Tach/Dwell meter

I have a Craftsman Tach/Dwell meter it is for 6 and 8 cylinder engines. You can read the Dwell for a 4 cylinder by halving the 8 cylinder value.
It doesn't seam to work for the Tach...is there a way I can read the RPM's
The Tach in the car needs to go in for the usual rebuild.

Thanks
jay

I thought on those you had to multiply 8-cyl dwell and rpm by 2 to get the 4-cyl values, not divide.

Or are you not getting any tach reading at all?

Justin,

Your right I got confuuuzed:/
The dwell comes out at 50 on the money....or 25 actual

But The tach reads 3500 when the engine is just idling. Which would be 7000.....Just no way it's going that fast.

Is your ignition system stock?

.009 with points and Blue coil.....Static timed and then checked with a light.

Jay, Get rid of your points thus you no longer have to spend an inordinate amount of time setting the dwell. Compufire and Petronix make a great point eliminator and it's very easy to install.

NEVER set your timing via the static method. Regardless of which type of distributor you have, set the timing at 28 degree's Before Top Dead Center at 3,000 to 3,500 RPM's This ENSURES that your maximum advance is only 28 degree's. This will protect your engine from detonation and eventual destruction. If necessary, go out and buy a degree pulley so you can get the timing accurate.

Finally, get rid of the points and get the electronic point eliminator. It will make life much easier

Electronic ignition like the Pertronics are great but when they go bad you're on the side of the road. I carry an extra dizzy with stock points installed as a back up.

Hi Larry,

The engine I have 1915cc w/dual 34ICT carbs has a degree wheel with paint marks at 0* and 10*.

I grew up using John Muirs idiot guide where his rap is always static time and then check with a light.....I take it this is obsolete?

To time at 28* do I need to paint mark the pulley at 28*?
and then time it as you would with the strobe?

If only I could get a good reading from the tach as it's going to be a little bit before I can get the Chinese POS fixed

Jay

Is the tach reading stable or erratic and does it increase smoothly when you rev the engine? Or is it basically pegged at the top of the scale?

My only guesses are a bad meter or interference possibly from bad plug wires or maybe corroded points contacts.

Try wrapping some aluminum foil around the meter and around the green signal wire. Just keep the foil away from the exposed ends of the wires. If it's EMF interference, the reading should drop.

Jay - and while you're at it, wrap some of that aluminum foil around your head to prevent your brain from getting short-circuited by the gamma rays from the microwave. 8-)

also gotta be sure to keep some under your hat to keep them pesky aliens from readn your brain waves 8>)

Aluminium, really great stuff.

He owns a speedster, the brain's already too far gone to bother

Jay, Yes, it's not so much obsolete as not current with modified engines, distributors and fuel octane ratings. When the Muir books were written, all of our cars ran on leaded fuel and what we call Premium octane fuel today has octane ratings below regular leaded fuel of yesteryear.

I usually take a small chisel and mark the outer edge of the pulley at 28 degrees Before Top Dead Center. Since this procedure is new to you, have someone hold the throttle open at about 3,000 to 3,500 RPM's. This ensures that full advance is achieved by the centrifugal advance of your distributor. Move the distributor so the 28 lines up exactly where the engine case splits and lock down the distributor. Always do it this way to ensure that your engine doesn't advance too much and then detonate.

Thanks Larry!

I got my Tach sent off to Hollywood yesterday so in a couple of weeks I can reset the timing.

Jay

Jay, you don't need a tach to set the timing. Just rev up the engine and hold it at approx 3,000 to 3,500 RPM's and quickly set the timing and lock down the distributor. If in doubt, activate the timing light and when the distributor quits advancing, then set the timing to 28 degree's Before Top Dead Center.

On closer examination I notice that the pulley has two little punchmarks at 27* and 30*

Will get it timed this afternoon when I get the paying jobs done for the day.

Thanks for everyones help.
Jay

Timed the engine at 28*BTDC this afternoon.
The timing at idle ends up at 8* BTDC Am I right in thinking that I can time this particular set up at 8* BTDC at Idle in the future?

Thanks Jay

NO!!! Always time as I stated in previous posts. The reason for this is because your distributor can slowly wear and cause an increase in the advance mechanism.