Slow acceleration from stop, suggestions??

[Huicho417]

After messing with the transmission for a while I am starting to see positive results with the shifting. The solution was simpler than I thought, I had to adjust the three part kickdown linkage. I also had the incorrect rod that mounts to the carb stud.
However, my acceleration from stop is not very responsive. A couple of times when I floored the pedal I was able to immediately go and even burn a little rubber. But driving last week and today not the same results. Any suggestions?? The car is a 67 Coronet with 318 and 727 torqueflite. I have converted to a pertronix electronic ignition.

 

[beanhead]

My first thought would be to ask myself, "what did I change/work on last?"... but it's near impossible to diagnose from that post.
Here's some ideas though...Something slipped out of adjustment? Double all check the linkages and attachments again.
Try starting in low and shifting manually and see if it's any different?
Bad batch of gas or carb needs adjusting?
New vacuum leak? All un-used ports plugged like they should be? Has the idle or engine behavior otherwise changed at all?
Plug wire come loose or other ignition problem start happening?
Any tires leaking air, or have the brakes started dragging?
Better air/temperature last time? Engine temp much different between the good and bad results?
Different road surfaces and now you're getting more traction?
Because 318?
(okay okay that last one was a wee bit offsides)

Just start going through the easy stuff first to keep narrowing down the possible suspects.

 

[66 Sat]

Maybe a linkage issue where you are actually starting in 2nd occasionally?

 

[Huicho417]

Well, I can feel it shift from first to second, a little hard on the shift. But I know it is starting from first. The carburetor is a four barrel Edelbrock 1406 I installed and tuned recently with a vacuum gauge. Steady at 22 vacuum and idles at 650 rpm. Tires have the correct psi and brakes are working great. I upgraded to a CPP front disk brake power conversion and rebuilt the rear drum brakes. I have also upgraded to an aluminum radiator so the car runs at 190 degrees on temperature. I have replaced just about everything in the engine with new components with exception of the distributor. I changed to electronic ignition with the pertronix kit, but it’s still the original distributor.

 

[Wietse]

Did you check the carb throttle plates go fully open when the pedal is on the floor?
If not, have someone to press the throttle all the way to the floor and visually check the throttle plates in the carb.

 

[Lefty71]

What does it do??? Bog??. or just not have much power?

 

[HALIFAXHOPS]

Looks like you made engine mods and are running the stock curve in the distributor, prob needs to tailor the curve in it.

 

[69 Sleeper Bee]

Accelerator pump working / adjusted correctly ?

 

[Ron H]

I have a rebuilt poly teen, though not as built as it could be. Mild cam, solid lifters, bored .60, eddy, headers, also swapped the 3:23's to 3:55. Earlier had installed a shift kit, and mopar el ignition. I'm running full mech advance. I went with 15" and p235/60 radials. Performance? Before I could get some burn-outs - but - on polyglass tires, lol. The radials won't do much of this at all. My thrill days with burn outs are behind me with my old BB rides and while I'd like a bit more giddy-up...it is ahh 318 not stroked...

 

[TN Mopar]

something simple
but since you mentioned a Carb swap and distributor work
is the vacuum advance connected to the proper port?

 

[Huicho417]

Thanks everyone for the awesome feedback!

I have not checked the throttle plates to be fully open with the pedal all the way to the floor. That will be the first thing I check after work today.

When I floor the pedal it does not bog down at all, just not much power there. I do have the vacuum advance connected properly, per the carb. diagram.

I am glad to see a comment here regarding adjusting the distributor curve. I was on you tube yesterday searching the same issue. Many of the videos that came up were regarding the distributor curve to make the car jump at initial takeoff. What is the correct procedure to tailor the distributor curve?

 

[Wietse]

For the ignition i would give it 12-20* advance with the vacuum can disconnected and plugged off.
Try with increments of 2* (12-14-16-etc) and see what it likes, you should find a happy spot where it will react crisp with power.
Do know that this is assuming the carb is set correct, lean/rich and proper pump shot.
After you know where it wants to be you can reconnect the vac can and adjust if required, depending if you are on ported or manifold vacuum...don't mention here what you are using (ported or manifold) because you will get instant harrasment by the opposite believers
If you are on manifold vacuum you will need to check how much the vac can adds at idle and retard the distributor to get the same advance you had before without the vac can.
If you are on ported there should be no vac advance and you can leave it where it is, check and you can try retarding it slightly later on if needed.

 

[69a100]

Many of the videos that came up were regarding the distributor curve to make the car jump at initial takeoff. What is the correct procedure to tailor the distributor curve?

What? And you can't find a video on how to adjust your distributor curve? You're doing it wrong!

 

[beanhead]

Not to say the curve doesn't need work, but keep in mind....it WAS working good and then it wasn't, so odds are it's something you touched, or something is failing. Distributor curves don't usually just 'change' unless the distributor hold-down is loose..

 

[Huicho417]

When you say with vacuum disconnected and plugged off. Is that the line coming from distributor vacuum connected to carburetor?

 

[Wietse]

Yes, the small hose that comes from the vac can, it goes on a port on the carb, pull the hose off the carb side and install a cap on that tube, the hose you can just put on the side temporary.

 

[Ron H]

Not to hi-jack this thread; but since we're on the topic - after playing around with the timing, always got missing at various RPM’s. Set a bit more advance, misfiring around 2300, back it off misfiring at around 3000…like clockwork within the range of the engine idling decent. Always a miss…Only time it runs perfect is zero vac advance carb port plugged off. Motor fires up instantly. It has mopar electronic ignition. What am I missing – there’s a pun here. Am I missing some added giddy-up running it this way, other than poorer mileage and emissions?

 

[Wietse]

Not to hi-jack this thread; but since we're on the topic - after playing around with the timing, always got missing at various RPM’s. Set a bit more advance, misfiring around 2300, back it off misfiring at around 3000…like clockwork within the range of the engine idling decent. Always a miss…Only time it runs perfect is zero vac advance carb port plugged off. Motor fires up instantly. It has mopar electronic ignition. What am I missing – there’s a pun here. Am I missing some added giddy-up running it this way, other than poorer mileage and emissions?

Seems like you are getting too much advance, need more info.
What is the initial, mechanical and vac can advance?
What are you running, ported or manifold vacuum?