My(351C.) motor just started taping loud on a cold starts then after about 1 to 2 minutes it completely goes away and sounds like a smooth running motor. I was running castrol 10w40 and switched to valvoline vr1 20w50 but it still makes a loud tap on a dead cold start. I went with the thicker oil seaing how I live in Florida and its about 90 to 100 degrees every day but when I switched oil weight it didnt make any differance.

The first time I noticed this was about 2 weeks ago. I set the timing to factory specs at 0 and reset the points and replaced the springs in the distributar. I started it up and it made a very loud tapping noise so I shut it off and looked every thing over good and started it back up and it made the loud tapping noise for about 1 minute then it slowly went away till it sounded like a smooth running motor. So I changed the oil to (20w50) then drove the car for about 2 days and it didnt make any noise on a cold start, but after I let it sit for about 2 weeks and I started it up the other day it was making the loud tapping noise again.

I set the timming at 0 becouse I belive the motor has a factory size cam and thats what my books say for a 1972 351C. I dont realy know what to think, what do you guys think?

PS. I just want to get 1 to 2 years out of this motor until its rebuilt. It runs pretty strong and looks great, but I want some more power under the hood.

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68 ford fairlane:
351C.