Posts: 59
From: Placerville, CA (near Sacramento)
Registered: May 2003

posted 06-19-2003 03:07 AM               

I'll start by saying that the only kind of carburetors I have any experience tuning have been on 5hp Briggs & Stratton engines. Needless to say the Holley 600cfm 4V on my new project is "slightly" more complicated. I don't know what model it is, other than it has vacuum secondaries and I'm assuming its ~600cfm. When I stomp on it I get a fairly significant hesitation as soon as the secondaries open. Even a small backfire through the exhaust sometimes. After the hesitation it takes off like a pissed off gorilla though. Is this a jetting issue, or does it have something to do with the secondaries opening up too early or something? When I get the $$ I'm going to invest in one of those big jet and other small part assortments from Holley, but I was just wondering if this is something simple I can fix in the meantime.

Thanks

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Brandon
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'66 Mustang coupe
Fresh but stock 302
Holley 4V/Edelbrock Streetmaster 289 intake
Tri-y Headers/2.5" dual exhaust
C4
Front disk brakes
8" 300 open rear
Stock heads and cam

Purchased car 06/2003
Goal: 12 second beautiful but mean daily driver.

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Posts: 733
From: Clarion PA
Registered: Nov 2000

posted 06-19-2003 06:52 AM               

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'68 mustang 351 clevor- 10.92@124
'67 Stang, 351W -11.18@118
'69 351C Torino-14.90@100
'78 Pickup 351W-15.56@88
'79 Pickup 460 ET=??

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Posts: 4377
From: Arizona
Registered: Dec 2001

posted 06-19-2003 08:37 AM               

I agree... sounds like classic 'bog'. Using the casting numbers on the airhorn, go to www.holley.com to find exactally what you've got using the numerical listing. It should tell you what spring originally was put in that carb (they're color coded). There's also a tiny check ball in the vacuum line to the diaphragm; be mindful of that (make sure it's there, and don't drop it! )
Keep going stiffer on the spring until you eliminate the bog/hesitation. Then, do a WOT plug read (clean shut-off, no idling). Then, we can talk about jetting

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1965 GT coupe, 333ci aluminum headed/solid cammed stroker, four speed, 3.70:1 9"

All Blue Oval, no blue bottle
http://mustangsandmore.50megs.com/V8Thumper.html

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Posts: 298
From: USA
Registered: May 2003

posted 06-19-2003 09:23 AM               

A few fairly decent links on carb info and maybe tuning?...

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