[Gaz64]

"Hot" motors ie: cams, heads, compression etc can be harder to start hot for many reasons.

Starter motor current draw can be higher due to heat soak, resistance increases as temp increases, coupled with high compression and more static timing than stock only adds to the "drag" on the starter.

Try retarding your timing back to 7 - 10 degrees to see if starts easier, or even disable the ignition system and crank the engine without spark.

If it's still slow, then start looking at voltage drop loss up to the starter.

Could be a faulty starter motor.