Re: 305a V6 ignition parts
 

66 V6 C motor...Ignition Question: Today I pulled the spark plugs(after a healthy dose of carb cleaner and air pressure to blow away the gunk, leaves, rat hair, etc.) and what I removed were 6 Autolite #66 plugs. Half of the exposed threads obviously were covered in gunk and were not in contact with any threads. It is a long reach, medium heat range plug, I suspect. I went to the local O-parts store and they sold me, after looking up the data, the same long reach plug. The question I have is that the threads in the cyl hd are for short reach plugs, the 3/4 inch size plug with the long reach when tightened down seats into the hole by friction not seeming to torque down correctly and the plug gaskets are not being compressed. Does anybody have the correct modernplug type that fits this application? Thanks

Re: 305a V6 ignition parts
 

On the Jolly Page for "known good part numbers" it says for 1966: AC Delco AC4 (of course any equivalent is OK). 3/4 reach.
http://www.oreillyauto.com/site/c/se...kup&vi=1438134
16 to choose from, take your pick. Be careful of what they gave you, an Autolite #66 does not seem to cross to 1966 GMC 305. It is, as you say, a 3/4 reach, copper core. If you are saying that you measured the reach on what they gave you and it does not crush gasket, it has to be a dirty hole/threads or somehow the base diameter is too big? Make sure you find out what the torque should be and torque the correct plug to spec. Go to the counter at O'Reilly's and measure length and dia. of one of the one's I linked and compare to a #66.

Re: 305a V6 ignition parts
 

I have a 351E that came with the Autolite 65 plug basically a step down in the heat range from the 66 plug. It does have the corect 3/4 inch reach. I used it as a cross reference to come up with a plug compatible for my 478 and HEI to run .060 gap and came up with AC plug that was used in later model GM 4 cylinders.

Re: 305a V6 ignition parts
 

Thanks for the info guys.

Re: 305a V6 ignition parts
 

Scott, to help I.D. whether or not something has been changed on your 305A, I will go to the bldg and take shots of my 305A distrbutor, and see if that helps any - I have not had to hunt ignition parts yet, but will this coming year when we paint the truck and get her reassembled and driving again, so it will be good info to know if these are indeed hard parts to find for the 305A. I will post pics later this evening

Re: 305a V6 ignition parts
 

I decided to check distributer caps on several engines, 305 a small cap screw down, I found one 305e with that same cap, one with spring loaded 1/4 turn, one with 1/4 turn with window to adust points. 305 d 1/4 turn. I can see how this can get confusing with people making changes over the years. Bob