Reading spark plugs

[nick67vette]

I'm tuning up one of my 67s and pulled these plugs. It was breaking up upon acceleration over 3500 rpm. Just tooling along without dumping it ran fine. It is a 390 with AC and pings under load. Timing set to factory specs with stock ignition components.
Plugs seem to indicate rich carb and moderate fouling on several cyls? Any suggestions to improve performance? Plugs are AC R43XLS? Thanks.

http://img.villagephotos.com/p/2003-7/271178/ACR43XLSplugs6kmilesred390.jpg

 

[magicv8]

IMO step up a heat range to r44 - and if the wires havent been replaced in the last 20-30k miles - it would be good to do it at the same time. The plugs you use indicate late model heads, do you know what they are?

Since your out in the Buffalo area (where I grew up) will you be going to Hershey for the NCRS gig this Sunday?

 

[nick67vette]

Dave, thanks for the reply.

The engine was finished when I bought the car in the early '90s
The heads do not have the raised area between the middle exhaust ports, indicating to me that they are not late model. I never had the valve covers off so I don't know the numbers or dates.

I replaced the plugs with what was installed. I drive this car a few thousand miles a year at most. Usually driven with moderation, but given the opportunity I like to blow the snots out. A few road kills come to mind... The fresh tune up has revitalized performance. Still have mild ping upon hard acceleration with the AC on, perhaps need to play with timing a bit more? Fuel quality is always an issue as well.

I'm looking foreward to a busy working and fun week at the NCRS Nationals at Hershey, and hope to meet you there.

 

[magicv8]

Nic - I'm back, but did not see you at Hershey (we shoulda picked a spot). To get past the pinging with the A-C heat, I installed an accel adjustable vacuum advance - so I could custom curve he advance to allow easy starting, good throttle response, and no ping. My engine has dished oistons, and can easily runon 87 octane, but I use 89 octane with the current settings - for fewer hot start and ping problems with my timing set up.

The old heads use ac44 plugs from the factory, but I finally stepped up a heat reange (to 45) to keep them clean. After buying a Pertronix coil, I was no longer worried about overloading the old original coil by using BOTH resistor wires AND resistor plugs - so I now use both r45s and accel resitor-shielded wires.