tcrote5516

I'm going to pull my Edelbrock 600 and clean it out. I've been having a issue that I believe is related to my carb and will try my best to describe it:

Starts, idle, everyday drives fine.
The issue is a studdering/stammering/hessitation when you open the throttle 90% - 100%. It hessitates (feels almost as if its missing) until it hits 4 - 4.5K rpm then it pulls like a rape'd ape until redline.

Basically, if I go to do a burnout and dump the clutch...it falls on its face for a bit but once she's rolling and the rev's are up, HOLD ON!

Doesn't feel like a accelerator pump issue as it continues to studder for a while longer then an accelerator pump would have effect on.

Ive tried a few different deg of timing and if I remember correctly its seems to be running the best at about 12 advanced.

The only changes I've made since it was not giving me this issue was a larger intake manifold and new fuel lines.

Any ideas?

kalli

i don't have any proper ideas on this one apart from maybe the secondaries opening too early dumping fuel and it starts going when the revs are up as the engine then is thirsty enough? can you mess with the secondary spring rate (so the upper secondary plate opens later?). i'm with you on the fact it's not (only) accellerator pump issue. that usually is a less than a second 'hole': switch to lower gear, full throttle and your head will smack against the windscreen as you release clutch. and just when it hurts the car will go. That's what lean acellerator pump feels like.

Starfury

The secondaries on Edelbrock Performer carbs are nonadjustable. That said, you shouldn't really have issues with the secondaries on an Edelbrock like that. Under 3-4k rpm, you shouldn't have enough airflow to open the secondaries anyway.

I suspect you may just have a lean power mode. It gets by most of the time, but when you really load up the engine, it's lean enough to misfire. Switch to a set of rods with a smaller small diameter. Ex: go from a 70x47 to a 70x43 rod. This will richen up the power mode, hopefully making your hesitation go away. If it gets better but doesn't go away, keep going, or change to a different rod/jet combo.

001mustang

My edelbrock carb developed some pluggages in small pasages after sitting too long.

I dissassembled and inspected/cleaned every oriface, verified float settings, fuel shut off valve operation, etc. Suprizingly, it was pretty easy and fast.

Tuned each carb mode based on plug readings.

tcrote5516

Well, that could be the issue, the carb did sit a while. Thanks everyone for your help, I guess I'll know better once I get it apart.

mustangted

bad accelerator pump

001mustang

Was carb tuned and working right before?

Did you look into carb(engine off) to get a visual of pump squirting on both sides?

tcrote5516

Yea it was fine before. I did let it sit for 7 months without doing anything to it (fuel evaporated).
I just ordered a new Carter electric fuel pump and new lines front to back as I am also sick of the excessive crank time after letting the car sit for 2 weeks. When I get the new fuel system I'm going to pull the carb and tear it down.

001mustang

I run filter upstream of pump below fuel tank elevation. At least the filter always stays full. Startup time not to bad, but electric will be quicker.
Just remembered the old movies where they used to crank and crank as bad guy approached. Used to have to know your car before you could start it easy.

I have fuel line valved so I can run carb dry for long storage. I used stabil before but it did not help long term.

Is your electric fuel pump system regulated to 6 psi?
Fuel pressure indicator handy when trouble shooting.
Many PI's tend to be inaccurate unless calibrated.

tcrote5516

Yes I'm ordering a whole new system, -6AN lines, regulator, underhood fuel press gauge and 2 filters. One between the tank and pump and the other between the fuel pump and carb.