Re: Holley 670 SA or 750 3310 on 340?
[Re: Dart 340]
#259553
03/19/09 09:57 PM
03/19/09 09:57 PM
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Joined: Oct 2003
Posts: 7,506 Az
Crizila
master
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master
Joined: Oct 2003
Posts: 7,506
Az
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I wouldn't switch. Gonna be hard to beat that 3310 with your combo.
Fastest 300
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Re: Holley 670 SA or 750 3310 on 340?
[Re: Dart 340]
#259558
03/20/09 08:01 AM
03/20/09 08:01 AM
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Joined: Apr 2004
Posts: 1,396 Mass
dgc333
pro stock
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pro stock
Joined: Apr 2004
Posts: 1,396
Mass
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Quote:
Have been running a 750 3310 for the last year but got a great deal on a street avenger 670 and was thinking that might be a bettercarb for what I have. The Dart is also a 4 speed.
I have a 360 that is producing approximately 370 HP. I have had both a 3310 750 and a 670 Street Avenger on it (as well as a 600 Holley and a 725 Demon).
I have a self imposed 6000 rpm redline and up to that point the butt dyno can not tell a difference between the 670 and 750. BUT, the throttle reponse and below 3000 rpm driveability with the 670 is dramtically better. Plus the 670 gives my 5 mpg more than the 750.
The 670 is wet flow rated compared to the 750 so if it had been dry flow like the 750 it would be more like a low 700 cfm rating. Also, if you look down into the venturis of the 670 you will notice that the primaries are smaller than the secondaries (even though the throttle blades are all the same size). This accounts for the excellent low rpm driveability.
The 670 is staying on the engine until the day I decide to go EFI.
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Re: Holley 670 SA or 750 3310 on 340?
[Re: Dart 340]
#259564
03/20/09 09:45 AM
03/20/09 09:45 AM
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Joined: Jan 2003
Posts: 24,562 Brookeville, Md
Mr.Yuck
Not enough dumb comments...yet
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Not enough dumb comments...yet
Joined: Jan 2003
Posts: 24,562
Brookeville, Md
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Quote:
I actually think they are 34's ....
wow toooo big. drop them down
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Re: Holley 670 SA or 750 3310 on 340?
[Re: Mr.Yuck]
#259565
03/20/09 10:36 AM
03/20/09 10:36 AM
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Joined: Jan 2003
Posts: 5,443 Indiana
YO7_A66
master
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master
Joined: Jan 2003
Posts: 5,443
Indiana
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Dart 340: The size of the squirter affects how fast (in relation with the pump cam) the gas will be delivered into the carb. If you are testing with the same cam (as it appears that you are) and no other changes, a "031" squirter will deliver "more fuel faster" than a "025" squirter with the same pump cam. As 72 stated in your other post, your street 340 will like more rpms. A street 340 with its short stroke will not like a large squirter dumping allot of fuel at lower rpms. What pump cam are you using? Note: Holley pump cams from smallest cc to largest cc for 30cc pump (black, pink, white, red, green, orange and then the blue is the largest). The pump cams are fun to test with because you can feel the difference after swapping one out. For reference, if you start with a pink one and then install a blue one, you can definately feel the difference in the throttle at lower "cruising" speeds. The blue one might be too much for off idle in a mild sb, but for cruise testing you can feel the difference.
1970 YO7 A66 [Canadian Export] F8 Challenger 340 (Currently in shop for stroker assy.)
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Re: Holley 670 SA or 750 3310 on 340?
[Re: YO7_A66]
#259566
03/20/09 11:31 AM
03/20/09 11:31 AM
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Joined: Oct 2003
Posts: 7,506 Az
Crizila
master
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master
Joined: Oct 2003
Posts: 7,506
Az
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You could use a little steeper gear with your set up - maybe in the 3.55 range. Better seat-of-the pants feel ( typical with a smaller carb )doesn't always equate to better over-all performance. Ran a very similar engine set up to yours ( except 360 motor ) with a 3310 in a 4,000 plus pound automatic car and got it to run low 12.70's. Extending the squirter time ( longer duration ) helped for me. I also set the primary float level a little higher ( top of the sight glass ). Also went with a quick fuel secondary plate so I could change jetting easily. Can't remember for sure, but I don't think I deviated much from the stock jetting - maybe 2 sizes richer on both sides. Are you still using the stock sec vacuum spring? I think it is plain steel in color. I believe the stock PV was a 6.5 on that carb. Stick with it if you are idling at 9" - seems a little low? Don't know how fast your advance curve is, but you could try slowing it down a bit and see if that helps.
Fastest 300
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Re: Holley 670 SA or 750 3310 on 340?
[Re: Dart 340]
#259568
03/20/09 01:07 PM
03/20/09 01:07 PM
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Joined: Apr 2004
Posts: 1,396 Mass
dgc333
pro stock
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pro stock
Joined: Apr 2004
Posts: 1,396
Mass
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Quote:
She's almost an eye burner now at idle, and my plugs are at least brown.... changed the PV about 4 times last fall. I have a 4.5 in there now running at 9 InHg vacuum. I was thinking maybe the acc pump squirters might be the culprit?
You didn't mention what you are using for a cam. But anything with more duration than stock typically means more overlap which means you need more intital timing. I running a Comp XE268H cam and I get max manifold vacuum with 17 degrees BTDC for my inital. Anytime you tune an engine getting the timing dialed is the first step.
If you are pig rich at idle with a Street Avenger carb I would say you need more timing. When i went to the 670 it had to be the closest thing to spot on I had ever tried. Tweaked the idle mixture screws, set the idle speed and called it a day and have not touched it since.
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