I had a small block (basically stock)built by a shop to install into my street rod. After about 1000 miles, the motor has developed a loud lifter knock upon start up and at speed after driving about 10 minutes.

When the motor was installed I had a single electric fan mounted to an aftermarket aluminum radiator. The single fan would not cool the motor in traffic so I added a second, both pullers. These fans were mounted to a sheetmetal shroud loosely based on a Be Cool setup I had seen on a blown big block car. The setup cooled the car as expected.

THe engine builder is convinced the fans and shroud are cooking the motor and wants a conventional motor driven fan and standard shroud installed before he commits to replacing the lifters under a very generous warranty.

What are your experiences with stock vs. aftermarket fan/shroud setups?