Join Date: Aug 2006
Location: Arlington, VA
Thanked 13 Times in 11 Posts
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Sure, you can fit any number of after-market 7lb radiator caps.
However, I believe that can be penny wise and pound foolish. The cost of a new Perkins cap isn't going to break anyone, and it's a pretty important part. Maintaining a good fit and the right pressure is important to your engine functioning properly.
Over the years I've tried several different ones, but went back to the genuine Perkins cap. They last many years if you take reasonable care of your engine.