Tapping Under Valve Covers, Sewing Machine Noise?


New Member
Nov 16, 2017
my 66 coupe, 351W has a tapping sound that we can't seem to cure? like said its like a fast sewing machine sound and to cure it we've redone the cam/lifters/roller tip rockers and adjusted the valves several times? it's a comp cam (hydraulic), trick flow roller rockers 1.6, alum heads, edelbrock intake, and still the tapping. it's not as bad while cold and gets more pronounced the hotter it get? and added the tall valve covers as to give the rockers the room to move. any ideas??? tks a lot
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Yeah the oil shield isn't all that invasive and I went from big steel covers to the alum. tall versions. And going through the valve align again is on the list for this weekend. Have put about 500 miles on it since the new rockers, but still am not convinced it'll make any difference. Done this like 5 times. :( Just that sewing machine noise, can't handle it...lol
How thin a motor oil are you running ? Above 0 degrees 20w50 could be the cure you need..

These ran with leaded fuel to keep the valves from sticking. Are you on the original guides?

Products like lead additives and octane boosters could also help.

If I remember right , louder after it warms up means you need thicker oil.
I am running the conventional Valvoline 20w50 Racing Oil so I think I'm good there...would going with new rods and guides be something to do or would that not really affect the tapping noise?
Try a little penetrating oil on the guides and see if the sound goes away. Look for bad or bent stems. I think you problem is not letting the new or old work right. The lead really is needed for a stock head. After adjusting so many times , I think is worn parts or lubrication.
Just a thought, or actually a couple questions
What cam (lift, duration and lsa)
The reason I ask is because you could have valves touching the pistons, happend to me, sounded like a sewing machine like you discribe, not enough to bend anything
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