fuel demand?

[jordan]

I am having an issue in my big block stroker 6bbl.  When I am on it really hard, it breaks up a little bit at WOT at the top of the rev range.  If I roll into it a little slower so the revs don't spin up so fast, I don't have issues.  Is this a symptom of fuel starvation?  I am running a stock 6bbl fuel pump.  I am wondering if I need a little more fuel to those multiple carbs when it is spinning up.  If it is, do you have any recommendations for a pump as to flow rates? 

[cudabob496]

that was bad distributor cap points for me

[cudabob496]

they have electric fuel pressure gauges that can now go inside your car.
Came in real handy with I diagnosed I was getting vapor lock.  As car started
to miss/shudder, notice fuel pressure was going from 5.5 to under 4 psi.
Saved a lot of guess work!

[xtopfuel]

sounds like ignition to me but cant see or hear it, unless you have a valve train float issue under quick accel

[Flatdad]

Having identical issues with a 528 and dual quads, initially suspected ignition problems. Replaced my old points system with electronic first and didn't notice much of a change, if any at all. I just picked up a Holley blue electric pump and regulator to supplement my carter mechanical pump at WOT and I plan on running a new 3/8 fuel line to replace the old 5/16 line.... but the rear main seal failed over the weekend so the whole motor is coming out now. If I manage to get the whole thing put back together in a timely manner I'll try and post the results of the changes.

A couple things didn't get the chance to try yet before the failure were: insulating the fuel line between the pump and carb(s), eliminating the filter, and rejetting.

I know my valves aren't floating, because I accidentally winged it to 7k when the column shifter went between gears.

[cudabob496]

there's a saying that I'm finding to be true: If it ain't running right, 90%
chance its electrical, and 10% it fuel related.

[jordan]

I am not sure of this, just speculation.  If my carbs were running low on gas in the bowls at WOT, would it lean out the mixture?  Could this now lean mixture pre-ignite and cause knock?  Making it seem like timing, but really be fuel?  I feel as though I was pretty ignorant thinking a stock fuel pump could handle 550 hp. I also feel like its is my distributor cap. 

[cudabob496]

I am not sure of this, just speculation.  If my carbs were running low on gas in the bowls at WOT, would it lean out the mixture?  Could this now lean mixture pre-ignite and cause knock?  Making it seem like timing, but really be fuel?  I feel as though I was pretty ignorant thinking a stock fuel pump could handle 550 hp. I also feel like its is my distributor cap.

could also just need a normal tune-up, with new plug wires and plugs.
A new mag pickup in the distributor is only about $25 also

[xtopfuel]

the only true way to tune a 550hp engine imo is find a track or open road, bring 3 sets of new plugs, make a pass at wot and shut the car down at end of pass, remove plugs and read, don't idle back or cruise wot shut down

[cudabob496]

or get an AFR meter

[GoodysGotaCuda]

the only true way to tune a 550hp engine imo is find a track or open road, bring 3 sets of new plugs, make a pass at wot and shut the car down at end of pass, remove plugs and read, don't idle back or cruise wot shut down

This was a true many years ago, a wideband afr gauge is a far better solution.


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[xtopfuel]

im old

[734406pk]

Tee in a fuel pressure gauge between the fuel pump and carb (after all filters) and go for a test run. If the fuel pressure drops to zero on hard acceleration you do not have enough fuel delivery volume. If you maintain fuel pressure at all times, you have a different problem, carb, electrical, timing etc.

[onebadfish]

I run a six pack. In fact just spent the last three days re-jetting all the carbs. I was running rich. I have a high volume mechanical fuel pump. I believe it's a mopar pump. I'm running 623 dynoed hp. I find that you need an AFR gauge to really dial in your car. Also, in my case I have to run some race fuel. If I don't run some good gas I suffer run-on and the fuel overflows the bowel in the rear carb when I shut the motor down and leave the car overnight. We have such bad fuel now-a-days. FYI. I am at 3500 feet in Calgary. I'm running 68 jets on the center carb and 84-84 front and 84-86 (86 throttle side) on the rear carb. I have Promax metering plates on the end carbs. I cruise at 11.5 to 12.5 at 2500-3000 grand. Idle at 13-13.5. WOT IS 12.5. You don't want to be lean at WOT. I removed the vapour canister and the flared gas lines and replaced with AN black line and fittings and don't suffer any vapour lock. Also running a 180 stat. My car is a beast and fires up when hot without touching the throttle. Also running 6 AL box with mopar electronic ignition. Hope this helps.

[734406pk]

I run a six pack. In fact just spent the last three days re-jetting all the carbs. I was running rich. I have a high volume mechanical fuel pump. I believe it's a mopar pump. I'm running 623 dynoed hp. I find that you need an AFR gauge to really dial in your car. Also, in my case I have to run some race fuel. If I don't run some good gas I suffer run-on and the fuel overflows the bowel in the rear carb when I shut the motor down and leave the car overnight. We have such bad fuel now-a-days. FYI. I am at 3500 feet in Calgary. I'm running 68 jets on the center carb and 84-84 front and 84-86 (86 throttle side) on the rear carb. I have Promax metering plates on the end carbs. I cruise at 11.5 to 12.5 at 2500-3000 grand. Idle at 13-13.5. WOT IS 12.5. You don't want to be lean at WOT. I removed the vapour canister and the flared gas lines and replaced with AN black line and fittings and don't suffer any vapour lock. Also running a 180 stat. My car is a beast and fires up when hot without touching the throttle. Also running 6 AL box with mopar electronic ignition. Hope this helps.

I have the exact same setup! No issues here!