ScubaStevo80

When pistons 1 and 4 are at TDC, are the valves above cylinders 1&4 in the same positions? Basically, I'm asking if the actions of cylinders 1&4 and 2&3 occur simultaneously, or does something happen on cylinder 1 on one stroke and 4 on the other.

If the latter is the case, I assume the spark would only fire in one of the two cylinder at TDC and how do I know if I have that occuring at the right time vs the other piston thats at TDC? Hopefully I explained my question properly, this has been confusing me for some time.

JimBlake

When #1 & #4 are at tdc, their valves aren't in the same positions.

Let's say #1 is at the top of the compression stroke, both valves are closed & the spark fires. (Well, it just fired 16 degrees before tdc, but you get the idea...) Both valves stay closed because the piston it gonna move down on it's power stroke.

But #4 is at the top of the exhaust stroke. It's exhaust valve was open & now it's just about closed (just a little overlap). It's intake valve is opening since the piston is gonna move down on it's intake stroke.

The distributor only fits into the camshaft one way. Well, the blade at the end of the dist.shaft is off-center, so you have to pound on it to get it backwards. The range of adjustment of the distributor mounting won't go far enough to mess you up.

Does that answer what you want???

ScubaStevo80

Yes, thats the answer I wanted... just trying to make sure there's no way cylinder 1 is firing when cylinder 4 should be firing or vice versa when I put my head back on.

Or does the position of the cam affect which plug fires when. In that case I would assume it would be impossible to have the wrong plug firing at the wrong time.

JimBlake

To make the wrong plug fire (#4 instead of #1), you'd have to put the distributor on 180 degrees out. Or just put the plug wires on the opposite poles of the cap...