high output

[high output]

since rebuilding my 1972 455HO engine and installation, most everything turned out great.
one of my issues is : the tach works, but is reading way low on the rpm's.
whats going on please.

 

[EaOutlaw]

What rpm is showing on the tach?

Are you having stalling problems?

Has the engine carburetor timing etc been tuned?

What are the specifications of the engine, what cam, compression ratio etc can you tell us about the engine build?

What brand and size carburetor are you running?

What size jets are in the carburetor?

 

[high output]

my tach is reading approx 1/2 the actual rpm. engine's running strong like a beast, so no stalling problems, no missing or anything. carb is adjusted properly and flowing well, timing is correct. engine is a '72 455 H.O. (stock) and runs great. all other gauges are reading correctly.

 

[EaOutlaw]

Is this a stock tach or aftermarket?

You said the tach worked properly before the engine overhaul. did you make any changes to the wiring or ignition system while the engine was out?

Where is the tach wire connected to right now? is it coming off the distributor?

Are you running a hei system and a MSD box?

Again what is the RPM of the engine and what are you using to measure the RPM?

What RPM is the tach reporting?

______________________________

 

[melsg5]

If everything is stock the tachometer signal should come from the negative terminal of the coil.

 

[high output]

ok, thanks Melsg5

 

[melsg5]

you haven't answered any of the questions EaOutLaw asked, so we are just guessing and cannt provide further information.

 

[high output]

1 its a stock tach
2 it worked properly before the rebuild
3 no changes to the wiring, I used the same harness
4 the tach wire is coming off the distributer
5 no hei or msd
6 the rpm will not go over 2500 even when I floor it big time
7 I am using my eyes to look at the tach when accelerating
8 I have not measured the rpm with any type of instrument

______________________________

 

[EaOutlaw]

If you do not have HEI ignition and your running points, as melsg5 said the tach wire should connect to the negative side of the coil.

 

[melsg5]

how did you determine the tach is reading approx half the engine speed if you didnt compare the tach reading to any other instrument?
did you do the engine removal and install or did a shop do it?
if a shop did it is there any way they could have hooked up the tachometer connection incorrectly damaging the tachometer?
do you own a dwell meter and can check whether it is set for 30 degrees?

 

[high output]

a friend and I did the engine install ourselves
I will get a measurement of the tach as soon as I have the time
I will let you know my findings
thanks for your help in this matter
ill be in touch