Tach maxes out @ 4700 RPM

Hi All

this past weekend I took the car to its first swap meet and show. The car ran well and the only issue discovered on the trip was the tach maxes out at about 4700 RPM even though I can hear the RPMs rising above that point.

I was running about 72 mph at 44-4500 RPM which seams reasonable based on what I’ve seen on other posts on the forum. I’ve converted to negative earth and followed the recommendations per the related threads. Overall the tach is smooth and “seems right” up to that point.

Any suggestions would be much appreciated.

Darren

Darren

Could be a “mechanical” problem within the tacho mechanism…something sticking…and the only way to check is to take it apart and make sure there is no binding.

Mind you others may come up with other reasons…

John :wink:

You may be able to give the tacho mech a twist by hand if you remove it ( it’s all in the wrist )and see if it catches . this may clear the prob .

I always go for the easiet fix first. I can increase my oil pressure by five pounds tapping on the gauge.
I suggest tapping on the tach during high rpm, if it doesn’t work, I’d check ground wires.

I’ll try the tap, good call and them move on to to check other things. Wondering if the points are lazy and floating. I’ll check my point gap when I can borrow a dwell meter

Well, the tap tap tap worked. Problem is that while I was driving and tapping and not paying enough attention, when the needle popped free it jumped up around 6700 rpm. Realistically it was only up there for around 10-15 seconds max.

Is that high/long enough to cause serious damage? What if anything should I check. I’ll be more carefull next time!!!

… ten + seconds to back off the throttle?
I don’t think you have to check anything if you can pip 6700 rpm and not blow it up. The engines are good for (brief) @7000 revs, but…