If the distributor rotor is off by 180 degrees will the vihicle still start on a 1987 Chevy s10 pickup?

Answer 1

Maybe . . . but it will run like crap. It is easy to get it 180 off, most people check TDC but not exhaust/intake stroke. They just feel for compression. Take and hand crank the engine over with your #1 plug out and your finger over the hole, First you want to feel a vacuum, the plug hole sucking on your finger, then it blowing air out past your finger, that's the intake and compression you want.

When it starts to blow air out past your finger (the jobwill take two people) stick something like a wire or similar object that won't damage the pistion in the plug hole, crank the engine until it reaches top, it will push out the wire out to tell you if the pistion is moving up. Then when it starts to go back in, stop and crank it back a hair so it comes out, the key is to get it Top Dead Center, so it is all the way up.

Now it is up on your compression mixed stroke. Take your cap off, if your dizzy is 180 off the rotor will not be pointing to your #1 tower (the tower is what your plug wire hooks to and then runs to your plug, #1 tower goes to #1 plug, knowing your firing order will help this situation). You can (1. Use whatever tower it is pointing to as #1 tower and re run your wires, or (2. Take the dizzy out spin the rotor around and install cap & wires, lining up it with any tower that want to be your new #1.

Re do the plug wires to fit your firing order, 1 to 1 cyl, 2 to 2 cyl, whatever the firing order it, I can't tell you because you didn't list an engine. But you can find your firing order by an internet search.

If you get them exact your cold timing will be set. Your truck will run but maybe not the best, let it run and warm up then rotare the dizzy a little bit, which ever way you are off, until you get it set where it sounds good. (having a tach and knowing what your idle should be will help too, usaully I set vehicles about 600-800 rpms, warm running in park. The vacuum advance should be good for your vehicle unless it is a new distributor, if it is it should have instructions on how to set it with an Allen wrench. For small block performance dizzy's it is tighten in and four turns out, then road check and adjust.

The reason you want to feel the vacuum first is that is when the cylinder is drawing in gas and air mixture, then it compresses it and fires. So you get a vacuum effect with your thumb over the plug hole, then when is is pushing out it is compressing the air to get ready to fire.

The next stroke up the intake valve is close and the exhaust valve opens so there is no vacuum on the that stroke, it pushes out the exhaust when it comes back up. So you get that air being pushed out, but that is not when your want to plug to fire because there is no gas/air mixture.

-BM-