What is wrong with this engine? Accelerates like I am pulling a big trailer

[mustang70]

Where do you have your negative battery cable going? I had mine connected to the block and all of a sudden I started getting shocked when I would touch the engine and the car wouldn't turn over. I added a ground strap between the block and frame and everything worked normally. This might be something you can try.

And for those who are wondering...no, I don't know why it happened, but I think it has something to with the one wire alternator conversion.

 

[pa0101]

As to the choke if it's like the Holley we have it should get full +12v otherwise it will heat too slowly (open too slowly or maybe not fully, ever). This is worth checking, but you can visual the choke plate - does it snap close for start, open a little upon run, and open fully on warmup? Also the extra load of the choke on the "I" terminal will draw more current through the ballast resistor, dropping the voltage to the coil, too.

I doubt you want the choke heater on "I" unless I'm missing something. You want it to full +12v on the "on" position of the ignition switch.

As to your "I" terminal, too bad you can't send a diagram of how this is wired. If you look at a wiring diagram, usually +coil is fed through the ballast resistor from the ignition switch. The -coil terminal is fed by the points in the distributor. That means when the points are closed (I know you don't have points now) the full circuit drops the voltage to +9 or so at the coil, to keep the overall power in the coil lower, to avoid burning the points more than needed while running.

On crank for hotter spark, the "I" terminal is supposed to have full +12v which bypasses the ballast resistor. On no crank (any key setting other than start) the "I" terminal should be an open circuit. It sounds like yours is not, or I can't figure out some other miswiring from the words.

If, with the Pertronix, you are trying to get full +12v to the coil all the time, then you should NEVER have +9v anytime ... do you have +12v on the coil, key on? If you only have +9v on the coil, then maybe these are related. You say in another post you did bypass the ballast, but if you did, you would not have +9 from it. Maybe remove the ballast resistor entirely, unplug it, see what changes?

 

[oz]

Yes, I have very close to 12 V to the coil through the wire. When i hook it to the '+' terminal on the coil, it drops to ~9.5 - the Pertronix unit in the distributor puts a load on it and drops the voltage(?). I confirmed this by disconnecting both wires from the coil terminal and checked the voltage in the wire before and after connecting just the Pertronix.

As for the choke heater - same deal. The incoming wire (to 'I' terminal carries almost 12 V but when I attach the choke, it drops to under 10 V.
The choke operates normally - it closes when i poke the pedal and it opens slowly (and completely) within a few minutes of start up.

The coil only has 4 wires to it. '+' has the incoming 12 V from the key (bypassing ballast) and a wire going to the Pertronix under the distributor cap.
'-' has the tach wire and another wire going to the Pertronix.

I have good grounds. I checked the engine and frame to the voltage in the battery and it was all identical (I already have a ground strap between the engine and the firewall - my buddy forgot his and had ignition problems...)

I did wire directly to the coil from the battery and it did not change how the engine ran so this issue may effect my startup but I am inclined to doubt that it is the root cause of my poor idle, low vacuum.

I broke down and took the car in for the exhaust installation and my wife (who followed me) said there was a good amount of black smoke when I accelerated hard. Maybe at WOT it's running rich - but again, that wouldn't explain 8 to 10 inches of vacuum at idle since the carb seems to respond to idle adjustments as normal (dies if I turn the needles in all the way).

 

[bull999999]

How's your oil pressure? I found out the hard way that an engine without any oil pressure as about 13" of vacum at idle.

 

[pa0101]

"When i hook it to the '+' terminal on the coil, it drops to ~9.5 - the Pertronix unit in the distributor puts a load on it and drops the voltage(?). "

This is not good, there should not be such a drop. If the drop was solely due to a 1.5 ohm coil then that's like 6 amps in the coil which would melt it in short order at 100% duty cycle. Of course the whole point of the points or Pertronix is that the duty cycle is very short and the spark is generated on switching.

You should look again at this wiring!

 

[oz]

CRAP!
To clarify, the drop is from the Pertronix - if I hook the 12V line from the key directly to the pertronix (and don't connect them to the coil) there is a 2 V drop as measured between them and the battery negative. Suposedly one avantage to the Pertronix is that it will fire down to zero RPM - it would make some sense that it would draw something even when it's not turning I think.

Not sure where to start checking (or what I'm looking for) since the hookup under the dash was pretty straight forward (splice around ballast resistor, wire directly to coil...). I guess I need to pull the key cylinder down again and measure some voltages there.

I think i will call Pertronix and just go through it with them to confirm what I have is 'normal'
Thanks!

 

[ratio411]

If the Pertronix is drawing current or not, there will be no drop in voltage.
The drop will be in some other measure.
Does that make sense?
I don't know alot about electrical, but if the part is supposed to operate on 12v, then it will pull 12v if the battery has it to pull.
Dave

 

[pa0101]

Just to emphasize the point, if you know "ohm's law" then you know that voltage drop is a function of current in a resistor. Wire of any gauge has some resistance, so with enough current you'll get voltage drop. However, in practical terms, most of the voltage drop has to be with the device being powered. Think of the headlights. The resistance of the switch, wire, etc. must be a LOT smaller than the resistance of the bulb itself. Otherwise the wire would glow/burn up, like a fusible link does. So that 2 volt drop "when the Pertronix is connected" is a statement that there IS current flow, but so much that 2 volts is lost on a 6 foot length of, what, 16 gauge wire? One table I found has this as 4 ohms per 1000 feet, so let's just say it's 10 feet, hence 0.04 ohms. Two volts drop would imply 50 amps in the wire, obviously not possible. Meaning there must be more resistance in that leg. Has to be, unless the problem is with ground reference (the drop is in the ground leg of the circuit). That's why I think, somehow, the ballast resistor is still in the circuit. Or maybe there's a really crappy connection somewhere, high resistance.

 

[oz]

pa0101,
Yea, that makes sense... V=IR... I knew there shouldn't be a 2 volt drop from a ignition pick up.
I did check the main ground loop (body, engine block, battery) but I need to look at the key loop I think. Perhaps the key switch or the wires leading to it are weak or are not grounded properly. I guess i need to get a wiring diagram and really check every ground that exists (and every wire I removed and reinstalled during the restoration).

Thanks!

 

[Ozsum2]

pa0101,
Yea, that makes sense... V=IR... I knew there shouldn't be a 2 volt drop from a ignition pick up.
I did check the main ground loop (body, engine block, battery) but I need to look at the key loop I think. Perhaps the key switch or the wires leading to it are weak or are not grounded properly. I guess i need to get a wiring diagram and really check every ground that exists (and every wire I removed and reinstalled during the restoration).

Thanks!

You could always get the 12 volts needed from a different source under the hood.

 

[ratio411]

...Perhaps the key switch or the wires leading to it are weak or are not grounded properly...

Have you tried to run the car 'hot wired'?
As in battery power from the battery rather than key switch.
I thought one of your posts said you had...
If you have the same issue like that, then it is not your key switch or wiring harness.
Dave

 

[oz]

Yes, I ran the 12 V from the battery terminal to the coil directly and it made no difference. I will still go through the wiring to figure out where the voltage drop is occuring (because it does not want to turn over some times) but I am pretty sure that this is not the root cause of my low vacuum.

I am to the point where I may just bite the bullet and take the front cover off the engine and move the cam gear to the +4 degree keyway and see if I have better vacuum at idle. Instead of tearing the whole thing apart to degree it properly, it would be quicker and easier to just 'trial and error' it. If advancing the cam does not help then it will be back to the drawing board.

It's strange that the engine kind of acts the same as it did before the rebuild as far as sluggishness... I have thrown around the idea in my head that the crank keyway is in the wrong place such that a cam installed straight up is actually retarded a few degrees... just a thought though. Visually the piston was at TDC when the balancer was at zero so it doesn't really make sense.