I'm back to the tuning kabooky dance.

On a 130 mile trip north on I-95 showed a lean condition under slight throttle opening to maintain constant speed on level or very slight up hill running at around 65 mph, or 3250 rpm, something that does not occur at mid to low 2000 rpm range. The A/F gauge would drop the lean scale and when throttle was close flip to rich condition. Current jetting is 512, PV 5. I don't know exctly what vacuum level is at 3200 rpm on flat or slight up hill ground somewhere around 13 to 16" Hg. Off of throttle it pulls 19 inch Hg at 3000 rpm. At 1000 rpm idle it pulls 13" Hg, and in gear 10" Hg. Once above 1300 or 1400 rpm mechanical advance kicks in and vacuum jumps to 16 - 17" Hg.

Engine has OCG 346 grind 15* over lap and a bit of lop below 900 rpm.

I suspect around town and low speed to 40 mph or under 2500 rpm the transition and idle circuit are the major players. Out on the road traveling at 65 mph, pushing more air the main jets supply the greater amount of fuel. I have 53 and 54 jets on hand. and no power valves above 5.0.

When I got back home I pulled the plugs for a look-see. All were very light to white except #2; that one looked just right.


I think a re-jet to 54, and a 7.5 PV and or a 8.5 PV. What do you thing about that?

_________________
67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

A 3 jet size jump seems reasonable enough. The stock PV is a 65 so I'd be inclined to try that if I had it on hand. Also make sure the float level is not low.
Since I have never tuned or owned an 8007 I am waving my normal $.02 fee.

_________________
“Buy the ticket, take the ride.”
― Hunter S. Thompson

I'd try a 65 PV to start and then change jets if that doesn't do what you want. 3 jet sizes is a lot, go 1 or 2 and test.

_________________
Official Cookie and Mater Tormentor.

To do proper carb tuning you should install a vacc gauge in the cab...that's a mandatory gauge in my vehicles and will tell you a lot about what is going on...
attach to the nipple under the primary bowl, this will give you an idea of what is happening at the throttle plates, and their position...
That isn't necessary unless you have a vacuum leak, throttle plates closed and under load should return to 19-20"...that being said...if
during this maneuver you get popping ("shooting ducks") then your idle circuit is lean and can't cover the added airflow past the plates
(on a manual car, using a dash pot to slow the closing of the plates to keep it in the transition circuit until the load decreases)
That's not a good reading...it means that the engine combination needs more rpm at idle to have peak vacuum... having done
the carb shuffle, you won't use much more gas setting the idle at 1000 in gear instead of letting it drag down to 650-800rpm in gear...
Given the symptoms, it sounds like the secondary plates aren't opening to give proper enrichment under higher load...
I would have set the carb up to be 52 primary, 54 secondary in a metering block (if you are using the stock secondary plate it needs to go).
Set the PV back to 6.5 to start with.... Use a black secondary spring to test the primary mix, then switch to purple and see
if the secondaries engage in a timely fashion, go to tall yellow if they need to come in sooner.... this is similar in nature to
the calibrations for my sons Aspen (although his PV is set for 8.5 because of idle in gear is 15-16").


Now...with all that being said there are some other considerations that have not been brought up in your previous posts...
that you may want to play with before going off and changing jets, blocks, springs, PVs, etc...)

If you have a fair amount of compression and cam, your carb may be too small and the throttle plates and bleeds won't be
anywhere near where your engine would like them to be... I know my 10:1+ builds like the 600 cfm holley at base throttle
plate positions better than where the 390's plates have to be set to have reasonable air for idle... the sad part, is Holley
really sucks with mid range carb cfm selection (390 OK, 600+ OK... no 500cfm...and the 450 gets the same mileage as the 600
so why bother). This may help with setting the idle rpm lower.

One of the reasons the 500 cfm AFB is popular, is it works for the mod to hipo range of slant builds... where
street economy may be desired for street/strip builds, but need the extra cfm for the strip...

Another area you may check before going through the agony to change everything, is to plug your hi-speed air bleeds (on the 8007
the idle air bleeds are already plugged...)...putting a piece of wire into the bleed then running the length over the airhorn and securing it
with some rtv or glue...or make them long enough to tie to the air cleaner stud or sandwich under the air cleaner base lip).

This will lower the rpm that the mains come on line...I plugged mine by putting a dab of vaseline over the bleed hole,
then covering with a cap of RTV...that way you can you can easily reverse it using a knife and some carb cleaner. The result of completely
capping it, will be the main jets will come on at 1800-2000 rpm instead of 2500...this can help get more gas sooner when under load at say the 45mph +
range where you are almost near highway speeds but not quite, but don't need to be in the transition circuit... (On my 600...I use a standard paperclip
to partially block the high speed bleeds...the orifice is huge...)



As always be empirical and qualitative in nature, only make one change at a time, test, and see if the result works or not...in this case you may have a
few things that will overlap in nature (higher primary and secondary jetting, PV change, secondary spring tuning, high speed air bleed mod). You may find
that main jetting may not need to be increased as much if the PV comes in sooner, but you don't want to have the secondaries opened all the time either
as that will tank your mileage...


Good Luck (and 98 cents for a whole bucks worth of time under the hood...)

DI,

Later today I'll use my extended hose vacuum gauge that sits nicely on top of the dash and get some actual numbers at specific rpm. Before posting this 0-8007 Tune topic I had made a run rigged with vacuum gauge, but did not have clip board to scribble numbers while driving; another case for not trusting the old noggin.

My engine has 9.6:1 compression and is 0.040" over. I do notice it seems lazy off the line until rpm builds, and can hear and feel when secondaries open. I did not occur to me that the secondaries may have been cracking open while rolling down the interstate the other day. It did not feel like they were opening, but that would defiantly cause a lean out without that boost of power in the seat of the pants. Yesterday both float levels were checked, and secondary bowl was found to be a little low, and was adjusted.

Previous driving before rebuild, on steep hills the secondaries would open causing acceleration while trying to maintain consent speed, and backing off would cause them to close, and repeat the process. It feels like the accelerator is attached to a rubber band with engine surging with steady throttle.

During the drive on 95 there was none of that rubber band surge than no surge, just the A/F gauge would go off scale to lean, and speed stayed constant.

After the rebuild, and brake-in I did notice #'s 4, 5, & 6 plugs were much lighter than the front three of which the A/F meter is reading, and until now never considered secondaries cracking open just enough to lean out the back three cylinders. I have the lightest spring installed, as the engine always has and still does feel restricted taking off to when secondaries open around mid to late 3K rpm range while running on primaries. When primaries fully open under WOT there is a noticeable surge in power. No flat spot, just goes from a lazy pull to more power as if one was rapidly opening a valve. Carb has stock secondary plate

So perhaps a 600 cfm Holley or 500 cfm AFB replacement may be my best bet. This 390 is old, a relic from the early 90's when car was turned into a drag queen, has some slop in primary throttle shaft bushings, and about 90K miles on it.

I'll be back with more empirical data later today.

_________________
67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

Data gathering completed.

Called Oregon Cam Grinders to see what recommended idle rpm range is for their 346 profile, answer; I don't know... Big Help

Long yellow secondary spring installed:
Idle in gear:
650 rpm 8"Hg quivering needle
850 rpm 12"Hg with slight quivering needle
1000 rpm - 1200 rpm 12"Hg steady needle

Idle out of gear:
850rpm 12"Hg
1000 rpm 14"hg
1200 rpm 15" Hg
1500 rpm 16.5" Hg Mechanical advance is adding timing at this rpm


Car under way on flat to slight up hill grade:
1500 rpm 14"Hg to 12" Hg
2000 rpm 16"g to 12" Hg goes lean off the dial
2500 rpm no data
3000 rpm 18 to 14"Hg lean off the dial

Climbing hill steady throttle opening

1500 rpm no data
2000 rpm 10"-8" Hg lean off the dial
2500 rpm no data
3000 rpm no data


Black Spring installed:
Flat or slight up hill grade

1500 rpm no data
2000 rpm 13"Hg rich
2500 rpm no data
3000 rpm 13-12 lean to ideal

When off the throttle, the second green light is lit through out the above rpm range. Probably need to lean out idle circuit some. I set the idle mixture shortly after the rebuild when engine was real tight. My method is to read o2 sensor voltage with VOM, and vacuum.

Black Spring in stalled up hill grade

1500 rpm no data
2000 rpm 8"Hg lean note power valve is 5.0
3000 rpm no data


We have 30 & 40 mph speed limits around here so 2000 rpm is a common speed. I 395 speed limmit is 65, has only slight elevation changes at around 2% grade. We are a few 100 feet or less above sea level. Other roads are too jammed up with summer people heading back to the city this week to mess around collecting data. After all Maine is called Vacation land.

The last time I set the base timing it was dialed back from 16* to 12* to lessen back spin when shutting down engine. The last time I checked there was just a square of transition slot showing at idle. I regulated idle speed by adjusting timing.

As previously listed, main jets are 512, PV 5.0

In the past I have drilled the throttle plates to get it to idle better, currently those holes are soldered up.

Running on just primary's car has same take off feel, but gets weak out on the interstate over 65 mph

The air bleeds on the old 390 look to be plugged.

looks as if I need to lean out transition circuit, and fatten up main jets. So my next step will be to lean out idle mixture if possible by turning mixture screws, if that dog won't hunt, than I open the drill holes and see what happens, test, and go from there. You are right, most of the around town driving I do is on the transition circuit.

I have a 7.5 PV coming from Summit on Thursday, along with some high zinc motor oil, and carb bowl gaskets just in-case the old ones stick and rip.

One way to get this thing to run right would be to convert to one of the new self learning Fuel injection units. It would be the cheapest up grade to install compared to brake and suspension project this year, and last year's engine & transmission rebuild. LOL

_________________
67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

850 RPM idle at 12" Hg sounds about right for that cam. You might do better with looser valve lash or other tuning. What valve lash? I think I ended up around 0.022"/0.026" to get best idle and performance without clattering.

Lou

_________________
Home of Slant6-powered fun machines since 1988

I followed your advice on loose lash during brake-in to around 1000 miles. There was a lot of clatter, and idle was ok, than I set lash 0.002" looser then cam card recommendation of 0.010" both intake and exhaust, much less noise from valve train now. There is a little loping below 900 rpm, exhaust smells OK, and will idle down to 550 rpm with more lope without stalling.

Yesterday I tried leaning out idle circuit via observing A/F ratio and vacuum gauge, got it to run part in ideal, and rich then it would dip to off the gauge lean, it wasn't happy. Then I tried to add a little more timing above the 12-13* previously set. Wrench retarded distributor the slightest bit while loosening its lock and it killed engine before I could blip the throttle. More frigging around to no good outcome, and I set it all back to where I started. I must say, after reset tone, and a pull on the redneck dyno at the end of my dead end road, she was able to break loose both rear new 235/60 15 tires on clean pavement during power braking. This is something unobtainable in the past, so engine has more grunt, and with secondary black spring installed.

Black spring should prevent opening of secondary’s, but it sounds and feels like secondary’s are opening above 4500 rpm. I haven't tied a twist tie to secondary activation rod to see it they are indeed opening. It’s on the honey-do list after new PV and jets are installed later today.
I'm getting close to purchasing a new carburetor, eleven years of frigging with that 390 are beginning to wear me down. This 390 must have been messed with in some way for drag racing back in the early 90's. Are the Edlebrock Performer and AVS2 carbs less fussy to tune than my 390 Holley, and can they tolerate a non stock cam?

_________________
67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

Where did the summer go? Poof it's gone.

Yesterday I got a chance to remove 512 jet and 6.5 Power valve (which I had thought was a 5.0 PV) replaced them with 53 jet and 7.5 power valve. During level travailing under very slight throttle opening and hill climbing the A/F Gauge now spends a lot of time in Ideal zone where before it would drop off the deep end of lean. ( Yup it's this cheapie) Throttle response is much more crisper now, and engine feels a bit stronger below 2500 rpm. Over 2500 to 3200 rpm A/F gauge hovers on Ideal with slight dip into lean, at which time Power Valve seems to be picking up the slack which makes sense, over 65 mph this brick is pushing a lot of air.

One hard acceleration down an on ramp at WOT it sure feel like the secondaries are opening although be it a slow to come on opening. I have yet to use the twist-tie secondary opening indicator method to confirm said opening.

There will be no testing today, we are partaking of rain bands thrown off by Dorian speeding on its way to NS CA.

_________________
67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

I haven't driven the car much for a while since last test run. I did attach a twist tie to rod from below secondary vacuum actuator on choke side of carb. It did not indicate any retraction of actuator with black spring or short yellow spring. Since installing short yellow spring there have not been driving on interstate to let it run at WOT for a distance into the 4500 rpm range and above; perhaps today I'll get her out.

_________________
67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

I just looked at your lash setting. I run that cam around 0.024" intake and 0.026" exhaust. 0.010" is a total fiction... It sounds like you care tremendously about idle and low/mid range behavior, so opening up the lash will make a big difference.

Lou

_________________
Home of Slant6-powered fun machines since 1988

last post I had decided the secondaries were not opening with black or long yellow spring installed. This had me puzzled for a while, granted I have not spent much time noodling over the situation due to other nagging projects occupying my days of late. When this past Sunday while assisting #1 son on a Chevy PU front brake job, it hit me.

Lets back up here, several months ago, and not a lot of miles ago, several times after a heat-soak or cold start, engine would give a robust lean back fire up through carb when coming off idle to enter traffic. Those back fires were strong enough to jam the choke butterfly tightly closed requiring a hammer to free it... Yup I was the guy with the hood up, bent over a fender blocking the out lane from Harbor Fright with his 52 year bright yellow old boat anchor

Sunday it occurred to me that perhaps the secondary throttle plates could also be jammed closed also due to the above lean problem. Sure enough they were just snug enough that the vacuum diaphragm was unable open them. A fuel injection retro fit is looking better to me all the time.

The lean out problem has been solved turning choke richer and changing power valve to one that activates at a higher vacuum (in other words comes on line sooner, and the going up to 53 jet. That momentary lean spot is gone at low rpm, and lean running when on main jets. Now the idle and transition circuits need to be leaned out they show rich. I think a bit more idle air from the secondary side of carburetor may help that problem.

_________________
67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC