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Joined: Jul 2010
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Hello!
My hood tach used to be fine, but then the lights went very dim and the functioning became erratic. Turns out the hot & ground were just old wires with bad connections. Ran new wires..
Lights are bright and hood tach works, but maxes at 3k RPM. Engine revs higher, but the needle stays at 3k until the RPMs come below 3k.
Any guess as to where to dig?
Thanks!
1968 Firebird 400 Convertible Original: Engine, Intake manifold, Heads, Body, Stereo, 3.08. THM400. Engine rebuilt by Ken Keefer early 2012. New: Holley 4bbl 670 HP, hidden iPod setup, RobbMC mini starter, A/C, front disc brakes 
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Joined: Apr 2010
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Hello!
My hood tach used to be fine, but then the lights went very dim and the functioning became erratic. Turns out the hot & ground were just old wires with bad connections. Ran new wires..
Lights are bright and hood tach works, but maxes at 3k RPM. Engine revs higher, but the needle stays at 3k until the RPMs come below 3k.
Any guess as to where to dig?
Thanks! Did you change your ignition system?
Engine Test Stand Playlist: https://www.youtube.com/playlist?list=PLwoxyUwptUcdqEb-o2ArqyiUaHW0G_C88restoring my 1968 Firebird 400 HO convertible (Firedawg) 1965 Pontiac Catalina Safari Wagon 389 TriPower (Catwagon) 1999 JD AWS LX Lawn tractor 17hp (my daily driver) 2006 Sequoia 2017 Murano (wife's car) 202? Electric car 203? 68 Firebird /w electric engine 2007 Bayliner 175 runabout /w 3.0L Mercuiser__________________________________________________________
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Joined: Jul 2010
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Ignition went from points w/external coil to generic HEI a little over a year ago.
I think that is around the time my leads seemed bad... which was just fixed a couple of days ago (and now the 3k max)
So there is a chance this all coincides.
Is there a way to test that case?
If it is the case, any ideas on what can be done to fix this?
1968 Firebird 400 Convertible Original: Engine, Intake manifold, Heads, Body, Stereo, 3.08. THM400. Engine rebuilt by Ken Keefer early 2012. New: Holley 4bbl 670 HP, hidden iPod setup, RobbMC mini starter, A/C, front disc brakes
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Joined: Oct 2009
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Could it be the needle is mechanically stuck. Also I have noticed that mine takes a while to get "activated" after sitting a while. Not sure if it is mechanically hanging up or some leaking caps, but its almost like it needs to be waken up.
Larry
1967 Sprint Convertible
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If you go to an HEI ingnition you usually need a "tach adaptor" to go with it. It boosts the signal. Accell makes one and so does MSD. The output signal is different on most HEI systems, it puts out a much different pulse to the tach that is quicker then a set of points puts out.
86 Pontiac 2+2
69 Firebird Coupe(Under Construction)
69 Firebird 4 speed Vert Driveable but Under Construction
64 1/2 Mustang (Under Construction)
86 Z28 Convertible Weekend driver
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Joined: Jul 2010
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Thanks for the info.
Looked up those adaptors. They seem to be specific for those brands (and even model #'s) - do you think they all work the same way?
1968 Firebird 400 Convertible Original: Engine, Intake manifold, Heads, Body, Stereo, 3.08. THM400. Engine rebuilt by Ken Keefer early 2012. New: Holley 4bbl 670 HP, hidden iPod setup, RobbMC mini starter, A/C, front disc brakes
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Joined: Jan 2010
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nOT SURE BUT i WILL CHECK INTO IT IN THE am. What brand of HEI did you install?
86 Pontiac 2+2
69 Firebird Coupe(Under Construction)
69 Firebird 4 speed Vert Driveable but Under Construction
64 1/2 Mustang (Under Construction)
86 Z28 Convertible Weekend driver
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Joined: Jul 2010
Posts: 214
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Mechanic did it. Seems to be an imported generic.
1968 Firebird 400 Convertible Original: Engine, Intake manifold, Heads, Body, Stereo, 3.08. THM400. Engine rebuilt by Ken Keefer early 2012. New: Holley 4bbl 670 HP, hidden iPod setup, RobbMC mini starter, A/C, front disc brakes
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Joined: Jan 2010
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I FORGOT ABOUT THE AUTOMETER UNIT # 9117...THIS IS THE BEST ONE THAT WILL WORK WITH ALMOST ANY CONFIG OF HEI SYSTEM HERE'S THE LINK http://www.egauges.com/pdf/AutoMeter/561.pdf
86 Pontiac 2+2
69 Firebird Coupe(Under Construction)
69 Firebird 4 speed Vert Driveable but Under Construction
64 1/2 Mustang (Under Construction)
86 Z28 Convertible Weekend driver
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Joined: Jul 2010
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I get no signal through that unit for some reason.... I wonder if the hood tach itself is suspect.
1968 Firebird 400 Convertible Original: Engine, Intake manifold, Heads, Body, Stereo, 3.08. THM400. Engine rebuilt by Ken Keefer early 2012. New: Holley 4bbl 670 HP, hidden iPod setup, RobbMC mini starter, A/C, front disc brakes
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If it was working fine, then began having issues, it's the tach!
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