Running out of fuel on the big end..

[cjshaker]

You either need more horsepower, or....

This answers 99% of the questions on the forum

I'll let the others give serious suggestions, but it sure is very odd to not have a MPH change with that wide of a jetting change. Could you "borrow" a similarly set up carb from a fellow racer, just for comparison? I'm sure somebody would be willing to do that. At least it would let you know for sure if it was the carb itself.

[machoneman]

 I am definitely mounting a fuel pressure gauge on the cowl before the next track visit. Fred

Good idea but even that may not show a tank vacuum at the end of a run.

[Joe-JDC]

Just a hunch, but if you can borrow a gasket matched Edelbrock RPM, you may find the added torque to keep pulling on the top end with those gears.  Have you tried a shorter tire?  Joe-JDC

[babybolt]

What is the rpm going through the lights downtrack?

[Barry_R]

The RPM question is important - you might just be running out of motor versus aero.
You read plug color way up into the plug - not out at the tip - especially on any sort of unleaded fuel.
Still should be reactive to that gross of a jetting change - even if its "wrong".
Sounds like a fuel restriction upstream of the carb or in the metering blocks.

JDC might have something with the RPM versus Victor depending on the RPM range.   The RPM will be better everywhere below torque peak and often for several hundred beyond it.

[Stangman]

Had sort of the same thing, wasnt sure if it was fuel or to much gear. Went from 4.11 to 3.70 with a 26 inch tire
pulls hard all the way through. Im running the same times and weight 3-400 lbs less than you so sounds to me like she is running good. I always thought that the MSD runs so hot that it was hard to get a good read on the plugs in general. Maybe thats why they read the same no matter what jets you are running.   

[Posi67]

My .03 worth is I think you have some good power to run that kind of ET and agree the MPH seems off. By a bunch in my opinion and I'd think you should see at least 5-6 more on the top end. The plug readings also seem off but I don't think you're running out of fuel. Any time I've had that happen the car stutters or just noses over. You can also burn the ground straps off the plugs or hole a piston. Someone who REALLY knows how to read plugs would be helpful but there's a lot of good info online.

A couple things I can think that would cause the low MPH is valve float or convertor slip. Otherwise, nice ET's for a boat and I think once your problems are sorted out a 10 is in your future. 

[64PI]

The converter flashes to 5000-5200 area on launch. I shift around 7200-7500 and trap rpm is around 6800 on a 29” tire. A little higher with a 28”. I’ve had several people look at plugs with me and agree it’s strange not to see any changes with the jet change.

[Posi67]

Okay, I'm not an auto guy but think you're shifting too high and not going through the lights high enough. Without knowing the limits of your engine I doubt it's making any power anywhere near where you change gears. Normally the shift point is somewhat lower than trap RPM. I'd like to see you shift at 6400 and run whatever it needs at the stripe.

As for the plugs, I'm also no expert there either and agree that you "should" see some change given what's been tried. My point was that a good plug reader can tell you a lot more than a casual glance. I've been through the so called plug reading experts only to get conflicting results. Much can be told with a proper magnifying tool and look at the burn line on the ground strap. Also as previously mention, some fuels just don't give the reading you'd expect. The 10% ethanol may or may not affect what you're seeing. 

[Barry_R]

Have to agree with "posi67.." - the RPM band "feels pretty high" but car performance trumps feelings every time.  I think its only 3 or 4 mph light, but it could just be aero pushing back against the converter slippage too.  It would be educational to have driveshaft RPM data to plot against engine RPM to see what's going on.  Did this package get on dyno or are we developing the combination in car?

[64PI]

I have no dyno results. Im still developing this set up. It’s been a 12 year long progression from the car running low 13’s with a mild 390. To low 12s with a 390 with angle cut heads and a 294s. To where we are today. The converter came from Edge and it’s based off all the information I gave him. I could very well be shifting too high and never tried shifting below 7k. I’m by far no expert and appreciate your guys help. I’m working on building another dedicated drag car so I can start getting more track time. I guess I set my expectations a little on the high side for this set up. But I’m still going to have pro systems check the carb out and I’m going to make sure I have nothing wonky going on in the fuel system. I should also invest in a plug reader.  I still can be proud to say I have a street driven pump gas low 11 galaxie! Thanks. Fred.
https://www.facebook.com/VromanSpeedShop/videos/10155066592063479/ Here’s a video of the car running with drag radials

[My427stang]

Although it won't show the effects of the launch on the carb, may be good to get it on a chassis dyno.

FWIW, stabbing in the dark, but still hung up on the fact that: With the fuel you run, when on the street operating in the primaries, you get some color on the plugs, when WOT on the track, you don't and jetting hasn't changed it

I do agree that fuel supply overall could be an issue, but may need to get more precise than just fuel line pressure, although the easy stuff should be checked first.

If your secondary bowl only is running dry, or more likely, can't keep up, it could do what you describe.  I'd look close at the dual feed line, filter if there is one, machining on the inlet of the bowl, needle, seat, float operation and even check if the jets are too far back and being inhibited by the bowl

If all that is good, maybe a secondary metering issue, but seems like jet would always add more fuel unless a passage is partially blocked

[Stangman]

To me listening to the video it doesn’t sound like he’s shifting to high or running out of motor at the top end, so it must be the way the car feels to him while driving. I can’t hear anything from video except (NICE RIDE)!!!!.

[Joe-JDC]

Ok, here goes.  If you are using 4.20 gears and going through the lights at 6800, but shift at 72-7500, you need 4.57 gears to get you to your shift point in the traps.  That will pull the car harder on the top end. At 7200 you need 4.44 gears, at 7500 you need 4.63 gears, all else being equal.  Joe-JDC

[64PI]

I wonder what kind of 60’ improvement I would see with a gear change.