Top End Miss

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For the record i run a Holley Blue and regulator which is set at 8.5 psi .On the other hand i have a freind that runs an 11 second 55 Chevy with a nasty solid roller small block sporting a Predator carb ,and spins it all the way to 7500 rpm with a Holley Red pump and has for years ,but i wouldnt do it .I still think the OP problem is in the valvetrain ,and i dont think the carb is too small either.My 408 in my Dart has a 750 Demon on it and i ran a 7.13 @ 95.04 in it a few weeks ago .Not braging on my car or my freinds ,just giving you sum comparisons on carb size vrs ET vrs CU ...
 
:burnout:What kind of 1/4 mile times should you be running ?

Just because you have fuel pressure doesn't mean your fuel bowls aren't dry.

The higher the pressure, the lower the flow.

Those holley red pumps don't flow. Get rid of it. :wav:

Too big a carb will lean you out too !

I think with those big gears, you're running out of fuel.

That's my 2 cents.
 
hemicop said:
I've read through all the responses & opinions, even have seen Ed's car run in the past (fun to watch, BTW) & while I generaly agree with most all the responses, the "glaring" problems that seem to catch my eye is wiring & the fuel delivery issue.
Now assuming the valvetrain is all correct & the new gears only amplified an existing problem, we're bac k to fuel issues & wiring. Many enthusiasts add to existing wiring instead of re-engineering their electrical system for the rigors of racing. IF IT WERE ME, I'd find someone I know & respect to go through the entire car to assess its wiring. Sure it can get expense, but a "third eye" might find something you overlooked or simply wasn't familiar with. WE all have our "gurus" in the hobby, but I'd find a veteran, different source, just to ease my mind. Anyway, with that done, I'd first get rid of that red pump (NEVER saw one on a racecar, always blue or another brand), set the pressure to 7-8 psi, as the fuel has to overcome inertia going downtrack, and perhaps consider a carb in the 550-650 range.
Of course don't make ALL the changes at once otherwise you'll never know what cured the problem (besides it's expensive). He's operating his motor in a range alot of strret big-block guys do & they don't have the sort of problem he's describing. My suspicion is the problem is one of assembly & not necessisarily componentry
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in my defense my dad bought this car as a PARTS car for 500 bucks... i saved it and then saved it from an electrical fire lol...

depending on the outcome of my recent electrical issue i may be do a new harness altogether so that would no longer be an issue lol...
 
ATX said:
Get R done,I want to see what it runs!
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i do to... but its just gonna be sitting for awhile...

need to do Mikes dart and buy a new wet pan for my swamp cooler... the previous owner never cleaned it and with out bad water its holey...

but once i get back on it im gonna get the electrical issue fixed, buy a craigslist 750 vac carb, rebuild it, and try it... if no dice and runs slower i'll sell it and buy a new pump, maybe a holley 125, not taking chances LOL...

if still no dice im gonna burn it... just kidding... i'll get it... just have stuff i need to do that i have been putting off... so she sits till my chores are done lol...

BUT i would like these ideas to keep coming! gives me something to think about when im wet sanding... blah...
 
Hey,
I was just throwing out ideas for ya...Maybe it is that fuel pump.
Sorry to hear of your electrical issues my 72 fried the instrument cluster before I bought it.I replaced the cluster and bypass that amp gauge.
On that swamp cooler ,I got one in my shop that I fiberglass the bottom and the inside 2 years ago and had an A/C guy make me a drip pan for cheap,just in case because it is inside my shop on pallet...Has not leaked a drop.Just a thought.
 
Just tossing out an idea. Sounds like you've replaced/checked a lot of items. Spark plug wires with a high resistance open will cause missing at higher RPMs. A while back I put in new 8mm SPWires (well known supposedly top of the line wires) and developed a miss at higher RPMs. I took them back within hours of buying them and the parts dealer told me these wires are the best and didn't want to give me new ones. I bought some Taylor's and put them in and the miss was gone, he then gave me my money back for the other wires.
 
TXDart said:
Hey,
I was just throwing out ideas for ya...Maybe it is that fuel pump.
Sorry to hear of your electrical issues my 72 fried the instrument cluster before I bought it.I replaced the cluster and bypass that amp gauge.
On that swamp cooler ,I got one in my shop that I fiberglass the bottom and the inside 2 years ago and had an A/C guy make me a drip pan for cheap,just in case because it is inside my shop on pallet...Has not leaked a drop.Just a thought.
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yea i found a new pan, its powder coated and everything so im not worried about it... just tracking on down lol... and i dont think a glass one would work to well here but it might...

GT340 said:
Just tossing out an idea. Sounds like you've replaced/checked a lot of items. Spark plug wires with a high resistance open will cause missing at higher RPMs. A while back I put in new 8mm SPWires (well know supposedly top of the line wires) and developed a miss at higher RPMs. I took them back within hours of buying them and the parts dealer told me these wires are the best and didn't want to give me new ones. I bought some Taylor's and put them in and the miss was gone, he then gave me my money back for the other wires.
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hmm... i'll ohm them abd if i get anything odd i'll buy a new set...
 
Had a nearly identical issue with my 440 powered Cuda. After a season, like yours, of changing and tuning, found that the mild cylinder head porting I done, had caused them to absolutely stall at 5500 rpm. Hot, humid weather seemed to magnify the issue and that August I knew what it had to be.
Put the heads on a flowbench at the end of that season and was relieved to find the problem, finally! I've not had a need to dig in the ports of a Slanter, but they are from about the same engineering timezone.

Good Luck!
 
sst3193 said:
Had a nearly identical issue with my 440 powered Cuda. After a season, like yours, of changing and tuning, found that the mild cylinder head porting I done, had caused them to absolutely stall at 5500 rpm. Hot, humid weather seemed to magnify the issue and that August I knew what it had to be.
Put the heads on a flowbench at the end of that season and was relieved to find the problem, finally! I've not had a need to dig in the ports of a Slanter, but they are from about the same engineering timezone.

Good Luck!
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well this head is heavily ported so i dont think its that... but good to know..
 
ok so i fixed my electrical issue and am now playing with the miss again!

so i went out for a drive and the miss is still there... 5800 and up...

but i did let off a bit and it didn't go away... really it didn't stop until i was at least 1/4 pedal out of it...

an old timer said to swap my valve lash, and run the exh tighter, so currently im at .016 int/.020 exh... worth a try?
 
bOb shingler said:
did you check the main feed going in the junction box on the firewall for corosion?
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by main feed i assume you mean the power lead to/from the alt? if so i already cleaned all of those when trying to figure my electrical issue i just fixed, well mended...

i lost charging instantly about a month ago... ended up being a break in the harness somewhere, so i ran a direct lead from the Alt to the Battery... fixed the charging issue but not the miss...

everything still works inside so everything is still getting power...
 
ok so my carb guy has a 750 Vac holley! so he is gonna give it a once over and then i will give it a try...

but here are some things i have been thinking about...

with the original 7.25 and the 3.91/suregrip it would it 6 grand like nothing, didn't lean over or anything... no with the 4.88's its 5800 and bam, shooting ducks...

now the 4.88's do a couple of things,

first and i think the biggest is make the engine rev alot faster... now that makes me thing more air and fuel (bigger pump and carb)

cam turns faster and so do valve events (bigger springs and pushrods) and

lastly with gears it is effectively taking load out of the engine by allowing it to spin faster... now could it be causing the cylinder to fill more but due to a lower load on the engine its just getting overly rich?

just thinking out loud here... oh and over advancing the cam? its a 106LSA installed @ 102...
 
805moparkid said:
by main feed i assume you mean the power lead to/from the alt? if so i already cleaned all of those when trying to figure my electrical issue i just fixed, well mended...

i lost charging instantly about a month ago... ended up being a break in the harness somewhere, so i ran a direct lead from the Alt to the Battery... fixed the charging issue but not the miss...

everything still works inside so everything is still getting power...
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sorry, i should have been more clear. it's the main wire goiing into the bulkhead that feeds the entire inside. i think it's a red #10.
 
My guess...either the gears are accelerating the car so much better the springs cannot keep up (my first guess) or your running out of fuel...or BOTH!

If you do not know what your spring pressures are...THIS is what's most likely wrong.

However, you may have a fuel volume issue as well. You could easily try larger needle/seats and raise your float level noticably...this should change something even if only 100 or 200rpm. If nothing changes at all, then I'd look at springs. This is truly what I think is wrong.
But I could be wrong too ;-)
 
ou812 said:
My guess...either the gears are accelerating the car so much better the springs cannot keep up (my first guess) or your running out of fuel...or BOTH!

If you do not know what your spring pressures are...THIS is what's most likely wrong.

However, you may have a fuel volume issue as well. You could easily try larger needle/seats and raise your float level noticably...this should change something even if only 100 or 200rpm. If nothing changes at all, then I'd look at springs. This is truly what I think is wrong.
But I could be wrong too ;-)
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ok im a stoop... i thought i posted the results from testing the springs!

old were 75 seat/240open, new are 135 seat/306 open after the 10% break in
 
Pressure is not always a guarantee the springs are correct for the application. Like I said, unless this is just a big coincidence and something else went wrong during you adding the gears, I'd say FUEL or SPRINGS. Fuel would be easier and cheaper to test at this point.
 
ou812 said:
Pressure is not always a guarantee the springs are correct for the application. Like I said, unless this is just a big coincidence and something else went wrong during you adding the gears, I'd say FUEL or SPRINGS. Fuel would be easier and cheaper to test at this point.
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have a 750 3310 holley being rebuilt as we speak and gonna get a black pump when money allows...

if its better i'll put the 600 back on to see if it was pump or not...
 
ok did some more with the dart...

ground all the grounds clean... starting with the fire wall ground... then ran a 10ga wire from that to the head, cleaned that to.

then cleaned the block ground and cable to battery...

so i ohmed it and i had .1 from the fire wall sheet metal to the batter post...

then ohmed the wires and they were all less then 500ohms per foot...

also tried a known good coil and no dice... my blaster coil was at .9ohms primary and 5500 cold/6700hot secondary.

something else is when i installed the MSD is my volts cycle by 1 volt... back and forth, dosn't matter what is on (pump or fan)... but in the upper rpm's it almost goes away... also cleaned the ground to the regulator and ohmed the alt to battery and again .1 ohms...
 
i dont think its spark so i ordered a holey black pump and reg... if its not it i'll have one on the shelf...
 
805moparkid said:
ok so found 67 posted this and tried it...

http://www.forabodiesonly.com/mopar/showpost.php?p=1797906&postcount=3

removing the lead from the harness and directly running a wire from bat to ign side of regulator stabilized the output! now how to fix what ever is wrong lol...
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ok so i re grounded the regulator... now have 0.0v drops and no ohms between the reg case and battery post... still have surge...

now i also did as specified and ran a wire directly from the bat to the reg. voltage smoothed out at all rpms... the bulkhead connectors are firmly together, made sure from the back side...

so now what?
 
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