scca28
NAXJA Forum User
- Location
- N.E.Philadelphia
Half way through rebuilding a '90 4.0. Crank and cam are installed as well as a new timing set. Now, I have the two timing marks on the sprockets pointing towards each other in a straight line through the center of both shafts. Number one piston is at TDC. So far, so good. Only problem is in this position, the two cam lobes are facing upwards, which means the exhaust would have just finished closing and the intake would just be starting to open as that piston is going down. Now, if I rotate the crank one full revolution, the cam lobes are pointing downwards which would indicate both valves closed. That would be the "firing" stroke. So that is where I should install my distributor, pointing towards the number one plug terminal, right? But, in this position, the cam sprocket timing mark is now 180 degrees away from the crank sprocket. It don't make sense. Why wouldn't they design everything so that the dist goes in with the two marks lined up? I double checked this with all the old parts that came out, and it's not a mistake.
I guess they figured that:
1. If you are just replacing the timing set, you won't be moving the two shafts so timing should stay the same, or:
2. If you are R/R the dist, you would just crank the engine around until you feel the air come out of the plug hole to find the compression stroke.
But the directions I have seen so far don't take into account a total rebuild.
It's just a good thing I noticed this, because nothing I have read so far makes mention of this. I would have set that dist in towards piston one with the timing marks lined up and...and then I would be throwing wrenches when the engine didn't start.
Anyway, am I making too much out of this, or is this something anyone rebuilding should be aware of???
I guess they figured that:
1. If you are just replacing the timing set, you won't be moving the two shafts so timing should stay the same, or:
2. If you are R/R the dist, you would just crank the engine around until you feel the air come out of the plug hole to find the compression stroke.
But the directions I have seen so far don't take into account a total rebuild.
It's just a good thing I noticed this, because nothing I have read so far makes mention of this. I would have set that dist in towards piston one with the timing marks lined up and...and then I would be throwing wrenches when the engine didn't start.
Anyway, am I making too much out of this, or is this something anyone rebuilding should be aware of???