Isuzu SUV Forum banner

Early vs Late SOHC Crankshaft

408 Views 4 Replies 3 Participants Last post by  Buster28
I’m in the middle of throwing in a rebuilt 3.2 SOHC longblock. Slowly. I work on it 5 minutes at a time. Anyway, I recently came across a thread here where it was mentioned that early and later SOHC crankshafts are not compatible due to the change in ignition types (waste-spark to coil-on-plug). That all makes sense, but how can I tell if the engine I have from Engineworld is the one for my early system (93 Trooper)? Everything has swapped over so far, including the crank sensor. But the valve covers were slightly different, a few different mounting points compared to the ones on the original engine. Is there an indicator I can look for? Did I miss read and any year SOHC block will work? I’d hate to start over, but I’d hate more to get it completely reassembled before learning any bad news.
1 - 3 of 5 Posts
Thanks. That is the info I am looking for. This is going to be one nervous tooth count.
  • Like
Reactions: 1
Thanks Ed Mc for the guidance. I count 6. Well technically the cylinder 1 TDC notch is a double gap, but that's how the system locates itself. Posting some pictures here in case anyone else needs to ever clear this up. Not sure what the coil-on-plug crankshaft pulse wheel looks like. But this is what the early style waste-spark (3 coil packs mounted on the ignition module) pulse wheel looks like.

First turn the crankshaft to the cylinder 1 top dead center (TDC) position by aligning the notch in the crank pulley/balancer with the zero on the timing belt cover.
Tire Automotive tire Camera lens Reflex camera Camera accessory


Then remove your crankshaft position sensor and look for gaps in the pulse wheel when still at the zero position. Unless something is seriously wrong, you should have a double gap here. The double gap allows the system to tell the difference between cylinder 1 TDC, and all the other points in the rotation.
Motor vehicle Automotive tire Automotive design Rim Gas


As you rotate the crankshaft 360 degrees back to zero (cylinder 1 TDC) you will count 5 single gaps like this.
Automotive lighting Automotive tire Automotive design Motor vehicle Rim


In total you will have 6 points on the pulse wheel that excite the crank sensor. One of those points is a double gap, five of those points a single gap. Hope this helps.
See less See more
3
1 - 3 of 5 Posts
Top