Wrong distributor for 69 318?

[Tylinol]

Hey everyone. I've got a weird distributor issue that took me way too long to diagnose (since I kept thinking it was fuel - classic mistake...)

This is a recently rebuilt 318 original to my '69 Barracuda. Pretty much stock except for dual exhaust and 4 barrel intake/carb.

My (probably original) distributor's housing was broken, so I replaced it with this one:

https://www.oreillyauto.com/detail/...95368caf/wai-global-distributor-new/wair/ch05

I know for a fact that my timing marks are correct, timing gear is good, firing order is correct.
My vacuum advance is plugged in to the ported vacuum port on the Edelbrock, not manifold.

I've set my timing to 13* BTDC at 700 rpm and have a great idle out of it. Timing all in is 36* at ~3000rpm. This was all timed with the vacuum advance disconnected. However, light-moderate throttle is almost undrivable with this setup, popping and stuttering like crazy no matter my AFR (I played around with everything from 11.5-14.5 when I thought it was fuel). If I lay into it 80%+ throttle, the stuttering goes away.

I tried unplugging the vacuum advance and driving it, and it drives fine that way. No popping or anything. It seems like the vacuum advance on my distributor is somehow too aggressive - maybe the part I got was a "generic" SBM distributor that doesn't work well with my '69?

 

[67Dart273]

Hard to say. What got you to "this point?" In other words what is the story on your old one.
Are you CERTAIN about the timing? Any chance the marks are off? Is this a "dial back" light or just a straight no frills light?

NORMALLY a generic "all purpose" "replacement" distributor would NOT give you the figures you posted. Normally a every day pass car dist. would have a much longer advance curve, maybe 5 or less BTC and maybe 32 or so full advance and THAT would be quite high RPM. "Smog advance curve" in other words.

One thing would be to examine the centrifugal advance. Pull the cap and twist the rotor. IT should move freely, but against a spring, and should "spring back" counter clockwise when released

There might also be a possibility of "rotor phasing" problems. Google that term. You can easily check it with a chopped up old cap and a timing light

There has been cases when the pickup leads were reversed, and THAT will through phasing "off." China imports, who knows?

 

[awg329]

Adjust your vac advance so that takes more vacuum to apply it.

 

[67Dart273]

Adjust your vac advance so that takes more vacuum to apply it.

May not be adjustable. I'd suspect the advance is just plain too wimply AKA advances too fast with too little vacuum. OP insists this is ported vacuum, maybe better double check

 

[PRH]

What have you changed in the engine build that would warrant the initial timing be changed from the factory setting of “0” to the 13btdc you have it set at?

In other words, if you took a factory original 69 318, and cranked up the timing 13deg...... wouldn’t you expect it to ping?

If you want to an increased initial timing setting on a basically stock engine, you’ll likely have to limit the amount of both mechanical and vacuum advance, along with slowing the curve down.

FBO has limiter plates for the mechanical part.

 

[69FBCuda]

. If I lay into it 80%+ throttle, the stuttering goes away.

Plug(s) and/or wire(s) do you have a plug wire tester, also could be crossfire(arching between wires)

 

[Tylinol]

I'll double check - it's on the passenger's side port on the Edelbrock, which *should* be ported according to the manual.

My engine does make a lot of vacuum, though. 15-20" at idle.

 

[Mattax]

As far as the new distributor goes...
Assuming the condensor and points are OK (and that's a big assumption) the thing to determine is the mechanical and vacuum advance.
Mechanical advance is probably where the issue began (again assuming the condensor is OK).
You can get away with a super quick mechanical advance when not using any vacuum advance. This is how the DC/MP race distributors were set up - and there is a slight advantage when the engine is relatively cold, such as when drag racing.

Mechanical advance on a real '69 distributor is going to be very fast and go quite a few degrees until around 1600 rpm when it will slow down.
Advances were set up like that so the initial timing could be set retarded toreduce certain emissions at idle.
IF that's the type of advance curve in the WAI distributor you got, then setting the initial at 13* instead of 0* at 700 rpm results in way too much timing between 1000 and 2800 rpm to work properly with vac advance.

I recall you had some threads about setting this engine up more as a hot rod. So with that in mind, 10 or 12* at 700 rpm might be close to what it wants. That you can test by observing rpm drop when placing it into gear, or how much throttle you need to add if its a manual shift. In both cases less indicates more power.

To solve this, measure the timing at 800, 1000, 1200, and every 200 or 250 rpm. Then you'll know what has to be done next.
If it advances alot in the first few hundred rpm, then a limiter plate will not solve the problem.
=> The easier may be to set the timing at 0 or 5* at 650 or 700 rpm. Then use manifold vacuum for the vacuum advance. With a strong idle vacuum like your engine seems to have, this will increase the advance at idle. If its relatively stable and consistant then this is a crutch that you can probably live with.
=> The more technically correct approach is to weld up the inside of the governer slots. If the idle is unstable (often happens with engines that idle rough) then this will be the best solution.

 

[Mattax]

Example I posted for someone last year.
Brown lines are the specs from the Dodge Shop manual.
Gray are examples of actual measurements someone made on the car.

Red indicates the two timing measurements from post 1.

IF the distributor has an advance curve similar to a factory '69 318, then timing between 700 rpm and 3000 would look something like this. And that's going to be a problem when used with vac advance. This is illustrates the problem @PRH was posing about advancing the initial as you did.

Once you measure and plot the timing between 700 and say 2400 rpm, then you'll have enough info to decide what needs to be done.

Depending on the cam and compression, the engine's combustion efficiencies may have changed so maybe the long secondary advance of the 2 bbl 318 is no longer necessary. In which case, look at presmog 273 4 bbl as a timing guide. That's what we did with Ricks70Duster here.

Remember more timing is neccessary at idle for hot rods because the burn is somewhat cold and getting contaminated with exhaust from the valve overlap. The 318 2bbl was pretty efficient burner at idle. Even without CAP, a 318 would be happy at 5* BTC.

 

[Early a body]

with the engine at idle and the vacuum advanced plugged in, what is your timing. if its not 13 then your vacuum advance is pulling at idle. Then unplug the vacuum advance and what is your timing. if 13 there is your answer. Simply put your vacuum advance is coming on too soon. You can adjust those oreily vacuum pods on the distributors, i have several of those my self. you want the know what you vacuum is at cruise assuming 3,000 is your cruise rpm. That is when you want the vacuum advance to kick on . Also doubled check the gap between the reductor and the pick up in the distributor make sure its at spec.

 

[PRH]

Excellent...... a picture is worth 1000 words.

That’s exactly what I meant.

 

[318willrun]

You can simply unplug the VA and take a test drive (cap off at carb). If it runs great then it's your VA causing the issue. IF it runs the same, then it's something else. It could very well be that since you've added "additional" timing to it, it doesn't want the VA pulling even more into it.

 

[Tylinol]

That's what I've noticed - with the VA off and capped, it drives just fine. Plugged in, and it won't cruise without popping and stumbling.

 

[318willrun]

That's what I've noticed - with the VA off and capped, it drives just fine. Plugged in, and it won't cruise without popping and stumbling.

ok, then back the timing off and use the VA, or leave it where it's timed and don't run the VA and problem solved. I don't run a VA on a lot of my cars. Many believe that's a crime. So far, I've not been caught and had to pay for my repeating offence of the VA crime

 

[Bewy]

Couldn't find that dist. Is it elec? If so, because of poor quality or adjustment, reluctor may be contacting the pole piece, causing a misfire.

 

[jas0162]

I have had a few point distributors over the years do what you are describing, I suppose an electronic one could do the same thing. The vac can rotates the point/pickup plate around the cam/reluctor on a pivot. When the pivot gets worn and the vac can pulls the plate the point dwell goes out the window and the engine runs like crap. The same could happen with electronic if the air gap gets way out of whack, but i have never run into that.

If you have points watch your dwell angle and apply the vacuum can, with electronic check your air gap with and with out vacuum on the can.... you will probably be able to see if something is wrong

 

[Tylinol]

I've gone ahead and done the scientific thing - here's a graph of the advance with the vacuum unplugged, and put on ported.

The advance numbers (vertical line) are the timing minus my initial timing (11* right now, which still seems to be too much for it with the vacuum advance plugged in). This is with the
car sitting still in park. Vacuum goes right to 20" when I crack the throttle.

 

[Mattax]

I've gone ahead and done the scientific thing - here's a graph of the advance with the vacuum unplugged, and put on ported.

The advance numbers (vertical line) are the timing minus my initial timing (11* right now, which still seems to be too much for it with the vacuum advance plugged in). This is with the
car sitting still in park. Vacuum goes right to 20" when I crack the throttle.

View attachment 1715900014

Seems like everything is functioning properly.
Yes. Ported vacuum provides little to no vacuum advance at idle. Chrysler (and many others) used vacuum advance strictly for low density mixtures. In other words, when leaner mixtures were in the engine, light to moderately heavy throttle. At when richer mixtures were called for, idle and full throttle, there was no vacuum advance.

We can see the vacuum advance can add as much as 15*, although the vacuum needed to do so may be something more the 20" Hg. Come back to this later.

Lets look at the timing on the engine and advance in the distributor.

We see the advance curve is just on the low side of the factory specs.

Set at 11* at 700 rpm, its still igniting much earlier than the engine needs or wants.
Given this distributor's advance curve, setting the initial around 5* BTC would put the timing pretty close to acceptable working range. Using premium fuel you could try that and see how it does. If no problems, then you'll have a baseline to work from. Problems that are more subtle than you've experienced so far are light detonation (pinging or gurgling) which under sever load would also show as specs of aluminum on the spark prorcelain.

Just from my experience and looking at hte facotry specs. Highway driving (50 -70 mph, 2600-3000 rpm) the engine should be fine with around 50* while cruising. So lets say you rest the initial so the timing at 3000 rpm ends up at 25 or 27*. With the vac advance connected, the timing will be 50 to 52* while crusing. That should be OK.

Now, if the engine has been hot rodded to some extent, its probably worth reshaping the advance curve because the combustion will be quicker in the mid to high rpm range than a facory 2bbl 318.

 

[Tylinol]

So, I tried backing the initial timing all the way off to 0* TDC. It's a little bit better, but I'm still getting a lot of hesitation and stuttering that I didn't get with the vacuum advanced unplugged (this, mind you, is on 93 octane gas). Especially just off-idle

My engine is far from a hotrod, but it is probably a little healthier than stock. I've got:

- KB pistons with about 8.75 (iirc, high 8s but less than 9) compression ratio
- 2.5" dual exhaust from TTI
- Factory 69 manifolds
- Factory heads
- Bored 40 over
- 4 barrel intake and carb
- this cam COMP Cams CL20-208-2 COMP Cams High Energy Cam and Lifter Kits | Summit Racing

I've also switched the distributor to Petronix vs. the points a few weeks ago, but the symptoms didn't change.
Am I going to need to recurve my distributor, or even just buy a different one like this? PerTronix D141710 PerTronix Flame-Thrower Plug and Play Billet Distributors with Ignitor II® Module | Summit Racing

 

[PRH]

You should drill a hole in the cap, on top, even with one of the terminals.

Sounds like the rotor might be getting way out of phase when the VA is activated.

Shine the timing light down into the hole when the vacuum is applied and see where the rotor is pointing, and see how far out the rotor alignment is.

As in:

 

[6pak]

Seen this. Put springs in to curve faster and cruising, and the engine would surge when trying to smooth cruise.
And you are running short curve w more initial? Jus makes it worse.
* Cruise AFR needs to be richened up.
If you had an AFB, it would be a rod change.
- opinions and assholes* - a lot out there.
- but, bet it will cure it.
Would like to know.
BUT, as far as points go, use a dwell meter.
My replacement dist. Ate the lubricated rubbing block down in less than 800 miles. Wore/ melted ? - nevertheless, messed me up for a while, couldn’t believe shi—. Stuff so cheap.

 

[Tylinol]

I've got it richened up quite a lot right now - 3 steps richer for cruise, and two stips richer on power (according to the edelbrock chart for me carb).
I also have an AFR gauge. AFR with the vacuum advance unplugged at cruise and idle is really rich - 11.5-12, down to 9-10 at WOT. With the advance plugged in, it
goes up to 14.2-14.8 at cruise. I'm assuming this is because it's pre-detonating from too much advance but I'm not sure.

 

[Mattax]

Seen this. Put springs in to curve faster and cruising, and the engine would surge when trying to smooth cruise.
And you are running short curve w more initial? Jus makes it worse.
* Cruise AFR needs to be richened up.
If you had an AFB, it would be a rod change.
- opinions and assholes* - a lot out there.
- but, bet it will cure it.
Would like to know.
BUT, as far as points go, use a dwell meter.
My replacement dist. Ate the lubricated rubbing block down in less than 800 miles. Wore/ melted ? - nevertheless, messed me up for a while, couldn’t believe shi—. Stuff so cheap.

Yup. Unfortunately a lot poorly made junk out there. Mystery distributor

So, I tried backing the initial timing all the way off to 0* TDC. It's a little bit better, but I'm still getting a lot of hesitation and stuttering that I didn't get with the vacuum advanced unplugged (this, mind you, is on 93 octane gas). Especially just off-idle

With that cam and the 4 bbl, I'm guessing 5 to 10* BTC would be a good starting point for idle.

Unplugged? I'm hoping you mean the line from the carburetor is plugged with a golf tee, or the port is capped.
If so, then PRH is giving a likely explanation to investigate.
If not, then what we're seeing is the engine likes that air leak under the throttle.

I've got it richened up quite a lot right now - 3 steps richer for cruise, and two stips richer on power (according to the edelbrock chart for me carb).
I also have an AFR gauge. AFR with the vacuum advance unplugged at cruise and idle is really rich - 11.5-12, down to 9-10 at WOT. With the advance plugged in, it
goes up to 14.2-14.8 at cruise. I'm assuming this is because it's pre-detonating from too much advance but I'm not sure.

Good to be suspicopus of the AFR readings in these cases. Timing doesn't change the actual AFR even if the WBO2 picked up a difference in oxygen,

Is it predetonating? Or is it just misfiring?
Detonation will occur under load and sound like gurgling or pinging. Under heavy load it can cause serious damage, but under light acceleration, damage is quite small if any. Small specs of aluminum will show on the porcelain when there has been detonation. @PRH can probably be more specific. He's seen far more than I have.

Too early a spark can cause backfire through the carb. If spark is early and the intake valve is open, then backfire can occur.

Misfire will result in lots of unused O2 in the exhaust and yes the AFR meter will misinterpret the meaning of the higher O2 content.

On all of the carbs we're dealing with here, the jets and rods have little effect on idle and off-idle. They only really restrict fuel to the main venturies. Basically when the car is cruising at interstate speeds or when accelerating from 30 or 40 mph up. Off the line its the 'idle' or low speed circuits and acclerator pump.

 

[Tylinol]

It's probably just misfiring - I don't have a good ear for this car or American V8s in general yet (used to aircooled 4cylinders and Italian stuff...) but I don't hear anything
that sounds like pinging.

By "unplugged" I mean I remove the vacuum line from the carb and cap off the carb.

I tried 5 and 10* as well, before trying 0*. Both had the same issue, although slightly lesser with less initial advance. I figure if I have to go to ATDC just to compensate for the vacuum advance adding too much timing,
then something is not right.

Rotor phasing actually sounds like a pretty likely culprit here, since it does seem to be a misfire more than a pre-detonation scenario. But if that's the case, how do I fix it? Can I? The rotor itself isn't adjustable on this distributor AFAIK.

 

[PRH]

The VA changes the rotor phasing....... the mechanical advance does not.

Since it seems to act up only when the VA is activated, regardless of the timing....... I think the rotor phasing should be looked at.