New edelbrock 1406

[Isaac nickerson]

Hey guys, just replaced my old 4160 with a brand new edelbrock 1406. So far it's awesome. No hesitation and way better power. The only thing is I have this subtle backfire/popping at deceleration plus some wierd ticking/sputtering coming out the exhaust mainly at idle and off idle. Obviously its fuel/air ratio. All I've done is play with the mixture screws a little bit but that accomplished little to nothing. I have heard these carbs are just about perfectly set up for stock engines so I am hesitant to mess with it too much. Also my fuel pump is at 8 psi so I was wondering if that could do it. Either way was wanting advice on whether i should try and set the idle myself first, try and install a regulator, or if it could be another factor. Any advice is appreciated. Stock 350, and manual trans.

 

[Bextreme04]

Hey guys, just replaced my old 4160 with a brand new edelbrock 1406. So far it's awesome. No hesitation and way better power. The only thing is I have this subtle backfire/popping at deceleration plus some wierd ticking/sputtering coming out the exhaust mainly at idle and off idle. Obviously its fuel/air ratio. All I've done is play with the mixture screws a little bit but that accomplished little to nothing. I have heard these carbs are just about perfectly set up for stock engines so I am hesitant to mess with it too much. Also my fuel pump is at 8 psi so I was wondering if that could do it. Either way was wanting advice on whether i should try and set the idle myself first, try and install a regulator, or if it could be another factor. Any advice is appreciated. Stock 350, and manual trans.

8psi is way too much for an edelbrock. Take a look down the primaries while its running and see if you are getting fuel dripping into the throat. Do you have a wideband or other way to tune the carb? They are usable out of the box usually, which is why people like them. But they will almost always need to be fine tuned for the application to get the best performance. They are almost always pretty rich all the way through the operating range. I bet if you pull a plug it will be covered in carbon from being excessively rich.

 

[Isaac nickerson]

I will take a look down the throat like you said. I do not have a wideband. I have a vacuum gauge though I could use for the idle.

 

[dsteelejr]

I run Edelbrock carbs on both my squares, a 650 cfm AVS2 on a 350 and an 800 cfm AVS2 on a 454. I love ‘em both. Speaking from experience, @Bextreme04 is 100% about too much fuel pressure. You’ll never be able to get the carb fully tuned as long as you’re running too much fuel pressure into. Edelbrock carbs like about 6 psi, 6.5 max. One solution is to get a 6 psi fuel pump. Edelbrock sells them, but they are expensive at around $140. I recently found a similar fuel pump that is also 6 psi max, but slightly less volume (80 gph vs Edelbrock’s 110 gph) for about $50. Links below. Otherwise you’d need a fuel pressure regulator.

Edelbrock Performer RPM Series fuel pump for SBC and W Series Chevy

Edelbrock part #1721 Performer RPM Series fuel pump is for Small-Block and "W Series" Chevrolet designed for use with all Edelbrock carburetors used in Performer or Performer RPM applications

www.edelbrock.com

Speedway Motors SBC Mechanical High Volume Fuel Pump Kit

This convenient kit from Speedway Motors is sure to help complete your fuel pump installation in no time. When it comes time to replace your mechanical fuel pump or just need to finish off your SBC fuel system on a new engine rebuild, add this kit to your cart. It comes with fuel inlet/outlet...

www.speedwaymotors.com

 

[Bextreme04]

I will take a look down the throat like you said. I do not have a wideband. I have a vacuum gauge though I could use for the idle.

Setting idle using lean of peak A/F ratio works fairly well. You will know if the fuel pressure is blowing fuel past the needle and seat when you go to set the idle mixture and can't find the peak. Basically you will screw the idle mixture screws all the way in and it won't die, this is because fuel will be leaking into the throat instead of the idle screws.

To set the correct lean of peak idle, you need to get it nice and warm with the choke off. I like to set it under load, so I set the parking brake and put it into gear with the wheels chocked. Start with the idle mixture screws about 1-1/2 turns counter-clockwise from bottomed out. Make sure you have the idle set to about 700-750rpm. Then turn one mixture screw out 1/4 turn at a time until the RPM tops out and starts going back down again. Once you find the peak RPM, turn the screw clockwise until the RPM drops 50-100rpm from peak. Then repeat that with the other screw. If the idle screws don't do much of anything, you have either too much fuel pressure that is blowing fuel past the seat or you have the float set to high(maybe both).

None of that will help you with tuning the carb jets and needles to be correct while driving though. You will need some kind of dyno tuning or a wideband to dial in the part throttle and jet size unless you just get an edelbrock tuneup kit and do some trial and error.

 

[Isaac nickerson]

So let me get this straight. If I don't visibly see any fuel leaking into the throat (which I checked and didn't see any) and my idle screws work as they should and kill the engine when screwed all the way in. Than my fuel pump is fine at the pressure it is and the problem lies in tuning? Or is a regulator still a good idea.
I appreciate all the responses

 

[86 SCOTTSDALE]

You must regulate your pressure below 6.5 with a pump or regulator. I have a edelbrock 1400 and after I regulated my fuel pressure down below 6.5 truck ran better and I gained 2 mpg.

 

[Bextreme04]

So let me get this straight. If I don't visibly see any fuel leaking into the throat (which I checked and didn't see any) and my idle screws work as they should and kill the engine when screwed all the way in. Than my fuel pump is fine at the pressure it is and the problem lies in tuning? Or is a regulator still a good idea.
I appreciate all the responses

Yes, that is correct. However, the pressure being that high could cause the needle to stick open at any point and cause it to randomly start flooding and running terrible. You should be able to tune it and dial it in correctly if the previously stated conditions are met that show it isn't pushing past the needle right then, but you should still get the pressure down to prevent a future issue.

 

[Isaac nickerson]

So.... I took a spark plug out and found that I was running lean. Here is what I found. The pcv valve seemed to have a vacuum leak, which is strange because I replaced that and the hose. It almost seemed like the valve was sucking air down through the grommet and up the valve as the valve was very loose in the grommet. So, I plugged the valve cover with a breather cap, plugged the carb, tightened the idle and now she idles pretty darn perfect and no backfire. What are all your thoughts on this fix? Will a breather cap do the job? Or should I try a breather with an integrated pcv valve.

 

[dsteelejr]

So.... I took a spark plug out and found that I was running lean. Here is what I found. The pcv valve seemed to have a vacuum leak, which is strange because I replaced that and the hose. It almost seemed like the valve was sucking air down through the grommet and up the valve as the valve was very loose in the grommet. So, I plugged the valve cover with a breather cap, plugged the carb, tightened the idle and now she idles pretty darn perfect and no backfire. What are all your thoughts on this fix? Will a breather cap do the job? Or should I try a breather with an integrated pcv valve.

Oh man, there was thread some months ago about whether to run with a PCV valve or two breathers. Everyone had something to say and it turned into hair splitting over which side the PCV valve should be on because of the crankshaft counterweights creating air swirls in a certain direction in the crankcase and finally devolved into a mob of square body enthusiasts beating a dead horse.

I haven’t seen or heard of any gains by not running a PCV valve, but like most everything on these trucks it was put there for a reason. I would get a new gromet, new hose and clamps and run the PCV valve. Otherwise you end up with crankcase vapors building up under the hood and possibly seeping into the cab instead of getting sucked back into the carb and burned.

 

[Isaac nickerson]

I am very confused. I got another new pcv valve checked the hose, new grommet, and hose clamps and it still sounds like a vacuum leak and makes my truck idle rough and higher even with the idle screw backed out all the way it is running at about 800 rpm. I took the PCV out and put my thumb over it it goes away and back down. Now my understanding is that the valve should not be open all the way. I'm inclined to just stick with dual breathers and change oil more frequently but I don't want to needlessly harm my motor. This is not a complicated system so what am I missing?!?!?

 

[SirRobyn0]

Oh man, there was thread some months ago about whether to run with a PCV valve or two breathers. Everyone had something to say and it turned into hair splitting over which side the PCV valve should be on because of the crankshaft counterweights creating air swirls in a certain direction in the crankcase and finally devolved into a mob of square body enthusiasts beating a dead horse.

I haven’t seen or heard of any gains by not running a PCV valve, but like most everything on these trucks it was put there for a reason. I would get a new gromet, new hose and clamps and run the PCV valve. Otherwise you end up with crankcase vapors building up under the hood and possibly seeping into the cab instead of getting sucked back into the carb and burned.

Ya, I remember that thread what a nightmare. I remember one of the guys trying to tell me GM put the PCV valve in the wrong side of my engine (I have stock tin covers). And then there was someone that thought running 2 PCV valves was a good idea, shesh.

I am very confused. I got another new pcv valve checked the hose, new grommet, and hose clamps and it still sounds like a vacuum leak and makes my truck idle rough and higher even with the idle screw backed out all the way it is running at about 800 rpm. I took the PCV out and put my thumb over it it goes away and back down. Now my understanding is that the valve should not be open all the way. I'm inclined to just stick with dual breathers and change oil more frequently but I don't want to needlessly harm my motor. This is not a complicated system so what am I missing?!?!?

It sound like you know you need to run PCV valve. Good. A couple options I can think of. #1. post a video of it both with the PCV valve and with it plugged off. #2. Try a different brand of PCV valve, sometimes manufactures have a bad batch of parts sent out without knowing it, especially these days where that valve was made who knows where and subject to who knows what in transportation. #3. When you shake the new valves will they rattle and does it seem like the pintle is spring loaded? it's not a heavy spring at all but it should have a light spring in there. #4. A video would help because we'd be able to tell you what we think of what we hear, but do remember a PCV valve is a metered vacuum leak so to speak, is it possible that the carburetor just needs to have it's idle mixture enrichened? If you attach a vacuum gauge to the manifold port will you get different readings with and without the PCV valve?

 

[Isaac nickerson]

Alright, I'll take a video tomorrow or monday and send it. The valve does rattle and it does feel a little spring loaded. Richening it does improve the idle quality some but doesnt get the rpms where they should be.

 

[Turbo4whl]

I am not much on Edelbrocks, but I do know PCV valves. Different valves, different flow rates and checks, even between brands. Your truck; ACDelco CV774C, but if you have the owner's manual, check the part number listed.

Aftermarket will sell you a valve that fits the hose and grommet. May not be the correct flow rate.

 

[SirRobyn0]

I am not much on Edelbrocks, but I do know PCV valves. Different valves, different flow rates and checks, even between brands. Your truck; ACDelco CV774C, but if you have the owner's manual, check the part number listed.

Aftermarket will sell you a valve that fits the hose and grommet. May not be the correct flow rate.

FYI that part # if not available at your local parts store is available on amazon.