How can I test that my rpm gauge for accuracy? My rpm's seem to be on the low end of the 4600 - 5000 range for a 454 Mag EFI 385hp motor. I am playing with props and I want to make sure I am using the proper baseline before I have a prop labbed. I have been told I can attach some type of gauge to my distributor and see how it compares to my Livorsi / Gaffrig Red Line tach gauge. The problem is I don't know what the tester is called in order to purchase at local automotive store. Thanks for the help!

you can calibrate Tachs with signal generators.....we used to do that with our snowmobile tachs every season. I havent done it in about 4 yrs since i got out of sledding but thats what we did...there may eb other ways....

A snap on Timing lite or a Mac will shed some lite.
No pun intended!

Gerry

Most digital timing lights will have a tach function, I prefer the Snap-On model but at 400 buvks it's alittle much for home use, you should be able to get one that will do the job for around 100 bucks. you can also use an old dwell meter they all have a tach function as well.

If you've got a RINDA tester you could read the RPMS off the EFI controller and correlate with anaolg tach.

speed,
call one of the manufactures of tachs.. maybe auto meter?? Doesnt matter. Ask them what frequencies for indicated rpm and which of either a square wave or saw tooth, to use to calibrate the tach, like Wally said. Then go to a radio repair shop and ask them to inject the signal from the signal generator.. You vary the frequency and the tach will register. You can see where the analog tach falls short. I found some on at the high end, but off at the low or middle..

I used to do it and had a sheet with some numbers. I have not seen that peice of paper since I switched to a digital tach. That is the end all answer. With an anolog tach the pulses have to be converted to an anlog voltage to move the needle. With a digital tach, the pulses are counted and the number is displayed.. +/- one pulse..

Cheapest deal,, get a new digital tach, you wont look back.. I could see the motor hitting the rev limiter with the digital tach..
Dick