Early 70's electronic distributor
The advantage of the dual point is mostly at the drag strip. They provide more time for the coil to saturate at engine rpms where the time between cylinders firing is less than half the time available at idle.
Here's the range of timing expected with an original '69 340 distributor for automatic transmission.
It's based on the specs in the Dodge Service Manual.
According to Dodge (sometimes Plymouth was different) base timing should be set at 5 *BTC
And here's the comparison with the advance of a Chrysler built MP distributor using 7.5 *BTC for the initial.
That 5 degree initial was spec'd to reduce CO and HC emissions. With advance curves like the ones above, it would be worth setting initial a few degrees higher.
If it doesn't cause any ping or detonation, it should prodiuce better milage, throttle response and slightly cooler engine temperatures. For a comparison, the initial timing in the 1967 Plymouth manual for the 273 -4 bbl engine was 10 *BTC (non-emissions versions)
The vacuum advances of the original 340 may come in earlier. I know the '68 version does. But the MP vacuum advance can be adjusted to come in earlier as well. So as far as advance curves go with magnetic pickup distributors, these look like reasonable options.
The advantage of the dual point is mostly at the drag strip. They provide more time for the coil to saturate at engine rpms where the time between cylinders firing is less than half the time available at idle.
Here's the range of timing expected with an original '69 340 distributor for automatic transmission.
It's based on the specs in the Dodge Service Manual.
According to Dodge (sometimes Plymouth was different) base timing should be set at 5 *BTC
And here's the comparison with the advance of a Chrysler built MP distributor using 7.5 *BTC for the initial.
That 5 degree initial was spec'd to reduce CO and HC emissions. With advance curves like the ones above, it would be worth setting initial a few degrees higher.
If it doesn't cause any ping or detonation, it should prodiuce better milage, throttle response and slightly cooler engine temperatures. For a comparison, the initial timing in the 1967 Plymouth manual for the 273 -4 bbl engine was 10 *BTC (non-emissions versions)
The vacuum advances of the original 340 may come in earlier. I know the '68 version does. But the MP vacuum advance can be adjusted to come in earlier as well. So as far as advance curves go with magnetic pickup distributors, these look like reasonable options.
