Merry Christmas everyone!

I am trying to determine what is causing the engine timing to move after I have set the timing to 8 btdc? I have the dwell set a 30 and also the emmision vapors are very strong. The engine is a 72 455 with an Edlebrook carburetor on it and I am not sure which one. I have also tried adjusting the fuel air mixture. Is it possible that the vacuum advance could be bad? The engine does run smoothly but is hard to start when cold. I have an HEI distributor to put on it but just no yet.

 

Set timing with the vacuum advance disconnected. Check to see if the mechanical advance "moves" to differentiate vacuum vs. mechanical advance issues. Timing should always be set with vacuum advance disconnected. If the mechanical doesn't stay the same, check for binding, rust, wear in the system, on weights or stiffness of the tube moving meaning oil has varnished and gummed up the clearance to the shaft.

 

If you'r timing mark is not the same after you run it a while, Check the harmonic balancer. they are known to come loose on the inside and spin a little bit throwing you'r mark off. Especially if it has some age on it.

 

Bring your # 1 piston to tdc , check you'r timing mark, if it is not on the pointer .make a mark with a chalk on the balancer and see where the chalk mark is with a timing light on it. run the engine for a while and see if your chalk mark is in the same place .if not, your balancer is spining on the inside this should let you know if you'r balancer is bad. Hope this might be of some help.

 

Your rocker arms aren't too tight are they?

 

the rockers are torqued @ 25lbs. I did replace the valve seals because the exhaust maniford on the drivers side was smoking some what out of the tail pipe and when I replace the seals that corrected that problem. this engine was rebuilt by who ever had it beore me and he said that it had not been driven after the rebuild. When I removed the heads there appeared to be no carbon buildt up on the pistons and the valves were new and there was not any carbon on them. OLDS 442 I am leaning towards the harmonic balancer being bad because from what I am thinking the timing mark should not change especially since I tightned the distributor shaft down really snug.Also the previous owner sent with the car a Rochester quadajet but is it not for a 72 when I looked up the casting numbers on it, it is for a 77.

 

When you install your HEI you'r #1 spark plug wire will be on a different post on the distributor . they are not programmed like the points style caps. firing order does not change, only the placement of wires on the cap. You will also need to change spark plugs.Elecrtonic hei calls for a different plug .Use plugs for a 1977 or so. I think the #1plug wire will change from the front of the cap to the rear of the cap next to the firewall. I have done went through this and the harmonic balancer fix. Sounds like my car all over again. Hope you find this helpful.

 

Think timing chain - they stretch more after warm, and if you're hitting an area where the upper gear has a few teeth broken off - more slack!!
Remove the distributor cap, and see how much you can turn the balancer before the rotor begins to move.
10 to 20 degrees - time for replacement!