Backfire on load - idles nice

[jp16v]

Well I think it's an anti-climactic end to the brief saga.

Tonight, I dialed in the dwell and grabbed my can of starter fluid again to look for vacuum leaks. No leaks...

I went and grabbed my neighbors cap and wires and carefully routed the wires to the appropriate locations. In doing so, I bumped into the exhaust by the #4 and expecting to be burned (again), reflex took over and I jerked back. It was for nought because the pipe was stone cold. It was the same for the #2 cylinder. After placing the wires and cranking her up, the backfire was gone.

Now, I'd like to say, "yep, them there wires were faulty" (and they could very well be), but there is the distinct possibility I had them miswired

I still have to tune out a flat spot when you stab the throttle, but the backfire is gone. My preheat tubes are nice and toasty now, too (at least 2nd degree burn hot). My timing signal is now dead on (which makes me once again want to blame the wires). I'm ordering a set of Bosch plug wires (cap & rotor, too) for good measure.

[Scott Novak]

I'd recommend that instead of a Bosch distributor cap that you buy either a Blue Streak cap, or the Magnition cap that CB Performance sells. I strongly suspect that CB's cap is made by Blue Streak. It's a higher grade plastic than Bosch and stronger. I used the Bleu Streak cap on my Bosch distributors until I switched to a Mallory distributor.

The Bosch resistor rotor should be replaced with a non-resistor rotor, or you can modify the Bosch rotor and solder a jumper wire across the resistor to bypass it.

DON'T buy carbon core or ignition wires with resistors built in to the spark plug ends. Buy low loss magnetic suppression ignition wire.

By eliminating all of that spark power wasting resistance, you can increase your spark plug gaps by 0.005" for better performance, and still have radio noise suppression.

If you want a truly great set of ignition wires that won't let you down and will probably outlast your engine, try Jacobs 8.5 mm Energy Core silicone ignition wire. The boots are permanently bonded to the ignition wire so you can hose them down with a garden hose and they will still fire your spark plugs. They are rated for 65,000 Volts. Granted, you can never use the 65,000 volt potential in a Bosch distributor, however the thicker silicone insulation makes them very low loss.

Summit Racing sells them for $73.69
JAC-4009412 Spark Plug Wire Set; Ultra Fit Silicone; Spark Plug Wire Set

But if you watch e-bay and the Samba sometimes you can find them cheaper.

Scott Novak

[peter213]

What pressure were you actually getting from the fuel pump??

Uncap the retard side of the vac can. Leave vented to atmosphere..

You actually have ~12V going into the coil on the hot (+) side when running? Points connected to (-)?

Brake cleaner can work better to find vac leaks and is non flammable, it will slow/kill the engine if it gets sucked in, puts the fire out.

The resulting exhaust can put you out too, only try this in a WELL ventilated area.

Sorry to regurgitate an old issue, but I noticed you comment about the coil voltage.
My '74 T2 bay 1800 (I think) has 12V when ignition is on, about 5.5V when idling and between 2 and 3V when revving.
Do you know what governs the voltage?
I couldn't find any info about this.
Thanks in advance.