Popping sound in exhaust

-
dart_68 said:
That was it! Pulled the vacuum hose and plugged the port on the carb and it runs great and NO popping. Never would have thought le weekends. Changed points and condenser ,plugs gas filter,cap and rotor..checked all pushrod.
dart_68 said:
That was it! Pulled the vacuum hose and plugged the port on the carb and it runs great and NO popping. Never would have thought of that.
:thumbsup:
Click to expand...
Click to expand...
dart_68 said:
What did you finally do to rectify the situation? Did you get a new vacuum advance canister?
Click to expand...
Mine is a stock points distributor from 1966. I have a new big block in the works. I run without it at the moment. It doesn't get much use working 6 days a week so it sits..I think that you could replace the canister or distributor.
 
69383valiant said:
Mine is a stock points distributor from 1966. I have a new big block in the works. I run without it at the moment. It doesn't get much use working 6 days a week so it sits..I think that you could replace the canister or distributor.
Click to expand...
Get an adjustable vacuum advance, you will like the tuneability.
 
Good deal! Now I gotta ask.... where on the carb/manifold was the vacuum advance hose connected? I gotta admit that I am scratching my head on why this changed if it was on the port for ported vacuum. (Maybe I am just tired after a long day....)
 
nm9stheham said:
Good deal! Now I gotta ask.... where on the carb/manifold was the vacuum advance hose connected? I gotta admit that I am scratching my head on why this changed if it was on the port for ported vacuum. (Maybe I am just tired after a long day....)
Click to expand...
I dont know which port the OP had the vacuum advance connected to, but it should be connected to full manifold vacuum for performance tuning.
If it is bone stock I would follow the factory vacuum line schematic. Some were connected to ported vacuum for emissions alot depends on the advance itself.
 
3310 with 2 metering blocks is a 4150 model. Usually these 3310's are rated at 780CFM for some reason. OEM carb for a BB Chevy one year. Metering plate is a 4160. We had a guard mount 4sp IH 2 ton truck that would backfire every time you let off the gas in gear to create a high vacuum and then blip it. Was like a cannon after the mufflers blew out their packing. The driver would pop that thing about 10 seconds from your post to either wake you up or get you up off your ***! Motor T guy said we probably had a leaking valve
 
If you have it connected to a constant vacuum source, It may be over advancing the timing? Have you checked the timing?
 
nm9stheham said:
Good deal! Now I gotta ask.... where on the carb/manifold was the vacuum advance hose connected? I gotta admit that I am scratching my head on why this changed if it was on the port for ported vacuum. (Maybe I am just tired after a long day....)
Click to expand...
The vacuum was attached to a barb at the base of the carb for full manifold vacuum.
 
dart_68 said:
The vacuum was attached to a barb at the base of the carb for full manifold vacuum.
Click to expand...
Ah OK, makes sense. Certainly sounds like too much advance. If it was on ported vacuum, then disconnecting it would not be expected to change things at idle. So your advance pod sounds like it may be working just fine, just at the wrong time. See if the pod leaks under vacuum; just connect a hose and suck hard on it, or use a manual vacuum pump. You can also watch to see if the advance moves the plate inside the distributor.

And yes, time to break out the timing light!

The rich desposits on the plugs may or may not be connected to this issue.

512Stroker said:
Check this out it works
How Vacuum Advances Work
FBO Ignitions also recommends full manifold vacuum connection
Click to expand...
FBO talks about full manifold vacuum in this type of system in just a few cases, to fix specific issues, not in general.....per that link.

If you look across many mfrs, there are so many variations on vacuum advance and vacuum retard, and pods that have both, it is hard to make generalizations.
 
I agree
There are alot of variables, vacuum advance is not for every application.
I myself have converted 2 hi performance mopars engines to ignition systems that utilize a vacuum advance. In both situations it worked out very well and made the cars alot more street driveable without loosing any performance that I could feel in the seat of my pants.
 
Broken insulator on one of the plugs? Had this happen before, and the plug still fires so it’s hard to tell!
 
Update:

When I pulled and plugged the vCan that solved my popping problem. Motor runs pretty good and I got the idle down to 800 in neutral by turning the idle speed screw. I put a timing light on it and it was at 40* advanced. Wth? I'm wondering how it can idle that low and smooth with 40* initial advance? Is it possible that the dizzy pickup wires are reversed?

FYI, it has a Mopar distributor with HEI.
 
dart_68 said:
Update:

When I pulled and plugged the vCan that solved my popping problem. Motor runs pretty good and I got the idle down to 800 in neutral by turning the idle speed screw. I put a timing light on it and it was at 40* advanced. Wth? I'm wondering how it can idle that low and smooth with 40* initial advance? Is it possible that the dizzy pickup wires are reversed?

FYI, it has a Mopar distributor with HEI.
Click to expand...
I think you need to check if the TDC mark on the balancer is in the right place. You'll need a piston stop ans some patience. There are directions on this site someplace. Or watch this video, although he shows an adjustable pointer which you probably don't have. You need to mark the balancer exactly 1/2 between the two marks:
 
Last edited:
dart_68 said:
Update:

When I pulled and plugged the vCan that solved my popping problem. Motor runs pretty good and I got the idle down to 800 in neutral by turning the idle speed screw. I put a timing light on it and it was at 40* advanced. Wth? I'm wondering how it can idle that low and smooth with 40* initial advance? Is it possible that the dizzy pickup wires are reversed?

FYI, it has a Mopar distributor with HEI.
Click to expand...
The distributor pickup wires being reversed would not make the timing off, just erratic. (You adjust the timing based on when it actually fires.) But yes, if the damper ring slips you will read a more advanced timing on the damper versus timing cover marks than you actually have.

With that much ignition advance, the torque pulses are very strong so you can idle way down. Does not mean it is good.....Lord knows how much advance you had at idle with the v-can attached to manifold vacuum! LOL
 
I put a timing tape on the balancer and checked the marks before I put the tape on. The ring hadn't slipped. I've only run the engine about 5-10 minutes since putting the timing tape on.
 
Actually I have heard of reversing the polarity in a magnetic pickup distributor doing just that. Put 30+ degrees of timing in it.
 
furrystump said:
Actually I have heard of reversing the polarity in a magnetic pickup distributor doing just that. Put 30+ degrees of timing in it.
Click to expand...
However the timing changes with a polarity flip, that would happen only if you did not move the distributor after making the polarity switch, and just measured the timing before and then after.

My impression of this sitaution is that the OP has been adjusting the timing with the pickup polarity not getting changed, just with polarity as it was when he started this process.
 
nm9stheham said:
However the timing changes with a polarity flip, that would happen only if you did not move the distributor after making the polarity switch, and just measured the timing before and then after.

My impression of this sitaution is that the OP has been adjusting the timing with the pickup polarity not getting changed, just with polarity as it was when he started this process.
Click to expand...
Yes. I had been working on just getting the engine to idle...which it is now. It wasn't until I got it to idle that I could get a good reading on the timing. It was then that I discovered that it's 40* advanced. With that much initial advance @ 800 rpm I would think that it would run worse than it does. Which prompted the question about the polarity being possibly wrong.
 
dart_68 said:
Update:

When I pulled and plugged the vCan that solved my popping problem. Motor runs pretty good and I got the idle down to 800 in neutral by turning the idle speed screw. I put a timing light on it and it was at 40* advanced. Wth? I'm wondering how it can idle that low and smooth with 40* initial advance? Is it possible that the dizzy pickup wires are reversed?

FYI, it has a Mopar distributor with HEI.
Click to expand...

This reads like it was the first time for timing light, but could be wrong.
 
dart_68 said:
Update:

I finally got the engine running well enough that it will idle and was able to get a short video. You can hear the "popping" I'm talking about. Any ideas what the problem may be?
Click to expand...

that really sounds like distributor is 180 degrees off
 
furrystump said:
This reads like it was the first time for timing light, but could be wrong.
Click to expand...
When it was popping it ran so bad that it wouldn't idle on its own. I had to keep blipping the throttle to keep it running. Once I pulled the Vcan it didn't pop any more and got it to run fairly smoothly. It was only then that I could get a good timing read.
 
You must log in or register to reply here.
-

Back
Top