"Testing" the correlation between the balancer mark and the rotor as you have described does nothing more than what you have already done with a timing light.

I disagree...

If the timing chain & gears are sloppy, you cannot set the timing.
The cam (and thus the rotor) will not be following the crank.
Any timing adjustment made with a sloppy chain & gears is a waste of time.
The mechanical relationship between the crank, cam, and rotor is all over the map.
Setting the timing to 8 degrees (or any setting) under this condition is just a "guess".

I've seen this many times, and it's taught in High School Auto-Mechanics 101.
Physical verification was done using a properly adjusted (endplay) distributor with no vac or mechanical advance on an engine with known sloppy chain & gears.

I've been building engines professionally for over 35 years and worn timing chains & gears are a common problem that can cause backfiring.

In addition to all of the good suggestions above, carbon tracking in a bad distributor cap can also cause plugs to fire out of sequence.

The outer ring of the balancer can slip rotationally... that is, not in a way that you can just look at it and tell. Sometimes it slips fore & aft as well. Then you can see it.

As suggested above, verify that the timing mark on the balancer is indeed TDC aligned and go from there.

 

You can check for worn timing chain/gears by removing the distributor cap and rotating the engine via the crank snout or a v-belt. As soon as you begin to rotate the crank the rotor in the dist. should turn. If not, you have a worn timing set.

Brett

 

When I go this car 5 years ago,it was in a bad way.The front clip was missing,brakes were non-existant & the steering was loose,(hard to believe people can treat a car this way),so taking this car on the road was not an option.I drove it around the yard a little thats all,I never really looked at the engine at that stage.
I sent the original carb in to be overhauled,& was told they could not repair it as it was shaped like a banana(been overtightened I guess),so I bought a reconditioned carb from them.When I removed #1 plug I noticed it was sooty black,would that be a rich condition or what.I don't mind removing the carb again,just need to know what to look for.
Thanks Neil.

 

Neil... yes.... sooty black plugs indicate an over-rich condition.

I am going to assume you have a Q-Jet carb on the 79.
If it were a Holley, then it would be important to note that one backfire can blow the power valve and it would leak to cause the over-rich mix. But Q-Jets operate on a different principle.

I'm also going to assume that it was NOT running well when you replaced the carb, and this is the reason you began your quest.

RE: The bananna.... yes.. that can happen. I just replaced a Bananna'd Q-Jet with a spreadbore Holley. The air horn was twisted up so bad that the accelerator pump would shoot fuel out the top instead of down the venturi because the air horn gasket would not seal the required passage. I tried to straighten it, but it was too far gone.
The replacement (new) Q-Jet was $792, rebuilt $500+. (electronic carb)
The Holley was $300. In your case, since you mentioned "restoration", you should probably stick with the Q-Jet.

It doesn't sound like you have a real organized approach yet.... so I will suggest something. The carb is probably out of adjustment, but no matter how well you adjust it, if the engine has been abused like the car supposedly has, you need to assess the damage.

1) Check to see if the timing chain & gears are shot
2) Check to see if the balancer outer ring has moved
3) Check for worn out cap, rotor, spark plugs, and plug wires
4) Check the distributor endplay

All of these things affect your ability to set the engine up properly.

Then re-address the carb adjustment.

"Lars" here on the forum is the resident Q-Jet expert and he has provided some great resources for working on Q-Jets... look 'em up. There are also a few very well written books on the Q-Jet that would be a wise investment.

You might find that the engine is in need of some mechanical repairs before you can set up the carb & timing.

Tom

 

Tom,
Yes it is a Q jet carb,I have all of papers written by Lars,& I have contacted him in connection with the carb.I removed the top air horn off the carb,& adjusted the primary rods,which were way to far out of the jets when the power piston was fully down,& adjusted the float which was set to low.When I went around a right corner the car would cut out,so I am hoping the float level will correct that.
As for the valve timing,is there any way other than removing the valve cover to check the chain.I don't like the idea of removing the fan,balancer & replacing gaskets to find that the chain is OK.
I will probably have to wait till the weekend now anyway,winter is fast aproaching now,it's getting dark when I get home.Daytime temperatures are plummeting to 20deg celsius( 68deg.F).
Thanks for your help,Neil.

 

See above to determine timing set wear. :rolleyes:

Brett :thumbs:

 

From my previous post above...

Remove the distributor cap so you can see the rotor. With the car in neutral (and preferably with the plugs removed) put a socket on the crank bolt. Rotate the engine in one direction until you see the rotor just begin to move. Now rotate the engine in the other direction.... if the rotor takes a "long" time to respond in the reverse direction, the chain & gears are worn too much to time the valve events properly & need to be replaced.

Removing the plugs lowers compression which reduces the possibility that you will accidentally loosen the crank bolt, which is a PITA to re-tighten when the engine is in the car.


Even a new gear set will have a tiny bit of slack, and the cam/distributor gear interface will introduce a little slack at the rotor as well. If the gear set is worn a lot, the excessive slack will be obvious.

 

To retighten the crank bolt, feed a lenght of rope into one of the spark plug holes to stop the piston from coming up. Thighten and then back up and remove rope :cheers:

 

Thanks Tom & Brett,I will do that on the weekend
:thumbs: