bigmanjbmopar
Newb with a view
I have a Holley 750 DP and was able to get rid of the surge by increasing the shooters size from 30 to 35 and replacing the throttle cam. fixxed a lot of out the box issues with the Holley. Good luck.
Low power surging, help needed
- Thread starter wsutard
- Start date
wsutard
Well-Known Member
My dist doesn’t have a vac advance.
Do you know if you were experiencing a lean surge or something else? My situation is not a lean surge. I’m getting the surge at rich AF levels, 11-11.7.
Anyone know if there is a rich surge?
andyf
Well-Known Member
Add more timing and see how it runs. You'll have too much total timing so don't run it at WOT, just add more timing and drive it around the block to see if it solves the surging. If it does then you'll have to figure out what to do.
My 512 will surge if the timing is 16 at idle but if I give it 20 degrees at idle then it runs nice and smooth. Giving it 20 degrees of advance at idle also cleans up the AFR. The problem you'll have is that if your engine needs more timing at idle then you're going to have to "hack" the distributor to make it work. I eventually gave up on the MSD billet distributor for a street car and switched to a digital distributor which allows me to control the timing curve. The MSD billet is a good race distributor but it doesn't have the ability to do what a street car needs. If a different timing curve solves your problem then you'll need to switch to a digital distributor or to EFI. Either one will solve your issue.
My 512 will surge if the timing is 16 at idle but if I give it 20 degrees at idle then it runs nice and smooth. Giving it 20 degrees of advance at idle also cleans up the AFR. The problem you'll have is that if your engine needs more timing at idle then you're going to have to "hack" the distributor to make it work. I eventually gave up on the MSD billet distributor for a street car and switched to a digital distributor which allows me to control the timing curve. The MSD billet is a good race distributor but it doesn't have the ability to do what a street car needs. If a different timing curve solves your problem then you'll need to switch to a digital distributor or to EFI. Either one will solve your issue.
This company has 10* and 14* limiter bushings for the MSD Pro Billet distributors, allowing you to run more initial with the same total: http://4secondsflat.com/MSD Distributor Tuning.htm
RVW
Well-Known Member
Timing play with your timing
wsutard
Well-Known Member
Thanks for the options guys. I will play with the timing this weekend. As an update, I installed a fuel regulator and that didn’t help. I moved my magnetic pickup wire from the 6AL to the dist away from any potential noise sources and that didn’t change anything. It is shielded and grounded anyway so I wasn’t expecting much.
Timing is easy enough to mess with m, and free to change, so I will jump on that and report back.
Timing is easy enough to mess with m, and free to change, so I will jump on that and report back.
Sweet5ltr
Well-Known Member
If it is timing, it's really simple to lock out the advance on an MSD Distributor.
Video from Roadkill Extra: https://www.motortrendondemand.com/detail/msd-distributor-tips/0_moum183y/
MSD Instructions: https://www.jegs.com/InstallationInstructions/100/121/121-85551.pdf
MSD 6AL2 ignition box to control the timing curve, this will allow full-control and is a one-time investment.
Even better, invest in a Holley Sniper EFI kit and Hyperspark Ignition System. Best investment you'll ever make at this point (before buying another carb or going down that route).
Stupid simple to install and get setup once you run a Sniper EFI kit, never mess with timing again - >
Last edited:
andyf
Well-Known Member
You should try more initial advance as an experiment. I understand that more initial means more total that is why it is an experiment. Just bump the initial timing to 20 degrees and drive it at part throttle. Do not go WOT. Just try it to see if it eliminates the surge. If it does then you know what you have to do.
Suregrip391
Well-Known Member
I had the same conditions as the original poster on a 68 383 2-bbl car. I swapped out 3 different carbs. Changed entire fuel system,set timing, new chain and gears, checked for vacuum leaks, did everything under the Sun! I got frustrated and took it to a local mopar guru that could not figure it out, I ended up taking off the 2-bbl setup and installed an original cast iron 4-bbl intake ( purchased from someone here that sells tons of parts, thank you) and slapping a 600 Edelbrock on top and that fixed it. I was never able to track down the original issue and can only say something with the 3 carbs or the original intake was plugged up some how. That was frustrating.
wsutard
Well-Known Member
Sorry for the delay guys. Started a new job and finally found the time to hack at this problem.
1. Got in on the timing. For some reason it was at 0. advanced it to 14, which is where I thought it was originally and nothing changed. Advanced it to 18 and nothing changed. I could try 20 but I doubt anything will change.
2. Purchased a new coil, MSD blaster 2 high vibration, no change
3. Replaced my MSD distributor with a used OEM distributor I found on CL. No change.
Now I am down to either the MSD 6AL Digital box as the culprit or the plug wires or plugs. That is if the ignition system is the issue. Plugs and wires are new.
Here is another symptom, I was idling down a hill in 3rd gear, about 1200 rpm, slow and the car just starts bucking rather violently. Same pattern as what I feel under low power low RPM.
I'm not convinced at this point that its ignition system. This MSD box was on the car prior to swapping in the 440. I never moved from its location so the chances of something happening to it are slim.
1. Got in on the timing. For some reason it was at 0. advanced it to 14, which is where I thought it was originally and nothing changed. Advanced it to 18 and nothing changed. I could try 20 but I doubt anything will change.
2. Purchased a new coil, MSD blaster 2 high vibration, no change
3. Replaced my MSD distributor with a used OEM distributor I found on CL. No change.
Now I am down to either the MSD 6AL Digital box as the culprit or the plug wires or plugs. That is if the ignition system is the issue. Plugs and wires are new.
Here is another symptom, I was idling down a hill in 3rd gear, about 1200 rpm, slow and the car just starts bucking rather violently. Same pattern as what I feel under low power low RPM.
I'm not convinced at this point that its ignition system. This MSD box was on the car prior to swapping in the 440. I never moved from its location so the chances of something happening to it are slim.
Sweet5ltr
Well-Known Member
Just lock out the distributor, it's a breeze with the MSD, this will verify completely that it isn't timing related. No reason for guesswork and spending money that you may not have to.
Similar threads
