Tach meter ??????
Thread Starter
Instructor
Joined: May 2010
Posts: 172
Likes: 3
From: Hesperia California
Tach meter ??????
Hi all,
Trying to get the best of both worlds here, as a former 69 corvetter and waiting and looking for that next 69 big block, Id like to ask a question about my 72 z28 #s and bone stock original. Yesterday on a 40 mile trip to a car show at a glance the tach was reading about 2500 at 60 I don't push it with the m22 and 4.10s but i know at 70 the tach will be around 3500 + but on my way back home the tach seamed slow, showing 2100 at 55-60 so id put my foot in it the tach would climb to 2500 at 65-70, tach seamed slow and about 1500-2000 rpms slow, or off. When stoped, reving the engine Im knowing that the revs should be upwards of 5000 but only showed 3200-3500, at idle going to the show tach showed 800to 850 on my way back at idle showed 550-600 something is not right, any idea what is going on. The tach reacts to reving the engine but just not, lets say it seems to be slow in reaction to throttle, tach OK going the 40 mile trip, 40 mile return trip tach not ok, whats up. THANKS for any and all input because I know you guy out there are the wisest...... Thanks again, don't thump on me about the z it will be replaced with another corvette big block in the near future when I get this z looking better than it does............................ Garry
Trying to get the best of both worlds here, as a former 69 corvetter and waiting and looking for that next 69 big block, Id like to ask a question about my 72 z28 #s and bone stock original. Yesterday on a 40 mile trip to a car show at a glance the tach was reading about 2500 at 60 I don't push it with the m22 and 4.10s but i know at 70 the tach will be around 3500 + but on my way back home the tach seamed slow, showing 2100 at 55-60 so id put my foot in it the tach would climb to 2500 at 65-70, tach seamed slow and about 1500-2000 rpms slow, or off. When stoped, reving the engine Im knowing that the revs should be upwards of 5000 but only showed 3200-3500, at idle going to the show tach showed 800to 850 on my way back at idle showed 550-600 something is not right, any idea what is going on. The tach reacts to reving the engine but just not, lets say it seems to be slow in reaction to throttle, tach OK going the 40 mile trip, 40 mile return trip tach not ok, whats up. THANKS for any and all input because I know you guy out there are the wisest...... Thanks again, don't thump on me about the z it will be replaced with another corvette big block in the near future when I get this z looking better than it does............................ Garry
Le Mans Master
Joined: Dec 2003
Posts: 5,727
Likes: 38
From: Fremont CA
Sounds to me like the ground wire in your distributor between the points mounting plate and distributor body has broken. This happened to me in my 69 Z/28 and finding the cause took many hours. To properly fix it, you will have to remove and disassemble the distributor, the wire is wedged between 2 tabs below the points mounting plate and then is terminated at one of the vacuum advance mounting screws.
To perform a quick test to see if this work is required, take off the cap, take a piece of 16 guage or thicker wire, bind it below your points mounting screw, run it out the points adjusting window, then ground it to the engine block. Restoring the ground will eliminate the feedback you are seeing coming through your tach circuitry.
To perform a quick test to see if this work is required, take off the cap, take a piece of 16 guage or thicker wire, bind it below your points mounting screw, run it out the points adjusting window, then ground it to the engine block. Restoring the ground will eliminate the feedback you are seeing coming through your tach circuitry.
