They should make a little noise, if not they are more likely to burn.

I agree with Tim, every 3 or 4 thousand miles, and if they ever sound suspiciously loud or quiet in between then.

Read the shop manual, and with the engine hot after a minimum 20 or 30 minute drive adjust them closer to the fat side of the recommended range.

Grigg

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
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"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-