You might want to use copper elbows, I have had PVC get brittle from heat in a custom indoor pool heating system, the boiler was set at 180 degrees which is roughly the same as our engines are running.

1957 Chevrolet 5700 LCF 283 SM420 2 speed rear, 1955 IH 300U T/A, 1978 Corvette 350 auto, 1978 Yamaha DT175, 1999 Harley Davidson Softail Fat Boy