I love these Engines

A couple of really simple things to check.
1. One bank rich in 94-95 the EGR gas flow was pulled off from a port on the exhaust manifold these crack and leek Air into the exhaust manifold causing O2 to read lean and BLM to go up.
If the little tube is cracked it will make that side rich.
If you have the cast iron manifolds you may also have a crack there.
Any exhaust leak from the head down to the sensor will make it rich on that side.
2. Correct PCV valve for old engines I use a 774 standard it works and does not lean out on old rings.
3. The 94 throttle body had a tendency to clog where the PCV goes into the top of the throttle plate right under the badge plate on the throttle body without PCV you will foul the O2 sensors.
4. Oil fouling often people think that low miles old cars mean that they are in better shape, this can be problematic if the owner actually let the car sit for extended periods or worse the car was only driven 3 miles a day.
These engines are designed to run with the oil in the block at or above 220 F if the oil does not get to 183 F then it will be soaked with ethanol from the gas letting the car sit the low tension rings get damaged.
If you get oil on the plugs then the sensors will foul and it will go full rich. I had valve guide seals go bad after an overheat that did this to one of mine. I used a spark plug extension drilled out to move the O2 sensors out of the exhaust flow to allow normal driving until I overhauled it.
Heres a link to some one else describing how to use them.
https://www.evolutionm.net/forums/ev...cel-light.html
5. Persistent miss, I have used a lot of these coils and modules for all kinds of builds a couple of common things on the coil that will cause a miss is that the epoxy fails look for white powdery residue around the coil body and bracket. If found replace the coil and coil wire. Another area that the OPTI had issues with is the short wire harness between the Opti and the engine harness on the passenger side behind the water pump.
6. To localize the miss pull one injector lead off at a time and find the missing cylinder. If none change then look at the ignition closely the wires that are clipped to the block behind the exhaust manifolds may be sorting out.Take off the serp belt and use a test light to puncture each plug wire and watch for miss. If no miss found pull the valve covers off and look at the rockers as you rotate the crank the early roller lifters where common to fail and wipe the lobe of the cam.




One of my project builds is another LT1 engine
I am going to use a set of CompE Speedmaster heads on one I have the heads already On these the oil return passage can be plugged to open the reverse cooling port to fit Gen1 heads on the GenII block.
I love really old school tech fusion so the plan is to use the LT1 lower end with TRW1157 flat tops and 3.75 stroker crank after market main caps and a girdle.
With the new build looking for monster torque.

I have one of these motors that had a LT4 cam and wildly ported heads 280cc intake runners with Orange springs and a lifter REV kit It turned 9000 Rpm.
Stock coil won't even pull 6K The OPTI pickup works great all the way high as you want to go MSD cap and rotor held up pretty good. I used my own Ignition controller and CATS tuner to tune the ECM OBDI.
The old screamer will be getting new springs pistons and a overhaul looking to put 4 small turbos on it.

FYI the stock injectors are like 26lbs so if you are tuning it you could have bought a really cheap set of 44lbs EV1 style micro drilled injectors for less than 80USD.