Timing problem after partial rebuild

[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

 

[Hrtbeat1]

Thje timing marks should be facing each other (crank at 12 O'clock cam at 6 O'clock). It will run that way but very poorly, much the way you describe. Basically its 180 out, hopefully you haven't bent any valves.

 

[bwarren]

Thanks for the reply Heartbeat1. What I can’t understand is if I have the cam timing mark at 6 o’clock, the pin on the cam for the rotor is in the 3 o’clock position witch has cylinder #6 firing. For #1 to be firing the cam pin needs to be in the 9 o’clock position. Witch one do I have 180’ out, the cam or the crank? Thanks

 

[Mad-Mic]

in order to check TDC with the heads on pull the plug on # 1 cylinder and put a feeler gauge in it so you can feel when the piston is at TDC then line your marks up.


when you pulled the plugs on those dead cylinders were they coated with fuel? could it be a bad opti? firing order on the opti is on the boot connector with a listing 1 2 3 4 ect. just match that with the right cylinder and you know thats right atleast

good luck

 

[ecss]

When you installed the new timing chain, the dot on the Cam shaft gear should be in the 6 o'clock position and the dot for the Crank shaft gear in the 12 o'clock position.

The keyway for the Crank shaft gear will be pointing at the 2 o'clock position.

With the engine in that position here's what the manual says about how to install the optispark.

Do not attempt to fully seat distributor assembly using bolts/screws. If distributor assembly will not seat by hand, it is not properly aligned with the camshaft assembly.

Rotate crankshaft until engine is at number 1 cylinder TDC compression stroke.

(camshaft sprocket pin at the 9 o'clock position).

Rotate the distributor coupling until the camshaft sprocket pin slot aligns with the distributor base timing mark.
The base timing mark is a marking on the backside of the optispark.

Install distributor assembly using hand pressure to fully seat it.

 

[bwarren]

Sorry but I still need some clarification. I understand the timing mark (dot) on the cam gear needs to be at 6 o’clock and the crank gear at 12 o’clock and the cam pin dowel pin at 9 o’clock when cylinder #1 is at TDC. This is a picture similar to the cam gear I am using. The set I am using is actually an AC Delco unit, but the pin hole and marks are the same. In the picture, the timing mark is down (6 o’clock) and the cam pin hole is in the 3 o’clock position. If I turn the engine so that the mark pin is in the 9 o’clock position, the timing mark will be at 12 o’clock. What part of the picture am I not getting?

 

[ecss]

You're correct in your description of what's happening.

When the Camshaft gear dot is at 6 o'clock and the Crankshaft gear dot is at 12 o'clock the camshaft pin is at 3 o'clock and the Optispark rotor should be pointing to the number 6 spark plug.

When the Camshaft gear dot is at 12 o'clock and the Crankshaft gear dot at 12 o'clock, the Camshaft pin will be at 9 o'clock and the optispark rotor should be pointing to the number 1 spark plug.

It appears when
Camshaft gear dot is at 6 o'clock
Crankshaft gear dot is at 12 o'clock
Camshaft pin at 3 o'clock

Cylinder 6 is TDC compression
Cylinder 1 is TDC exhaust. When the camshaft pin is at 9 o'clock is when Cylinder 1 is TDC on the compression stroke. (That's the only explanation I can think of).

You can't install the cam pin driven optispark in the wrong position. The older optispark was driven by a splined coupler.

I'd say, re-adjust the valves.

Here's an animation of the rotation of the camshaft.
It takes a while to load but a picture is worth a thousand words.

Click on this link. Let the program load and you'll see all of the firing positions in relation to the position of the camshaft pin.

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

 

[bwarren]

Thank you for clearing this up, I really thought I was going crazy. So I think it is safe to say the book is incorrect in stating that the dowel pin will be at 9 o’clock position when the gears timing marks are facing each other. I will go through the valves again, but can’t figure out how I could have screwed up one hole side of the engine. I did not even do the 1 full turn, but did 3/4. Stranger things have happened. Thanks for all your help and the pictures are great. I will reply when I finally get things running perfectly.

Brian

 

[ecss]

A quick check of the valve adjustment is to look at the good side and count how many threads are showing on the rocker stud. Then compare it to the side of the engine you're having problems with.

If the engine sat for a while, the lifters will bleed down. A proper rocker adjusment is hard to do until the lifters are full of oil. (engine needs to run a couple of minutes).

An good indication the rockers are adjusted properly is you'll see a good flow of oil from the rocker tip.

I'm assuming you have the stock stamped steel rocker arms with a oil hole in the tip.

 

[bwarren]

Got everything back together and the car runs great. Looks like the only change I made was the valve re-adjustment. When I had first gone through the valve set-up, the engine had not been started for about 4 months. Looks like things had drained down sufficiently that it made my adjustment bad and once the pressure came back up things were too tight. I should have done a compression test and saved my self a lot of time. Thanks for all your help.



Brian