Question on plugs for dart 320 heads
 

I have a set of dart 320 heads and plan to put them on a 509 dart block. The dome on the Ross pistons I have could hit the plugs. I was told to run an Autolite 23 plug. This plug has a short projected tip. What plug would work better and offer more clearance? Someone sugjested Bosch +4 but I don't have a number for the plug.
Thanks Steve

On my 539, I run the Dart 320 heads along with Ross pistons. I had to cut "fire slots" in my pistons, run the Autolite race plugs, and index to keep from closing up the gaps. I have two different sets of the Dart heads and one set uses the gasket seat plug AR3933, and I have also used the NGK plug R5671A-8 (stock #4554). But the other set of heads use the tapered seat plugs and I can't remember the numbers, right now.

Bill M

Index your plugs,I had the same heads........Had no choice but to do
indexing......I would index multiple sets of plugs on the engine stand so I wouldent break my back while the engine was in the car.
If you do it this way you wont even need washers...


Also,Bosch plugs would not be what I would use on a BBC race engine

Steve use AR3933 Autolites you should be fine if its a standard deck and the heads haven't been shaved,you won't need to index them either

When you do the freshing up on the engine, you might want to look at using JE pistion. They already have the fire slots machined in them. We had the same problem with the 565 ci and the 598 we use now.