Tuning help?

[moparchris]

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

I read this a few times and I am going to repeat what I understand your problem to be. From what I read you state that your Runner has a bog when the throttle is opened from idle with the car in gear. If this statement is true then you have an accelerator pump issue (the device that squirts fuel down the throat of the carb when the throttle plate is opened). Timing can help it, but in the end the accelerator pump is either too rich or too lean.

As far as setting the timing. First do like George said and buy a $10 timing tape and stick it to the balancer. Then disconnect the line to the vacuum advance and plug the port on the carb. Put your timing light (non-adjustable) on and shine it on the balancer with the engine running in nuetral. Then bring engine speed up till the timing quits advancing. If its a Mopar distributor it will be around 5000rpm. Take note of the total timing in degrees off the timing tape when its stops. Lets say its at 40 degrees at 5k and 15degrees at idle. I would then take 4 degrees out at idle to make it 11 degrees. Then rev it up again and see where the total timing is at. You will need to do this a few times to get it where you want it. Be careful of moving parts as 5k is a lot of rpm to have your face a few inches from the motor. I hope this gives you some helpful info. I can clarify on some things if you need to. I hope I dont step on any toes as there has been a lot of good advice given by the knowledgable board members here.

I have no idea how to fix your accelerator pump problems, I am not familiar with Edelbrocks. Carters on the other hand, well I am having my own problems. :facepalm:

 

[a6t9vette]

Thanks for all the help guys, no offence to retarding (I've heard all the terms before but never put them into application so im trying to get it right)... Im a mechanical engineer so anything mechanical im usually good to go, and have no problem ripping anything apart and getting it back together, but when it comes to tuning from the seat of my pants, or ears, etc I just dont have the experience. So now once I learn this I'll be good to go.

I didnt get to do any work on the car yesterday as I ended up doing landscaping all day. Hopefully I will get some time today, and I plan to do the following:

1) set car to 5Deg +/- 2Deg BTDC (per Mopar Performance Dist. instructions), with hose disconnected, and port on carb plugged. Im going to assume this is result in me needing to reduce the amout of timing I have now, as if i rememeber correctly I was at about 11 Deg BTDC as a result of having 38Deg Total timing.

2) Test Drive

3) Adjust Accelerator pump. The carb Im using has a rod that connects to the pump with three holes, factory setting is to the center hole and one move either side of center will either increase or decrease the stroke and therefor the "squirt". I need to move one hole closer to the carb body to increase.

4) Test Drive

5) If good increase Total timing ~2 Degrees and Test drive again.

6) use propane to check for intake leak.

7) Scrach my head some more......

Thanks Bob

 

[69hemibeep]

The accelerator pumps on these carbs as you said have three holes for the duration of the pump. They will also be effected by low fuel bowl level which I doubt is the problem, and if memory serves me there is a replaceable jet below the pump in the fuel bowl. They are a simple carb by removing the choke and pump linkage and all the top screws the top comes off exposing the jets. The metering rods will be hanging down at this point(warning) do not try to put the top back on before you loosen the two screws above the metering rods and swing the little caps to the side to allow the rods to come up. You don't have to remove them just let the springs push them up. If you try to replace the lid without doing this chances are you will bend a metering rod. Refer to how to buy a Hemi RR cheap, the previous owner of mine did this. When the top is screwed back down the metering rods will go in with a little wiggle. Try the three holes first if you believe its the carb, then the jet which you will have to either get a strip kit which has jets and metering rods or find a shop with jets. I wish I were there I work on these in the field all the time when we go jeeping

 

[Big John]

Good advice here!

One question I have is if the vacuum advance is attached to the correct port. It should go to whatever port has venturi vacuum and not manifold vacuum. Venturi vacuum increases with engine speed (air flow through the venturi) and manifold vacuum decreases with throttle opening.

 

[69hemibeep]

Good advice here!

One question I have is if the vacuum advance is attached to the correct port. It should go to whatever port has venturi vacuum and not manifold vacuum. Venturi vacuum increases with engine speed (air flow through the venturi) and manifold vacuum decreases with throttle opening.

As John says here, the vacuum to the dist will come off the left side of the carb plug the other. Also I just took mine apart, there is no jet to the pump inside. OOPS so much for memory serves

 

[a6t9vette]

Ive actually tried both sides of the Carb and have read contradicting remarks on which side to go, I will go back to the passanger side and start from there.

 

[moparchris]

Good advice here!

One question I have is if the vacuum advance is attached to the correct port. It should go to whatever port has venturi vacuum and not manifold vacuum. Venturi vacuum increases with engine speed (air flow through the venturi) and manifold vacuum decreases with throttle opening.

As John says here, the vacuum to the dist will come off the left side of the carb plug the other. Also I just took mine apart, there is no jet to the pump inside. OOPS so much for memory serves

Hey Bob, your memory is correct on my AVS on my Runner. It has a jet that looks like a check valve. I am having fits with mine right now, I am not going to hi jack this thread so I think I will start a new one.

On another note, is the squirter nozzle for the accelerator pump replaceable like a holley? Just a thought.

 

[69hemibeep]

Good advice here!

One question I have is if the vacuum advance is attached to the correct port. It should go to whatever port has venturi vacuum and not manifold vacuum. Venturi vacuum increases with engine speed (air flow through the venturi) and manifold vacuum decreases with throttle opening.

As John says here, the vacuum to the dist will come off the left side of the carb plug the other. Also I just took mine apart, there is no jet to the pump inside. OOPS so much for memory serves

Hey Bob, your memory is correct on my AVS on my Runner. It has a jet that looks like a check valve. I am having fits with mine right now, I am not going to hi jack this thread so I think I will start a new one.

On another note, is the squirter nozzle for the accelerator pump replaceable like a holley? Just a thought.

The squirters are but Ive never had to change one :yesnod:

 

[a6t9vette]

Well after several different timing settings, and several more rounds of carb adjustments (no part swaps, just adjustments), each of which required a test drive (my neighbors really love me now), I went out one last time and at the top of my driveway she cut out on me and couldnt get it started. On closer inspection there was no fuel squirting into the carb so after some pushing I got her back to the garage....

So I turned my attention to the fuel filter, which was a new canister piece from Year One (I was getting other stuff so shiping was already paid for, so it was worth the price). I swapped it out with a clear glass filter so I could see what was going on. The way I had it installed the filter was vertical and after several minutes of cranking I could only get the glass cylinder half full, but couldnt really see the center of the filter, but there was no way fuel was getting to the carb. Pulled the non-vented cap off the gas tank, no change (the tank is only a few years old, and I cleaned out the lines and vent last fall). So off came the fuel pump. My wife agreed to run to the parts store for me (mainly to get away from the screaming kids for a bit), but they didnt have one. So I pushed the car back in the garage and will have a new pump tomorrow. Im hoping it was just limping along and might be the cause of many if not all of my problems. Hopefully I will get a few test drives in before its too late tomorrow.... To be continued....

 

[Basketcase]

just throwing my :cents: in, when I was having my running troubles, we found several weak lifters. the timing chain was off a tooth or two. It rattled worse than cold diesel. after we changed the lifters and set the chain right, it took the rattle away. but was a dog. just for shits and giggles, and by chance( after we pulled the electronic iginition off, we swapped the MSD coil for an old stocker. Ran great. It wasn't backfiring or anything like you'd expect, just ran lousey. different coil and made a world of difference.