Issues with a 1972 Daytona

Back in the 70s and 80s, I serviced quite a few Daytonas but the one I'm working on now has me puzzled.
It's a 1972 US version with the six lobe distributor cams. It also has coils that have a third wire that goes to ground.
The car had been sitting for around four years.
A while back it was fitted with MSD point-triggered ignition modules.
When I went to start it, I noticed that there was no spark from either bank. I bypassed the MSDs and attatched the proper wires to the points.
Immediately, I had a nice strong spark.
I started it and it settled into a perfect idle but when I opend the throttles, it backfired violently through the carbs.
I drained the fuel (which had turned brown) and put in fresh fuel.
I checked the resistance of the spark plug wires and the value was between 900 and 1700 ohms.
The point resistance is within limits - very low.
Still backfiring.
Any suggestions?

Bob Z.

 

Check the distributor advance. Use your timing light - run up the RPMs and see if the strobe advances. I don't know the Daytona spec, but it should advance 15º or 20º.

 

What did you change?

It's possible that the advance mechanism is stuck but I've had enough adventures with those distributors to know to think "outside the box".

Are you certain that the plug wires are all on correctly?

Is the problem in just one distributor or both?

If it was here I'd probably pull the distributors and check them on my machine.

 

Hi Bob, I had some backfire issues on my single distributor C4 once and I found the wires on the resistors attached to the coils were loose .My OHM meter showed way more than the expected value along with intermittant current.Might be worth a look. Good luck,Mike

 

Sounds like timing, Did you try it without the MSDs?

I recall full advance being at 5K.

 

Hi,there is a thread in the Vintage section,search under Dinoplex,that refers to the Daytona ignition wiring that maybe of help.

 

I could be completely off the mark but I had a TR6 with the same problem, turned out it was just way too lean on the mix. Idled fine, pop the gas pedal, and it backfired through the carbs like crazy.

Any number of possibilities, I guess, but too lean is a pretty easy one to eliminate, right?

D

 

With six Webers, random fiddling could be trouble. Better to narrow down the problem first. He started with the ignition system, I'd make sure that's right before introducing more variables.

 

Sitting around for years, fuel turned brown=blocked carb passages

 

The coil with the third terminal is a BAE203A, that would be the correct setup with a late US Daytona with an AEC103A Dinoplex. As already posted, remove the distributor and check the advance mechanism, the backfiring indicates a timing problem if the air/fuel mix is ok (check this first).

Does the Daytona have the original anti pollution/air pump setup which was standard for the US models? The retard mechanism activated via the microswitch on the weber carbs could have a similar effect if the points setup in the distributors has been modified or incorrectly wired (as example, by reversing the connection to R1 and R2).
Would recommend disabling the anti pollution setup/advance retard if it is still active. I can walk you through the necessary steps, let me know.

Best
Adrian

 

Gentlemen - thanks for all the good tips.
Here is a bit more info.
All emission controls have been removed or disabled, including the air pump and secondary points.

I am running it with just the points, condensers and coils.
There are no ballast resistors in the circuit.

Question: the spark plug wires are the resistance type, stock to the car. Will they work with a standard non-electronic ignition?
Is there any problem using the BAE203A coils with just points?

When the car was idling, there was subtantial leaking from all carbs. I have ordered rebuild kits and will install them next week after a thorough cleaning.

When I worked on the car last week, I did not have time to check the timing or advance mechanism. I will do that next week. BUT, when the car was put in storage, it was supposedly running OK.

More suggestions?

Bob Z.

 

Not sure if those coils are a problem but I expect they should work if hooked up right. Plug wires should be okay if resistance isn't too high. If timing and advance are reasonably close, it should run. Is it hitting on all 12?

It's possible that the carbs are part of it. If the accelerator pumps don't squirt it might lean out and cough. What happens if you throttle up slowly? Does it follow or go all crazy?

 

The BAE203A should have the standard red Marelli resistor mounted on the coil bracket, this is required for a points setup. You don't need to add it for the tests you are running right now but would recommend to add it if you ever need to drive the Daytona with points only to avoid overheating the coil and burning out the points quickly.

No problem

No problem, the BAE203A actually contains two coils, one for the AEC103A CDI ignition setup (terminal K & 31) and one for points emergenza mode (terminal +B & 31). In the factory Daytona US setup the Marelli ballast resistor is wired inbetween terminal 31 and the points.

 

It might be a good idea to open up at least one of the carbs and take a look inside to check for corrosion or gunk clogging ports or jets.

 

I have run mine on the coils with the factory wires.