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I have a 64 GTO with a TriPower setup. Engine runs well until it fully warms up. When it does, and it sits idling for a few minutes, the idle RPM will start to dip for about 1 second, and repeat every 6-10 seconds, sometimes even shutting off during a "dip". Also, if it is shut off for a short period, as when it's refueled, it takes some effort to restart, and then difficult to get under way, having to feather the throttle. Once rolling, it again runs OK. Measuring the coolant temp with IR shows a solid 180 deg at idle. I don't have a temp gauge yet, but I don't believe it's ever boiled over. I'm 90% convinced that the carbs are overheating during the 2 conditions I mentioned, and it's been suggested that I buy 1/4" phenolic insulators for under the carbs, but no guarantee that this will fix the problem. The engine is a 455 +.040, and I'm pretty sure the radiator is the original for the 389 that was in the car. I use only no-ethanol 93 octane, & timing is set to 9 deg @ idle, and the cooling fan is a flex.

Full engine specs:

460 c.i.d. (455 bored .040 over).
1973 350 heads with 1.6 ratio steel roller rockers.
Hydraulic competition cam, 230̊ duration @ .050, .440 intake & .460 exhaust.
Compression ratio 10.2:1
Intake valves are 1.66" dia
Exhaust valves are 2.11" dia

All suggestions are welcome!
 
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