Need help finding a gremlin

Ok I have been fighting an issue with what feels like the car is running out of fuel at wot, sounded sick running down track and popped once out of the exhaust
Verified 6 psi all the way down track
jetted up 2 sizes from 84 Sq to 86 Sq (car ran best et @84)
timing at 34*
had the heads re done springs checked good
all filters clear, psi on pump verified with visual into a tank
I am down 3 MPH in the 8th and 2 in the quarter
thinking it has to be in the distr. or box or coil
running msd distr, firecore wires, msd coil and a msd 6Al box grounded to the batt. alter is showing 14 volts
best today was a 10.447 @128.98, 1/4 6.642 @ 103.25 1/8th
best ET is in sig
Help me find the gremlin

strip the carb, blow out all the air bleeds & fuel holes, reassemble & try again.

done that, did the same thing with a different carb too

A pop out of the exhaust would tell me fuel is in the pipes. Look at the ignition system.

Is the positive wired direct to the batt? My 6al die competely last summer(no spark). Before it die, the car just wasn't running right,

If the carb has high speed air bleeds they might be too small? Had similar problem adjusted air bleeds and fixed the problem on the dominator.

Could be msd box, or maybe valve float. Check spring pressure lately?

See if a buddy has a MSD box you can try... I
had a high end miss that you could barely hear
and I did a A-B-A test with the box.. it was a box
issue.. sent it in to MSD for a rebuild.. they said
it was fine.. when I got it back it worked great...
but I know the box was the cause(A-B-A) test proved that
then try another coil

If it has a RPM chip in it, run it without it. If the problem goes away the chip is bad.

Tug on the wiring where it is crimped and see if any wires pull out of the terminals.
Doug

[quote=fbs63]If it has a RPM chip in it, run it without it. If the problem goes away the chip is bad. [/quote
This is worth a try. I had it happen to my 64.

Yep.. worth a try.. its simple... I've had a few that
would change.. they would start dropping out a good 500
rpms below what they were set for... just pull all the
chips and try it

THIS............Was testing a friends Torino at night before a race and same thing, popping way before the redline so I suggested removing the chip and problem gone..........Not to say this is your problem but start w/the simple ones first........

Had a bad shift light that did the same thing..

if the chip dont do it what about subbing in a spare regular electronic dist/ECU for a test? it'd be a bit of doing but it'd cut right to the chase by getting the Might/Sputter & Die system out of there

RPM chip has already been removed
have a line on another box and coil to try
Valve springs checked good
I will let you know what I find

Those kinds issues almost always ignition---MSD distributors use an odd metal for the reluctor--it does corrode fast--we spray new units with WD40 and blow off before install--check it first--I have seen them where you take cap off and it looks like a piece of iron that came from bottom of the sea--first thing I check when trouble comes--if you have real 12 volts to fuel pump it is usually not the issue--a "fill the can" test is best way to check fuel system --if carbs don't have trash they don't change all of a sudden--clean filters, can fill test, voltage test , check grounds but check MSD reluctor First--if that is good throw the coil in the ebay pile and get a new one

Pos. is wired to the starter and has been that way since day one

I had the distr. out and all cleaned up it was pretty rusty

I chased a burble at the stripe. Turned out to be the exposed part of the #2 exhaust guide in the combustion chamber disappeared. Evidently, there wasn't enough material to allow it to seat concentrically. Spring pressure was good. New guide, problem solved. I now have a complete spare MSD ignition system.

OK got a borrowed MSD box and coil wired in to run AB tests tomorrow at the test and tune.
Will update if I catch the gremlin and let you know what I found

My money is on the MSD. I had A digital 6 box that missed in high gear. I took it to the MSD trailer on drag week and they ran it through all kinds of tests and it passed, jumped spark like 4" on the test machine and they gave it the clear. I fixed it by changing to another digital 6 box. Fast forward two years and that box catches fire on drag week. I changed back to the original box and got my high gear miss back lol.

Had the same thing years ago. Intermittent miss in high gear. But would do it about every 3rd pass or so.
Chased it most of a summer. Ended up being the MSD box.

I agree w/ these guys...I bet it's the MSD box. The coil is probably fine so change one at the time. I've also had weird high speed misfire issues w/ the MSD digital boxes. That's why I'm still running the old style 6AL. Usually when they die, they just stop firing completely, but not always.

Pat Collins at TechWest Racing in NC repairs MSD products.
http://www.techwestracing.com/

Well did the AB test with the borrowed box first same issue, then tried the borrowed coil same issue, went back to the originals system and it cleaned up a bit but it was so hot out that I think
it may be a carb issue?,
Going to go back to a slick instead of the drag radial to take out one variable...best time in sig I found the air and it was about 900', im sure we were at 2500' or so today, search continues
Good thing is my daughter at the age of 17 is hooked and the Duster
is running pretty spot on at 12.90-13.00 and she is cutting pretty good lights, watch out Woodburn

How old are the plug and coil wires? I had a set of Accel Super Stock 8MM wires wear out on three wires on the passenger side, #4,6,and 8. It burnt the graphite coating off the nylon center conductor at the distributor cap back about a 1/2 inch into the wires with 90 degrees ends on that set. I found that out with a ohm meter, these where not the newer wires with the stainless wires wrapped wound the cores like sold today, it would start a intermetent miss around the 1000 Ft mark in high gear at night during eliminations, it ran fine in qualifying during the afternoon I cut the bad part off about 1/2 inch back and resued the ends and dust caps and it ran fine after that IHTHs
I can't believe your daughter is 17 now, it seems like she was 10 two years ago

Just yesterday I found a dead wire on a fairly potent SB Chevy and was hard to catch w/that choppy cam but found it w/an ohm meter.........

Wire are Firecores and maybe 2 years old with very minimal passes
I put an Ohm meter on the wires and then again thru the cap nothing seemed out of whack

Do you have a wideband and if so what does it show during this problem.........

I do have a FAST 2 sensor wide band that I may try this weekend

So you haven't used it yet then............

Is there any possibility of the ground for the whole system or power for the whole car varying? A loose(or almost loose) connection may cause trouble? As a last resort, you could put it on a chassis dyno and see what shows up, if they give the right readings? I found a slightly loose 12v+ connection to my MSD and command center, luckily it didn't mess things up.