Edelbrock Carb. question

[Chucks72Longbed]

Gents, I have a 402 BB that is stock. I just bought it a month ago. It has an edelbrock q-jet replacement carb on it. It runs a little rough at idle and doesn't jump when you add throttle. It runs strong when you stomp on it. I know it needs a tune up which I'm gonna do this weekend. However, the reason for my post is I have seen some info on some of the posts here about these carbs being sensitive to fuel pressure. Can someone tell me what the consequences are of too much fuel pressure? Thanks. I really enjoy this site. Can't stop going thru all the posts every chance I get. Such a pleasure seeing how you all are willing to share your intimate knowledge regarding these great trucks.

[Mike C]

Floods. Too much fuel pressure blows the needle off the seat. I have one on my boat and a Jeep and have not had any problems on either with OEM type fuel pumps. Getting ready to put another on my short step as they are pretty reasonable to work with and not real expensive. Your bog is from the accelerator pump being worn out or misadjusted in addition to probably some gummed up idle passages.

[Chucks72Longbed]

Thanks Mike. It wouldn't make it idle rough though? It doesn't flood. The idle jets being gummed up would make it idle rough right. Carburetor and I don't get along too well. Appreciate your help.

[hugger6933]

Get yourself a pressure regulator that has a dial on it to dial up the pressure you want you can find them at some auto parts stores and put in 4.5 pounds. You can run it up to six maybe a little more but any more than that and it is gonna start to flood. Also if it has trash in the lines or tank it will cause all sorts of problem like the sticking needle and seat.

[geezer#99]

You don't need a regulator!
It's a quadrajet that was built by edelbrock.
Quadrajet is good to 7psi.
It's the afb style eddy carb that's sensitive to fuel pressure.
Get a vac gauge and a timing light when you tune it up. Start with your initial at 12 degrees and adjust your mix screws with the vac gauge for highest idle.

[dirtyjim]

i would at least check the fuel pressure and add a regulator if it needs it, the mech pump I have on mine is just a stock replacement from autozone and was putting out right at 10psi.

how old is the carb? if its over a couple years I would go ahead and rebuild it, edelbrocks are very easy to rebuild. at the least I would pull the top off and see how it looks inside

[hugger6933]

Get yourself a pressure regulator that has a dial on it to dial up the pressure you want you can find them at some auto parts stores and put in 4.5 pounds. You can run it up to six maybe a little more but any more than that and it is gonna start to flood. Also if it has trash in the lines or tank it will cause all sorts of problem like the sticking needle and seat.

[Mike C]

The rough idle is probably several things. Check for a bad plug wire or bad spark plug. If the carb is several years old and it has set for any period of time, many of the smaller passageways and jets could be restricted causing a rough idle.

The "idle" circuit handles fueling up to 2500 rpm or so depending on the carb, so a stumble can be because the accelerator pump is not delivering enough fuel to overcome the lean situation that is generated when the throttle blades open. This is exacerbated by a reduction in fuel in the idle circuit because of clogged passageways.

On my boat it was a combination of the two but mostly the accelerator pump. The pump was an additional purchase on top of the rebuild kit. That may have been marine only though, so do your research.

[GASoline71]

Is it a true Edelbrock Q-jet replacement? Or just an Edelbrock square bore bolted where the Q-jet used to sit with an adapter plate?

Gary

[Chucks72Longbed]

Thanks Guys. I haven't pulled the carb yet but will dig into the plugs and wires this weekend and will post what I find out about the carb. You guys are the best. I just wanted to get some ideas on all of this. I'll take some pics of the truck and the carb and will post this weekend. Can't wait!

[Chucks72Longbed]

Hello gents, well I pulled the air cleaner and the carb is a 8867 edelbrock. Square bore with a spread bore adapter on the stock chevy intake. Guess I should check the fuel pressure and get a regulator if needed. The reason for my original post was just to ask what was it about the fuel pressure that I kept seeing posted. Wanted to make sure it would not cause damage to the carb. But from what you all say it's just that a hi pressure will cause the needle to lift and cause flooding. I'll get the tune up done this weekend and then look into a possible carb rebuild. Thanks

[Steve Cole]

If too much fuel pressure is the culprit you can always go with an Edelbrock fuel pump. Only puts out 5psi yo the carb. I have one, works great.

[Chucks72Longbed]

Cool, thanks