bwarren

Ok, need some help here? I may rattle on for a bit, but please stick with me and go easy on me. 1995 LT1 100,000 miles. I recently replaced the oil pump, all crank bearings, valve guide seals, timing gear/chain set, and water pump. I have done some engine rebuilding in the past and felt confident completeing this work. I used a Haynes manual for reference. After getting everything back together, the engine seems to be only running on 4 cylinders. With a timing light, I verified current is passing through all plug wires. I verified plug wire locations 4 times. Removing injector connectors on at a time only seems to affect cylinders 1, 3, 5, and 7. 2, 4, 6, and 8 seem to be unaffected by disconnecting the injector when the engine is running. Plugs on 1, 3, 5, and 7 are clean. Plugs on 2, 4, 6, and 8 are black. Moved plugs from one side to another, no change. Thinking I must have messed up the timing when installing the chain, I tore everything back down. I opened the Opti so I could see where the rotor was when #1 was DTC and it was pointing to #1 on the distributor. I ohmed out the distributor so I could label the outside of the opti for firing order reference. I went through the entire fire order and valve and piston position seemed to match what the distributor indicated. With everything at TDC for #1, I noticed that the timing marks on the cam gear and the crank gear were both at the 12 o’clock position. The Haynes manual says for 92 and later models, the marks should be facing each other. The cam at 6’ o’clock and the crank at 12 o’clock. At this time if I line the marks up to match the manual, the rotor is firing #6. I do seem to remember when I removed the old gear set, that with the marks facing each other, #1 cylinder seemed to be transitioning between intake and exhaust. That’s how things are now. I compared the old timing gear set with the new and they are the same. Could the crank have been 180’ out of position when I installed the chain? How can I get #1 to be TDC and have the rotor pointing pin #1 on the distributor? Is the Haynes manual wrong? Could I have too much pre tension on the lifters for 2, 4, 6 and 8? Could a previous owner messed things up and rerouted plug wires to make things work?
Thanks for reading. Brian

csheerin

According to Hooked on Vettes:

Cam gear is at 6 o'clock
Crank gear is at 12 o'clock
Cam pin will be at 3 o'clock
Cylinder 6 is at TDC on Compression stroke

Rotate the assembly till
Cam gear is at 12 o'clock
Crank gear is at 12 o'clock
Cam pin will be at 9 o'clock
Cylinder 1 will be at TDC on Compression stroke

Here's a animation which shows the firing of all of the cylinders. It takes a while to load.

http://shbox.com/1/cam_timing_ani.gif

bwarren

If you can believe it, I tore everything back down and actually opened the distributor in order to verify everything was where it should be, when it should be, and of course it was. Since there were no changes to be made here, I went through all the valves again. Got everything back together and things ran great. Only drove it about 8 miles. About a month later it was time to get it inspected. On the way to the inspection station, it kept feeling like there was a miss. After the inspection I went for a 20 mile run. The more I drove, the worst the engine was running. By the time I was 2 miles from the house, I could barley keep things running. A lean O2 code was being sent. I had a lot of black carbon on the driver’s side rear bumper. Once I got home I started going through things again. A timing light verified I had fire at all cylinders. A fuel pressure was a steady 35-PSI. As I started pulling fuel injector connectors, everything on the driver’s side had no affect as I pulled all the injectors. The driver’s side plugs were fouled. After the rebuild the trouble was all on the passenger side. Since readjusting the valves seemed to work last time, like an idiot, I was going to try it again. I had pulled the valve covers and was thinking more about what was going on. It just did not make sense that it could be the valves. Using a good screw in type compression tester, all chambers were from 190 to 195 PSI. With 100,000 miles on he clock, I thought this was more than adequate. I put everything back together and the engine once again ran great and has for the last 200 miles. I am now thinking the problem is more related to an electrical connection. As each time I did work, I hade to unhook connectors and things. The connection I am most suspecting is the module on the heat sink next to the coil. I’m not sure what it does, but its connector does go down to the opti unit. Right now the car is running real solid so I have not been investigating any further.

Thanks for the help, Brian

frank j. moran

sounds like an elctrical connection to me and its common to the injectors, did you pinch a wire to ground anywhere?

Redeasysport

I am curious how did you determine the rotor was pointed at #1 in the distributor? I did not notice any numbers inside the cap.With the ridge on the balancer hub at 12 O'clock (my #1 TDC I thought)rotor pointed to 7 O'clock.

bwarren

I actually removed the opti unit completely and removed the distributor cap. From there I ohmed out each ignition wire terminal to a contact inside the distributor. There is a number molded into the distributor next to the wire terminal. After a couple you can just follow the firing order for the rest, but I ohmed them all out anyway. As I verified each connection, I wrote the number on the outside of the distributor unit with a sharpie for reference. I then loosely attached the opti back onto the front of the engine without screwing the cap and everything back together. As I turned the engine and watched the valves, I could peek inside the opti to see where the rotor was pointing. Since everything is keyed or pined, I should have realized you really can’t mess this part up.

As I recall, 7 o’clock was pointing to #1.