the wires all measure below the lower spec for resistance in the shop
>> manual. 250 ohms per inch is the minimum spec. Mine are at about 200.
>
> Which shop manual specifies ohms per inch?

Page 8D-10 of the

Chrysler Motors 1987 Shop Manual

2WD and 4WD Pickups

Dakota Trucks

Like the one shown he

http://cgi.ebay.com/ebaymotors/1987-...3756.m20.l1116

From the manual:

CABLE RESISTANCE CHART

Minimum---------------------Maximum
250 Ohms Per Inch 600 Ohms Per Inch


>
>> At this point, I should probably mention that I have an MSD Blaster
>> Ignition, model PN 5900, installed:
>>
>> http://www.msdignition.com/ignition_1_5900.htm
>>
>> More precisely, it was installed when the truck failed the test and not
>> installed when it passed, but I don't think it had anything to do with
>> the failure. The non-functioning EGR system definitely played the major
>> role, IMO. I unconnected the MSD unit for the retest because I thought
>> that perhaps the more powerful and longer duration spark it supplied
>> might be contributing to the hot combustion chamber conditions that
>> caused the high NOx reading.
>
> Again, hot combustion chambers do not contribute to NOx formation.
> Hotter combustion does contribute to NOx formation.
> Hottest combustion typically occurs if the mixture is 2 percent
> richer than stoichiometric.

Right... I went and re-read what you wrote about it in your first post.

>
>>> Without an air pump diluting the sample a stoichiometric air/fuel
>>> ratio would read .5% CO and .5% O2 give or take .1% either way.
>> So the truck has an air pump, and given what we have hashed through here
>> so far, I feel that, just to be sure, I should replace the plugs, wires,
>> cap and rotor before concerning myself with the jets or the float level,
>> even if I think they are in good shape.
>
> It's cheap enough to do on that engine.
> My hunch however is that the carb is a little lean.

I feel certain that the reasoning for this must be in one of your past
posts. It appears counterintuitive at first glance, though... a richer
mix to lower HCs at the tailpipe.

Would you suggest bigger main jets or a higher float?

Mike suggested leaning out the idle mixture screws to get lower HCs.

At this point I am a bit more knowledgeable, but not quite sure what to
do with it. What I need is tailpipe emissions wand like the one at the
shop so i can monitor the changes that take place for a given tweak.

>
>> BTW, do you happen to know if plug wires can *lose* resistance over time?
>
> Outside of leaking insulation, I can't say I've ever seen it in
> 37 years in the trade. The typical failure that would account
> for high HCs would be an open plug wire.
>
>> I hope all is well in your part of the world.
>
> Ask me again tomorrow 8-) they're forecasting 8-14 inches of snow
> for our area. We've already had over 100 inches this season
> though most of it had melted in the last two weeks.
>
> Good wrenching and let us know the results.

Will do, and thanks for all the input.

"aarcuda69062" > wrote in message
...
> In article >,
> "Mike" > wrote:
>
>> "Simpson" > wrote in message
>> ...
>> > aarcuda69062 wrote:
>> >> In article > ,
>> >> Simpson > wrote:
>> >>
>> >>> This would explain the low vacuum at the EGR port. The lack of EGR
>> >>> function, plus the vacuum leak, which would cause a lean condition,
>> >>> would
>> >>> combine to create a higher than normal temperature in the combustion
>> >>> chamber resulting in the abnormally high NO readings.
>> >>
>> >> Not to nit pick but lean air fuel mixtures don't burn hotter. They burn
>> >> slower which causes associated component temperatures to rise. Lean
>> >> doesn't cause higher NOx, the extra O2 in the exhaust from a lean
>> >> mixture
>> >> makes the reduction bed of a 3 way catalyst less efficient resulting in
>> >> higher NOx at the tail pipe.
>> >
>> >
>> > Nit picking appreciated! It's always valuable to learn more precisely
>> > what
>> > is going on. It makes perfect sense to me the way that you explained it.
>> > Perhaps you could enlighten me on the effect of ignition timing on
>> > emissions.
>> >
>> > I just got back from passing the smog test after initially failing it.
>> > The
>> > failure was caused by improper vacuum to the EGR valve deom the
>> > carburetor
>> > and a minor manifold vacuum leak. The vacuum being supplied to the EGR
>> > valve
>> > by the Holley 2280 carburetor was insufficient to open the EGR valve,
>> > even
>> > at over 2000rpm. This non-functioning EGR valve and the minor manifold
>> > vacuum leak caused a measurement of over 3600 PPM of NOx. Anything over
>> > 1195
>> > PPM is a failure. Below is the failed test results.
>> >
>> > --------------------
>> > Percent of CO2
>> >
>> > 15mph 1333rpm - 10.8
>> >
>> > 25mph 1309rpm - 10.7
>> > --------------------
>> > Percent of O2
>> >
>> > 15mph 1333rpm - 5.9
>> >
>> > 25mph 1309rpm - 6.0
>> > -------------------
>> > HC PPM
>> >
>> > 15mph 1333rpm - 34 - PASS (maximum allowable is 134)
>> >
>> > 25mph 1309rpm - 26 - PASS (maximum allowable is 106)
>> > -------------------------
>> > Percent of CO
>> >
>> > 15mph 1333rpm - 0.01 - PASS (maximum allowable is 0.90%)
>> >
>> > 25mph 1309rpm - 0.01 - PASS (maximum allowable is 1.14%)
>> > --------------------------------------------------------
>> > NOx PPM
>> >
>> > 15mph 1333rpm - 3641 - GROSS POLLUTER (maximum allowable is 1095)
>> >
>> > 25mph 1309rpm - 3225 - GROSS POLLUTER (maximum allowable is 1140)
>> > -----------------------------------------------------------------
>> >
>> > After failing the test, I checked the action of the EGR valve and found
>> > the
>> > condition I described above. After correcting the condition I took the
>> > truck
>> > back and passed the test with the following results.
>> >
>> > --------------------
>> > Percent of CO2
>> >
>> > 15mph 1333rpm - 10.4
>> >
>> > 25mph 1309rpm - 10.7
>> > --------------------
>> > Percent of O2
>> >
>> > 15mph 1333rpm - 6.7
>> >
>> > 25mph 1309rpm - 6.1
>> > -------------------
>> > HC PPM
>> >
>> > *15mph 1333rpm - 132 - PASS (maximum allowable is 134)*
>> >
>> > 25mph 1309rpm - 65 - PASS (maximum allowable is 106)
>> > -------------------------
>> > Percent of CO
>> >
>> > 15mph 1333rpm - 0.01 - PASS (maximum allowable is 0.90%)
>> >
>> > 25mph 1309rpm - 0.04 - PASS (maximum allowable is 1.14%)
>> > --------------------------------------------------------
>> > NOx PPM
>> >
>> > 15mph 1333rpm - 626 - PASS (maximum allowable is 1095)
>> >
>> > 25mph 1309rpm - 606 - PASS (maximum allowable is 1140)
>> > ------------------------------------------------------
>> >
>> > I'm a bit concerned that the truck passed the 15mph test for HC by only 2
>> > PPM. I would like to try to lower the HCs from the tailpipe. The
>> > catalytic
>> > converter is a brand new replacement. Would changing the ignition timing
>> > lower the HC reading? Or changing the air fuel ratio through either
>> > resizing
>> > the main jets or adjusting the float level? The ignition timing is
>> > currently
>> > set at 7 degrees BTDC with the vacuum line disconnected from the
>> > transducer
>> > at the computer, as per the shop manual.
>> >
>> > The carb is a new (not rebuilt) Holley 2280. It is the non-feedback
>> > version
>> > of the Holley 6280 that came stock with this 87 Dakota V6. The mixture
>> > control solenoid for the Holley 6280 is no longer available as a
>> > replacement
>> > part so I tracked down a new 2280 on eBay and bolted it on. This
>> > configuration no longer benefits from the input from the O2 sensor, but
>> > it
>> > was the best I could do on short notice.
>> >
>> > The way I see it I have three main ways to lower HCs:
>> >
>> > 1. Advance or retard the ignition timing
>> >
>> > 2. Enrich or lean out the fuel mixture by increasing or decreasing the
>> > size
>> > of the main jets in the carb.
>> >
>> > 3. Enrich or lean out the fuel mixture by raising or lowering the level
>> > of
>> > fuel in the bowl via the float setting, which is currently stock.
>> >
>> > From the test results, I have more room to increase NOx than HCs so if
>> > lowering HCs cause NOX to rise, there is some headroom there.
>> >
>> > Please feel free to nitpick away. It would go unappreciated.
>> >
>> > Jack
>>
>> I don't know why your HC's went up just from fixing an inop EGR valve ?
>
> Why wouldn't the HCs increase? When the exhaust gas
> recirculation valve opens, what is it allowing into the intake
> manifold/ combustion chamber?
> CO2, CO, O2, NOx and HC.

Yep, the EGR valve allows exhaust gas back into the combustion chamber, but,
it is only a very small percentage of the total combution chamber volume. The
exhaust gas was already burnt once in the combustion chamber, how does running
it through the combustion chamber a second time cause the HC to increase even
further ? Isn't the HC reading from the smog test unburned hydrocarbons ?

>
> When the exhaust gas recirculation valve opens what happens to
> manifold pressure?
> It goes up.
> What does the power valve do when manifold pressure goes up?
> It opens and allows more HC (gasoline) to flow into the venturi
> in the carb.

Yep, that's how the power enrichment works as well but why such a jump in
HC ? This is the first time I remember seeing a NOx problem fixed were the HC
reading jumped up like that. Does this have anything to do with the vehicle
being equiped with an air pump ? We don't see too many air pumps on the east
coast.

In article > ,
Simpson > wrote:

> From the manual:
>
> CABLE RESISTANCE CHART
>
> Minimum---------------------Maximum
> 250 Ohms Per Inch 600 Ohms Per Inch

Okay, if Chrysler says so.

> > Again, hot combustion chambers do not contribute to NOx formation.
> > Hotter combustion does contribute to NOx formation.
> > Hottest combustion typically occurs if the mixture is 2 percent
> > richer than stoichiometric.
>
> Right... I went and re-read what you wrote about it in your first post.
>
> >
> >>> Without an air pump diluting the sample a stoichiometric air/fuel
> >>> ratio would read .5% CO and .5% O2 give or take .1% either way.
> >> So the truck has an air pump, and given what we have hashed through here
> >> so far, I feel that, just to be sure, I should replace the plugs, wires,
> >> cap and rotor before concerning myself with the jets or the float level,
> >> even if I think they are in good shape.
> >
> > It's cheap enough to do on that engine.
> > My hunch however is that the carb is a little lean.
>
> I feel certain that the reasoning for this must be in one of your past
> posts. It appears counterintuitive at first glance, though... a richer
> mix to lower HCs at the tailpipe.

When a cylinder gets lean enough it begins to misfire and HC goes
up. The whole thing is a teeter totter balancing act.

> Would you suggest bigger main jets or a higher float?

I'd play with the main jets. A higher float can cause other not
so desirable results. (like dripping upon shut down)

> Mike suggested leaning out the idle mixture screws to get lower HCs.

Both of you should look at the chart on the first page of this PDF

http://www.autoshop101.com/forms/h56.pdf

See what I mean about teeter totter?

Which side of the bold black line is your high HC on?

Then look at the chart on page 2, pay attention to where O2 and
CO converge at stoichiometric, like I said earlier, .5% give or
take tenth.

Mike is certain that your high HC is because the mix is rich,
based upon -what- I have no idea since your gas numbers are
skewed by the false air from the air pump.
I'm saying that I "suspect" that it's actually too lean, maybe in
part because I thought you had mentioned that the plugs were
white.

> At this point I am a bit more knowledgeable, but not quite sure what to
> do with it. What I need is tailpipe emissions wand like the one at the
> shop so i can monitor the changes that take place for a given tweak.

http://www.autologicco.com/AllProduc...htm#GasPortabl
e
(sorry about the line wrap)

This is (IMHO) the best deal out there.

Mike Romain wrote:
> Simpson wrote:
>> Does anyone have any idea how much vacuum should develop at an EGR port
>> on a carburetor with the engine revved to about 2000rpm?
>>
>> I installed a brand spanking new Holley 2280 carburetor on my 87 Dodge
>> Dakota V6 engine and failed the NO part of the California smog test. The
>> HC and CO tests passed well below average. I came back home and checked
>> the action on the EGR valve. No movement on the visible piston when the
>> engine was revved.
>>
>> The EGR valve checked out okay when tested. It opened with less than 10
>> inches of vacuum and stayed open indefinitely. The Coolant Vacuum Switch
>> Cold Closed (CVSCC) is operating correctly. The vacuum hoses involved
>> are all in good shape, no leaks.
>>
>> I checked the vacuum at the EGR port on the brand spanking new
>> carburetor and only got about 1 or 2 inches of vacuum at about 2000 rpm.
>>
>> Manifold vacuum is 19 inches at a 700rpm idle.
>>
>> What gives?
>>
>
> I don't know that particular carb, but have seen that kind of failure
> before. When I saw it it was a gasket in wrong or the wrong one in so a
> notch in the base plate was covered when it was supposed to be open.
>
> The other times I have seen the base plate in upside down. There are
> notches in some that need to be on the carb side, not the manifold side
> and if folks don't know this, the plate can be in wrong.
>
> I would figure the port you are using was blocked or it would have one
> or the other types of vacuum.


>
> Mike
> 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
> 'New' frame in the works for '08. Some Canadian Bush Trip and Build
> Photos: http://mikeromainjeeptrips.shutterfly.com


Mike,

I just popped the top off the carb and removed the boost venturi to get
at the area around the throttle plates. The barrel that has the
designated EGR port has a perforation just above the closed throttle
plate just as I expected. When I attach a hose to the designated EGR
port I can blow air through the perforation. When I plug up the
perforation inside the venturi with my finger, the air flow stops. This
is the case with the other barrel that has the designated spark vacuum
port. The only difference between the two seems to be the relative size
of the venturi perforations, the EGR side being slightly smaller and the
height relative to the closed throttle plate.


three hours later... I just got back from ripping the carb out of its
moorings and teraing it down and comparing it with the old original.
Same body - different porting. I cut a new slot for the EGR port and
widened the holes that feed the canister purge line into the the venturi
just above the throttle plates, both mods to conform to the original.

The new carb also differed from the original through a hole in the
gasket that connects the throttle body to the main body. This hole in
the gasket on the new carb connected the EGR hole in the throttle body
just above the throttle plate in one barrel to a hole in the base of the
venturi. The original carb did not have this hole in the gasket or the
hole in the base of the venturi, so I flipped the gasket to put the hole
on the other side where nothing is happening and the hole is not
connecting anything to anything.

I am about to go out now and take it for a test drive to see what
happens after it warms up and the EGR circuit kicks in. I have a vacuum
meter teed into the vacuum line to the EGR valve so I should be able to
see if the mod works like the original. If not, I will negate that
particular mod in some fashion and go back to running the EGR valve from
the park vacuum port, which is what got me passed smog.

It's a frikken obsession, but I bought this truck new and I refuse to
let it die for want of a replacement mixture control solenoid.

Thanks Chrysler.

Thanks Holley.

Way to stand behind your products.

In article >, "Mike" >
wrote:

> > Why wouldn't the HCs increase? When the exhaust gas
> > recirculation valve opens, what is it allowing into the intake
> > manifold/ combustion chamber?
> > CO2, CO, O2, NOx and HC.
>
> Yep, the EGR valve allows exhaust gas back into the combustion chamber,
> but,
> it is only a very small percentage of the total combution chamber volume.

So? If the air fuel mixture is lean to begin with, how does adding
exhaust gas make the flame propagate better?

> The exhaust gas was already burnt once in the combustion chamber, how does
> running
> it through the combustion chamber a second time cause the HC to increase even
> further ?

See above.

> Isn't the HC reading from the smog test unburned hydrocarbons ?

Yes it is.
Ever open an EGR valve at idle?
Did the engine run better or worse?
Do you suppose HC goes up or down if you open the EGR at idle?

> >
> > When the exhaust gas recirculation valve opens what happens to
> > manifold pressure?
> > It goes up.
> > What does the power valve do when manifold pressure goes up?
> > It opens and allows more HC (gasoline) to flow into the venturi
> > in the carb.
>
> Yep, that's how the power enrichment works as well but why such a jump in
> HC ? This is the first time I remember seeing a NOx problem fixed were the
> HC reading jumped up like that.

Not for me.
It's very common on some engines to repair a non functioning EGR for a
NOx failure and have the car fail on HC. Typical 4 cylinder where the
EGR feeds into the intake ports individually (4 separate EGR passages)
and 2 or 3 are plugged. The 1 or 2 that do flow EGR are over fed and
cause a misfire. Roto-Root the passages and everything is fine...

> Does this have anything to do with the vehicle
> being equiped with an air pump ?

The high HC? Maybe yes, maybe no. That's why there's a thing called
'diagnostics.' I'd watch the reading with the air pump disabled.
The OP has a 21 year old truck, what are the odds hat the air pump is
original? I couldn't get the air pump on my bought new 85 F-150 to last
more than three years.
Air pumps tend to have a generic universal design, what if instead of a
4 CFM air pump made for a 3.9 liter engine, he got a 10 CFM replacement
pump made for a 7.4 liter engine.
You -can- pump too much air into a catalytic converter and snuff out the
fire.

> We don't see too many air pumps on the east
> coast.

Dunno why, they were pretty common in the day that the OPs truck was
built.
Now they're likely to be electric.

aarcuda69062 wrote:
> In article > ,
> Simpson > wrote:
>
>> From the manual:
>>
>> CABLE RESISTANCE CHART
>>
>> Minimum---------------------Maximum
>> 250 Ohms Per Inch 600 Ohms Per Inch
>
> Okay, if Chrysler says so.
>
>>> Again, hot combustion chambers do not contribute to NOx formation.
>>> Hotter combustion does contribute to NOx formation.
>>> Hottest combustion typically occurs if the mixture is 2 percent
>>> richer than stoichiometric.
>> Right... I went and re-read what you wrote about it in your first post.
>>
>>>>> Without an air pump diluting the sample a stoichiometric air/fuel
>>>>> ratio would read .5% CO and .5% O2 give or take .1% either way.
>>>> So the truck has an air pump, and given what we have hashed through here
>>>> so far, I feel that, just to be sure, I should replace the plugs, wires,
>>>> cap and rotor before concerning myself with the jets or the float level,
>>>> even if I think they are in good shape.
>>> It's cheap enough to do on that engine.
>>> My hunch however is that the carb is a little lean.
>> I feel certain that the reasoning for this must be in one of your past
>> posts. It appears counterintuitive at first glance, though... a richer
>> mix to lower HCs at the tailpipe.
>
> When a cylinder gets lean enough it begins to misfire and HC goes
> up. The whole thing is a teeter totter balancing act.

I just got back from modding the carb. See my last reply to Mike.

While I had the carb off, I removed the limiter caps and will try
readjusting the idle mixture screws as I have a rough idle. Apparently,
this truck has always idled rough, from what I hear and read. The HCs on
the successful test at 15mph test are double those at 25mph test - 132
to 65. The engine rpms for both tests reads virtually the same, though,
which is a mystery. But that mystery aside, I would guess that the idle
circuit plays more of a part in the fuel mixture at 15mph than at 25mph
and this transmission will go all day in third gear at 15 mph. Anyway,
what I guess I'm trying to say is that I will try riching up the idle
circuit first. Being as it would cost me up to 30 bucks for a dry run on
the dynamometer, I want to try everything that I can to get the ideal
adjustments lined for a try.

>
>> Would you suggest bigger main jets or a higher float?
>
> I'd play with the main jets. A higher float can cause other not
> so desirable results. (like dripping upon shut down)

I have some smaller jets from the old carb that worked in conjunction
with the mixture control solenoid. I hear that it's not always a good
idea to drill out jets because the shape of the jets is important to the
flow of the fuel, but is it always a bad idea?

I guess I should mention again that the carb that I put on this 3.9L
(239 cu) V6 was designed for a 318 from the early seventies. It probably
was designed for a Lean Burn system as it had a throttle position sensor
on it, which I took off, as this 87 Dakota is not a Lean Burn system, I
don't think. Anyway, there was no throttle position sensor on the
original carb, so off it came from the new one.

In any case, this 2280 Holley that was used on the 318 V8 is the same
body and capacity as the 6280 that came original on the 239 V6, so I am
assuming that it can be tweaked to run the 239 just fine.

>
>> Mike suggested leaning out the idle mixture screws to get lower HCs.
>
> Both of you should look at the chart on the first page of this PDF
>
> http://www.autoshop101.com/forms/h56.pdf


Wow, love it! Thanks for posting that!


>
> See what I mean about teeter totter?
>
> Which side of the bold black line is your high HC on?

The 15mph test, 132 PPM, is on the left, but the HC line on the graph
does not come down to 65 PPM, which was the result of the 25mph test.

>
> Then look at the chart on page 2, pay attention to where O2 and
> CO converge at stoichiometric, like I said earlier, .5% give or
> take tenth.
>
> Mike is certain that your high HC is because the mix is rich,
> based upon -what- I have no idea since your gas numbers are
> skewed by the false air from the air pump.
> I'm saying that I "suspect" that it's actually too lean, maybe in
> part because I thought you had mentioned that the plugs were
> white.

I will pay this the attention it deserves after I get back from a test
drive, or maybe tomorrow morning after a big mug of tea

>
>> At this point I am a bit more knowledgeable, but not quite sure what to
>> do with it. What I need is tailpipe emissions wand like the one at the
>> shop so i can monitor the changes that take place for a given tweak.
>
> http://www.autologicco.com/AllProduc...htm#GasPortabl
> e
> (sorry about the line wrap)

Not a problem.

>
> This is (IMHO) the best deal out there.

Yeow! Prices are on the high side for shade tree mechanic.

Simpson wrote:
> Mike Romain wrote:
>> Simpson wrote:.
>>> The way I see it I have three main ways to lower HCs:
>>>
>>
>> One more way, a fresh oil change using conventional oil.
>>
>> High HC's can come from oil getting past the rings also so a really
>> thin oil or old oil that goes 'thin' can bump them up.
>
> Oil is fresh and the rings seem to be in good shape. I can go all the
> way between oil changes at 3,000 miles without having to add a quart. I
> bought it new and changed oil and filter fairly regularly.

Mine has read high HC's with a lean miss on mine once.

>>
>> Mike
>> 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
>> 'New' frame in the works for '08. Some Canadian Bush Trip and Build
>> Photos: http://mikeromainjeeptrips.shutterfly.com

aarcuda69062 wrote:
>
>
> When a cylinder gets lean enough it begins to misfire and HC goes
> up. The whole thing is a teeter totter balancing act.

I have had that happen to mine once.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
'New' frame in the works for '08. Some Canadian Bush Trip and Build
Photos: http://mikeromainjeeptrips.shutterfly.com