Moparts
Holley 670 SA or 750 3310 on 340?
Posted By: Dart 340
Holley 670 SA or 750 3310 on 340? - 03/20/09 01:48 AM
Have a 340 that is stock with the exception of
some stock head work, air gap RPM manifold and
performer rpm cam. 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 better
carb for what I have. The Dart is also a 4 speed.
Thoughts and experiences?
Posted By: Crizila
Re: Holley 670 SA or 750 3310 on 340? - 03/20/09 01:57 AM
I wouldn't switch. Gonna be hard to beat that 3310 with your combo.
Posted By: Dart 340
Re: Holley 670 SA or 750 3310 on 340? - 03/20/09 02:10 AM
Will I get better throttle response and vacuum with
the 670 vs the 750? My rear gears are 3:23's with
14" wheels. I've always had a little "dead spot" off the punch with the 750 but maybe I just need
a different squirter for the acc pump.
Posted By: landon1
Re: Holley 670 SA or 750 3310 on 340? - 03/20/09 02:20 AM
i'd go with a 670...i have a 650 on my 440 b/c that's what holley recommends for my engine size and max rpm (5K on a 440) and it's perfect imo
but, if it's all good, i'd leave it alone
Posted By: Dart 340
Re: Holley 670 SA or 750 3310 on 340? - 03/20/09 03:49 AM
for my 340 they show for 6K and under the 670 and
for 6500 and up the 750. I know the 670 has jets in
the secondaries instead of the plate.
Posted By: AdamR
Re: Holley 670 SA or 750 3310 on 340? - 03/20/09 11:01 AM
You have it, may as well try it.
I believe the Street avengers are also flowed different then the older 4150s and the 670 flows more then 700 cfms.
Posted By: dgc333
Re: Holley 670 SA or 750 3310 on 340? - 03/20/09 12:01 PM
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.
Posted By: Dart 340
Re: Holley 670 SA or 750 3310 on 340? - 03/20/09 12:26 PM
Dave,
Thanks, that is really good information.
I spend weeks tweaking the 750 last year to get
it to the point it worked well, but it still has
a little dead area on the bottom end. I was hoping
the 670 might give me better low end response.
Thinking I will start tweaking on the 670 and see
what I can get her to do.
Posted By: Mr.Yuck
Re: Holley 670 SA or 750 3310 on 340? - 03/20/09 12:35 PM
Posted By: Dart 340
Re: Holley 670 SA or 750 3310 on 340? - 03/20/09 12:43 PM
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?
Posted By: Mr.Yuck
Re: Holley 670 SA or 750 3310 on 340? - 03/20/09 12:59 PM
what squitters are in there now? I had 28's in my 750HP series. The 31's were too big
Posted By: Dart 340
Re: Holley 670 SA or 750 3310 on 340? - 03/20/09 01:16 PM
I actually think they are 34's ....
Posted By: Mr.Yuck
Re: Holley 670 SA or 750 3310 on 340? - 03/20/09 01:45 PM
Quote:
I actually think they are 34's ....
wow toooo big. drop them down
Posted By: YO7_A66
Re: Holley 670 SA or 750 3310 on 340? - 03/20/09 02:36 PM
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.
Posted By: Crizila
Re: Holley 670 SA or 750 3310 on 340? - 03/20/09 03:31 PM
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.
Posted By: Dart 340
Re: Holley 670 SA or 750 3310 on 340? - 03/20/09 03:59 PM
I know a better gear would help, but I found a
great deal on the 3.23 and considering I drive
a lot on the freeway it seemed like a good
choice to go with. It had a 2.76 when I bought
it, talk about a clutch riding killer!
Using the plain steel spring in the secondary's
and the stock PV was 6.5 but changed it to 4.5.
Vac is around 9-10 but the cam has a long duro
and I was told from eddy this is common for
that grind so I do not think I have a leak
anywhere. I will check the shot size to see
what that is and I believe I have the white
cam on the acc pump.
Posted By: dgc333
Re: Holley 670 SA or 750 3310 on 340? - 03/20/09 05:07 PM
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.
Posted By: Dart 340
Re: Holley 670 SA or 750 3310 on 340? - 03/20/09 05:21 PM
Dave,
Cam is 234 int and 244 exh at .050 and lift
is .488 int and .510
the 3310 took a long time to run "acceptable" I
just tried the 670 last evening and it seems to
be pretty close. I still have a little trouble
with idle being high enough the transfer slots
are uncovered a little too much I think, but
advancing the timing should help with that. I
am only at 12 btdc and think I will go up to
16 or 18.
Posted By: Crizila
Re: Holley 670 SA or 750 3310 on 340? - 03/20/09 06:21 PM
Quote:
I know a better gear would help, but I found a
great deal on the 3.23 and considering I drive
a lot on the freeway it seemed like a good
choice to go with. It had a 2.76 when I bought
it, talk about a clutch riding killer!
Them trade-offs are always a [Edited by Moparts - Keep it clean] arent they. For a streeter with that gear, the Avenger might be more suitable. Let me know if you ever want to sell that 3310.
Posted By: Dart 340
Re: Holley 670 SA or 750 3310 on 340? - 03/20/09 06:48 PM
Give me a few days to see if I can dial the 670 in
and if so I'd sell it to you for a good deal. Lord
knows it's clean and works pretty good.
Posted By: dgc333
Re: Holley 670 SA or 750 3310 on 340? - 03/20/09 08:27 PM
Quote:
Dave,
Cam is 234 int and 244 exh at .050 and lift
is .488 int and .510
the 3310 took a long time to run "acceptable" I
just tried the 670 last evening and it seems to
be pretty close. I still have a little trouble
with idle being high enough the transfer slots
are uncovered a little too much I think, but
advancing the timing should help with that. I
am only at 12 btdc and think I will go up to
16 or 18.
16-18 should be real close and it will certainly let you dial back the idle stop screw and most likely cover the transfer slots back up.
Don't forget that you will likely need to limit the total mechanical on the other end to keep it in the 35-36 range.
Posted By: Dart 340
Re: Holley 670 SA or 750 3310 on 340? - 03/20/09 08:46 PM
Dave,
I think I have a pretty much stock points disty
with the exception of a pertronix kit. To I need
to take it to a speed shop to limit timing or
can I set it up myself?
Posted By: Crizila
Re: Holley 670 SA or 750 3310 on 340? - 03/21/09 01:35 AM
You can do it yourself if your dampener is degreed or you have a cut-back timing light, but it's a pain, especially if your existing idle is up over 1000rpm and you are in to the mechanical advance already at idle. Most mopar point distributors had 12-13 mechanical advance degrees built in to them ( that would read 24 - 26 degrees at the crank - distributor turns 1/2 crank speed). If you want to set your initial at - lets say 18 crank degrees and you want a total of 36 degrees, you will have to limit the mechanical advance to 18 degrees ( 9 distributor degrees ). To do this you will have to limit the advance travel in the distributor by welding up part of the slot that the pins travel in. You can do it, but a lot of in and out and trial and error to get there - and you still have to address the rate of the curve by ploting it out at maybe every 500 rpm. I'd say find a shop with a distributor machine, give them the parameters you want, and let them have at it. They can also check your distributor for firing point accuracy -warn bushings, bent shaft and your vacuum advance curve if you are using one.
Posted By: Dart 340
Re: Holley 670 SA or 750 3310 on 340? - 03/21/09 02:25 AM
Hmm so it sounds like I might be better if I disconnected the vacuum advance or used full manifold vacuum on it then....
Posted By: Crizila
Re: Holley 670 SA or 750 3310 on 340? - 03/21/09 02:57 PM
If your distributor has a vacuum advance system om it, I would use it in your application. Although it has nothing to do with your problem. It is mainly there to improve fuel mileage at cruise by dumping in an additional 15 - 16" of vacuum ( on top of your mechanical advance )at light load ( cruise ) conditions to improve mileage. If you are running some boarder line temperature issues it can help there also. The minute you mash on the gas peddle, the vacuum advance system is out of the picture. Weather you use it or not is mostly a matter of preference. A lot of street performance guys don't use them and most race oriented distributors don't even have them. If you drive on the street alot, and it sounds as though you do, I would use vacuum advance.
Posted By: 70duster340
Re: Holley 670 SA or 750 3310 on 340? - 03/21/09 05:10 PM
My 340 came with a 3310. It never ran well at all. It was always rich, and I had to remove the plugs at least once a week and clean and dry them to get it to start. I bought the 670SA, and it never ran so well! I haven't looked back since. My 3310 is still sitting in the garage. It needs a good rebuild, I believe. I don't believe I will ever reuse it, though. Maybe I sould sell it?
Posted By: dgc333
Re: Holley 670 SA or 750 3310 on 340? - 03/22/09 12:52 PM
Quote:
Dave,
I think I have a pretty much stock points disty
with the exception of a pertronix kit. To I need
to take it to a speed shop to limit timing or
can I set it up myself?
If you are ambitious to take the distributor apart you can limit the advance yourself but either welding up the slots or using epoxy to shorten them. If you don't want to tear into it then having it done or buying an adjustable distributor like the Mopar Performance unit is the way to go.
Find the initial advance your engine wants then subtract that from 35-36 to get the total mechanical advance number you are shooting for. Buy and $.39 protractor at the stationary sore and glue it to an old rotor (center of protractor over center of shaft). Tape an old coat hanger to the housing to use as a pointer.
With the point plate and pertronix unit removed twist the rotor against the springs and measure the rotation. Double this number to get the crank degrees. Now remove the top half of the shaft with the slots and weld epoxy the outer end of the slot to reduce the length. Trial an error until you get the number you had come up with earlier.
Posted By: Dart 340
Re: Holley 670 SA or 750 3310 on 340? - 03/22/09 03:41 PM
I set the timing to 18 for idle yesterday with
the 670 on the car. Set idle to 850 and adjusted
mixture screws. Took her out and mashed on it
and the car is running very good. No knock or
ping from off the line or from higher speed
even from 4th gear at say 2000 rpm.
I will look into the disy curve also. Happy to
have had weather break enough to drive her!
I think the 670 will be staying on the 340. I
cant really tell much of a higher rpm difference from the 3310 and it seems to give me zero
bog or lag issues and throttle response if much
better. Thanks all!
Posted By: Mr.Yuck
Re: Holley 670 SA or 750 3310 on 340? - 03/22/09 03:51 PM
Sounds good. The only thing you'd notice w/ the smaller carb is a few mph in the 1/4.
Posted By: gch
Re: Holley 670 SA or 750 3310 on 340? - 03/22/09 04:02 PM
Quote:
I set the timing to 18 for idle yesterday with
the 670 on the car. Set idle to 850 and adjusted
mixture screws. Took her out and mashed on it
and the car is running very good. No knock or
ping from off the line or from higher speed
even from 4th gear at say 2000 rpm.
I will look into the disy curve also. Happy to
have had weather break enough to drive her!
I think the 670 will be staying on the 340. I
cant really tell much of a higher rpm difference from the 3310 and it seems to give me zero
bog or lag issues and throttle response if much
better. Thanks all!
Did you ever try bumping the timing up with the 750?May have improved it as well.
Posted By: Dart 340
Re: Holley 670 SA or 750 3310 on 340? - 03/22/09 04:11 PM
I did try the timing higher last fall with the 750
and could never get rid of the weird hesitation
even under no load. I am guessing it was the
acc pump or cam, but never got it tweaked in just
right. Maybe I will play with it some more. Now it's
off the car I can pull the acc nozzle off and double
check the shot size.
I've done so much to this car in a year it's hard to
keep track of it all. It was a non running trailered
no dash mess, electrical mis wired nightmare. Now
everything is working pretty darn well. Thanks for
all the input guys, it's appreciated.
Posted By: Dart 340
Re: Holley 670 SA or 750 3310 on 340? - 03/23/09 01:56 AM
I checked the squirters tonight and they look like
31's or even 34's.
The 670 is surging a little so I might have to pull
it and do a rebuild.
And ideas on the 3310 for acc cam color and sizing etc before I wright her off completley?