Have a '69 GS 350 with a T/A 212 cam and Pertronix conversion. Everything else stock with 3.23 gears and AT. I am running a 750 Eddie on it through an adaptor to stock manifold. The car idles great/steady at 700 rpm but has an off idle stumble and when cruising at steady speed I can feel a slight missing kinda thing and when I give it gas it goes away. Is this a lean condition during a higher vacuum situation? I have already gone up from the stock spring and have gone up a size in jets. Should I increse jet, spring or both? Thanks, Dan
Sounds like it is leaning out due to cam in midrange. Best bet is to get it scoped, then you can chekc misture throughout whole range, ignition etc.....well worth the money. I had the same thing on a 455, jetted up two sizes and it went away... later Tim
I am having the same problem on a Holley Street Avenger I put on my dads Vette. Cant get it figured out. Runs great everywhere except right off idle.
I hate to send you to a Mopar site, but over in the Performance section of Moparchat.com, they have an archive section at the top. Look for an archived thread by a guy whose name starts with Cuda and ends with a bunch of numbers. I'd be more specific, but they block Moparchat here at work because it has the word chat in the domain LOL Anyway... the guy's name is Don and before he decided that Eddy's sucked (for him anyway), he wrote a VERY good thread about tuning them up. PM me if you can't find it and I'll dig it up when I get home this evening. Other suggestions I might have are to verify you're not "light" on the initial advance timing and, check which hole your accelerator pump is connected to. My GTX stumbled initially, too, but once I got the timing boosted up where it needed to be, the majority of the stumbles went away. I still have a lot of tuning to do though.... never ending saga LOL
I have had this happen on three different vehicles I have worked on. Two out of the three it was related to the mechanical advance springs and weights "sticking" until you got it revved up a bit. Spent hours tuning the carb and I couldn't get the stumble to go away. Put in a new performance advance spring and weight kit and voila, stumble and cruising hesitation gone. I know some people have been having trouble with the pertronix stuff as well. You still may need some carb tuning also. After you look at the ignition I would try heavier step-up springs in there. The metering rods may be staying in the hole too long due to a light spring/high vac condition. What jets, rods, and springs are you using right now? The best thing you can do is only change one thing at a time, and if it doesn't work, put it back the way it was. It really sucks trying to diagnose ignition/fuel delivery problems because they have the same symptoms.
Thanks guys, I put a new/reman (Advance Auto) distributer in and I'm sure the weights are well greased. My initial timing is set to around 8-10 deg. I don't remember the rods and jets I have in but I am sure they are one step higher than what the Edelbrock 1407 carb comes with. I will try going to a stiffer spring first. I guess I should check my plugs as well to determine if I need to jet up.
Check your mechanical advance You may want to recurve the distributor to get the mechanical in a little earlier. The reman distributors usually have gobs of advance very late in the curve. I would not expect this to cause a stumble but it would make the low rpm/off idle performance soft and down on torque.
I have put in lighter springs but I have no idea what the total mechanical is. Don't seem to have pinging problems at the initial I'm at now but maybe I need to get those bushings in there to limit my mech and up the intial, maybe that will help the stumble a bit. Dan
Here is the thread I mentioned earlier about tuning the Eddy carbs: Edelbrock Tuning If you have or can borrow or can buy an advance timing light, you can run 'er up to 2500 RPM or so, check the total mechanical and set that... then run it back down to idle and see where the initial falls. I have no idea (yet) what the big Buicks like to see, but my 440 runs 34deg total and about 13 or 14 initial. As that Moparian carb author Don puts it, it depends on the engine and what's in it. Hopefully someone better in the know can give ya a better starting point for the advance specs?
playing with Edelbrocks Dan I have been playing with my edelbrock 600's on my dual quad. with this stumble have you checked where the pump shot is set at. On the front drivers side there is a plunger with three holes the closer to the carb the rod goes in the more of a shot you will get. This seemed to help me a great deal with the stumble. Joe
I have never seen any difference when moving the pump linkage. I am also going to a higher stall converter and maybe that will help. Could the stock converter be miss matched to the cam and gear ratio?
Glen's Edelbrock Tuning Link in Moparland Boozoo - looks like they don't allow guests to browse over there - I get a page that wants me to either log in as a user, or register as a new user. Any way to get a peek at that information??? I'd go for a copy/paste into an off-line email if that's what it takes.
