Kyle802009-08-22 18:03:09

Well hold on, If with your motor on the engine stand and if you rolled #1 piston to TDC before you installed the timing chain and if you installed it as shown on your diagram, then it is correct according to the diagram, personaly Ive never done it that way Ive allways done it 6-12 as shown in the GM manual, I don't want to see you pull the motor down for nothing, and fly to Ca. to kick my AS, did you bring # 1 up before install, Ive never seen that method discripted in a GM manual before, I have the GM info scaned already on my computor its yours at the speed of light if you desire  anips2009-08-22 19:08:34

The engine would run 180* out, but not very well, and the timing marks would be so far off, you wouldn't be able to get a 30* BTC reading...you prolly wouldn't be able to see the mark at all. It would also be spittin and snortin pretty bad...

I'm thinking the confusion here is really more common than most folks think...putting the timing marks toward each other(6&12) doesn't always mean you're ignition timing will be correct. I've had to swap plug wires on the dist cap MANY times after someone has given up on getting the fool thing to run...it's easier than pulling the dist out and resetting.

It is possible that the timing marks are off by 1 tooth, if timed by the "both @ 12" method, which could give you the weird timing light readings, and the rough running.
If you run the #1 piston up to TDC, pull the dist. cap off and see where the rotor is pointing. It should be pointed directly at the #1 terminal, or really close to it. If not, the cam timing is prolly off by a tooth or two, or the distributor itself is off...

Kyle info is on the way.

My '67, and '74 service manuals show the timing marks at 6 & 12, but my '85 service manual shows it the way Kyle80's post has it, with #1 at 12 also. This is what adds to the confusion. The thing to do if you're not sure, is look for "rabbit ears" on the cam lobes for the #1 cylinder. By "rabbit ears" I mean that the intake and exhaust lobes for the #1 cylinder will be pointed up: one to the right, and one to the left....just visualize a set of rabbit ears. This will indicate the cam is set on #1, and not #6 cylinder.
I have also seen some timing gears that had marks that were NOT where they should be, and some that actually had two sets of marks.

                                         

Guys, think about this.  It is IMPOSSIBLE to set the timing chain off 180 degrees.  If it is at 6 or 12 it is right.  Just turn the crank on complete revolution, and the cam is now the opposite of what it was.  This happens when the engine is running every rotation.  

Yes distributor is pointing to one, when #1 is on comp. stroke at tdc.   Checked balencer already, dead on 0 at tdc.  Ive gotto be off a tooth, could not tell it both marks looked right in line.  guess thats y u line up 12- 6, will do that this time.   

Also consider the possibility that the carb may be running to lean.  This can prevent idle at normal timing, but can idle with a lot of timing advance.

Well checked the timing chain.  checked  it with #6 @ tdc this time, and its right 12 & 6 aligned.  So could the carb running lean make it run off 24 degrees, the base timing is 36.  Seems like if you were having to adjust timing to keep motor runing that a little would help, but that much advance would kill the motor.  having to be 36 seems like something is off with the cam. either, im missing something here? or cam off somehow? defect ? or could it have worn off somehow in break in ? or what, I dont know.  dont know enough to  figure this out.       Kyle802009-08-25 18:24:16