Hi,
Just looking for some ideas or suggestions for an issue I'm having with my car. 1970 base engine (350/300hp) automatic THM400 transmission. I'd like to first mention that my carb was rebuilt by Lars about 1.5 years ago, so I know that it was done right, and likely not the cause of any issue I'm having...

About a month ago, I was experiencing some hesitation from a dead stop, or even at low speed (2nd gear) and accelerating a bit... and also on wide open throttle there would be a hesitation. It only appeared to happen when the engine was hot. When cold, I wasn't experiencing any hesitation. I stopped at my mechanic's place, and he drove with me, and could see what it was doing... it basically was doing it just acceleration from a stop in his driveway. He had a spare coil, so he replaced my coil with his, (my coil was very hot, could barely touch it, not sure if it's supposed to be that hot or not) and as soon as he put his in, the problem completely disappeared... I had a spare MSD Blaster coil at home, so I got that one and he installed it for me. From then, I wasn't experiencing any issues.

Yesterday I went for a drive, and drove at high speeds (60-70mph) for about 45 mins, then for a good section of the ride on backroads (about an hour) i drove at 25-35mph... when I arrived in town I was at a stop light (idle is spot on at 600-650, so issue idling), then the light turned green, and i pressed the gas, it almost stalled, let off the gas, it didn't stall, then accelerated a bit, and then I could start feeling hesitation when accelerating. At a constant speed, there are no issues. I drove back home on the highway, and it runs really smooth with no hesitation, wide open throttle was not an issue either.

So to me it's only if I'm driving 25-35pmh for an extended period is when it seems to hesitate.

I have a "stock" distributor except that I installed a Breakerless SE system to replace the points... and the coil that I bought was an MSD Blaster 2 part#82023... Is this possibly an incorrect combination... I read some things about resistance, but know nothing about it.

Can a hot coil produce this type of issue? My mechanic is leaning towards a spark issue and not fuel. I put new MSD spark plug wires about 4 months ago... it has a new fuel pump from last year...

Just looking for some ideas... the car is "finally" close to running perfect, except for this latest hesitation...

Thanks.

 

Tell us about your fuel pump.

 

What do you want to know about it? It’s a new mechanicsl fuel pump that was installed last year.

 

new oil-filled 82023 coil --- did you maintain OE mount or similar vertical mounting?

Breakerless SE instructions specify it's for use w/ OE coil or with coil having primary resistance between 1.2 - 1.8 ohm. Seems as though 82023 coil resistance 0.7 ohm --- TOO LOW

 

Thanks pedantic...
It is mounted OE which on my car seems to be at a 45 degree angle... so would a too low resistance cause this type of symptom?

I measured the primary resistance at 0.9.

 

Do you know of a replacement coil that has the proper resistance?

 

standard Ignition Blue Streak UC12X --- repeat UC12X
local NAPA or RockAuto $21

 

FWIW, and in general, resistance increases as temperature increases. Yes, that's an over simplification; but true.
Unless I was broke down with no other way home, I'd pass on the lesser UC12 --- as the UC12X is the premium "blue streak" version --- that "X" matters

CF member 69427 is an ignition pro here, and, if needed, can correctly explain in detail.

 

I don't know much about pre-HEI ignition days.
However, you stated you went from point / condenser IGN system to a breakerless system.

Its my understanding that the starter solenoid has the extra wire stud marked "R" for the old IGN. Different voltage for the dizzy?
Now you have the newer IGN.
Did you remove that wire from the solenoid, or do you need to remove it?

 

Ordered a UC12X yesterday... going to give it a try. Thanks for the info.

 

Even though the carb was built 1-1/2 years ago it doesn't mean the accel pump can't go bad. With the engine hot and "off," remove the air cleaner and look down the primary throttle bores. Flick the throttle about as much as you would move it when accelerating from a stop and verify that you have an instant fuel shot coming out of the accelerator pump discharge nozzles. It should be an instant and strong fuel stream. If fuel only "dribbles" out the nozzles, or if there is some travel range on your throttle movement when there is no fuel discharge, you have an accel pump problem.

Lars

 

No idea about breakerless, but this is what I first thought reading this. Might not matter.

I think it's the S lead on the solenoid that goes to the coil so when you when you turn the key to start the coil gets full 12v. When the key rotates back to run that stops. The coil has a second lead from the harness via a 'resistive wire' that provides juice to run. That wire does the same function as a ballast resistor did in C2s. It ain't quite the full lightning bolt that the S lead provides by design. This is why you're supposed to find somewhere else to connect an electric choke lead.

 

That's not correct. The wire going to the solenoid "S" terminal is the wire from the ignition switch that engages the solenoid to turn the starter over. When power is applied to "S", the solenoid slams in, and the starter cranks. When the solenoid slams in, it puts full battery voltage to the "R" terminal, which has a wire going to the "+" side of the coil so the coil receives full 12 volts as long as the starter is cranking. The second wire attached to the "+" side of the coil is the ignition power wire from the ignition switch. It is usually a cloth-wrapped wire, and it's a resistor wire providing reduced voltage when the engine is running. Some aftermarket electronic conversions and coils require that the resistor wire be bypassed so the coil receives a full 12 volts during running. Other conversions do not require a change. You do not need to disconnect the wire coming from the "R" terminal on the solenoid no matter which system you have, since it provides a clean 12 volts during engine start. Determine what manufacturer conversion you have and read their installation instructions. Or convert the car back to a good set of points with a stock coil and eliminate the problem...

Lars

 

Thanks for the information Lars... I will take a look at the accelerator pump, although it was replaced last summer "for the heck of it" to see if it would resolve an issue I was having last year, but turned out it wasn't the accel pump... but I will certainly look at it again... the reason I am leaning towards ignition is that about a month ago, it was hesitating during mild to heavy acceleration when the engine was hot and as soon as my mechanic friend changed the coil to a coil he had in his garage, the hesitation disappeared immediately. I then had a coil at my place that he put in for me to replace his... the one I had at home is the MSD Blaster 2...
When I look at the Breakerless SE instructions it lists the following related to the coil:

COIL The Breakerless SE is optimized for use with either the factory original coil or Breakerless Replacement Plus series coil. Substitute coils that have a primary resistance of 1.2 to 1.8 ohms are also compatible. Very low resistance MSD Blaster and Accel Super coils are supplied with a supplemental resistor to raise the primary resistance to 1.5 ohms. Failure to use this supplemental resistor will damage the Breakerless SE module. IMPORTANT: Ballast Resistor - This ignition is designed to work with the factory installed ballast resistor. The ballast usually takes the form of resistor wire that is part of the engine compartment wiring harness. It may also be in the form of a small white ceramic block mounted on the firewall in series with the +12V supply to the coil. Its purpose is to limit current to prevent coil overheating and point burning. The ballast typically has a resistance in the range of 1.2 to 1.8 ohms. The ballast resistor (or resistance wire) should not be removed when installing the Breakerless SE If the points have been wearing normally, then the ballast is in place. If the points burn up in about 300-500 miles (or less), then the ballast may be missing or damaged. If the stock coil has been replaced with low resistance (CDI or HEI) type, this would also cause the same effect. Correct any problems before operating the ignition. IMPORTANT: Ballast Bypass – The draw of the starter motor will cause a modest to severe voltage drop in the electrical system. To assure the coil will develop sufficient spark voltage, the ballast resistor is bypassed during cranking. This is typically accomplished by a wire in the factory installed engine harness that runs from the starter solenoid (R) terminal to the coil (+) terminal, or splices into the harness near the coil. The Breakerless SE will usually function if the bypass is missing; however, to guarantee starting under all conditions the bypass must be in place.

It mentions that it's optimized for factory original or one with a primary resistance of 1.2 to 1.8 ohms. The MSD Blaster 2 is rated at 0.7 ohms. It states that it could damage the module if it's not 1.2 to 1.8. I'm not sure maybe I have damaged the module since this coil has been installed for about 3-4 weeks now with no supplemental resistor to raise it to 1.5 ohms.

Another solution is to put it back to points as you mentioned.

Thxs