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  carburation and a "flat spot", help please...

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Author Topic:   carburation and a "flat spot", help please...
goldenbob
Journeyman

Posts: 86
From: medford, or., United States
Registered: Jun 2002

posted 08-07-2002 08:44 PM     Click Here to See the Profile for goldenbob     Edit/Delete Message   Reply w/Quote
when I am cruising at constant rpm (any rpm) and give it some gas it starts to "go", then has a flat spot, and then she rips (like a bat out of hell). I can feel the accel. squirters working and then a little flat spot. The engine has 12 inches of vacuum at an idle (@700rpm), and an 8.5 power valve on a holley 4160 (750cfm).

any help would be appreciated

ps. ran my best 1/4 last fri, 13.77 secs, with a sad 60 ft. of 2.12...

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67 coupe (my first car in '78)
10:1 302, 4spd, 9" (lsd)posi
windsor jr heads*
*(tweaked by Lindvig mach.)
crane rollers
performer rpm (match ported)
holley 750 (#4160)
hooker super comp.
full msd
drag radials (oops, ran out of $$$)

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Moneymaker
Administrator

Posts: 25883
From: Lyons, IL, USA
Registered: May 99

posted 08-08-2002 10:29 AM     Click Here to See the Profile for Moneymaker   Click Here to Email Moneymaker     Edit/Delete Message   Reply w/Quote
Could be not enough "squirter" or not a long enough duration pump cam. It may be running out of pump shot before you have primary WOT.

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Alex Denysenko
Co-Administrator and Moderator/ non 65-66 Mustang owner sensitivity co-ordinator

NHRA/IHRA/SRA member
NHRA and IHRA SS/LA National Record Holder '00, '01, & '02
Fleet of FoMoCo products including 88 ASC McLaren Mustang #28
Part time secret agent license #0089
Professional Manwhore
The Barry of BarrysGrrl

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goldenbob
Journeyman

Posts: 86
From: medford, or., United States
Registered: Jun 2002

posted 08-08-2002 10:33 AM     Click Here to See the Profile for goldenbob     Edit/Delete Message   Reply w/Quote
i know you guys have covered this before, i just dont want to purchase a 10.5 power valve if i dont need to...(starting to have a collection)

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Moneymaker
Administrator

Posts: 25883
From: Lyons, IL, USA
Registered: May 99

posted 08-08-2002 10:49 AM     Click Here to See the Profile for Moneymaker   Click Here to Email Moneymaker     Edit/Delete Message   Reply w/Quote
A 10.5 power valve will only enrichen the carb at part throttle and idle. It won't do anything for you at WOT.

------------------
Alex Denysenko
Co-Administrator and Moderator/ non 65-66 Mustang owner sensitivity co-ordinator

NHRA/IHRA/SRA member
NHRA and IHRA SS/LA National Record Holder '00, '01, & '02
Fleet of FoMoCo products including 88 ASC McLaren Mustang #28
Part time secret agent license #0089
Professional Manwhore
The Barry of BarrysGrrl

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goldenbob
Journeyman

Posts: 86
From: medford, or., United States
Registered: Jun 2002

posted 08-08-2002 12:12 PM     Click Here to See the Profile for goldenbob     Edit/Delete Message   Reply w/Quote
problem occurs at any steady rpm, worse with a slight application application of throttle than WOT (didn'y really expain this well) even the slightest throttle increase will find the flat spot immediatly after surge in speed from the squiter...

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Moneymaker
Administrator

Posts: 25883
From: Lyons, IL, USA
Registered: May 99

posted 08-08-2002 12:38 PM     Click Here to See the Profile for Moneymaker   Click Here to Email Moneymaker     Edit/Delete Message   Reply w/Quote
Then it's simple. You need to reduce the power valve as it is running too rich at part throttle. Install a 6.5 or 5.5. That should cure your problem.

------------------
Alex Denysenko
Co-Administrator and Moderator/ non 65-66 Mustang owner sensitivity co-ordinator

NHRA/IHRA/SRA member
NHRA and IHRA SS/LA National Record Holder '00, '01, & '02
Fleet of FoMoCo products including 88 ASC McLaren Mustang #28
Part time secret agent license #0089
Professional Manwhore
The Barry of BarrysGrrl

IP: Logged

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