| Author | Message | ||
| Mike Florio (Mike_in_nevada)
New member Username: Mike_in_nevada Post Number: 33 Registered: 6-2003 |
After looking at acquiring an old Sun tester I decided to build my own because (1) They are expensive ~$300 (2) they weigh about 100 pounds, and it costs a bundle to crate and ship them. (3) Most of the cost is tied up in the vacuum advance, which we don't need. For RPM control I used a positive-feedback loop with the opto sensor on the driven shaft and a digital tach I picked up at a surplus store for $5. I think it is far more accurate than the Sun. | ||
| '75 308 GT4 (Peter)
Advanced Member Username: Peter Post Number: 3063 Registered: 12-2000 |
Interesting set-up there Mike. Sounds as effective as the other. In respect to position, it shouldn't matter. These distributors have been mounted at all sorts of different angles (on Ferrari and other engines). My orginal inquiry was inspired by an Ebay auction of a vintage Sun tester. Old equipment like this looks cool, but not the price. I know I could make one for less. The key aspect I need to pay attention to would be to know and regulate accurate distributor shaft speed (all the more important to set the dizzy up properly). | ||
| Mike Florio (Mike_in_nevada)
New member Username: Mike_in_nevada Post Number: 31 Registered: 6-2003 |
Sorry about the late post, but I've been out of town and just catching up. I built a complete distributor machine using a sewing machine motor, a light dimmer as a speed control, a 8" clear plastic circular protractor, and a couple of 5-1/4" hard disk drive platter blanks. One platter has slots every 90 degrees to trigger an opto sensor, which feeds into an electronic tach. The other has an LED under a slot that illuminates through the protractor. It reads as a (green) lighted arc under the protractor when the points are closed. I'm going to switch the indicator to show lighted when the points are open. I dial through the speeds from 500 rpm to 2000 rpm (half crankshaft speed) and read the dwell, or the advance. My question is: do you think the advance responds differently with the distributor mounted vertically rather than horiziontally? | ||
| '75 308 GT4 (Peter)
Advanced Member Username: Peter Post Number: 3050 Registered: 12-2000 |
Thanks guys, big help (and yes Mitch, that's the post that I remembered, but couldn't find...).  | ||
| Andy Falsetta (Tuttebenne)
Junior Member Username: Tuttebenne Post Number: 237 Registered: 3-2003 |
My 308 has two distributors that require points. To make the set up easier, I took the distributors out of the car and rigged up a way to run them on the bench. I used a regular variable speed drill (that allows you to lock it at a given speed). I purchased a flexible drill drive for fifteen dollars. This is kind of like an extension for the drill. If you can imagine this, it works like a speedometer cable with a chuck on one end and a drill shaft on the other. I put the distributor into a bench vise and connected the flex drive to the drill. In the chuck on the flex drive I put a bolt. I then connect the bolt to the distributor drive shaft with a short piece of rubber hose. Fire up the drill and you'd be surprised how easily this allows you to spin the distributor at speed. Then I took a 12 volt power transformer from some old tape recorder lying around the house, snipped off the connector and put alligator clips on the wires. This gets connected to the points and ground enabling you to simulate the ignition if the distributor was in the car. Next you add a dwell meter. (This is where my memory gets foggy. I think I had to set the dwell meter as if it was connected to a four cylinder engine). Spin up the distributor using the drill, then read the dwell angle and adjust the points while its spinning - almost like you used to do on a small block Chevy distributor (remember to take off the rotor first). I was amazed at how easy this was and eliminated working in the cramped engine bay, trying to "trial and error" the points, and having to put the distributor cap on each time prior to starting the engine - just to find out you still don't have the dwell exactly where you want it. Granted, this is not a distributor machine, and I just assumed my advance was working well (and later proved it when I put the timing light on each bank) But I did this 16 years ago and have at least 1000 track miles on the car and 1000 street miles and I've never had the distributors open since. Its worth a try if you want to save some trouble and have the necessary items around the shop. | ||
| Mitchell Le (Yelcab1)
Member Username: Yelcab1 Post Number: 663 Registered: 11-2001 |
Posted on Monday, March 04, 2002 - 6:45 am: -------------------------------------------------------------------------------- I had mine apart last year and found a number of shims under the springs that were used to adjust the advance curve. As the weights rotate out from the pivots due to centrifugal force, they sequentially press the springs against the outer housing. Adjusting the number of shims under the particular springs is what appears to be used to adjust the advance curve. If I remember right, one of my distributors had anywhere from 0 to 4 shims under the different springs, while the other distributor had 2 or 3 under each. This had me a little concerned so I made a mount on my drill press and rigged up a distributor test machine with a degree wheel. I mounted the distributor and drove it with a v-belt off the drill press. I also hooked up the coil and spark plugs on the same fixture so the full system would work. Then I just used a timing light to read the advance off the degree wheel as the distributor was turned at different speeds. I found the advance on the 1 distributor was at least 5-6 degrees off from the other one and was able to get them both to match the advance curve in the manual by adjusting the shims behind the springs. Was quite interesting. ---------- I searched under "drill press advance distributor", all words anded together. It helped because I started the thread. | ||
| '75 308 GT4 (Peter)
Advanced Member Username: Peter Post Number: 3046 Registered: 12-2000 |
Someone posted here, I'd say maybe two years ago, a description of a distributor tester they made in their garage, using commonly-available parts (electric motor from a drill press[?], automotive multimeter, strobe light, etc...). Usually I'm very good at finding obscure info here using the "search" function, but this one has stumped me. I've tried different word strings/patterns and other methods and I can't find this info. Does anyone remember who it was and could they re-post, or send that info to me? Thanks, |