fluctuating tach
hello fellows, I've a question/ concern. I only have 4 - 1/4 mile passes in my camaro and I'm still working the bugs out. I've got 1 problem that I'm concerned about. Above 7000 rpm my tach flutters a lot, causing it to bounce off the rev limiter much sooner than I expect it to(7600rpm). (555ci dart cnc 355's, hp unknown est. 900, t-400, 9" 5000 stall conv - 33.5 inch tire/ 4.88 gear - 3300 lb w/ me in it). once I turned the dial up to 8000 on the my last pass, it still fluttered, but not high enough to hit the limit .It pulled strong thru the traps and recorded my quickest pass to date which is 9.41 @ 142.??. Now, the 60ft was a 1.35 spinning with a soft 3000rpm launch off the t-brake with old slicks. I have yet to really turn it loose, due to other concerns.
Now, the tach is an autogage that was in the car when I got it and my 1st thought was to replace that and go from there. but a friend mentioned it could be bad valve springs. Now that made me think - the tach is only showing the signal that it receives from the msd, is that right?
the springs are comp cams 947's that were not new when I got the heads which came off of a 572 that had been out 9 times, maybe 50 passes. So far, it's a tough read for me.
What are your thoughts?