Edelbrock carb issues...

[Spedy7]

Hey y'all, been dealing with this ever since I bought my truck a few months back. The throttle rests open just a little bit (jumps from a stable 800rpm to 1400rpm), enough for it to diesel some after running for awhile. Wasn't a huge issue prior to my engine rebuild, but it's starting to get annoying now having to lift up on the throttle to keep it from dieseling. Anyone heard of this before? It's a 1406 and the truck was sitting for 6 months or so unused.

[68 P.O.S.]

How are your throttle springs? Are they pulling it closed all the way?

[Spedy7]

Originally Posted by 68 P.O.S.

How are your throttle springs? Are they pulling it closed all the way?

It should, it's a thick a** spring. When I shut it off and let it sit for even a few minutes and start it back up, it idles at 800 right away - dab the throttle and it jumps back up to 1400. Rebuilt it recently too with the motor.

[RodnRudy]

Any chance the throttle plates are hitting the edge of the opening of the manifold or the base gasket causing them to stick open?

[kaycee]

x2

[Spedy7]

Originally Posted by RodnRudy

Any chance the throttle plates are hitting the edge of the opening of the manifold or the base gasket causing them to stick open?

Highly doubt it. It's sitting on an Edelbrock intake so I would assume there wouldn't be any binding there. I'm gonna take it off today and check it out, maybe use a little sand paper on the throttle blades to get rid of any possible burrs. Think I'm just gonna replace it with a Holley once I get the money.

[B. W.]

don't want to sound stupid here but... when you dab the throttle is it jumping up onto the fast idle cam? Post a pic of the driver's side of the carb (both idle screws) with it running @ 1400

[70's luvr]

Mine does the same thing. I can pull down on the linkage and it will close a bit more and drop idle a bit. Not as extreme as yours though.

[RodnRudy]

B.W. makes a good point. My Eddy's electric choke was set two notches rich and would stay on the last notch of the fast idle cam. I loosened the choke housing screws and rotated it two marks counter clock wise and backed off the fast idle screw a quarter turn, solved the problem. Wasn't a problem in the hot summer but on these cooler Fall days.

[geezer#99]

Originally Posted by Spedy7

Highly doubt it. It's sitting on an Edelbrock intake so I would assume there wouldn't be any binding there. I'm gonna take it off today and check it out, maybe use a little sand paper on the throttle blades to get rid of any possible burrs. Think I'm just gonna replace it with a Holley once I get the money.

Changing the carb won't fix the problem.
Get your idle turned down to 650 - 700 rpm.
At 800 rpm you're likely just starting to kick in the mechanical timing in the distributor.
What's your initial timing and what's the elevation where you live in Arizona?

[Spedy7]

Sorry, been busy lately. I'm stationed out here in California (yay...) so around sea level. Initial timing is around 10 or 12*, can't remember. Lowered the idle a notch and leaned it out more (was idling super rich), think I still need to get it dialed in. Lowered the choke a notch too, but didn't change anything.

Set the idle to around 700 and it felt way too low, plus it was getting warmer than I need it to (still breaking it in). With the throttle sticking open some, it'll idle at 800 or so in gear and 1400 in park/neutral (as it should be I'm guessing - first older automatic I've owned). The only problem is dieseling if everything is fine (got 305 heads on it too, so compression ratio is up a little).

Not a fan of Edelbrock ether...and I don't know why lol.

[toolboxchev]

My truck does the same thing all the time. I have learned to deal with it. It did not matter the carb, did the same with the original q jet.

I have the hottest plug I can run in it. I want that crap fuel to burn!

When I did my top end rebuild the tops of the pistons were gunked up with carbon goo that could not be removed without heavy scraping and I did not wish to slip and scour the cylinder walls. Todays modern fuel needs typically an engine that runs at roughly 180 degrees and a high voltage coil and hot spark.

Correct me it I am wrong on this.

Eddy carb, Accel HEI super coil, Accel wires, AC Delco R45 TS plugs. Tried using R44 TS plugs, I lost some power and economy.

Anyone have any insight on this? The 44 plugs seemed to foul out with my rings being a bit worn.

[geezer#99]

Originally Posted by Spedy7

Sorry, been busy lately. I'm stationed out here in California (yay...) so around sea level. Initial timing is around 10 or 12*, can't remember. Lowered the idle a notch and leaned it out more (was idling super rich), think I still need to get it dialed in. Lowered the choke a notch too, but didn't change anything.

Set the idle to around 700 and it felt way too low, plus it was getting warmer than I need it to (still breaking it in). With the throttle sticking open some, it'll idle at 800 or so in gear and 1400 in park/neutral (as it should be I'm guessing - first older automatic I've owned). The only problem is dieseling if everything is fine (got 305 heads on it too, so compression ratio is up a little).

Not a fan of Edelbrock ether...and I don't know why lol.

Confirm your timing!
Set initial at 14 degrees.
Super rich idle is likely due to too much fuel pressure. Eddy carbs don't like more than 5 psi. You might need a fuel regulator. Likely flooding doesn't make it happy idling at 700.
It should have no problem idling at 700 in gear and 800 in park if the initial timing is set right.

[GASoline71]

Still breaking it in? As in breaking in a flat tapped cam?

What cam? Is the cam compatible with the 305 heads? More compression traded off for low flow can kill the top end.

Gary

[hugger6933]

The sticking could be the type of intake. Some of the performer type needed a thicker gasket to work properly without binding on the primary side of the intake. Remember that intake is a dual pattern and the carb is a square bore. So that is kinda like fitting a oval peg into a round hole if that makes sense.
I think the op's problem is in the timing though.

[71meangreenc10]

Originally Posted by hugger6933

The sticking could be the type of intake. Some of the performer type needed a thicker gasket to work properly without binding on the primary side of the intake. Remember that intake is a dual pattern and the carb is a square bore. So that is kinda like fitting a oval peg into a round hole if that makes sense.
I think the op's problem is in the timing though.

Had one bind because of the spacer.........Ensure you check there....


Smitty

[Spedy7]

Originally Posted by GASoline71

Still breaking it in? As in breaking in a flat tapped cam?

What cam? Is the cam compatible with the 305 heads? More compression traded off for low flow can kill the top end.

Gary

Yup. Got lucky actually, the heads I found already had a valve job done with bigger intake and exhaust (1.94 or 2.02 intake, 1.84 exhaust I think). The cam I got is Comp Xtreme 4X4 #12-235-2 (210/218 duration at 50 .447 .462 lift) and 12cc dished pistons to keep it around 10:1. I was aiming for a torquer setup and not for higher rpm power. Also, my old smogger heads were beat to hell from whatever was in the chamber, so had to find something to replace them.

I think it should be idling around 800-1000 rpm in park and drop down some in gear, a 600-700 rpm drop from park to drive just doesn't sound right, I could see 1200 rpm in park - but no more than that. Maybe my torque converter is going out or at a higher stall? Automatics aren't my thing, but kinda need one for all the traffic here (otherwise I'd go manual). Also, hitting the throttle sharply will cause it to hesitate real bad. I set the accelerator pump to get more leverage to combat it, but still getting some hesitation.

Might also need to change my plugs...I got RT44's and might look into 45's to get a better spark. Got HEI on it too with a Summit Racing rebuild kit for it.

[RichardJ]

>> it'll idle at 800 or so in gear and 1400 in park/neutral (as it should be I'm guessing <<

No and hell no.

@ 1400 rpm you are not putting the transmission in gear, you are banging it into gear.

Your post isn't saying what year or what engine, so this chart is for 1968 with 327.

Distributor timing - Note #2. "At idle speed with vacuum for vacuum advance, disconnected and plugged". Leave it disconnected until timing, idle speed and mixture have been adjusted.

"Timing" is listed as 8* or 4* for non-A.I.R. /327 so there is NO reason to set it more than 8* at this time.

"Idle RPM" for non-A.I.R. / Auto, is 500 or 600 rpm. I would set it as close to 600 as I could and hope for it to not drop much more than 50 rpm in gear.


I see that you are not using the center four bolts on the intake manifold. You need to make sure you don't have a vacuum leak.
Are you checking to see if the choke is OFF and the choke blade fully OPEN? Don't worry about the choke notches. It just needs to be barely closed when cold, then open fully when warm.

[Spedy7]

Originally Posted by RichardJ

>> it'll idle at 800 or so in gear and 1400 in park/neutral (as it should be I'm guessing <<

No and hell no.

@ 1400 rpm you are not putting the transmission in gear, you are banging it into gear.

Your post isn't saying what year or what engine, so this chart is for 1968 with 327.

Distributor timing - Note #2. "At idle speed with vacuum for vacuum advance, disconnected and plugged". Leave it disconnected until timing, idle speed and mixture have been adjusted.

"Timing" is listed as 8* or 4* for non-A.I.R. /327 so there is NO reason to set it more than 8* at this time.

"Idle RPM" for non-A.I.R. / Auto, is 500 or 600 rpm. I would set it as close to 600 as I could and hope for it to not drop much more than 50 rpm in gear.


I see that you are not using the center four bolts on the intake manifold. You need to make sure you don't have a vacuum leak.
Are you checking to see if the choke is OFF and the choke blade fully OPEN? Don't worry about the choke notches. It just needs to be barely closed when cold, then open fully when warm.

I'll have to double check timing and the choke. As far as I know, the choke is closing and opening fully. Engine isn't stock - 416 305 heads, block is a 3970010 casting, dished pistons, RV cam, HEI, and headers. I got my shop manual, so I'll take a look in there.

I do remember setting my vacuum advance way low or high before rebuilding the motor to see if all the knocking it made was a spark knock (turns out it was pre-detonation or some small fell in the cylinders).

[Spedy7]

Quick update, think I've got it near where it needs to be. It turns out it's not the carb (who would've figured that lol). Unplugging the vacuum advance leads to a lower rpm - swapped in the heaviest springs I got and it's better - rpm drop is still oddly high. As it sits it'll idle at 1000 just fine and in gear it'll go from 700 and slowly creeps down to 550-600, doesn't really sound like it's struggles ether (some vibration, but doesn't putter). Could probably use some springs that start the advance at 1200 rpm though.

[71CHEVYSHORTBED402]

Replaced my Rochester with an Edelbrock on my Super c-20 today. It's a driver/parts truck. I didn't replace it, but I needed a choke I know nothing about, and I'm busy with the 71.

Results of that Edelbrock is it feels like there's less power and no kick-down. Perhaps the secondaries aren't opening or it's vacuum. Other than that it runs well. I'll see if I can figure out what's what tomorrow, but they want to see the truck in a few weeks anyway.

[HO455]

It's very common for the weights on the mechanical advance to hang up and not fully return after they are spun out. This means the idle RPM will not be consistent. Check your timing at idle with the vacuum advance disconnected and plugged. Then wing the throttle and check the timing again, then rev it up again and let the throttle close slowly. The timing should come back to the same number every time. If not then you will have to check the weights for wear on the bottoms, in the hooked areas, and at the pivots. Polishing the advance plate can help. Avoid using lubrication as it will end up gumming it up over the long run. Changing to heavier springs will just screw up your advance curve by making the timing retarded and robbing you of horsepower. If you can pull the distributor and put it on a distributor machine you will find it easier to solve the issue as you can watch to see where it is hanging up. Sometimes you may have to change the plate out. Brand new distributors can have this problem too, as they may be a good design, but most are assembled by the cheapest labor possible. Good luck

[67chevy_hotrod]

Holley However x2 on the fuel regulator

[Mrturner1]

NOT USING THE 4 MIDDLE INTAKE BOLTS???!!!

you have a vacuum leak.

[Toms67]

Amen to that.