Vac Advance and roughness....

[68RRFlyer]

I finally worked out the issues I had with an overcharging situation and have been cruising around trying to work out a few last kinks in the engine.  Here's what I have as my combo:  383 stock lower end, Weiand dual plane intake, Edelbrock 1406 carb, Electronic Ignition upgrade (distributor with orange box) from Bouchillon.  In gear I'm idling at 800rpm and it runs like a champ except for this problem:  surging and bucking at sustained cruise RPMs no matter what level (1400-2000, etc).  The idle is smooth, cold idle is set right, and enrichment screws are set according to Edlebrock.  I have a slight pinging under hard acceleration but it's very, very slight so the timing may be a bit too advanced, but that's not causing this issue (I don't think, anyway  ).  Unplugging the advance removes the stumble almost completely yet it seems I lose a little "oomf" out of the car at cruising speeds.

So based on the surging and such, I was thinking I may be having a lean condition at cruise.  I've enrichened the screws on the carb and all that does is make me, and everyone else around me, smell like gas and does nothing for the problem.  Do I need to install the next size up meetering rods in the carb or would backing off the advance some cure this bucking problem?  And on that note, is my advance adjustable?  Like I said, it's an electronic distributor from Bouchillon and does not have the hexagonal base of others that are adjustable.  Any ideas?  Thanks guys.

Cheers    

[gers1968rt]

What is your timing set at? Initial and total mechanical, measured when the vacuum hose is disconnected? Your timing should be 10 to 15 degrees initial and 38 degrees total all in by 3000 rpm. Your vacuum advance should pull in another 5 to 12 degrees, at your highest vacuum level. If your vacuum advance pulls in too much advance on your timing it will cause the surging and stumbling. My hemi runs best at 15 initial, 36 total and 5 more vacuum advance for a total of 41. The hemi was very rough at the same rpm range as yours and I had to retard the vacuum advance by 6 or 7 degrees to get it running good. Gerry

[firefighter3931]

It sure sounds like a lean surge issue. If the timing is correct you will need to focus on jetting up to fix it. 

The 600cfm eddy is a little small for a 383 and i would think slightly lean out of the box. 


Ron

[68RRFlyer]

Running like a top now, purring like a kitten, screaming like a banchee...or whatever saying you want to insert!  .  I found I was I had too much initial timing.  Backing that off a bit solved the surging issue.  Thanks for the tips~!  Glad I didn't have to order anymore parts.  Gotta love this forum! 

Cheers