Tuning help?

[a6t9vette]

Ok now that I have everything back together from my engine compartment re-do im having trouble getting the car to run right.... Im about running out of options to check and starting to get frustrated....

Current issue is there is a major stumble/bog/hesistation when I stomp on it, in some cases almost wants to stall, after that stumble it picks up like id expect it to and runs good. With no load the car runs great.

set-up:
"Stock" 383 with; stock heads, Cast Manifolds, Edlebrock DP4B intake, New Edlebrock 1406 Performer Carb (600cfm) (did similar with the older carb that I just replaced), MP electronic Ignition w/Orange Box, New plugs, new wires, new fuel filter.....

Timing is set at 38 Deg total (per MP Ingition instructions), ~11 Degrees advanced at idle. Im running the vaccum line to the lower vac port on the carb (full time vaccum). I have tried to adjust the accelerator pump on the car both ways, to either add or remove additional fuel on initial acceleration but that hasnt helped, since im not really sure if its getting too much fuel or not enough under this condition. Im doubting I have any lines that are collapsing, since its almost instant its not so much doing it once the bowls are empty.

I have tried moving the vaccum line to the other port on the carb with no help. Im starting to think that this could be more of a timing thing now as I belive I have chased down all the fuel avenues, but to be honest im not real up on timing set up. So im looking for some advice on what to try for timing, or for any other suggestions. Thanks

 

[BBillyC]

May or may not be any help to you but I set mine up with 46 degrees total at 2500 rpm. It seems to like it there. Is there a possibility of an IT manifold leak? What cam are you running? You say that the engine runs fine under no load, so what is pulling the engine down when you are under load thereby dropping your advance on the timing back. What are you running for tranny and gears?

 

[69hemibeep]

When you look at your idle timing is your vacuum line plugged off

 

[george68hemirr]

IT SOUNDS LIKE YOU ARE STARVING FOR FUEL.....the old carb did the same......i think you can adjust the fuel bowls with the metering rods......the timing seems to be too much.....should be 34/36 total timing......does it start hard??

 

[a6t9vette]

I hope its not an Intake manifold leak, and dont see and evidence of it externally (everything is newly painted etc, but I will re torque now that the engine has been through a few heat cycles.

When I set the timing at 38 it was at about 2500 rpm, with both smaller ports on the carb plugged, other big port still connneted to the PCV valve, I didnt plug the port on the distributer, just left the hose loose after removing from the carb.

Im not sure of the cam as I didnt swap it and dont have any data on if if was ever swapped by the previous owners.

As far as drive line its a 727, with 3.91 Suregrip. I adjusted the "kick down" and it feels that that is working well, as it was out of wack after the intake swap.

Is there a chance that timing could be causing this, meaning is this a possible symptom of a improperly set timing or am I wasting my time playing with it, if so what should I be looking/listening for?

"i think you can adjust the fuel bowls with the metering rods" You saying to swap out the metering rods or is there a way to adjust?

"does it start hard", no it starts up fine....

 

[69hemibeep]

You could take a little timing out of it and see if it cleans up, it depends on how the cam is installed, But I'm starting to think its lean like George mentioned

 

[george68hemirr]

i am not familiar with those carbs...maybe google up that carb for instructions on adjusting them......adjusting the total timing hold the timing lite pointing it at the make and bring the rpms up till you see no further advance ....then you can set your distributor.....intake leak....thats possible......do you have a propane soldering torch.....if so with the engine running turn on the propane{dont lite it] and point it to the bolts and gaskets on the intake and if the engine rpms increase you have a intake leak.....good luck

 

[a6t9vette]

George, can you elaborate on your timing remark? "adjusting the total timing hold the timing lite pointing it at the make and bring the rpms up till you see no further advance ....then you can set your distributor".

What I was doing (keep in mind im a newbie when it comes to this stuff). Start the engine, unplug advance hose from carb and plug port on carb, bring engine to 2500, with light set on 38 degrees I adjusted the distributer until the mark on the balancer and tag was at 0.
Out of curiousity I let the car go back to idle and adjusted to light till the mark again was at 0, and the light read 11. I will try to play with the timing, possible up or down as im hearing 34-36 as well as 46, but is there an issue with my method?

When I got the car running I had set it set to 5 Degrees below per the instructions, where it ran ok in the driveway, they i moved to their "performance tuning" which had me adjust to 38 like I mentioned....

 

[george68hemirr]

you have the marker on the engine and where the 0 is top dead center.....on you damper which is bolted to you crankshaft find the timing marks 34 degrees or 36.....mark it with a dab of with paint or soapstone....when you run up your rpms you will align the o- top dead center mark with the 36 degree mark by moving the distributor then snug down the distributor....then recheck after snug to see if its right on the money

 

[a6t9vette]

I guess Im just doing it slightly different since my damper only has the one mark on it, and the tab off timing chain cover only has +10 +5 0 -5 -10 marks on it, so I needed to use a light with an advance adjuster on it. So I set that knob at 38 and adjusted till the mark on the damper was inline with the 0 on the tab. Im assuming that would be the same as finding say 38, 36, 34 etc and putting a mark on the damper and then brining it to 0 at rpm?

 

[george68hemirr]

I guess Im just doing it slightly different since my damper only has the one mark on it, and the tab off timing chain cover only has +10 +5 0 -5 -10 marks on it, so I needed to use a light with an advance adjuster on it. So I set that knob at 38 and adjusted till the mark on the damper was inline with the 0 on the tab. Im assuming that would be the same as finding say 38, 36, 34 etc and putting a mark on the damper and then brining it to 0 at rpm?[/qu


IF THE DAMPER ONLY HAS 1 MARK ON IT .....THAT WOULD BE 0= TOP DEAD CENTER.....YOU WOULD NEED TO INSTALL TIMING TAPE[HAS TIMING DEGREES ON IT] WHICH MOPAR PERFORMANCE SELLS AND STICK IT ON TO DO TOTAL TIMING....YOU WOULD ALIGN YOUR ONE MARK ON YOUR DAMPER WITH THE ZERO MARK ON THE TIMING TAPE OR MEASURE IT FROM THE TAPE AND MAKE A MARK ON YOU DAMPER

 

[69hemibeep]

Did this thing have that bog when it was at factory settings?

 

[a6t9vette]

by factory setting if you mean when I set it to 5 deg below TDC, I never drove it like this, just used it as a point to get the car running, as the instructions recommeded doing the other adjustments before testing the car....

 

[69hemibeep]

by factory setting if you mean when I set it to 5 deg below TDC, I never drove it like this, just used it as a point to get the car running, as the instructions recommeded doing the other adjustments before testing the car....

Should be 5 before TDC or advanced 5. I would try it and that will let you know if its the carb. You will have more torque at this setting and if it bogs its the carb. :cents:

 

[george68hemirr]

by factory setting if you mean when I set it to 5 deg below TDC, I never drove it like this, just used it as a point to get the car running, as the instructions recommeded doing the other adjustments before testing the car....

Should be 5 before TDC or advanced 5. I would try it and that will let you know if its the carb. You will have more torque at this setting and if it bogs its the carb. :cents:

YES I AGREE WITH THIS...TRY WHAT BOB SAID

 

[a6t9vette]

You say "Should be 5 before TDC or advanced 5" To make sure I have my lingo correct, is 5 Deg before TDC the same as 5 Deg advanced, i.e. its firing 5 degrees ahead/below/before TDC? If thats true what do you call when you are 5 deg after TDC?

 

[dutchrunner]

I had same problem with my 383 . When we changed the accelator pump lever(more juice)and squirter it was gone.( sorry for any in correct spelling).

 

[ACME A12]

You say "Should be 5 before TDC or advanced 5" To make sure I have my lingo correct, is 5 Deg before TDC the same as 5 Deg advanced, i.e. its firing 5 degrees ahead/below/before TDC?

Exact Same Thing.

If thats true what do you call when you are 5 deg after TDC?

The Chinese call this "Someting Wong"...

 

[droptop]

Set the timing to where the car starts and runs best, then start working on the carb...... bog=lean

 

[69hemibeep]

You say "Should be 5 before TDC or advanced 5" To make sure I have my lingo correct, is 5 Deg before TDC the same as 5 Deg advanced, i.e. its firing 5 degrees ahead/below/before TDC? If thats true what do you call when you are 5 deg after TDC?

I'm not being a smart azz, when you move your timing back its called retarding it. You shouldn't be after TDC,you want to be to the left of 0 or TDC. As your engine rotates clockwise and your timing mark moves counter clockwise, you are advancing your timing. This is when your looking at the front of the car. You said your kind of new to this and not knowing you or your knowledge base, I hope this helps and doesn't offend you