[Crowbarman55]

Engine: 350 GM creat (290 hp).
Distributor: Mallory Unilight vac advance
I put a vacuum gauge to full manifold vacuum just to see what was going on and the vac gauge won't hold steady. It's not much movement but not steady. Gauge reads 15 hg showing late ing. timing. So I tried adjusting the timing. every time I move the distributor one way or the other the engine runs rough no matter how much I move the distributor. I tried compensating with idle mixture screws made no difference. Any thoughts on what could be going on? I should be able to turn the distributor and the engine not run rough. Thanks
Todd

 

[oldchey57]

Dizzy

Possible you have vacuum leak somewhere, carb base, intake manifold, etc.

Dangerous Joe :viking:

 

[Pops @ Tri-5.com]

Todd....What carburetor do you have on the engine?

 

[Crowbarman55]

Edelbrock 600 CFM electric choke. I do have a heat gasket underneath the carburetor to prevent heat soak.

 

[Jims56]

Engine: 350 GM creat (290 hp).
Distributor: Mallory Unilight vac advance
I put a vacuum gauge to full manifold vacuum just to see what was going on and the vac gauge won't hold steady. It's not much movement but not steady. Gauge reads 15 hg showing late ing. timing. So I tried adjusting the timing. every time I move the distributor one way or the other the engine runs rough no matter how much I move the distributor. I tried compensating with idle mixture screws made no difference. Any thoughts on what could be going on? I should be able to turn the distributor and the engine not run rough. Thanks
Todd

Sounds electrical to me.

 

[topdog]

You should always run with full manifold vacuum.

 

[hotrodchevy]

With only minimal movement of the distributer causing it to run ruff I would be looking at the plug wires .

 

[Crowbarman55]

Thank you all. Will look at all of this.
Todd

 

[bler57]

How old is the distributor? Check the cap and rotor as well. I am leaning toward something electrical. Check plug wires as stated before. And also distributor electrical connections. Make sure there is no binding of the wires when you rotate the dizzy.

 

[Crowbarman55]

Distributor is 11 years old. Could be time for a new one. I can't fit a HEI. And Mallory is not around any more. Any suggestions on a good reliable distributor? Need vacuum advance. Points are NOT a option for me. I will get new plug wires and check all wires first. But still thinking I want a new one. Todd

 

[bler57]

MSD 8361. Been using it now for over 10 years. Never skips a beat and is easily adjustable with bushings to set your advance.