Will a 400 run if the timing chain jumps a link?
My 400 runs but I have the best vacuum when the timing is set to 30* after TDC. If I set the timing to 10*BTC it will run but it has barely enough power to pull itself and my vacuum is almost non existent. I havent done a compression test yet but I have checked the spark plug wires several times and they are right. Should I jerk it apart and check it or am I chasing the wrong thing?

 

Is the distributor at the #1 post when the #1 cylinder is at top dead center? If it is its possible the balancer has slipped.

 

Same old question, are you timing with vacuum advance plugged at carb?

 

No and yes. The distributor is unplugged from vacuum hose from the carb is plugged off so no vacuum leaks during the timing process

OK, I thought the question would be a little more strait forward but I guess not.

OK, When I use a timing light to time the motor to 10*BTC the motor runs horable. It has absolutely no power and will barely run with the idle screw bottomed out and the needle valves 4 turns out. One trip around the block and the temp guage went 1/4 higher than normal run temp. I mean it has NO power, barely enough to pull itself. My vacuum runs around 4-5.

When I use the vacuum guage to set the timing, the 10*btc mark is about 30* away but my vacuum goes up to about 15. It runs better there BUT, stil stumbles all over itself. It has a little power in the top ten percent of the throttle but dogs out a bit if I push it harder. The temp stays cooler (about normal)

Ive been driving it like this for a while thinking a valve might be stuck our something and it might work free even though the vacuum guage doesnt indicate a stuck valve.

I checked the timing mark on the balancer and its correct. I put a half inch dowel in the spark plug hole and turned the motor till it stopped on the dowel, made a whitness mark and turned the motor the oposite direction till it bottomed on the dowel and made another whitness mark. 0*TDC fell right between the two marks(give or take a degree or two)
The rotor is not pointing at #1 when the motor is at TDC but of course the timing is so far out it wouldnt. It points in the general direction though.

At the present time Im getting about 3 miles to the gallon and it stumbles badly. The plugs are a redish brown color.

My question is " will a 400 run (as such) if the timing chain jumps one link?"

 

I haven't tried my 400 with a jumped chain... but I'm 99.99% sure it would run and maybe show symptoms like you describe. As posted above, a slipped damper could do the same thing plus its easier to check. Sometimes you can see indications of slippage by visual inspection. Another way to check is to verify TDC in the engine vs the timing indicator.

To do this buy or make a "positive stop" to install in the spark plug hole of #1. Screw it in and slowly turn the engine by hand. When it is in far enough in so it hits the piston top, mark the damper. Roll the engine the other way until it hits the piston again and mark the damper. half way between the marks is "true" TDC. If it is different from the damper markings by more than a degree or two, it has slipped. Time for a new damper.

 

Any recent carb work? Does the oil smell like fuel?

 

I had a 78 400 that ran like garbage. Had a horrible miss, would only run with timing way advanced, and exhaust smelled really rich. Turned out the timing chain was very sloppy and slipped one tooth.

 

Thats exactly what I did, The damper is not slipped.

 

Yes, recent carb work. Power valve needed replaced and I cleaned it up wit spray carb cleaner. It runs better since then but still acts like valve timing, Im not an expert though.

 

Thanks for the reply with your experience. Thats how mine runs, like garbage,. Using excessive gas and poor power having to advance timing just to hide the rough idle and get vacuum back?
Thanks, wasnt sure if it would even run with a timing cahin one link off.

 

I found myself at the same point last week only to find out after tearing the front half of the motor off that the timing set was fine and the carb was flooding the engine causing the same issues you are having. YMMV