just got me a 75 blazer.im kinda green when it comes to engines. had a re-built th350 installed, had a compresion check done and the motor is very strong (150 and even on all) it has Hei. anyway, it ran good when i got it except a weak tranny which i already replaced. its starting to run bad. power loss and hesitation. its taking longer to start as time goes by. is it a timing issue?