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Author Topic:   Tried out a 700 DP on the 331
bluestreek
Gearhead

Posts: 1289
From: Athens,GA
Registered: Jul 2001

posted 01-06-2003 12:06 PM     Click Here to See the Profile for bluestreek   Click Here to Email bluestreek     Edit/Delete Message   Reply w/Quote
I rebuilt a 4778 700 DP and tried it out on the 331 Saturday. It's one of the early models with the annular "bell" style boosters and it's jetted with #66 in front and #72 in the rear. The idle was smooth and clean and the engine seems to be responding great to the annular boosters. I decided to take it for a drive and the first thing that happened was the engine kept stalling as soon as I tried to let out the clutch to back it out of the driveway. After raising the hood and looking it over very carefully, I saw that the squirters were shooting before the throttle plate was even moving, causing a rich bog. So I removed the carb and put it on the bench and found about 1/4" of freeplay where the arm attaches to the throttle shaft. I took the throttle plate off and put a blunt center punch in the middle of the shaft and hammered it back tight. Once I put it back together and on the engine, it worked great. It responded nice and smooth driving it out of the subdivision. I took off down the open road in 1st gear and the tires would smoke up everytime I tried to give it a little gas. So I let off and eased it into 2nd and then tried to get into the secondaries again. They came in smooth and hard, and as it reached about 40 mph, I could feel the tires slipping again but the BFG DRs managed to hold on. I shifted into 3rd at about 6000 and the car went sideways!! What a blast! While I was in 3rd I was finally able to feel how the mechanical secondaries felt compared to the vacuum secs I had tried. There is some major torque being put on the tires when those babies are pushed wide open!

After a short cruise, I took it home and pulled a plug or two and noticed some black soot around the base ring and on the lower part of the insulator. I can't decide if it needs any changes at this point. It seems pretty close, but smells rich when I'm deep into the primaries . I'm hesitant about leaning the primaries down because it might make it really hard to warm up on cold days. Should I try a weaker PV than the 6.5, lower the jetting or maybe try enlarging the main airbleeds?

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1966 Mustang Coupe: Custom glass hood and BIG scoop sits atop a 289 stroked to 331 c.i., Steel crank and girdle, 5.4 H-beams, Forged slugs, ported TFS alum. heads, ported Stealth 8020 intake, CompCams Xtreme Solid Roller, Holley 750 HP, long tubes, 4speed, 9" 3.50 posi, BFG Drag radials..

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Moneymaker
Administrator

Posts: 19704
From: Lyons, IL, USA
Registered: May 99

posted 01-06-2003 01:36 PM     Click Here to See the Profile for Moneymaker   Click Here to Email Moneymaker     Edit/Delete Message   Reply w/Quote
Try a 4.5 PV for a leaner idle and tip in.

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Alex Denysenko
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V8 Thumper
Gearhead

Posts: 3467
From: Orange, Ca. United States of America
Registered: Dec 2001

posted 01-06-2003 07:45 PM     Click Here to See the Profile for V8 Thumper   Click Here to Email V8 Thumper     Edit/Delete Message   Reply w/Quote
Why the switch from the 750, and how was it jetted? Just curious... for comparison to the 72/78 jetting (vac secondary) mine seems to like.

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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

[This message has been edited by V8 Thumper (edited 01-06-2003).]

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bluestreek
Gearhead

Posts: 1289
From: Athens,GA
Registered: Jul 2001

posted 01-06-2003 08:17 PM     Click Here to See the Profile for bluestreek   Click Here to Email bluestreek     Edit/Delete Message   Reply w/Quote
I wanted to see how the little 331 would react to all out attack of 4 barrels slamming wide open!!

The 750 HP runs 72/82 jets and really performs well, but for some reason I'm still searching for more!!

------------------
1966 Mustang Coupe: Custom glass hood and BIG scoop sits atop a 289 stroked to 331 c.i., Steel crank and girdle, 5.4 H-beams, Forged slugs, ported TFS alum. heads, ported Stealth 8020 intake, CompCams Xtreme Solid Roller, Holley 750 HP, long tubes, 4speed, 9" 3.50 posi, BFG Drag radials..

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V8 Thumper
Gearhead

Posts: 3467
From: Orange, Ca. United States of America
Registered: Dec 2001

posted 01-06-2003 08:20 PM     Click Here to See the Profile for V8 Thumper   Click Here to Email V8 Thumper     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by bluestreek:
but for some reason...


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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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bluestreek
Gearhead

Posts: 1289
From: Athens,GA
Registered: Jul 2001

posted 01-06-2003 08:34 PM     Click Here to See the Profile for bluestreek   Click Here to Email bluestreek     Edit/Delete Message   Reply w/Quote
Todd, your running a Holley 3310 with a manual choke, right? Give me some details on your carb and howsit been working out for you.

Thanks

------------------
1966 Mustang Coupe: Custom glass hood and BIG scoop sits atop a 289 stroked to 331 c.i., Steel crank and girdle, 5.4 H-beams, Forged slugs, ported TFS alum. heads, ported Stealth 8020 intake, CompCams Xtreme Solid Roller, Holley 750 HP, long tubes, 4speed, 9" 3.50 posi, BFG Drag radials..

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V8 Thumper
Gearhead

Posts: 3467
From: Orange, Ca. United States of America
Registered: Dec 2001

posted 01-06-2003 09:57 PM     Click Here to See the Profile for V8 Thumper   Click Here to Email V8 Thumper     Edit/Delete Message   Reply w/Quote
Yes, 1450 list 3310 w/ manual choke, but I don't use the choke at all. With the above jetting and 8.5 pv's and a yellow spring it's killer . Suprisingly super crisp off idle; far better than I'd imagined. Secondaries are opening up full nuts by 6k without any bog; I feel them start to come in about 4k. I've only got 6-6.5 psi from a Holley mechanical pump , gotta recover from Christmas before stepping up to a regulated electric pump. When it's real hot out, it sometimes feels like its got a low rpm (1600-1800) lean stumble to it. Downsizing the squirter actually helped (timed it out longer), 8.5 pv helped further. I do believe that better managed fuel pressure will take care of it, just need the bucks to do it

------------------
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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sic67coug
Gearhead

Posts: 170
From: clearlake california
Registered: Dec 2002

posted 01-06-2003 10:51 PM     Click Here to See the Profile for sic67coug   Click Here to Email sic67coug     Edit/Delete Message   Reply w/Quote
sounds pretty damn good to me man power all the way to third yeaaaaaaah thats what i like too many horses to count

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bluestreek
Gearhead

Posts: 1289
From: Athens,GA
Registered: Jul 2001

posted 01-06-2003 11:06 PM     Click Here to See the Profile for bluestreek   Click Here to Email bluestreek     Edit/Delete Message   Reply w/Quote
Todd,
The 3310 is a great performer over at 3000 rpms, but they can be a little touchy on a SBF at low rpms. Sounds like you worked it over.
Don't let them low rpm stumbles fool you. It's not always a lean condition. This 700 DP would fall on it's face just trying to let out the clutch when I first tried it out. It was just a little too quick on the #28 squirters and it caused an instant overrich condition. I run premium fuel, 18 degrees base timing, 36 total, and it's all in by 2800!

BTW: The 700 DP and 750 HP both have no PV in the rear.

[This message has been edited by bluestreek (edited 01-06-2003).]

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steve'66
Gearhead

Posts: 6522
From: Sonoma,CA,USA
Registered: Mar 2000

posted 01-06-2003 11:17 PM     Click Here to See the Profile for steve'66   Click Here to Email steve'66     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by V8 Thumper:
I do believe that better managed fuel pressure will take care of it, just need the bucks to do it


Fuel pressure doesn't have anything to do with it, with a carb. As long as the bowls stay full you're ok. I'm running a little Holley red at the tank pumping thru 3/8" line to a stock mech pump up front feeding a 408w and a 850 dp'r. It's run a best of 10.82 and 125 mph in the 1/4mile. Nothing fancy here, so save your money.

SteveW

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bluestreek
Gearhead

Posts: 1289
From: Athens,GA
Registered: Jul 2001

posted 01-06-2003 11:35 PM     Click Here to See the Profile for bluestreek   Click Here to Email bluestreek     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by sic67coug:
sounds pretty damn good to me man power all the way to third yeaaaaaaah thats what i like too many horses to count

I would NOT want to be a passenger in this pony when I'm testing out a new carburetor!

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1966 Mustang Coupe: Custom glass hood and BIG scoop sits atop a 289 stroked to 331 c.i., Steel crank and girdle, 5.4 H-beams, Forged slugs, ported TFS alum. heads, ported Stealth 8020 intake, CompCams Xtreme Solid Roller, Holley 750 HP, long tubes, 4speed, 9" 3.50 posi, BFG Drag radials..

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sic67coug
Gearhead

Posts: 170
From: clearlake california
Registered: Dec 2002

posted 01-07-2003 01:15 AM     Click Here to See the Profile for sic67coug   Click Here to Email sic67coug     Edit/Delete Message   Reply w/Quote
so how many horses are you really puttin out in that thing?

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V8 Thumper
Gearhead

Posts: 3467
From: Orange, Ca. United States of America
Registered: Dec 2001

posted 01-07-2003 09:47 AM     Click Here to See the Profile for V8 Thumper   Click Here to Email V8 Thumper     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by steve'66:
Fuel pressure doesn't have anything to do with it, with a carb. As long as the bowls stay full you're ok. I'm running a little Holley red at the tank pumping thru 3/8" line to a stock mech pump up front feeding a 408w and a 850 dp'r.

With the exception of the 408w and 850dp , I've got a very similar setup. Here's the symptom: motor at operating temp it comes off idle just fine. If maintaining a low rpm range (1600-1800-ish) it wants periodically to 'chug'. It takes only a touch of pedal to snap it right out. 14 hg" at 700rpm idle, dosen't load up at all. I'd tried leaning it out, only accentuated the stumble. 25 squirter btw. If not pressure/volume related, where do I go with it?

------------------
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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bluestreek
Gearhead

Posts: 1289
From: Athens,GA
Registered: Jul 2001

posted 01-07-2003 11:33 AM     Click Here to See the Profile for bluestreek   Click Here to Email bluestreek     Edit/Delete Message   Reply w/Quote
That "chug" sounds like a common symptom of an engine having a lopey idle in front of a straight shift tranny. A straight shift tranny puts a dead pull on your engine at all rpms. During the off idle-2000 rpm range, the carb is going through the transition stage, and the air velocity and vacuum in the intake is very low with a performance cam. As long as you are at a contant idle rpm, the small idle circuit is adjusted to keep the mixture correct. As soon as you crack open the throttle plates, the transition slots above the idle passage begin to feed fuel and the main boosters aren't sensitive enough to meter the right mixture yet. The transition slots use the same metering jets as the idle circuit and pull in fuel by vacuum. This is where the problem lies. As you creep around in first gear, the engine vacuum is constantly changing and so does the transition mixture and air velocity. On top of that, If the intake pressure drops below the value of the PV, it too will try to get into the mixture. When you put all this together you get the "chug". Once you open up the throttle plates enough, and the rpms start to climb, the velocity through the venturis increase and the main boosters and jets take over.
An engine in front of a limited slip clutch or stall converter is much more forgiving on a carburetor.

I don't have a definite remedy for your carb, and most people just accept it when driving a straight shift hotrod. A carb shop could custom tune a carb just for your engine and cam, but that too would be tricky without many hours on a dyno. Maybe this info will help if you try to tune it further.

Dan

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1966 Mustang Coupe: Custom glass hood and BIG scoop sits atop a 289 stroked to 331 c.i., Steel crank and girdle, 5.4 H-beams, Forged slugs, ported TFS alum. heads, ported Stealth 8020 intake, CompCams Xtreme Solid Roller, Holley 750 HP, long tubes, 4speed, 9" 3.50 posi, BFG Drag radials..

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V8 Thumper
Gearhead

Posts: 3467
From: Orange, Ca. United States of America
Registered: Dec 2001

posted 01-08-2003 09:32 AM     Click Here to See the Profile for V8 Thumper   Click Here to Email V8 Thumper     Edit/Delete Message   Reply w/Quote
Great info
Thanks!

------------------
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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bluestreek
Gearhead

Posts: 1289
From: Athens,GA
Registered: Jul 2001

posted 01-09-2003 11:18 PM     Click Here to See the Profile for bluestreek   Click Here to Email bluestreek     Edit/Delete Message   Reply w/Quote
700 DP UPDATE:.......

I tried the 4.5 PV that Alex suggested and the mixture is better! I think the PV was causing a rich condition everytime I mashed the gas peddle. Without the PV coming in too quick, the plugs and pipes cleaned up but I started feeling a little "flatspot" at part throttle. I then went UP 3 numbers on the primary jets and it feels just about right. The BFG drag radials don't seem to be helping much anymore even in 2nd gear, but every now and then, the S/S bars will load the chassis up, and away we go!!!

Thanks
Dan

------------------
1966 Mustang Coupe: Custom glass hood and BIG scoop sits atop a 289 stroked to 331 c.i., Steel crank and girdle, 5.4 H-beams, Forged slugs, ported TFS alum. heads, ported Stealth 8020 intake, CompCams Xtreme Solid Roller, Holley 750 HP, long tubes, 4speed, 9" 3.50 posi, BFG Drag radials..

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sic67coug
Gearhead

Posts: 170
From: clearlake california
Registered: Dec 2002

posted 01-12-2003 02:33 AM     Click Here to See the Profile for sic67coug   Click Here to Email sic67coug     Edit/Delete Message   Reply w/Quote
hey man what kind of highway speeds do you get in that thing? any idea of howmany horses youre runnin?

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bluestreek
Gearhead

Posts: 1289
From: Athens,GA
Registered: Jul 2001

posted 01-12-2003 07:41 PM     Click Here to See the Profile for bluestreek   Click Here to Email bluestreek     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by sic67coug:
hey man what kind of highway speeds do you get in that thing? any idea of howmany horses youre runnin?

I have no idea what the top speed is on it. The fastest I've had it was when I ran an early Viper once from a dead stop and stayed in front until I hit around 6000 rpms in 4th gear (about 130 mph). This old '66 is not built for high speed!!

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1966 Mustang Coupe: Custom glass hood and BIG scoop sits atop a 289 stroked to 331 c.i., Steel crank and girdle, 5.4 H-beams, Forged slugs, ported TFS alum. heads, ported Stealth 8020 intake, CompCams Xtreme Solid Roller, Holley 750 HP, long tubes, 4speed, 9" 3.50 posi, BFG Drag radials..

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