Carb Troubles?? Or Timing?

[orange72350]

I had a mechanic install my new edelbrock 1406 on my engine. After the dude was done, i took it for a quick spin, and it ran allright, but pinged at wot. So,. i checked the timing, and it was waaayyy advanced. 18dbtdc. Woah, so i backed it way off to 10, turned the idle up, and away we go. Anyhoom, the engine has a stumble now at slow engine speed. It was there before, but defiently worse now. The stumble is really bad when i have the tranny in gear, and try to brake stand it. it just wont happen. engine dies/ it is also there right off of takeoff, it stumbles for a second, then picks back up. It also seems to get worse the colder it gets. this sounds lean to me, but not really sure. needed some expert advice. thanx guyz. much appreciated.
daledoe

[Hotrod70C10]

try to lean it out until it seems to idle down. I had the same problem for a while, leaning it out helped. Now if I would just get around to replacing the burnt plug wires Good luck, Maybe someone else can give you some more ideas.

[68 Suburban]

Is your engine stock? My 1406 was way to rich for my engine out of the box. I had to go down 2 steps on the chart that is in the book that came with your carb.

[tom hand]

If your motor would crank at 18 btdc, I would say your timing marks are off...pretty common on Chevys. Forget the timing light and advance the timing...run as much as it will run without pinging. May still need to tweak the carb, but I bet timing is your biggest problem

[danho]

I just had a similar problem with my new motor and edelbrock carb. I tried to time it with the light and it ran like crap, vibrating and stumbling, the works. I thought it was the carb so I fooled with that, no luck. Ditched the light and timed it by ear, got it running good and grabbed the light to see where I was at...just guessing i'm at 20-25 degrees initial or so. I doesn't ping or fight me on startup so i'm going with it.

HTH Dan.

[ksamps01]

I agree on the timing issue. I had the same problem. Big stumble off idle. Screwed with the carb for a couple of hours. Turned out my timing mark is off by probably 10 to 12 degrees. Either go by ear or find TDC and remark your balancer. Just my $.02.

[PR454SS]

Do you guys set your initial timing when you first drop in the distributor?
by that I mean bring #1 to TDC and then back it up 10* this will set your initial timing and then drop in the dist and line up w/#1 terminal, it'll line up with the timing tab everytime

[oldsub86]

Is the accelerator pump on the carb adjustable? It also sounds like it might need a little bit more gas when you step on it. I can't recall if these carbs have an adjustment but I recall that some have multiple holes and if you move to a different hole it increases the amount of fuel that the accelerator pump pushes in on initial pickup.

[orange72350]

Thanx Guyz. definaltey gave me a few idears. My main worry though is that i really dont think that it is a timing problem, as it did this even when the timing was advancedto the point where it was pinging like mad. Im not 2 sure though, as im not much of a carb guy., and i didnt put the carb on, so imnot sure what partner did to the carb to get it to run right. Any other ideas guyz? and where do i get a hold of parts for a 1406? can i just order a kit from edelbrcok????

[GMan69]

From the description of your engine in your signature, I think your carb is too lean. My 350 is slightly modified also and the 1406 was WAY too lean out of the box.
Your timing probably needs to be set accurately also. I question the 18* initial and am wondering if you had vacuum hose removed from the distributor. If not, do so to get a true initial timing. Also, limit total timing to 34*.
Back to the carb. Edelbrock markets calibration kits for their carbs. The one for the 1406 is part # 1487. It contains primary rods, step-up springs, jets, etc. Available through Summit, Jegs, Scoggin- Dickey, and other speed parts places. $40.00 or so. Edelbrock provides tuning tips in the box with the carburetor. I somehow lost mine but printed the manuals from their website. Take things one step at a time and you'll have that truck running great.

George

[robertwb]

you guys with the timing off by @10 deg probably have a mix of parts -somewhere around 1970 chevy changed the keyway position on cranks/balancers...by about 10 deg
my dad had one I tried to set it with a light and it ran like crap-he still refuses to use a light because of this experience-now my cousin has the truck and one day just to see what was going on(before I knew about the change) we put a stop in the plug hole and turned the engine by hand both ways and found TDC was...10 deg off- mystery solved

you also have to watch those aftermarket pointers or switching different year pointers

I forget which is which but the mark and the keyway are inline on one and offset 10 deg on the other

I've had 3 edelbrock carbs on 6 different engines-and while it's nice to fine tune them they have always worked good enough out of the box that you wouldn't even suspect that it wasn't perfect-so I doubt it's the carb-unless it's got trash in it somehow or it's not getting fuel from the pump-or a big vacum leak