Pertronix timing question

[B5blueGC]

I have a Pertronix electronic conversion kit installed for my 340. I am experiencing pinging under higher RPM. I have an Edlebrock AVS2 carburetor.

At idle I have 5 degrees before TDC. At 2000 RPM it only advances 2 degrees. The distributer vacuum was connected to "Timed Vacuum". I tried moving it to "Manifold Vacuum" and the car idled better and I had to reduce the idle speed. Checked the timing again and at 2000 RPM there is only 2 degrees of advance. Went for a drive and pinging continues. Running 93 octane fuel. Idle screws are at 1-1/2 turns from stumble.

Does the advance canister on the distributer work the same way as with points? Wonder if it is not functioning or is Pertronix doing something different?

 

[MOPARMITCH]

I have a Pertronix electronic conversion kit installed for my 340. I am experiencing pinging under higher RPM. I have an Edlebrock AVS2 carburetor.

At idle I have 5 degrees before TDC. At 2000 RPM it only advances 2 degrees. The distributer vacuum was connected to "Timed Vacuum". I tried moving it to "Manifold Vacuum" and the car idled better and I had to reduce the idle speed. Checked the timing again and at 2000 RPM there is only 2 degrees of advance. Went for a drive and pinging continues. Running 93 octane fuel. Idle screws are at 1-1/2 turns from stumble.

Does the advance canister on the distributer work the same way as with points? Wonder if it is not functioning or is Pertronix doing something different?

This guy can help you.... @halifaxhop

 

[Xcudame]

5° Before isn't enough. That's what plugging the distributor into the intake manifold is telling you. Try 12° before and plug the distributor back into the ported vacuum source. How does that run?

 

[halifaxhop]

Manifold vacuum will slam the vac advance full in so no wonder your not getting any advance at 2000 rpm. The vac advances on Mopars mostly all work the same. Sounds like you have really light springs in the mechanical advance.

 

[B5blueGC]

5 degrees before TDC came out of the service manual for the 340. I got the same numbers whether on manifold or ported vacuum. If I advance the initial timing isn't that going to cause more pinging?

 

[MOPARMITCH]

5 degrees before TDC came out of the service manual for the 340. I got the same numbers whether on manifold or ported vacuum. If I advance the initial timing isn't that going to cause more pinging?

What kind of modifications are there to your 340 engine? Even stock Mopar engines rarely like OEM settings for timing. I'm pretty sure you will find you need more initial timing. I am old school. I can still time an engine by ear and throttle RPMs and response.

 

[Xcudame]

@MOPARMITCH is right, using just an rpm gauge temporarily under the hood, you can time a Mopar by ear. Like my Dad taught me decades ago, "twist more timing into her (Before Top Dead Center) until she screams and then back her off a little!"

 

[B5blueGC]

What kind of modifications are there to your 340 engine? Even stock Mopar engines rarely like OEM settings for timing. I'm pretty sure you will find you need more initial timing. I am old school. I can still time an engine by ear and throttle RPMs and response.

It is a 340 block .030 over. Cam DUR@.050 218/224, lift .462/.470.

I am new to setting timing. The pinging is my fear of causing damage. Lots of videos out there on this subject. Ported vs. manifold, mechanical advance vs. vacuum. Trying to learn and set the engine up so I can drive it like I stole it (hee hee).

 

[halifaxhop]

It is a 340 block .030 over. Cam DUR@.050 218/224, lift .462/.470.

I am new to setting timing. The pinging is my fear of causing damage. Lots of videos out there on this subject. Ported vs. manifold, mechanical advance vs. vacuum. Trying to learn and set the engine up so I can drive it like I stole it (hee hee).

Its all about what curve you have in the distributor, If it is stock it needs to match the engine modifications made.

 

[halifaxhop]

Just noticed your in MD. Wonder how far from Mitch he can do the timing for you.

 

[B5blueGC]

Just noticed your in MD. Wonder how far from Mitch he can do the timing for you.

Looks like he would be almost 2 hours away.

 

[540HemiCuda]

The IMPORTANT number for timing is TOTAL, not initial.

LOTS of things go into how much initial and how fast a curve your particular combo would like, but the total is usually in a fairly finite range. Usually.

You are correct to be concerned about any detonation. Since detonation can damage an engine, it might be prudent to find someone experienced in curving a distributor and setting timing. Frankly, it is not difficult, but to do it the first time, does take time to figure out and set the one that your combo likes.

.

 

[Xcudame]

Do you know the static compression ratio? The early 340's had 10.5:1. Probably closer to 10.0:1, but would require the best crappy gas out there (93 octane). Not sure what you have for gasoline brands, but out here in the Southwest, Chevron has the best additives.

If you know the particulars of the engine, @halifaxhop can build you a distributor.

 

[Deathproofcuda]

Manifold vacuum will slam the vac advance full in so no wonder your not getting any advance at 2000 rpm. The vac advances on Mopars mostly all work the same. Sounds like you have really light springs in the mechanical advance.

I don't understand this comment. Why would he only get 2 degrees of mechanical advance at 2,000 rpm if he had really light springs in the mechanical advance? Unless you are saying that the mechanical advance is "all in" even at idle speed.

 

[Deathproofcuda]

I have a Pertronix electronic conversion kit installed for my 340. I am experiencing pinging under higher RPM. I have an Edlebrock AVS2 carburetor.

At idle I have 5 degrees before TDC. At 2000 RPM it only advances 2 degrees. The distributer vacuum was connected to "Timed Vacuum". I tried moving it to "Manifold Vacuum" and the car idled better and I had to reduce the idle speed. Checked the timing again and at 2000 RPM there is only 2 degrees of advance. Went for a drive and pinging continues. Running 93 octane fuel. Idle screws are at 1-1/2 turns from stumble.

Does the advance canister on the distributer work the same way as with points? Wonder if it is not functioning or is Pertronix doing something different?

Are you using a dial back timing light and any chance that you've confirmed your timing measurements with another good "known" timing light, because the numbers that you are posting here don't make a whole lot of sense.

Let's start with some basics. You said that when you hook the dizzy up to manifold vacuum that the car idles smoother and idle speed increases. Therefore, the vacuum advance is working. How many degrees does the timing change when you switch from the ported to manifold vacuum connection?

With the vacuum advance disconnected, what is your initial timing? What is your idle speed? Now rev the engine up until the timing stops advancing. What was the reading when the timing stopped advancing and at what rpm did it happen?

Some folks like dial back timing lights, others complain of potential inaccuracies with them. I just use an old school standard timing light and I have a marked damper.

You can also use timing tape: Pardon Our Interruption

Or just add extra markings on your balancer like shown in this Uncle Tony video: