Are my headers over heating my starter?

[Ed F]

My '70 C10 350 is the only vehicle I have ever had headers on. They were on it when I bought it and I plan to change back to manifolds eventually. Not always, but frequently when the truck has been running for a while and I shut it off, the starter rolls over slowly like the battery is low. Let it sit for 15-20 minutes or more and it fires right up. I have replaced the starter twice and now have a heavy duty starter on it. I installed a new battery and battery cables and have a ground strap from the firewall to the engine. Are the headers possibly overheating the starter? If so what are you guys with headers doing to eliminate this situation? As always thanks in advance for the help