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Bracket Talk Bracket Talk Forum Tech Talk - by Abruzzi Car Missing under full throttleGo | New | Find | Notify | Tools | Reply | |
| Car Missing under full throttle | Login/Join |
| DRR Sportsman |
Hey guys, looking for suggestions here. I'm chasing a Wide open throttle miss on the car. It was doing it at higher RPM (5750-6500) right around gear change, Just a couple Ba da da's. But last past last night at test an tune it was missing from about 100' on and slowed down 4 #'s total. What could this be? The other car the motor was in did the same thing (minor miss around gear change, never the bad one). This car has different MSD (7AL2) known good New Coil Newer MagnaFuel 500 pump New Magnafuel regulator Older plug wires (changing to the previous ones today, but motor still had the miss with those) It doesn't miss when I mat it. Only in the upper RPM range. Any ideas????? | ||
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| DRR Elite |
What plug, brand and # | |||
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| DRR Sportsman |
They're NGK plugs, not 100% certain on plug # at the moment. Gapped at .030 | |||
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| DRR Trophy |
Valve springs? | |||
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DRR S/Pro |
Engine info? Plug gap? Gas or alcohol? 272" Spitzer 540 Chevy The Blower Shop XR1 FTI XPM Series Converter FTI Level 6 Powerglide 3.69@199 .916 60' 2017 Bradenton Heads Up Madness Open Outlaw Champ 2018 PDRA T/D #5 2019 PDRA T/D #2 2020 Retired From T/D Competition.... 2020 Bradenton NMCA Hemi Shootout Winner 2021 getting back into bracket racing with a Gen3 Hemi powered 87 Cutlass. | |||
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| DRR Sportsman |
Engine is 468 with Iron 990 chevelle heads on Alky. Plug gap is .030 Valve springs have 280 lbs of pressure. Thats how i bought it, broke one of those red comp rockers, so I Put ultra pro magnum rockers on it to deal with the spring pressure. | |||
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DRR Sportsman |
Have you actually checked spring pressure or just think that's where they should be? | |||
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DRR Sportsman |
Have been plugs been changed? Try disconnecting the power and tach wire that goes to MSD. | |||
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| DRR S/Pro |
Try closing up the plug gap to .020...... 272" Spitzer 540 Chevy The Blower Shop XR1 FTI XPM Series Converter FTI Level 6 Powerglide 3.69@199 .916 60' 2017 Bradenton Heads Up Madness Open Outlaw Champ 2018 PDRA T/D #5 2019 PDRA T/D #2 2020 Retired From T/D Competition.... 2020 Bradenton NMCA Hemi Shootout Winner 2021 getting back into bracket racing with a Gen3 Hemi powered 87 Cutlass. | |||
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| DRR Sportsman |
They were checked. [/QUOTE] Have been plugs been changed? Try disconnecting the power and tach wire that goes to MSD. [/QUOTE] Old man is down there pulling the plugs right now. (He's retired, I gotta work lol). What would disconnecting the power and tach wire that goes to MSD do? I've heard of this but just wondering. | |||
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DRR Sportsman |
If it is on the rich side on alcohol it may cause it to misfire down track. Called a alcohol hiccup. Try taking some fuel away from it,and see what happens. IHRA ACDELCO Canadain Nationals Top/et Iron man Champion  Don Davis 57 Corvette Super Gas roadster  SDPC Race Shop 582 Head Hunter on alcohol | |||
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| DRR Sportsman |
Just checked plug NGK #8 Think you were asking that earlier | |||
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| DRR Sportsman |
I do still think its rich. Its not building heat going down track. Made 2 passes back to back yesterday with 168s. Car was 150 in burnout and after the 2nd pass was 160. Changed jets to 156s I believe, and it built a little temp but still not much. 165 or so in burnout, 170 stage, maybe 173-175 at trailer. Should i go down to 148s??? seems super small. Carb is a 950. | |||
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| DRR Sportsman |
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| DRR Pro |
Might sound stupid but I missed it. If you have a diaper and are connecting the diaper to the headers with straps make sure the straps are not too close to the plugs. I had one on the back of my engine on my Nova cause a miss fire. It would arch thru the boot and miss. Brand new plugs and wires. -------------------- Bob Payton S/P, T/D, S/C, TOP 309Z, 393, 3093, 8X93  www.apdracing.com www.diamondracecars.com www.callies.com | |||
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| DRR Sportsman |
Good to know. Didn't put the diaper on from the other car, but I was going to. Maybe ill check the relationship of the wires and the headers to see if it might be trying to arc | |||
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DRR Pro |
Just start it up and night and you'll see if you have a problem. Had a similar problem a few years back and it turned out to be a wire arcing on the header. Only found it by wiggling the wires at about 3k rpms at night. New wires too. I've got a 950 on the truck and we ended up at 154's and it's still a bit fat | |||
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DRR S/Pro |
Did this just start or new combination and it does it? If just started was anything changed just before? Small block or big block? ____________________________ 2017 and 2018 Osage Casinos Tulsa Raceway Park No-Box Champion 2018 Div4 Goodguys Hammer award winner | |||
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| DRR Sportsman |
The miss has always been there slightly right before gear change, but got real bad last night last run of the night. Has crank trigger New coil Different MSD (so i doubt thats the issue since it did it with the other one also) New regulator New fuel pump Putting different wires on it right now. Gotta be something in the carb in my opinion, just don't know what. I'm leaning towards the hiccup theory from being to rich that 57 Vette was talking about | |||
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| DRR Sportsman |
Have you tired a new crank trigger pickup? | |||
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Bracket Talk Bracket Talk Forum Tech Talk - by Abruzzi Car Missing under full throttle
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