I'm still trying to get my 396 in my 68 Vette to run decent. I've got an HEI distributor in it with a new, supposedly correct vac can for a 396. I've got a Q-jet 17058204 (which appears to be for a 78 350)that I put a kit in also. And a new fuel pump. I know that a1sensei always seems to have great knowledge in this area.
My major issues are, I have to pump & crank forever to start it when cold. Then I have to keep it running with the pedal until it gets warm enough to run on its own. I've got an electric choke which seems to be working. When I have it running in my shop (with the doors open & fans running) The exhaust burns my eyes. (too rich correct ?) I've set my base timing at 4. I also saw somewhere on the forum that I can set my timing by vacuum. Hows that done ?
I'll appreciate any input from anybody here.....Thanks

 

The choke plate should be almost completely closed when the engine is cold, tap the throttle and it should snap shut.
Once that is sorted out, you may very well be running rich and you can turn the idle mix screws in a bit to fix that. It could be that your jets arn't right, but get the rest setup first. Base timing is a little low, I would go to 6 or 8*. Then connect the vac can and see where you are, have you read the timing Sticky at the top?

 

Thanks SIXFOOTER....I just looked at another Q-jet that I have laying around. It does'nt have idle mixture screws in the front where they usually are. Whats up with that ? The # on that one is 17059206.

 

They all have idle mixture screws. Some of them are just capped to prevent adjustments. The caps can be removed though if necessary.

 

Yep, there should be plugs on the front of the throttle plate. You have to make small cuts on the bottom of the plate right below the plug and then drive them out with a punch. Details in most of the books on carbs

 

That carb came off of a 1979 chevrolet with an auto tranny
Here is some good info if your interested in learning it
http://www.newagemetal.com/
http://www.carburetor.ca/carbs/tech/...jet-index.html
http://www.florida4x4.com/tech/quadrajet/index.php

 

Is the motor a performance motor with larger cam and if so, how large? A stout motor will require some different tuning methods as opposed to a mainly stock motor. For example, if you have a stout cam, it will have much less vacuum at idle, which causes it to draw less fuel at idle and most peope will just turn up the idle but by doing so it will cause it to start drawing fuel off the main circuit and not the idle circuit, which will cause a very rich idle.

 

Your carb should look similar to this...



Having to crank and crank to start could be the fuel bowl draining overnight. Start it and let it run for a while, then let it sit overnight. Go out the next day and open up the choke flap (#2). Make sure you have plenty of light so you can see down the front two barrels of the carb. While looking down the barrels, use your free hand to run the throttle through a complete stroke. You should see two solid streams of fuel shoot down the venturii. If not, the plugs on the bottom of the bowl are probably leaking down. Not too difficult of a fix. I have also seen aged, cracked fuel vent and return lines (all of that shyt on top of the gas tank) create a vacuum and draw the fuel out of the bowl. Try the easy stuff first, though.
If it squirts fine, next thing is to make sure the choke and its pulloff (#1) are functioning properly. As has been stated above in another post, with the engine not running and cold, just blip the throttle to make sure the choke is engaged. Have someone crank the engine over while you are watching #1. The arm should start pulling toward the front of the carburetor, and pull the choke flap open about 1/8 of an inch. If it doesn't pull, either your pulloff is bad, or you don't have sufficient vacuum for its proper function.
Once the engine is started, the electric choke should slowly start to open the flap. It should be fully open in about a minute.
Check those out and tell us the results.

 

Thanks alot guys. I have no history of the 396 other than by appearances it appears to have been rebuilt some years ago & then just sat. To me & some other Vette Club buddys it sounds like it might have a mild cam. I'll check & try all of these suggestions as soon as I have time. I'll certainly get back to you after checking & trying your suggestions. I appreciate your input !