Running lean will cause the engine to run hot and ping. At 4200 RPM the spark advance should already be maxed out so changing advance springs won't do much. Try going back to the old jetting and make sure the float level is correct.

 

thanks Pete,

I did put the larger jets back in and I also found out that an 18 inch fan will clear a stock fan shroud. You're not going to get anything bigger than an 18" fan in there.

I haven't had a chance to run the car on the freeway yet, but running into and around our little town the temp stayed just shy of 180, so I'm pretty happy about that. BTW, the car really likes the larger jets. It's responsive and hits 4,000 rpm almost effortlessly where before even hitting 3000 rpm it just didn't feel, or sound right. So I think I'm moving in the right direction with the jets, even though I'm under carbed.

Wednesday I'll be doing some freeway driving and some metropolitan Detroit city driving, so I guess I'll find out how well the changes I've made help. We'll keep ya posted.

 

Stepping up to an 18 inch fan solved the overheating problem while sitting in bumper to bumper city traffic. It was mid 80's yesterday afternoon and I got stuck in a traffic jamb for about 30 minutes (6.5 miles) and the temp gauge never went above 180.

In the cool of the morning while cruising the freeway to the car show, the car ran about 170, even maintaining 3500 - 3700 rpm. It never got up to 180 till I was in the city, sitting in the morning rush hour traffic. Coming home, I pushed a bit harder and stayed with the flow cruising around 3900, 4100 rpm for about 20 miles and she ran great. I even pushed the car to around 5000 + rpm for around 5 miles on another stretch of freeway and the temp stayed at 180. So I'm sure the car running lean was the culprit.