Hello, Slant Sixers!

A few weeks ago I had a new friend. A Dodge Adventurer SE 1978 with a 225+904. The Carb is Carter BBD. This car has gone through a limited restoration, the frame is sandblasted and body has a new floor and a paint, transmission and the engine are said to be gone through too. A new remanufactured starter, generator and a new distributor is there, as well as the regulator. The brakes are in a beautiful condition. It is a daily driver, although, not a show item. Only the grille with small dents is not original and the interior is not gone through.

Anyhow, I have a few questions in my mind. I have gone through old topics but haven't found enough answers yet.

First: Having not been experienced with these cars, I (almost) immediately thought that something is wrong because the engine on a normal driving would very easily have knocking. All that was needed was a small amount of acceleration. So I measured the basic timing advance, it was about 25 degrees. No vacuum seemed to be there, nor seemed the vacuum canister to be working. Somebody must have tuned this by a rough hand, I thought.

So I reduced the basic timing to 10 degrees (read about it somewhere here at the forum...), tried to get some sense to the idle mixture, and set the idle to about 700 I/min. I had to open the idle mixture screws a total of 4 complete rounds (Some advice says 2,5 rounds for the Carter BBD...it runs with it, but the vacuum seems to be lousy). It idled now much easier, but still there was some knocking driving uphill...

So I had to go to parts store and buy a vacuum meter. The meter showed very low manifold vacuum, but the situation went somewhat normal when I reduced the timing to 5 degrees. Then the knocking sounds were almost gone, only a slight trace of knocking was heard sometimes. I once again reduced the basic timing, to about 3,5 degrees. At this point the knocking was all gone. Manifold vacuum seems to be normal, the ignition vacuum canister works OK.

Second: It seems that the Carburetor vacuum canister is not good, because it leaks slowly the vacuum when doing the choke pull-off test (I read about it Here in This Forum... ). So when cold, it starts, but slowly dies, if not trickled a little with the gas pedal. Maybe I will find one with a healthy diaphragm...

Third: The somewhat low generator voltage seems to be there, 12,95-13,10 Volts mainly. Having lights on, doesn't affect the voltage reading. At idle the headlights are a little dim, and lighten up when engine rews up a little. I have looked everywhere, but connections seem to be good. Maybe the ammeter is the only place which I have not tested...

It a pleasure to look, and a nice driver. Our first car in ten years which does not have V8! The gasoline prices here have gone up to senseless height, so it is nice to have a good mileage car available. At least after 1972 el Camino, 1988 Chevy Fleetside and 1987 Caprice classic stw...

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Everybody says I'm Wrong,
So I quess must be Right!

Welcome to the Mopar brotherhood, and to the Forum! Your English is quite good. None of my stock Mopar alterntors ever put out more than 13 volts at idle. They would put out 14 or so above an idle. The thing to check is to see if there is a voltage drop from the battery terminal on the alternator to the high side of the bllast resister. That would indicate bad connectors or a bad ammeter. You need a working vacuum pot on this distributor. It should cruise at about 15-20 degrees advanced plus the centrifical advance, but then drop out from 12 to 20 degrees of advance when the vacuum drops. This would depend on the canister you had, and how it was adjusted. You can get it to run fine without one, but your economy will suffer. If you add the initial advance plus the centrifigal advance you will get the "total" advance, which normally runs somewhere between 25 and 30 degrees advanced depending upon the motor, cam, gas, etc. But then you ad in the vauum advance for cruise economy, which pushes it another 12-18 depending upon theh canister you have. This can run you up to around 40 degrees advance at cruise, and gives you better economy. STep on the gas, and this vacuum advance drops out to avoid pre-ignition.

You might also be loaded up with carbon in the combustion chamber, which makes the pre-ignition problem worse. Get a good top end cleaner such as Power Foam or BG, and clean the carbon out. It will run better, and get rid of some of the preignition problems.
Sam

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Thanks, Sam!

I think the alternator gives steady 12,95-13,10 even above idle. Haven't tested at higher revs than 2000, though. Did also check if there would be voltage drop from battery + to alternator +, but didn't' get any. Shall dig further on... (Maybe it's just because my Caprice Classic's alternator gave so high voltages - 14,58 to 14,98 Volts I was constantly worrying it's too much...)

The vacuum pot started working OK, when I reduced the timing, which surprised me a little. Thought that too late ignition timing causes low manifold vacuum, but seems that too much advance did the same. I was worrying for the exhaust valves, but now thanks to You came to think of that it really is only at idle revs, when the timing is so late... Should have thought this earlier!

I really don't know much more of this particular piece of an engine, but think that it is all original, no hop-ups, at least. Maybe I should find the serial number for the engine first...

Total ignition advance seems to be now about 20 degrees at 1200-1300 I/min, at higher revs (2000 I/min) had about 35 dgrs total. But this naturally when revving at neutral. And this is at the basic timing advance set to 3,5 dgrs. Just this confused me because I read somewhere that normal is 10-12 dgrs basic timing advance. Didn't work anyhow this time.

I think that the cause for the pre-ignition was that manifold vacuum at 10-25 degrees basic advance was so low the vacuum pot didn't work at all. But now it works. Will check how much it gives at high vacuum (think that it was something like 10-15 dgrs). The manifold vacuum was about 10-12 inches of Hg, but is now about 20 inches Hg at idle 700 I/min. It drops a little when the transmission is engaged, and the revs come down to 500-520 I/min.

To get rid of carbon deposits from the combustion chambers, that's a good idea too!

I'm no pro at English, but this is good practise. Just like it is good practise to get familiar with the slant six...

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Everybody says I'm Wrong,
So I quess must be Right!

Well, checked the timing at various revs yesterday.

Half-warm it idled at 1230 I/min, manifold vacuum was a little more than 20 inches of Hg and timing 19,1 degrees BTDC, distributor vacuum canister: no effect on timing (=OK).

When warm it idled at 660-670 I/min, manifold vacuum was about 19 inches of Hg and timing 3,5 degrees BTDC, distributor vacuum canister: no effect on timing (=OK).

A little more revs, at 1130 I/min, manifold vacuum went a little over 20 inches of Hg and timing 16,9 degrees BTDC, distributor vacuum canister: no effect on timing (=Should it be so?)

Still more revs, at 2700 I/min, manifold vacuum was 22 inches of Hg and timing 41,6 degrees BTDC. When the distributor vacuum canister was disconnected, timing was 26 degrees BTDC. (This seems somewhere it should be, or?)

Each time the voltage stayed at 13,11-12,99 Volts, measured at battery.

Some notions?

Ilmo

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Everybody says I'm Wrong,
So I quess must be Right!

Most of what you report is good, You have a good engine to give strong vacuum at idle. What happens when you hook the vacuum back up to the distributor as in example 3. It should be seeing "ported" vacuum at this point, which would put more advance in for cruise. Find the port that has vacuum only above idle, and use this for the vacuum timing canister.
Sam

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Okay, shall find one.

Thanks again for the advice, Sam!

_________________
Everybody says I'm Wrong,
So I quess must be Right!