Tach Dwell measurement on 65 Scout 80

D

Duane Becker

New member
I found an old but good shape tach/dwell analog meter made by Instrument Service Company. I was wondering about the measurement of rpm's. After hooking up the neg to ground and the pos to the distributor side of the coil, I set the meter to dwell and get the dwell. Then setting it to tach, I get the engine rpm-correct? So is the dwell and engine rpm related? And the rpm measurement is obtained with my meter probes still connected to ground and distributor?
I can't find that much info about dwell and rpm of the old style breaker point days. Nothing that much on Youtube and the auto parts stores. The gal behind the counter at Oreilly's didn't know what dwell was. Anyway, I'm not too mechanical myself, so I wanted to check.
 
The gap that you set your breaker points to creates the dwell angle. DA is way of measuring that the physical point gap you set is optimum for your engine cylinder count and distributor design. I don't have experience with your particular meter, but you have the basic gist of it. Most meters have some type of switch for selecting either 4, 6, or 8 cylinders. Generally, one if not both leads will be connected to your ignition coil terminals. This is where you might get help from youtube. You need to make proper ID of your distributor, as IH used more than one design on the Scout 80/800 models. One was a Delco and the other was a Holley. The angles are different for each. Is your engine in running condition now?
 
Yes, the Scout is up and running. In fact, I bought a new engine which I picked up on craigslist a few years ago. Nice little 152. I had it installed last year by a shop. Works great. I had my distributor id'd on this site already as a Holly with straight points. Now mainly trying to get familiar with the tuneup, and using dwell meter and timing light. I did find an explanation regarding the rpm measurement in one of my auto machine textbooks. Book mentions connecting the rpm tach leads to the distributor side of the coil and the other to ground. Meter then converts into rpm. Same connection used for dwell angle and rpm's with the meters that provide both measurements. Thanks for you help.
 
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