Troubleshooting the Tuning of My 440

[HeavyFuel]

My engine has a CH4B on it now, and a manual choke.  I also jetted up a couple sizes on the primaries and secondaries.

The engine runs like crap now when pulling away from a stop.  Great response when I'm at about 25 mph or higher...when jabbing the throttle, I'm getting good pump shots, and the engine responds fast.

Thoughts:

1.  I have the manual choke adjusted so that when it's opened, it's opened ALL THE WAY.   Like the primary butterfly is totally vertical.  Is that too far, and the carb is going lean when I start out?  Should the choke be adjusted so that it butterfly opens just to a certain point, then the throttle opens it further when the motor needs it?

2.  The carb idle mixture is the same now as it was before the jet change.  Does that matter....does the mixture need to be re-adjusted?

3.  Does an intake swap effect the manifold vacuum?  And if so, do I need to re-adjust the vacuum advance on the dizzy  to pick up a little more advance, or maybe add in a little more initial?

4. Too much jet?  They were stock sizes before, and from what I've gathered, jetting up is usually necessary to help compensate for today's lousy fuel.

5. I had a 1/2 carb spacer on top of the CH4B last week, but removed it last night becasue of hood clearance issues.  It drove better with it on.  Why is that, or is my mind likely playing tricks on me?





Thankfully I can always go back to total factory stock where it ran halfway decent.


This is very frustrating.....help would be greatly appreciated.  

[John_Kunkel]

Choke should be wide open when engine is warmed up...if closing it a little increases performance the carb is too lean.

Contrary to popular belief, the idle mixture screws affect fuel delivery throughout the rpm range...IOW, the idle mixture feeds even at WOT.

Intake swap shouldn't affect vacuum much unless it causes a vacuum leak.

Changing jets without a before/after comparison is never a good idea, the guys who design carbs know about the modern fuel.

If it drove better with the spacer I'd say the carb is too rich.

[HeavyFuel]

Choke should be wide open when engine is warmed up...if closing it a little increases performance the carb is too lean.

Contrary to popular belief, the idle mixture screws affect fuel delivery throughout the rpm range...IOW, the idle mixture feeds even at WOT.

Okay...I'll recheck the idle mixtrue

Intake swap shouldn't affect vacuum much unless it causes a vacuum leak.

I'll check my vacuum with a gauge

Changing jets without a before/after comparison is never a good idea, the guys who design carbs know about the modern fuel.

 I have the original 4429 on there

If it drove better with the spacer I'd say the carb is too rich.

So I'll come down one jet size and see if that works.  I wish the Carter metering rods were available.      

I'll start trying/reversing one thing at a time to see if I can get it to run decent.

My brother thinks that I've dicked with this stuff so much that the obvious solution is to get a new carb and a modern distro.  He might be right.

[firefighter3931]

HF,

Like John said...it's not a good idea to change too many things at once. The spacer was adding plenum volume and you removed it at the same time as you increased jetting. The CH4B has a little more plenum vs a stock manifold but not that much more to accomodate the 2 size increase in jet.

Manifold vacuum should be pretty close because both intakes are dual plane.

The choke flap should be adjusted to wide open with the choke fully deployed. It sounds like you got that part right.  

I'd step back to the previous jetting and readjust the idle mixture to max vacuum on your vacuum guage. The fuel curve appears to be too rich and i bet your plugs will start to show evidence of this. A rich fuel curve will slow the car down significantly.


Ron

[HeavyFuel]

Thanks Ron and John.

I'll start with the jets and report back with results.   


My wife asked the other day..."Don't you ever get tired of working on that thing?"


"Never!"  (as long as I'm making progress)

[HeavyFuel]

Okay.

OEM spec jets are back in.  

Adjusted the idle mixture to highest vacuum......didn't seem precise as far as how many turns to go to get best vacuum.  Ended up about 4 turns out, at 16 hg.   The vac needle wasn't steady, it wiggled quickly with about 1/2 hg variance.

Ran a little better.  Still a pretty good bog off idle.

Checked the timing.   At 680 rpm it was at 14*.   All in at 2300 rpm at 32-33*.

That seemed a little low, so I bumped it up to 36* total.

Engine started a lot better, idled better, just sounds better with a few degrees more advance.   I wasn't able to get on it too much to check for pinging, but I've been down this road before...there will be some detonation.  That's why it was low.  

Right now I'd say the engine ran better a week ago when it had iron manifold and the original choke, original jets, crossover blocked.  The choke didn't work very well, so I decided to punch holes in the valley pan, and that's where the domino effect started and all of the other changes.

Could be the carb and dizzy are worn out.  

If I can't get this straight...it's going back to all stock with the crossover open.  That's the looking like the best option so far.

[fy469rtse]

Or upgrade to a firecore distributor , and oh no ! She called it a thing ,
Post what you want out of engine , could be that stock size cam isn't up to your goals,

[firefighter3931]

HF,

How about a rundown of the engine combination....can't remember all of the details ? 

Carb/cam/compression/exhaust manifolds/headers etc...


Ron

[HeavyFuel]

Pretty much a stock '68 440 HP....well sorta.


Stock Carter 4429s (freshened up a couple times.....stock jets. Metering rods: not stock but not sure how far off)

CH4B intake

Factory rebuild on entire engine
 stock for '69 6-pak MP cam
 stock compression as far as I know

Stock iron HP exhaust manifolds

*EDIT*  TTI  2.5" exhaust.  

X-pipe

Magna- flows

MP electronic Dizzy (modded to only allow 20* mech advance) with orange box.  Vac advance in use....ported.

Electronic voltage regulator

Good plugs...NGK XR5

Accel 8140 HV Coil

Resto plug wires (this may be a weak link)

4 pin ballast

Stock '68 unsilenced air cleaner cover


Stock 727 auto, 3.23 rear end, sure grip.



Car was A/C from factory, I left it off....so it has a carb for A/C car.....does that matter?


I'm not looking for the engine to be super awesome, just to run well.  Never been able to get it to spin the tires.   The go-fast pedal has never been to the floor (not from launch).....I can't get it to run that well.


I'm gonna hit up my son to use his GoPro, and post some start and run videos.

[firefighter3931]

In theory that carb sould work pretty well with the rest of the engine build 

Something is wrong if you can't break the tires loose. That beast should lay 30 feet of rubber....easily ! 

I'm thinking you have an ignition system issue. Time to do some digging 

Pull the #1 plug out and ground it to the exhaust manifold while cranking the engine over. We need to see what the spark quality looks like. Ideally you want to see a blue/white spark...if you're seeing an orange/yellow spark it's showing excessive resistance in the ignition system. 

Next, test the ignition wires with your ohm meter. You should have less than 250 ohms/ft of resistance.

Check the ground to your ECU....a poorly grounded box will make the engine run bad.

A word of caution : The new orange boxes are junk.....lots of failures reported since they moved production off-shore several years back. Those crap boxes pull timing out of the ignition system at higher rpm and rob power 

The carb itself may be a problem but i would start with the ignition system first then move on to fuel delivery.

Nick went through this very same thing awhile back and ended up replacing the old worn out factory carb resulting in huge performance gains.

http://www.dodgecharger.com/forum/index.php/topic,108795.0.html



Ron

[HeavyFuel]

Thanks, Ron.

I'll get to work.  



(the orange box is from 1992-ish.  that's when I originally bought the conversion kit.)

[HeavyFuel]

Alrighty...


Checked the ECU ground...it's gotta be good now.  I have a special ground wire just for it.    


Started pulling plugs.     This is probably a contributor to the problem.   With the intake crossover being blocked until last week, the divorced choke wasn't functioning very well.  Additionally, I read the the first set of plugs after a rebuild might get bad because it takes a while for the oil system to get settled.

The plugs are cleaned and re-installed.  

Reset the idle mixture screws back to where they were when the engine was running better.  Brought the initial timing back down to 14*.

The accel pump shot just seems to be nagging me, so I rechecked the length of shot.  It seemed a bit short, so I bent the connecting rod to give it a longer stroke.  

The wires and spark will be checked when I can get someone over to help.

Raining like cats and dogs today (what does that mean anyway?) so no test drive yet.  But starts and idles pretty well.    

[firefighter3931]

 Dang, those plugs look nasty !!! 

A choke that stays on too long will shit up the plugs. A weak ignition system will also do the same thing.

Try leaning out the idle mixture and see if that helps. 

It'll be interesting to see how much resistance those ignition wires have. 



Ron

[HeavyFuel]

Went on a test drive yesterday morning....about 20 miles of town and highway.  Running pretty nice.  Got home, seemed like the base idle was a little fast.  Checked it....right at 750 rpm   (dash tach said 1100...   )

Let 'er cool down a little and treated the motor to fresh Brad Penn green oil.  Went out for another drive last night with my other half.  Feeling good.

I have to say, the car feels like it runs better than it ever has.  That damn pump shot and the choke were probably the culprits.


But another question: My metering rods are the ones to go with the tall jets.  Only I've installed the short jets, the modern Eddy ones.  I'm thinking mixing the two together is a no-no.      Think I gotta locate some longer rods.  (that's what SHE said...  )  

Or, the flat cover from the AFB could be used, which effectively lowers the rod into the jet.  But that might necessitate a spring change..and if so, to what size (color)?    

[firefighter3931]

That sounds better  Just keep an eye on those plugs 

Not much experience with the AFB tuning so i'm no help there....sorry 


Ron

[HeavyFuel]

That sounds better   Just keep an eye on those plugs  

Not much experience with the AFB tuning so i'm no help there....sorry  


Ron

Oh, yeah Ron, I forgot to mention what #1 looked like after the 20 mile run.  It looked textbook.  Nice, clean, just a little bit of a greyish tan on the insulator, tip and prong.

My carb is an AVS....I'm gonna try the AFB plate because it's flat and not cupped.  That will hold the rod lower during the lowest vacuum periods.

[firefighter3931]

Oh, yeah Ron, I forgot to mention what #1 looked like after the 20 mile run.  It looked textbook.  Nice, clean, just a little bit of a greyish tan on the insulator, tip and prong.

My carb is an AVS....I'm gonna try the AFB plate because it's flat and not cupped.  That will hold the rod lower during the lowest vacuum periods.

Very good news on the plug reading 

Hopefully the issue is solved other than some carb tweaking 



Ron

[Nickrc3]

The carb itself may be a problem but i would start with the ignition system first then move on to fuel delivery.

Nick went through this very same thing awhile back and ended up replacing the old worn out factory carb resulting in huge performance gains.

http://www.dodgecharger.com/forum/index.php/topic,108795.0.html

Yup, thanks to Ron's recommendation, best thing I've done to my 69' was remove the original AVS carb, spray it with Marvel Mystery Oil and store inside a sealed bag. Replaced with a 750 DP ProForm. It completely transformed engine behavior.
Better starting characteristics, outstanding transition throughout RPM range, tunable, and most importantly, full instantaneous acceleration to 5600 RPM's.

[HeavyFuel]

Tested the plug wires tonight.

Resistance ended up being about 7k per foot.  Sounds high.  

Who makes good plug wires that will fit in the factory wire trees?

[Stegs]

im going to keep watching this thread

I basically have the same issue


If I mash the gas on my 69 with a 440HP, it will break the tires loose for maybe a couple feet. Its a dog at idle, very hesitant to want to move, but once it gets going it seems to scoot right along...but I feel Im in the same boat

[HeavyFuel]

My carb is an AVS....I'm gonna try the AFB plate because it's flat and not cupped.  That will hold the rod lower during the lowest vacuum periods.

Got the new OEM spec two-step rods installed (.062 cruise/.052 power) and fabbed a flat cover out of some scrap aluminum till I can get a set of originals from an AFB.

Still seems to run a little boggy from a stop with the factory rods/jets....maybe a little lean.     The operating temp has climbed a bit, sitting at about 200* when cruising around town.

Once the car is moving above about 15 mph, the engine seems to run great, but still not a ton of power.

I might order a few sets of smaller rods, and experiment a little.......and new plug wires!

[firefighter3931]

Tested the plug wires tonight.

Resistance ended up being about 7k per foot.  Sounds high.  

Who makes good plug wires that will fit in the factory wire trees?

HF,

7K per ft is waaaay high.  

The FireCore 8mm Factory Fit wires are 250/ft and are an exact copy of the OEM wireset. Designed to look stock and be routed exactly as the factory did it back in the day using the OEM wire looms  

PM me if you're interested in a set  


Ron

[HeavyFuel]

Got the new Firecore 7mm 250 installed.   (Super nice product)    Also picked up a pair of AFB flat metering rod covers from a local guy that had about 15 old AFBs on the shelf, and put those on the carb.

Don't think I picked up a ton of 'power' with the plug wire swap, but man, it seems to run better.  They were the icing on the cake, with all of the other changes that I've done recently, the off idle bog is pretty much gone.  

I can't stand on the pedal from a dead stop, but the car has perfectly normal street manners now.  

Gonna keep chasing the potential that this engine should have.  I've got a new coil and ignition box on the way.  Maybe a distro or carb swap is next.

[don duick]

I think there is one important item that has been overlooked. I read you have 2 1/4 exhaust ? these pipes are choking your motor. I have a similar setup to yours and had 2 1/4 exhaust and then changed to 2 1/2 and noticed a big improvement. I also have headers.
you also mentioned you had a carb spacer, was it an open spacer or 4 hole?

[HeavyFuel]

Just double checked my TTI order....it is 2.5"  

The carb spacer was open.  It's off the intake now.



Tonight I installed a new coil.   OEM.   It has a higher primary and secondary resistance than the super stocker.

Now...the engine temps are hotter than they've ever been.  Weird.  Like, I was running about 210* during the drive tonight.  (I did top off the coolant level in the radiator before leaving, but that shouldn't make it run hotter.)

Air temps were around 80*.

The car is running probably better than it has since it's gotten back together, but why so hot now?  Does the coil and plug wire change make it more efficient (more complete combustion) so it's running lean, and therefore hotter?    

It ran cooler when it was running lousy and fouling the crap out of the plugs.  

I'll pull a plug tomorrow and see what it looks like.