70' Is it the fuel?

[Alaw143]

Issue
Runs fabulous when initially started, after first stop, starts great than upon acceleration acts like its bogging. This also ocurs at long stoplights Or long/frequent stops. After pushing through it or good straightaway w/o stops it runs good. Than if i have to make a short stop its gone. It will only start acting up again after shutting off, a long stop light, or drive through
I had a solid mechanic ask me to check fuel pressure to see if too much fuel was continuing to fill the carb bowl after stop, putting too much fuel against accelerator pumpin carb.? Fuel pressure @7, no regulator on the line.
Also, this also occurred before rebuild. The only thing the same is the fuel pump off the motor.

1970 302 rebuilt within 1,000
4 barrel Edelbrock carb with 1/2 spacer
Small rv cam
New plugs, dizzy, coil
New fuel lines, (offchassis) new 23 gal tank

Fuel pressure 7 psi
Running temps, 160...no overheating issues

Your suggestions greatly appreciated, Andy

 

[broncnaz]

One thing I would check is the float level in the carb edelbrocks are kinda sensitive to float levels I'd also check the choke make sure its operating properly. You may want to try and watch the exhuast when it starts bogging if its blowing black smoke then its to rich for some reason.
7lb of fuel pressure might be a bit high for edlebrocks but hard to say

 

[Alaw143]

That's for the feedback. Do you think raising or lowering the float would help?
No black smoke, none at all.
My mistake 5 psi of fuel. I can put a regulator on tomorrow, maybe that fuel pump is fluctuating for some reason

 

[broncnaz]

Make sure the float is at the correct height. My brother had a issue with his it was a little to low and the accelerator pump well wouldnt fill up with gas and causes some similar issues.
5psi should be ok. If you dont have one try installing a fuel filter between the carb and fuel pump that might lower pressure just enough.

 

[Alaw143]

Ok...ill check the float level. There is a fuel filter between the pump and carb.
Its funny its intermittent. Like i said only after a stop..or long period s of stationary idling

 

[broncnaz]

Well if the float level is to low the long stop and idling could cause the fuel level to lower to the point that the accelerator pump is not getting enough fuel. Very hard to say. My only other thought is that you may have a intermitant vacuum leak could be a cracked hose or something. Might try retorquing the intake and carb.

 

[75junebug]

Just an idea...I chased what I thought was a fuel issue until my hair was pulled out....Turns out it was a bad pertronix module I had in the points/coil style conversion...

 

[70_Steve]

Well if the float level is to low the long stop and idling could cause the fuel level to lower to the point that the accelerator pump is not getting enough fuel.

The float level would have to be extremely low to cause a problem. I've got a .doc that details modifications to get the Edelbrock Performer/Carter AFB to run "better" off-road. One of the mods is to drop the float level about 1/2" over stock. I did all the mods, including dropping the float level, and never had the issues described.

 

[rastiss]

my edelbrock was doing similar to this. the idle mixture screws would also not hold a tune. pulled the topto find the primary float was too high and all the screws on the annular booster needed retightened as i guess the gaskets had squeezed out and were leaking a little. it runs like a sewing machine now.

 

[Jeff76]

That's for the feedback. Do you think raising or lowering the float would help?
No black smoke, none at all.
My mistake 5 psi of fuel. I can put a regulator on tomorrow, maybe that fuel pump is fluctuating for some reason

Had a similar problem with my 76. Put a cheap inline fuel pressure gauge on it and found that the fuel pressure dropped to less than 2 psi with temperature. Like when sitting at an extended stop light. Replaced the fuel pump and good to go. Also change out the fuel filter to eliminate the possibility of a clog.

Jeff

 

[broncnaz]

The float level would have to be extremely low to cause a problem. I've got a .doc that details modifications to get the Edelbrock Performer/Carter AFB to run "better" off-road. One of the mods is to drop the float level about 1/2" over stock. I did all the mods, including dropping the float level, and never had the issues described.

Not really one of the edelbrocks i was messing with had the accelrator pump well feed just below the fuel line when float level was set to spec try to lower it and you had no way to get fuel to the accelerator pump. That was the case with my brothers carb to on his mustang. I have a newer edelbrock sitting on the shelf havent look at it yet maybe the changed the design a little, Maybe one day I'll open it up and have a look.

 

[jckkys]

The metering rod pistons started sticking in the bore or bores in my AFB. I put stronger springs under the pistons and it helped. In other words the piston got stuck less often. If you look at the bores when the top cover is off; see if there's rings inside, if so it may be the problem. A ream may be a fix. I never was able to completely fix this problem. The same thing happens to Qjets. I noticed that by flooring it from the stop the lean bog won't happen because the piston is pushed past the ring and full enrichment is delivered until I let up on the throttle. This may not be your problem but your symptoms are the same.

 

[broncnaz]

thats one of the issues with edelbrocks and qjunks they dont like dirt so much a little dirt and the pistons hand up. But really the springs/pistons are your power valve so changing its operation is not always the best option. A good cleaning will usually take care of it for awhile.

 

[Alaw143]

You give it one day, the responses come! Well, bought a fuel pump, and accelerator pump this am. Pulled the carb off, cleaned. Accelerator pump is good, but some crap inside.
Upon putting back together ran rough, took back off, realized one of the metering rods was bent and missing spring...wasnt always like this, first tear down i lost 1 day ago, i think.
tomorrow new metering rod, spring.
What Jeff describes I think is my issue for some reason, fuel pump heating after a stop. Not sure but after putting back together tommorow I will update.