Distributor advance springs

Sometimes the spring anchors can also be bent or moved to refine the advance curve.

The ideal tool is a distributor test machine, but I doubt they can be found in working condition these days. So you have to use the timing light and the tractor's tachometer.

Too much advance is what would come from a spring broken and that could cause sputtering if its way too much advance.

I've also had a condenser in the distributor cause bad running.

Gerald J.

Its 6 degrees before TDC at 450 rpm and 30 degrees +/- 2 degrees at 2000 RPM. 0.022 point gap first.

The marks are to the right side of the hole that is on the left side of the block. On a flange, not the outside edge of the flywheel according to this picture.

I&T gives curve data for four distributors in terms of distributor shaft speed, not crankshaft speed.

For Delcco 1112457 advance should start at 250 distributor RPM, max of 6 - 8 degrees at 1000 RPM.

For Delco 1112458 advance should start at 450 RPM and get max of 11-13 at 1000 RPM.

For Delco 1112643 advance should start (o - 2 degrees) at 275 rpm. 6-8 degrees at 450 rpm, 8-10 at 650 rpm, 11-13 @ 950 rpm.

For Delco 1112644 advance should start (0-2) at 325 rpm, 5-7 @ 700, 9-11 @ 1000 rpm.

All these distributor specs show distributor shaft RPM, not crankshaft. Crankshaft turns twice as fast.

My parts book says for our MF-135 the distributor should have been 1112-644. The 1112643 was use on the Special and the 112457 on the Perkins gas.

So now all you have to do is mix and match springs to get the curve back.

I guess mine is OK, I used to plow with it, but I've given up plowing but haul a 65 gallon spray tank on the three point or pull a 4 row JD 7000 planter with it. Neither seems to work it as hard as mowing with the 6' flail mower. I had to switch to the 4020 with narrow rear tires for the last spraying this year, it fit over the beans and down the rows. Sure didn't work it hard, but I didn't chop beans off too much either.

Gerald J.

My I&T manual shows a little tin plate, mostly circular with a bolt off to the side making it tear dropped shaped down on the left side of the block below the starter, just a couple inches above the oil pan seam. My picture in my owner's manual hides that detail behind the left radius rod.

My parts book shows a snap plug for the timing hole, not the bolt on eydrop shaped cover.

In my list of timings for various speeds and distributors all advance angles and shaft speeds are at the distributor, half the crankshaft speed and advance angle.

My tractor is about 8 miles for here and I don't plan to see it soon.

Gerald J.

I looked at the left side of my MF-135 engine. Between the second and third ribs above the crankcase and on the flywheel flange of the engine there is a snap plug. Its domed and I didn't pull it, but that is probably the hole for the timing. Its about 7/8" in diameter and the dome is between 3/16" and a quarter inch. It should pry out with a screwdriver and snap back in place or it may need to be tapped back with a small hammer.

Gerald J.