Ever since I had the transmission out this spring to install a new valve body and torque converter I have been pulling my hair out trying to get this car to run right. I even took it to a transmission shop to have the kick down cable adjusted, as I couldn't make the thing shift the way I thought it should; big waste of money... Chalk that up to going to school.

A few days ago I decided to remove the carburetor for the millionth time this year to redrill the throttle plates 1/64" larger to see if idle quality would improve. I have not been able to get this engine to respond to the 1 1/2 turns out idle screw setting, I end up at 3 turns or so out, and a real loping idle at 600 rpm in gear on the ragged edge of stalling. Park idle is fairly smooth at 1000 rpms. The larger holes made in gear idle lope too much, causing a lot of stalling, and a higher Park idle did not help, but only exacerbated a flat spot when applying more throttle..

Yesterday off with the Holley 390 one more time, soldered up the holes, redrilled them to a smaller 3/32", and torqued the damn thing back down, I hope, for the last time for a while. Spent a long time adjusting the idle mixtrue screws with the aid if a vacuum gauge to obtain the highest reading possible. Still out about 3 turns, but engine responds to their turning more now. Got an in park idle of 1000 rpm, and in gear loping 600 rpm without stalling, however the engine tends to wander up & down in rpm about 50 rpm from the 1000, or 600 which has me scratching my head a bit.

Previous to this latest round of carburetor play, she would only kick down if traveling below 38 to 40 mph after mashing the accelerator for a second or two, in other words real slow response, sometimes no down shift at all... Now she will kick down at 50 mph almost instantaneously and shift at WOT at 4000 rpm as before, and hold in gear longer with light throttle before up shifting in all gears. Other than getting the carburetor dialed in better, I did not change the kick down cable adjustment. Whatever happened, the car is so much more responsive, and I'm happier.

Any hints on getting rid of the rolling rpm? Would a GM HEI up grade over the orange box help this condition?

_________________
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 have made the same mistake by letting too much air in. Glad you soldered it back up and re-drilled. It is better to have them back at the 1/8th size hole, then your mixture screw would be about 2 turns instead of 3.

What is your timing set at now?

What vacuum canister are you running?

What year distributor are you running?

What governor is in it?

Does your governor have the adjustable spring posts?

How stiff is the primary spring?

If you have the adjustable posts, shorten he throw on the primary side to keep the spring tight. Change to a medium (red tension) spring to keep that weight pulled in.

Use the ported vacuum for the advance and unscrew the can at least 3 turns out maybe 4 to keep it from engaging at park idle.

That will settle the idle down. Watch it with the timing light and make sure it stays steady. If not, unscrew the pod some more. Let us know how it goes........

That mystery cam is just making tuning a little more difficult!

_________________
Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

Hi Ted, Thanks for your input.

I went up through the drill sizes and backed off from 1/8" to 7/64" to 3/32" in May; then this week up to 7/64" and back to 3/32". I noticed that the 7/64 hole I drilled in this latest round was egged out a wee bit due to a real crappy 40 year old 1/4 drill motor I was using. The new 3/32" holes are more consistent thanks to the proper reading glasses added into the mix.

Timing is set at about +14*. Timing tab reads -10* to 0 to +10* so any higher than 10 is an eyeballed guess. I have tried to back it off a few degrees, but the distributor clamp tends to walk on a few extra degrees when being tightened. I may have to pull it out and address the uneven surfaces in order to better control the setting.

Vacuum canister is 7-R. I don't recall seeing any adjustment provision in it**.

I don't know the year of manufacture of distributor, tag reads:
0 m 22-9,
3690788

Mechanical governor is 11-R non adjustable.

Running short red spring, and long loop black spring. When I got the car it only had one spring, red, and the timing fluttered up and down. After adding the black spring the timing settled down.

I have ported vacuum that doesn't kick in until mid teens rpm. In other words my throttle plates are closed down so that only about 0.025" or a bit less of the vertical slot is showing below the throttle plates well below the ported vacuum hole.

I am getting some back spin when shutting down the engine when hot, but no pinging on the road, so I know the timing is advanced a bit too much, back to that distributor clamp mess. If I retard it to say +8*, where I can clamp her down with out walking, idle drops way down in P, and won't idle in gear with out stalling.

** I just looked through some "Dutra info" I down loaded 2/08 showing how the vacuum can is adjusted. I don't know if my unit has that capability, and if it dose how to figure out its present setting. Any hints on this are welcome.

_________________
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

"Back spin" is too high of an idle, 3 turns on the idle screws is scarey. My brain says vac leak.

I hate Holley's, I never learned how to work on them. We used to joke about them and say, "the way you rebuild them is throw them over your shoulder and get a new one."

What will this thing spin to if you manually shift it? My little Duster will spin easily to 5200. It is a shorter stroke 198. Stock cam. Max power according to the dyno was 4200 to 4400.

_________________
'72 Duster 198 stock cam, 3:23's Hookers on jack stands for 8 years in the driveway
'79 Maxivan 360 Offy Qjet Comp RV cam/rusting in the driveway.
93 D350 160HP Cummins Auto Dually Clubcab needs a injector pump
2005 Golden Couch Buick

Rug_Trucker: Spins easily to 5000 rpm with no ignition brake down, haven't wound it past that. I don't want to blow it up, don't know how strong the lower end is, or if it has been balanced etc. In auto mode she shifts to next gear at 4000 rpm. I have a self imposed redline of 4500.

There maybe some vacuum loss from the secondary's not having a positive close, or what feels like a loose seal on the bench. I have backed off the secondary throttle plate stop screw to get them to bottom out & stay put which helped. Mounted on the car & running, the secondary's feel seated with no play. Aside from that I don't think I have any more vacuum leaks. All the mating surfaces of the head & manifold were dressed at the machine shop this spring, and show no leaks. Earlier this year I discovered the carburetor base was warped, and fixed that problem which made a great improvement in idle quality. All the plugs have same correct color, so mixture is real close.

This car has an unknown hotter than stock cam. At 1000 rpm with a fairly smooth idle I pull 12" to 13" Hg, in gear with pronounced lope at 600 rpm fluttering needle between 0 and 8" hg, above 1800 rpm 15 to 16" hg.

_________________
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

Hot cams don't like low rpm what-so-ever... with my 280/270 erson I tossed any notion of idling below 900 rpm out the window... if your cam has tight lobe separation like in the 104-108 range and it is a hot cam the needle will bounce on the vacc. gauge and the carb will hunt as it trys to compensate for that pulse during overlap. Complicating the issue is the vacc. advance on the dizzy will alos be moderating your timing based on
the vacc. reading so if it's bouncing 12, then 8 then 10 then 6... unless the vacc. pod has been dialed to be all in at a range that these numbers don't affect your plugs are firing at odd points...if you are running strictly on mech advance then you'll have to set the idle where it's going to be happiest to make it behave in traffic (1200 rpm is about the ragged edge before being into the transition circuit on the carb...)

-D.Idiot

I have a trick,instead of drilling the throttle plates,use a PCV valve off a larger engine,like a 400,or 440.They have larger air bleeds in them.I have a 390 on my S/6 too,I'm having trouble getting the pump shot right.

_________________
V8?? We don't need no stink'n V8!!

wjajr,
Take a 3/32 allen wrench and put in the distributor hose snout until it engages into the socket head. Once it is engaged turn it clockwise, (screw it in) until it stops. Count the turns. That will give you a base line. All the way in will make the pod engage at the lowest vacuum. You don't want that with this cam. You want the pod to come in later so it doesn't affect your idle quality. No extra vacuum advance at idle.

The 73-78 or so electronic ignition distributors have adjustable spring posts so you can fine tune the tension on the springs. You don't want the vacuum advance prematurely kicking in or a mechanical advance weight coming out to soon throwing off your idle. That will just compound your carb tuning issues. It sounds like that was happening until you put the black secondary spring on. That is the problem I am trying to address. You need to be sure that your not getting any extra mechanical advance at idle.

Once your sure both vacuum advance and mechanical advance are out of the picture, then you can focus on dialing in the carb.

I agree with Rug_Trucker that you would be better off with a Carter AVS or the new Edelbrock version with this cam. Those carbs are almost stupid proof.....both of us have found them to be allot more forgiving.
I don't think this cam will ever be a high mileage cam. The street version 390 is designed to be a high mileage carb.
They may not be a perfect match!
You may want to consider the new 500 AVS. It is a bolt on and go carb! They are very nice and will probably solve are your headaches. At least you will be able to get some consistent cruising in before the summer is over.
However, if you don't get frustrated or mind fine tuning and have lots of time, you may make the 390 acceptable.

_________________
Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

Ted,

I conducted a vacuum advance port study just moments ago:

At in "park" idle of 1000 rpm zero inches of Hg.
1600 rpm needle just moves off of zero
2000 rpm 6" Hg.
2300 rpm 11" Hg.
2800 rpm 15" Hg.
3000 rpm 17"Hg.

Also checked initial timing at 1000 rpm and it was "guessing with calibrated eyeball" 18* Higher than I had set it. I than dialed it back to +10* @ 1000 rpm, and by the time I got the distributer secured it had inched up to +13*. Went for a little test drive, engine now stumbles off of idle with light foot, and still back pedals when shut off.
I wonder if I'm getting some mechanical advance from a too weak small spring. Also, could a sloppy timing chain be contributing to the kayos? How would one test for these conditions?

I'm going to have to pull the distributor and get rid of that notch the clamp likes so well so I can get a setting to stay put. While it is out I'll inspect for binding parts.
!

I'm getting 18 to 20 mpg on 200 mile trips, around town I have no clue, but it is less.

I'll skip the new carburetor for now, and keep on keeping on untill I get it. This war now. Becides, I rather blow the 300 bucks on a Firm Feel PS box first...

_________________
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

wjajr,

Well it sounds like your close on the tuning. You might do what I did and add a few more 10 degree marks on the damper with by filing in a notch or using some white pin striping. Just turn the damper by hand from zero to 10 and add a notch. I add 3 or 4 so I could see where the timing was going. Kind of a poor mans way of avoiding to buy a dial back timing light. The one I was using went on the fritz...
Once you have the extra notches painted white you can very the rpms and see if the chain has any slop by looking to see if the timing is wavering much. Unplug the advance first so you can just watch for chain slop and depending on the rpm when the mechanical advance is kicking in.

What is your rear end ratio? Looks like the ported timing is not that big of a factor at idle. If you cruise at 3000 rpm you got it made..... I cruise at 2500 rpm with a 2.76 so tuning has to be spot on.

_________________
Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

Rear end ratio is 3.55:1. I run 2600 to 3000 rpm around here on secondary two lane roads. New England has low speed limits compared to the rest of the civilized world on these roads; 45 to 55 mph, UGH!, and only 65 in the interstate.

I just pulled the distributor, inspected the moving parts all seam to be functioning as they should with no slop, and enough lube. I did give my big spring a good look, and it has a dark green tint to it, I had thought it was black. I don't know if this makes any difference or not.

Also the vacuum can was out 1 1/4 th. turns from full in. Any advice on this setting?

I dressed with a file, the two fingered distributor clamp, so each digit makes good equal contact on the hold down plate, and I'm on my way to reinstall the distributor...

I'll make some additional notches on the damper, and see what happens.

_________________
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

Hey wjajr,

Did you set your secondary idle screw to spec, or have you played with it to get the primary plates in the right position? I had to play games with the secondary idle setting to make the primary idle circuit work right on the 390 and 600 Holley. Once it was set, everything worked OK.

A tip in case you hadn't run across it:
Use a machine bolt in place of the screw to keep from having to pull the carb off to adjust the secondary idle screw.
Are you running a plate secondary, a conversion secondary metering block, or a 4150 four corner system? I can't remember.

I second finding a Carter or Edelbrock to avoid all the messing around the Holley requires. A change in weather can mess up a Holley's state of tune. Having primary metering rods and an air valve really cleans up the process. I will not go back to the Holley for a NA build.
The Carter or Edelbrock AVS variants would be a very nice way to go.
While metering rods and other hardware like jets and shooters will interchange from the Carter to the Edelbrock and vice-versa, the primary metering springs are a different length. This may affect the enrichment tip in point for the primary circuit. The length difference isn't much, so may not cause you problems.



CJ

_________________
Part of Tyrde-Browne Racing

Hey Ceej,
Had secondary throttle plated stop set to spec, then messed with it to let in more air before drilling, set it back to spec., messed some more with it, and now it is close to spec. however I haven't put a feeler gauge to it lately.
Good idea, the one I dislike is the high idle stop bolt... PIA to adjust with an electric choke after that first cold start.

No new carburetors for this cheep bastard yet.

Ted,

I got the distributor installed, still likes to inch up the timing as one tightens the hold down, but was able to get it set to +12* initial. Drummel tool made some mighty fine notches on the damper to fill with White Out.

Now at 1000 rpm in park, she has more pronounced lope than when timing was set at 18* or so at same rpm. In gear she drops to about 600 rpm just barely running with a nasty lope. At times it will drop to 450 rpm, and one can count the power strokes at that speed.

Using the additional markings It looks as if full advance is around +43* at 2800 rpm. I did not change the vacuum can setting yet. Mechanical looks to be 15 or 16 degrees.

Oh oh, got to go down river to a cook out at 6pm. No more car fun for me tonight...

_________________
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

wjajr,
Good work......
What number is stamped on the vacuum pod arm? That will dictate where to set it.....

_________________
Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

Ted: R-7

_________________
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