Help! I need a good mechanic!

carfan said
Just to give a different idea, back in the early 70s a friends shop had a then newer impala that had the same problem they did the carb, filter, fuel line clean and tune up and sent the car home, next day little old lady is back with same problem after checking every thing and coming up with nothing they did a valve job, sent car home, next day cars back with same problem out of desperation they replaced the 350 with new one and sent car home with granny, you guessed it next day same story.
They finally found the problem, remember this was a new car, a baffle in the muffler was lose and when it warmed up would block the tailpipe and the car wouldn't go over 25 mph

That was a very common occurrence in the 70's. For what ever reason GM decided to make their exhaust pipe double walled. The main problem was running into a water puddle when the exhaust was hot. The outer wall would cool instantly, crushing the inner pipe and blocking the exhaust. I can't tell you how many customers pipes we would cut and discover this had happened. Funny thing is, it would happen instantly, making the customer think it had something to do with water in their electrical system. I had forgotten all about that phenomenon till I read your post.