silverriff

Ok I finally got my Cutlassback with a new exhaust system. Sooooo nice!! But now I have discovered why I have to keep adjusting my rebuilt q-jet, because my timing keeps going crazy. A few weeks ago I posted about the heatsoak starting issue and after checking the timing discovered it had jumped to about 35 deg btdc at idle, or something crazy like that. After setting it to 10 Btdc and driving it up to the exhaust shop, after having driving home and having the timing sound off again, I rechecked the timing and it was all the way down to about 2 degrees AFTER TDC. So unless the exhaust shop is screwing with me, or my new timing light is bonkers, then something is wrong. I readjusted the distributor and triple checked that the hold down tab was doing it's job, and it doesn't move at all. Does this mean that the distributor itself is worn down? I just recently replaced the points, cap and rotor, but I didn't touch the weights or anything. I tested the timing advance from initial timing of about 9 BTDC and took it up to 32 deg at about 2,700 rpm. So everything looked good. It just won't stay that way after an hour or so of driving. Help!!

66ninetyeightls

Check your distributor. When you adjust the timing is the distributor bolt tight? Also check the advance to make sure its working properly. The springs could be weak or it could be seizing.

chequenman

I hope when you're setting your timing you've got your vacuum line plugged off, the engine warmed up and at an idle set at the correct speed.

Without your vacuum line plugged off you can't set your timing, and you hadn't mention that you had done this procedure.

silverriff

Yes I followed all the correct procedures....engine to temp, plugged vacuum. I loosen the distributor bolt just enough to turn it, then tighten it back down, and then recheck it to make sure nothing moved. But after a day or so of driving I find that the timing has moved to something completely different then what I had set it at. It does seem like the advance may be getting stuck or something, because it will never stay where I put it. It will either drop down way too far or turn way up. I need to do some more research into it, becuase I am not 100% on the whole advance thing, like when does the vacuum advance come into play? I know that the mechanical kicks in when the weights spin at a certain rpm. Like I stated I did test them per the steps laid out in previous posts and they seemed to check out. Can you spray some lubricant on the weights and bushings to make sure they are not sticking? Could the lobes and shaft itself be worn down and causing this issue?

mugzilla

Timing chain ...

mugzilla

https://classicoldsmobile.com/forums...tml#post152659

Olds64

Maybe the harmonic balancer is loose?

Then again, if the car's drivability changes as the timing mark moves that makes me think it couldn't be just the balancer.

silverriff

Well I replaced the timing set about a year and a half ago, and replaced the balancer a few weeks ago. Is there a point when turning the distributor that it meets resistance and "springs" back into place? I noticed that last time I was adjusting it. Grasping at straws here.... What about a vacuum leak? I am systematically changing out the hoses and fitting but I believe I still have a leak somewhere, would that affect it? I am going to drive it around today and see if I can get it to jump again.... Errrr

Run to Rund

Check for "varnish" build up betwen the shaft and the advance mechanism, meaning old engine oil that has congealed. You should be able to rotate the distributor easily when the bolt is loose. You should also be able to manually turn the advance mechanism and have it snap back smoothly.

Olds64

You should be able to detect a vacuum leak if the engine is idling poorly. You can also use a vacuum gauge.

silverriff

Alright well that is what I did, I finally went up to the store and got a vacuum gauge. I probably should have done this a lot sooner because I found some good info. After fooling with the mixture screws I got a steady manifold vacuum at 19 hg. Don't know if that's what it is supposed to be, but that's what I got. I don have my manual with me so I can't check, and i haven't search through the other forums yet. Anyway that's what I got. And I got a good strong ported vacuum when reved, nothing at idle. The ontresting thing was when I systematically when through all of the vacuum ports on both the carb and the electronic advance tree thing at the front of the engine, which in electrically dissconnected. Here is what I found....the line comming out of the top of the tree( don't remember what's it's called) was going from the tree, to a t fitting that split one line to the distributor advance and the other line to the carb port on the front drivers side, halfway down. The thing is that when I hooked the gauge up to that carb port, I was not getting any vacuum at all, ported or manifold. Could that be one of my issues? That means that for whatever reason the distributor is not getting any advance at all. Should that carb port be giving me something or is it just there for decoration? So just for shats and giggles I disconnected it front that port and plugged it into a working ported vac port on the passengers side base. Drove it around and seemed to really improve the feel. The timing actually seemed to hold steady also. What else I found was the 2 back carb ports, the pass. side which I had plugged after removing the choke stove , and the drivers side port which is connected the the bottom port of the "tree". Niether one of those 2 ports are getting either vacuum type. The top port of the three tree side ports is going to the manifold, and the center port is capped off, but it giving the 19 hg manifold vacuum. Lord what is going on here? It seems like the lines are screwed to hell.

Lady72nRob71

Sounds like you are narrowing your problem.

Carb ported vac should give little vac at idle to moderate vac as throttle is opened.

The TCS (transmission controlled spark) solenoid is that tree thing at the front of the engine. It switches between no vac & ported vac depending on transmission gear, or to manifold vac when eng temp gets too high.

Do a "TCS transmission controlled spark solenoid" search here and a vacuum diagram should be somewhere (I posted one I think).

Many people disable the TCS when they stick and no longer work as they are not reproduced. They run the disty vac right to either manifold vac (like mine is now) or to ported vac on the carb. All the other ports they cap off.