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Follow the bouncing tach?

Alpine 1789

SAOCA President
Diamond Level Sponsor
Just to update/close this thread, I finally replaced my distributor - swapping the old, Pertronix-converted, one* with a full Pertronix unit - and the bouncing is better but still there. The car is running great with the new dizzy - I got it from Rocco/Mototron; it used to be on his race car and he thought it had a better advance curve for my engine - and I think I can live with the remaining bounciness. My inclination is to not worry about it and just leave well enough alone.

To prove some before and after comparison, I had a wonderful drive in perfect Alpine weather yesterday afternoon! The impact of the new distributor is subtle, but very nice. I really smooths things out. As for the tach, here is a video made in about the same area, at the same point in the drive.

https://youtube.com/shorts/zDqN1L0d_K0

For comparison, here is the old one that is most comparable:

https://youtube.com/shorts/KbDV757se1E?feature=share

Jim

*My old distributor was not the stock vacuum advance unit, but the mechanical advance one used in the H120 Rapiers. I switched to that one when I was running the DCOE's and never bothered switching back. The Pertronix unit is also mechanical advance.
 

Alpine 1789

SAOCA President
Diamond Level Sponsor
Just to update this, Tom had suggested earlier here - and in a PM to me - that the problem might be heat related and, no surprise, it looks like he was correct. I took a short drive this morning and the tach was steady. It was about 55 out, although I am sure the garage was a little warmer. Still, while it wavered a bit when I changed RPM's, it was pretty much rock steady the rest of the time. So, it would appear that the problem is definitely temperature related. Tom and I have been in communication and he is going to be doing some testing on other tachs to see what he can learn. I am sure he will update this thread when he knows more.
 
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