carb help

[drat]

Well ive been putting in some time on my 69 avanti.

I put a 6al box and coil and msd distributor. Now that ive got some reliable good spark i have been trying to dial my carb in.

I am running 202 heads, sanderson headers, performer intake, and a 1405 eddy carb. The block is the stock 350 motor with stock cam that came with the car. It has been rebuilt. My timing is set at 4° at idle which to my understanding is what early 1st gen 350s like.

I believe i set the floats right, and i am running 5.5 for fuel pressure using a holley regulator.

Whats happening is the car is slightly sluggish when punching it off the line.

I thought i had a timing issue but im fairly certain i am in the ball park as i cant dial it out with timing.

So today i moved the accelerator pump linkage from the middle spot to the top. It made the car bog a little, and if i bliped the throttle it would almost die before regaining idle.

So i went to the bottom hole and it got better off the line. But still not perfect.

I picked up some new springs for the metering rods too.

So i guess my question is. Am i running too rich or lean off throttle? Which way should i go with springs?

Am i going about this the right way?

As far as timing goes, most everyone says 32° ish total advance, which is 8°ish at idle, but i have been told some early first gen replacement(crate) motors for vettes (what my engine code is) ran at half that.

Lay your sweet knowledge upon me!

[WayneC]

I don't have much sweet knowledge to lay on you, I've never played with an Edelbrock carb.

But, it seems to me you are on the right track with the accelerator pump, considering the car seems to only have an issue off a dead stop. I would not fool with those metering rod springs until you get the stumble fixed.

You might check to make sure the choke is properly adjusted.

4 degrees advance timing at idle (with vacuum canister vacuum hose disconnected and plugged) should be fine.

Is your idle set at 600 to 700rpm in drive, engine warmed up, tranny in Drive, with the brake on?

There are a number of Edelbrock carb tuning videos on youtube, have you perused those?

And, do you have this:

http://www.edelbrock.com/automotive/misc/tech-center/dl/carb-owners-manual.pdf

[drat]

Choke is discontented, wired open.

I though i could help the sluggishness with springs. I already tried the accelerator pump arm in through all of its adjustments. And tried dialing it out with the air mix screws.

What else besides springs would i try? If the timing is right the springs would be my next step right?

[drat]

Choke is discontented, wired open.

I though i could help the sluggishness with springs. I already tried the accelerator pump arm in through all of its adjustments. And tried dialing it out with the air mix screws.

What else besides springs would i try? If the timing is right the springs would be my next step right?

[Gunslinger]

Why don't you simply contact Edelbrock? Let their techs know all the engine specs and the problem and see what they have to say. The headers (Sanderson are excellent) give less back pressure and may change the required carb specs...jetting, etc. It's likely a simple fix but the shotgun approach wastes a lot of time and effort.

[WayneC]

You said: "So today i moved the accelerator pump linkage from the middle spot to the top. It made the car bog a little, and if I blipped the throttle it would almost die before regaining idle. So i went to the bottom hole and it got better off the line. But still not perfect."

...I thought I understood that when I read it, but on re-reading I am not certain I did... is the "bottom hole" on the lever closest to the carburetor pivot point or furthest away? I expect the hole closest to the carb pivot point gives the earliest & longest squirt.

If the bottom hole was best (furthest from the carb pivot point), that would give the softest squirt, but that still apparently wasn't soft enough. Am I understanding correctly that you had the best result with the rod in the furthest hole from the carb?

Did you adjust the idle mixture in accordance with the Edelbrock pub? (see "Idle Mixture" on page 6 of the Edelbrock manual linked in my prior post).

Out of curiosity, have you tried simply removing the linkage rod (to the accelerator pump lever) for a test?

In perusing the manual I linked in my prior post, it appeared to me that it is possible to change the jet size for the accelerator pump, although that manual does not list other available sizes (there is a chart showing the accel pump jet size that comes standard in each Edelbrock carb type, and the 1405 uses the smallest/leanest size). Can you see a strong fuel stream from the accelerator jets when you blip the carb linkage off idle in the garage?

A vacuum leak can give similar "stumble" symptoms at low rpm, so you might check for gasket leaks or loose vacuum hoses.... Vacuum leaks usually result in an uneven/rough idle, too, but not always, because you may have masked that while adjusting the idle. You can use a propane torch (valve opened a bit without lighting it, and pointed away from the carb, air cleaner removed) as a method of finding leaks, by directing the propane flow closely and slowly around the seams at the base gasket of the carb, around the outer edges of the intake manifold, along vacuum hoses, etc, listening for the engine idle rpm to increase noticeably when the propane stream passes a leak. Do it outdoors so the propane gas doesn't collect in your garage

Edited November 14, 2014 by WayneC

[mfg]

Sure sounds like an accelerator pump issue to me. Are you getting a healthy squirt of fuel out of both nozzles when you work the pump by hand? (linkage disconnected)

[Avanti83]

I'm bringing this topic back because I was just reading Hot Rod mag (01/15) issue pg 122 and this exact question was addressed. That should be the current issue on the news stands.

[CaffeineRacer]

And what was the answer they have in the hotrod magazine?

[drat]

I had to step away from the car for the time being. Ill try to find that article. But in the mean time i am xuriois too on what it talked about in general?

[drat]

Cant find the magazine. They already have February on the shelves.