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Author
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Topic: going to smaller carb??
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Rare67
Journeyman Posts: 16
From: Jefferson. MD
Registered: Mar 2004
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posted 09-16-2004 11:09 AM
   
Check out the engine specs here:
https://mustangsandmore.com/ubb/Forum12/HTML/008578.html
In efforts to make my car a bit more
streetable, I'm considering going to a smaller cam (Comp 270s), as well as a smaller carb.
I currently have a Holley 700DP with a milled choke tower, and 4 corner idle which runs good. (6"-7" of vacuum at idle), but doesn't pull hard when the secondaries open. I'm thinking a smaller carb would help in the throttle response and acceleration area and a 4 hole carb spacer would help with velocity also. 600DP or 650DP, and whats your reasoning for your selection? Thanks
Paul
[This message has been edited by Rare67 (edited 09-16-2004).]
[This message has been edited by Rare67 (edited 09-16-2004).] [This message has been edited by Rare67 (edited 09-16-2004).]
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Fastymz
Moderator Posts: 20708
From: Reno Nv USA M&M#1240
Registered: Apr 2001
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posted 09-16-2004 12:51 PM
Paul, I'd start with jetting down the 700 alittle and using a 1" 4hole spacer with it.You say the car runs good but does pull hard when secondarys open. Does it pull good until they open, and does it pull good after the RPM's get alittle higher ? ------------------
SCOOP oddly obsessed with big scoops on little Mustangs 65 coupe,351w,C4,Big Boss 429 hood scoop,8" 3.40 TracLoc. My Pics
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capri man
Gearhead Posts: 7249
From: doerun, ga.
Registered: Nov 2000
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posted 09-16-2004 01:13 PM
im a long way from an expert but here is my humble theory. with that big of a duration helping make the low vacuum readings, the signal (or air speed ) going into the engine is reletivly low. if the spacer dont cure it i would go with the 600 dp. the reason being that the butterflys on the 600 are smaller than on the 650. 650-750 are the same size. the smaller holes will increase your signal (speed) of the air going into the engine. i would guess that you might also have a little stumble when you floor it from a low rpm.
did any of this make any sence?? just my opinion, i could be wrong. good luck------------------
mike r
racing is real
everything else is just a game.
81 capri-302-7.33 @92mph 1/8
1.54 60 ft. http://community.prestage.com/Member+Pages/789.aspx
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Rare67
Journeyman Posts: 16
From: Jefferson. MD
Registered: Mar 2004
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posted 09-16-2004 03:26 PM
If I jet down it'll lean out...tried that.Let me clarify a bit. From a stop, it will pull hard through the gears. From cruise speed...say 40-50mph, if I floor it, or downshift and floor it, it doesn't pull hard...which seems strange because its in the powerband at that point. Paul
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Rare67
Journeyman Posts: 16
From: Jefferson. MD
Registered: Mar 2004
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posted 09-16-2004 03:29 PM
quote:
Originally posted by capri man:
if the spacer dont cure it i would go with the 600 dp...the smaller holes will increase your signal (speed) of the air going into the engine.
This is what I'm thinking also. Get that velocity up a bit. Paul
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capri man
Gearhead Posts: 7249
From: doerun, ga.
Registered: Nov 2000
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posted 09-16-2004 03:30 PM
well then, heck i aint got a clue!!!!  ------------------
mike r
racing is real
everything else is just a game.
81 capri-302-7.33 @92mph 1/8
1.54 60 ft. http://community.prestage.com/Member+Pages/789.aspx
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Fastymz
Moderator Posts: 20708
From: Reno Nv USA M&M#1240
Registered: Apr 2001
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posted 09-16-2004 04:37 PM
quote:
Originally posted by Rare67:
If I jet down it'll lean out...tried that.Let me clarify a bit. From a stop, it will pull hard through the gears. From cruise speed...say 40-50mph, if I floor it, or downshift and floor it, it doesn't pull hard...which seems strange because its in the powerband at that point. Paul
That would do more with your cam and gear selection in my opinion. 
At 40-50mph in fourth what are at about 2500rpm or so ? With that cam I'd think once you get into the 3000-3500 range it'll start pulling better. I'd start with a four spacer, and work from there.
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