Several Questions

[Phil76]

Okay, so we got her running a couple weeks ago, but have been having issues of rough idle, dies when in motion, etc. The plugs are pretty black, telling me either a rich state exists, or there's something wrong ignition wise. I'm leaning toward the choke not opening all the way for some reason, causing too much fuel to enter,and foul the plugs, and make things rich. I purchased a long block which is a 1980-up, with one 78 head, and one 87 head, hydraulic lifters and unknown camshaft. I pulled the distributor from my 74, added a 40,000 volt coil, and MSD wires. My main question is: what should my spark plug gap be? I've read anywhere from .30-.50. What should I base this off of, the distributor, or the engine? Also, what is the ideal point gap? I have an Edelbrock 1406 which we rebuilt, and know this is the main culprit behind my issues. I want to make sure once I get that fixed, everything else will be good. One final item: it has the dual vacuum advance, but no valve installed in the thermostat. Should I plug the outlet closest to the distributor, or leave it open? Thanks

 

[shamu]

Do you have a vacuum leak?

 

[Rustytruck]

Point ignition gap it at .032.
If your not using the dual vacuum canister leave the back port nearest to the cap open but plug the vacuum line running to it. That is the vaccum retard diaphram. If you plug it the front vacuum advance cannister will have to pull the load on both diaphrams in order to advance and retard the vacuum advance. Leaving it open it will add no resistance.

 

[Phil76]

@Shamu None according to a vacuum gauge, and even tried the old carb & choke cleaner method

@RustyTruck Thanks, I'll try that. I gapped them at .035, so I'll pull them and re-gap. We had plugged the vacuum port closest to the cap. I'll unplug that and see how it does.

 

[broncnaz]

Thats kind of a scary sounding mix matched engine to start with. I believe 78 302 heads have 69 cc combustion chambers where the 87 head has 64cc chambers. not a good idea to mix and match as power levels will be different on one side of the block it could cause some issues down the road but shouldnt be causing your running rich issue.
Definetly check the operation of your choke. probably need to go through that carb again carefully. I would also suggest getting rid of the dual vacuum advance.
As for points gap .017 for new points probably .015 for used points plug gap about .034. .035 is close enough doubt if its causing the issue.