Now that I have working A/C, I thought I would try to drive my Barracuda some more now that I won't be roasting on the black vinyl seats.

The car began popping back whenever I would drive on the interstate and suddenly take my foot off the gas to exit (car turning @3000 rpm at interstate speeds). It also developed a rough idle.

Went back to basics:

Changed plugs (they had only been in there for 9 years)
New Accel cap and rotor
New MSD wires


Checked timing (according to my dial back light) vac advance disconnected

15 degrees initial and 26 degrees total. All in by 2200

I thought that was kinda weird. I thought there would be more
centrifugal advance than that.

Since I had a spare ignition box I swapped it just to see what would happen.

Now I have 19 degrees initial and 30 degrees total.


Is it normal for timing to change when you change ignition boxes?

And should there be more than 11 degrees centrifugal advance?

I don't know if changing the ignition boxes has solved the "popping and missing" on the interstate as I haven't had a chance to get it out there.

Just wondering if any you had similar issues.

kev

MSD dist or MP (mallory or old style) dist?. 2 commmon SB slots are stamped 11 & 17 (22/34 on crank) on older electronic dists. not normal at all for the box to change the timing. it might "take out" (improperly delay) timing at higher RPMs a common complaint of the new (er) orange boxes but not at idle. is your idle speed changed which it would some if the initial was changed 4 deg. I'd open up the dist & see what you see for starters. what box did you have & what did you swap in?

We put a mopar performance electronic ignition in this car in 1986.

In around 2008 or 2009, there were some issues and we replaced that distributor with the one that's in it now.

It turned out that it was the orange box that failed so we replaced it with a black box (probably from napa as well)

All I know about the distributor is that it's a reman from Napa. I'm sure we just set the initial timing and called it good enough. It was more important at the time to get the car running than it was to be set up optimally.

The original mopar performance distributor has gone on to other projects along the way.

I replaced the black box with a chrome one of unknown origin that I had laying on a shelf. I bought it at a swap meet for $10 to use as a spare.

I know using unknown parts makes it more difficult to answer the question.

I'm definitely going to have to remove the distributor as the vacuum advance is not working for some reason. (tried to advance it with a mity vac; wouldn't pull a vacuum)

I'm just curious about only having 11 degrees of mechanical advance.

Actually mixing and matching ain't the end of the world. lets see what's up with the dist (including the can). Holler when you find out anything

you can change the vacuum part of the advance with an allen key, stuck into the vacuum port of the distributor . . . at least on stock distributors - that way you can add or subtract vacuum advance . . . for the mechanical you can play with the springs, and the slots . . . good luck . . .

adjusting the vacuum part of the can with an allen wrench will only change at what vacuum point the advance will start moving.

To limit the degrees it provides, you need to open the distributor and block part of the travel.

pvp, I wonder if distributor has a heavy spring with a slot in it. That keeps some timing out until waaay high in the RPMs, thus making it look like you only have 11 total mechanical. Usually best to replace it with a light spring from the Mr Gasket set to get the total timing in at a lower RPM.

I am pretty sure the vacuum can is toast. I hooked it up to the mi-t-vac and couldn't pull a vacuum at all. I tested the mi-t-vac on another component and it was working fine. Just in case, I borrowed a friends mitivac and had the same results. Fortunately my dad has a collection of vacuum cans that he has collected throughout the years and he has tested each of them. So I am pretty sure I can get that fixed.

I ran the rpm up to 3000 rpm without seeing any more advance. If it's got a super heavy spring to keep it from advancing past that, then I definitely need to pull the distributor and look into it.

I wish I knew someone with a sun distributor machine. This would be so much easier

Thanks for all of your replies. I will keep you posted.

kev

I really need to change my signature pic.

I no longer have that house (ex got it) and the taurus driver ed car and the minivan in the background are looooong gone

first we gotta fix the popping/rough idle (the can may be leaking-vac leak & there are other possibilities) & we can dial in the dist spot on WO a dist machine. you might plug the line to the can & take it back out & see if it straightens out. one thing at a time. EDIT with a bit of thought the can is almost certainly leaking which is causing the vac leak. I've never seen a can hang up to where it will not advance, it'd have to be something that got loose/hung up in the dist, not likely. holler when you can

If it's a stock replacement distributor it's going to have close to 30 degrees of mechanical advance , even wit ha heavy spring the weights will keep pulling it. you need to go higher than 3k rpm to see the full advance ... and get rid of those mopar electornic ign units , crappy old technology.

I realize that many of you have been dying to know how this turned out.

Well, I went to my dad's to get one of the extra distributors out of the warehouse.

I went to install it and discovered that I had been given a distributor for a low deck big block.

I didn't bother to check the box and since he doesn't have a low-deck big block, I couldn't think of any reason why he would have one.

So, this weekend my goal is to remove the distributor I have and disassemble and clean and try again.

As far as getting rid of the old technology, there is no money in the budget for that at this time.

Will let you know how that goes.

I finally found the problem:

I was reading the wrong part of the timing tab. I kept pointing at the mark in the center of the timing tab instead of the zero at the top of the tab.

A combination of poor eyesight, poor lighting and too much paint on the timing tab.