Still having problems

[Rolling_Thunder]

Alright...   Timing is set at a stock TDC on my 383....    stock Resto cam from mopar....     Backfiring still on acceleration....   adjusted the carb every which way and looked at the spark plugs and it looks like it is running rich...    so i ask if anyone can help me because quite frankly I am getting pissed off.  It runs great when it is not under load...  but then the car is moving it is an entirely different story...    any suggestions would be greatly appreciated....     

[RD]

do you have electronic or points?  what kind of carb are you running?  "b" engines love being advanced like 36-38 degrees.  did you clean up the spark plugs before putting them back in? regap? file flat?

[Chryco Psycho]

bad ign wires ?

[Rolling_Thunder]

new set of plug wires...    plugs gapped and cleaned....     electronic ignition....     edelbrock 750....   Cam timing is at TDC as is stock settings....      camshaft is mopar "resto" cam...    running a MP distributor.....     

[RD]

if your missing at top it could be because you are:

• too far advanced
• too retarded (sounds bad, but not a personal shot I assure you hehe )
• ECU is bad or not grounded properly
• Coil is weak

Things I would do first:

Check the ground on the ECU to the firewall to make sure its clean and without corrosion.

Make sure the ECU wiring is connected properly.

Buy a el' cheapo ECU and replace your current one temporarily (or permanently) to see if that cures the problem.

I would ohm test each ignition wire to make sure they test the same.

I would buy another coil and swap yours out to see if there is a difference (you will always need a spare anyways).

Tuning your carb:

with your car running at idle, go ahead and adjust your two idle/mixture screws by turning them (one at a time) clockwise until you hear/see the engine about to stall and die, then turning the idle/mixture screw counter-clockwise 1/4 turn.  Do this for both screws.  You can turn it 3/8ths of a turn to rich'in it up a tad if you run high rpm's or just to make sure you do not lean out.  The only true way to make sure you have a proper fuel/air mixture is to attach O2 sensors and go from there, but this will be approximate.  You can then adjust them later on after your first 50 miles.  I would pull #1 spark plug to see how it looks.  If it is carbonized, lean out the mixture, if it is looking burnt, richin' it a tad (tad = 1/8th of a turn).

hope this helps.  and if anyone knows the wiser, please chime in, even if it is to correct me on something.  Lord knows I do not know it all by far.

[Rolling_Thunder]

thanks alot guys....     Frustrating to say the least....     tomarrow I am tearing the ignition apart and re grounding the modual, "borrowing" a coil to test it, and playing with the carb yet again....    The timing is around where it should be...    so...   i doubt thats the problem...    I will give you all updates tomarrow.

[original72]

also you might look into the 5 and 7 plug wires causing inductance firing.... if they are run parallel then one can pick up enough power thru inductance to cause both to fire.... try running the 7 wire around the back of the engine and see if it helps...

[79JON]

I was gonna say,  check the coil.    And make sure your plug wires aren't cross firing due to being tangled together.   Hopefully you have those plug wire spacers to keep them seperated.

[greenrt_se]

coil. I was a same problem 2 years ago,when motor runnin everything is ok,release the cluth, then 
I chance the coil and everything was ok again

[Rolling_Thunder]

Well i just regrounded the orange box, traced all the wiring, and replaced the coil...     still does it...    any more suggestions ?

[rt green]

make dam sure you have the cam-oil pump gear correct. i had this happen to me once. same symtoms.

[Runner]

check your alernator voltage.  and also check your firewall conectors for corotion. ive been down this road.  mine was an alterator going south.  try it with the headlights on and headlights off and see if the rpm that it happens at changes.

[Rolling_Thunder]

alrighty...    thanks for the suggestions guys...   I'll redo the timing tomarrow...     get it to TDC and the gear points to #1 correct ?

[BigBlackDodge]

alrighty...    thanks for the suggestions guys...   I'll redo the timing tomarrow...     get it to TDC and the gear points to #1 correct ?

Correct....on the compression cycle.

Is it possible that timing marks on the crank and the cam are off by one tooth? I know you can't see them now with the motor closed up but I wonder if there's a way to check if the #1 cylinder is at it's peak when the mark on the crank is at zero??

BBD

[Rolling_Thunder]

well it would be that the balancer ring slipped or this or that...   tomarrow im going to get it to TDC and reset the oil pump gear and go from there...   

[firefighter3931]

RT, pull a plug and ground it to the engine. Crank it over and have a look at the spark. Is it bright blue or dull orange ? Dull orange/yellow means the spark is weak. If the spark is blue then adjust the timing with a vacuum guage. Advance the timing to the maximum vacuum reading then lock the distributor down and take it for a spin. Report back.

Ron

[Rolling_Thunder]

well...    today i reset the oil pump drive gear and now it wont start...      no click, nothing...      turns out my starter magically worked itself loose so...   gotta tighten that thing up - then maybe i can run it some...        Tomarrow is looking really fun...   

[dayclona]

The symptoms you have, sound like you have no vacumm advance?, if you 've removed the rotor, and pulled too hard removeing it, sometimes the advance pin, which is under the plate that holds the point(s)/ transducer, "drops out" giving you the problems you mentioned!,.......simple test , remove the cap, remove the vacumm hose from the carb, suck the hose end hard, while looking at the above mentioned plate , if no movement , advancement,.................bingo investigate................................next up did you replace PVC valve, if so don't assume its OK, plug hose end , test drive?.............................my two cents, hope it helps!


Mike G.

[max]

Well i just regrounded the orange box, traced all the wiring, and replaced the coil...     still does it...    any more suggestions ?

get another ecu, the MP orange boxes had trouble from the factory. i have heard of this problem on other boards and it seems for some reason the boxes were bad from the factory and they would do what you are experiancing.
if that really suprises anyone

btw i ran an extra ground wire from my ecu bolt to the block to be sure i got a good enough ground.

[Rolling_Thunder]

I am not running a PCV valve - just an oil cap and breathers....       i pull the vaccume hose at idle and the timing changes so i assume that the vaccume advance is working in the distributor....       I ran another wire to ground the orange box as well...      is there an definate way to know it is the orange box ?

[Chryco Psycho]

if the timing changes at idle you have the vacuum hooked to manifold vacuum NOT ported vacuum where it should be , you  should have no advance at idle & it should increase with rpm , where it si hooked now it will drop with RPM & retard timing as rpm increases

[Rolling_Thunder]

   So would that be the problem ?   where is there a "ported vacume" fitting ? on my edelbrock there are three ports...   one large on in the center and two smaller ones on either side...    i have the advance hooked up to the driver's side small one.

[firefighter3931]

  So would that be the problem ? 

Yep ! I mistakenly assumed you had the vacuum advance disconnected. I hate those vac cans on performance engines....nothing but problems. I allways disconnect them and tune the advance curve with lots of base timing and a quick curve. 

If you're using ported vacuum then the timing is retarded as soon as the vacuum drops. If you must use it, set the base timing with the vac advance disconnected to ~15* @ idle and try that out. The ported outlet will have no idle vacuum....put your vac guage on the 3 nipples and isolate the one that reads zero at idle....that is the port you should be using.

Ron

[Rolling_Thunder]

figures...      thanks for the help guys....    now only if the damn thing will start....     if this solves the problem im going to kick myself in the ass VERY hard....     

[grouseman]

I was going to delicately ask the same question: are you disconnecting the vacuum advance when you set the timing? 

grouseman

[Rolling_Thunder]

yes i disconnect it...    but if i hook it up to the wrong port maybe that is the problem

[Chryco Psycho]

probably

[tecmopar]

I agree with ff3931, I also never use the vacuum "retard" as I like to call it, but again if you feel you must hook it up, when looking at the ports on the front of the carb, you want to use the higher of the 2. Its only a little higher but you can see the difference, this one is above the throttle blades. Good luck.

[Rolling_Thunder]

OK - heres an update....    Engine backfires still....     Vacuum is hooked up to the correct port (I have tried both ports and disconnecting and plugging ot)  tried adjusting the mixture screws to just about every possible setting, resetted the oil pump drive gear, replaced the coil, made sure the ECU is grounded, timed to 10BTDC, made sure no spark plug wires can be the problem, and the end resut is.....        it still is backfiring.....     Any more suggestions ?   

[69chargeryeehaa]

i had simmilar problems on a 440 in my 69 charger.  start with the timing, i know you've been thru it but hear me out.  i hope you have a advanced timing light, one that you can dial in the advance.  disconect the vacuum advance and plug it, (by the way the ported vacuum port on your carb is the small one on the passenger side, looking at the engine from the front it's the left small one next to the big centre one) set your timing for 10* initial (remember vac is disconnected and plugged), then rev the engine while advancing the light to the tdc, rev until it stops advancing, note the rpm where it start's advancing, it should stop before 3000rpm.  typically, although everyone likes different advances, you should have roughly 20* advance, and it should (for good performance) all come in before 2500rpm.  then connect a vacuum guage to the non ported vac of the carb, check how much vac u have at idle, below 15 inches of vac at idle will make that carb a real pain to tune, trust me i played this game ALOT!!!  then connect the vac advance and rev the engine again and see what your total advance is, you should see about 14*deg of additional advance from the vacuum advance hooked up on the distributor.  if that all checks then focus on the carb.  if the vacuum comes in to early or late it will give you light to mid-throttle issues, at wot (wide open throttle) there is no or low vacuum where the advance does nothing.  to adjust the vacuum advance you insert a 3/32" alen key into the hole of where the vacuum hose connects to the distributor, carefull you don't damage the diaphram.  you can turn it, from memory 1 turn = roughly 2* deg.  once you have the timing all set, and your sure it's ok, your problem is in the carb, i would take it apart and check everything, making sure your jets, metering rods and springs are all stock calabration and go from there, also check the floats, and needle seats, usually back fireing is caused by flodding.  hope this helps.

[firefighter3931]

How do the plugs look....white or black or tan ? Sounds like it's running lean...you might need to jet up. Perhaps the floats are set too low ?

Ron

[tecmopar]

Just how much vacuum does it have, when you connect a vac gauge is it steady or does the needle jump around. Have you done a compression check. This is starting to sound more like an internal problem, stuck ring, bad valve, stuck valve, cam not indexed properly, etc etc, good luck.

[Rolling_Thunder]

Well I am going to take up my weekend tearing apart the carb and changing jets and metering rods       

[69chargeryeehaa]

Well I am going to take up my weekend tearing apart the carb and changing jets and metering rods       

check out this edelbrock manual, i found it really helpfull for understanding what does what, and the charts for jetting:
http://www.edelbrock.com/automotive/eps_intro.html#contents

also you might want to give edelbrock tech dept a call, i found them really helpful:
If you need to speak with an Edelbrock technician by phone, please call 1-800-416-8628 from 7:00am to 5:00pm, Monday-Friday, PST.

don't worry it's free!!! and these guys really know what they're talking about, they even sent me jets, metering rods and springs for free, just sound like a unhappy customer, but concerned with the carb and they will go out of their way to help you if your polite.

[BrianShaughnessy]

   Did anybody bother to check the fuel pressure on this?   Could be one of them super duper carter race pumps that spits out about 9 or 10psi to the carb.   Usually way too rich and the plugs get all fouled out in a hurry. 

[Rolling_Thunder]

well I have the car running alot better now...   now my only problem is slight stumble when i put my foot to the floor...   but It runs...     I set back the initial timing, richened up the mis some, and adjusted the mechanical advance in the distributor...    runs better except like i said - stumble on HARD acceleration....    I think the secondaries might still be leaning out at higher RPM's

[68 RT]

My car did this to with a 750 edelbrock. Changed step up piston springs. Cured the problem. But still ran lean. Ended up changing rods and jets up one step. Buy a tuning kit for your edelbrock. I believe this will solve your stumble.

[69chargeryeehaa]

My car did this to with a 750 edelbrock. Changed step up piston springs. Cured the problem. But still ran lean. Ended up changing rods and jets up one step. Buy a tuning kit for your edelbrock. I believe this will solve your stumble.

i agree