Holley Avenger 770 vs 750

[Purple440]

Hi all,

I'm about to buy a new carb and replace my BG 750 and I'm going with a Holley.  Called Holley, Jegs tech, and a local speed shop and they all recommended a Holley 750 or 770 Avenger, and they all recommended a vacuum secondary.  I'm going to look at the documentation on these two carbs when I'm done typing this, but I'd like to know everyones preference between the two.  Opinions please 

Build:
440 .030 over, m1 dual plane, 230@.050 480 lift lunati, 1 3/4 headers, compression unknown, but higher than it should be (9.5:1). 3:55 28'' tire, and soon to be A&A Converter stalling from 2400 to 2800 depending.

Also they said not to go with the DP.  Ron I know you like those, and I've done a forum search on this topic and read up.  It seems like the DP would perform well if one knew how to tune them but at this point I don't know how to tune the accelerator pump/cam ect..

P.S. Ron, my A&A Converter came today!    new MP flex plate too.  Those A&A guys were great to work with.  Installing on Saturday morning   

[firefighter3931]

Doug, go with the holley 750 dp'er. No vacuum secondary carbs on performance engines. 



Ron

[Purple440]

The only reason I hesitate on the DP is fear of a bog from too much fuel, because of the extra pump and mechanical secondaries opening right away.  I'm sure the higher stall would help with that. 

- Doug

[firefighter3931]

Doug, if you haven't seen this thread have a look....Alan just upgraded from a vac sec to a double pumper with excellent results. 

http://www.dodgecharger.com/forum/index.php/topic,33725.0.html



Ron

[Purple440]

Yep I've read that a couple of times 

I'm not sure what Alan's build is, but that sure is a nice looking Charger 

It's not that I don't trust your advise, it's just that I don't believe I have the ability to tune a DP at this point.  But I'm willing to learn of course, I love tinkering with with my BG750 so...and I talked to my dad and he doesn't care if we get a DP or a vac secondary so I guess I'll try the DP.  Hope you don't mind a few more questions when I get it though 

- Doug

[aifilaw]

get the DP'er..... there is the same learning curve with a DP'er as with a vac sec. the difference is after the learning curve is over, you will be much happier with one than the other... I'll let you guess which...
I'm the disappointed owner of a holley 870 avenger with vacuum secondaries....on my old engine after tuning that carb... I put the edelbrock back on for the dragstrip.... that tells you something

[Purple440]

Even on a 727 auto that will never see the track?  well maybe once or twice, if ever.

[aifilaw]

track be darned, you will want it on the street more than anywhere....
if your trying to get high gas mileage and that is your only concern, and you never plan on pushing the pedal more than halfway down... get the vacuum secondary... otherwise, don't.

[69chargerR/T]

purple440, go with the 750dp you will not be sorry!!!!!!!!!!!! I had an eddy 750 on my car and hated it, had off idle stumble, so I was looking to go with a holley 750dp so I called holley and asked them about it and the guy on the phone talked me out of it said it wouldn't be good on auto car and told me to get the 770 avenger. So, I got the 770 put it on the car did run good, but I had to do some tuning and I still had a off idle back fire , and even with the lightest vac. secondary spring I still felt the car should be quicker!!! I asked guys on this site about the 750dp they all said it was the way to go, and they were right!!! Get the 750dp with 4 corner idle screws make sure the front and rear throttle plates are even, check the acc. pump adjustment ( its very easy we can tell you how ) and put it on it will run great    I'm very happy with the 750dp I wish I didn't listen to the guy from holley and got the 750dp in the first place!!!!!!!!!! My car runs awesome now Ron and jg68 and I, I'm sure will help you with any tuning problems  these carbs are very easy to tune and run great


                                                                                                         Alan



          PS: your car will run like mine

 

[69chargerR/T]

Doug, Forgot to tell you your engine build is almost the same  as mine , but you have a milder cam than I do. I have the mp 484 which has a lot of duration and is a little harder to tune. With your cam you could probable put the 750dp on right out of the box, adjust the idle and mixture screws and it would run great!!!!! I wouldn't worry about any bog when the secondaries come in, I had no bog problems at all, your 440 build will handle the 750dp with out any problem


                                                       Alan

   

[Challenger340]

Doug, go with the holley 750 dp'er. No vacuum secondary carbs on performance engines.



Ron

BUMP !

[jg68]

Purple, why not just send me your 750 Demon, i'm sure i'll get it dialed in for you for a fraction of a new one, i don't remember if i offered before, if you pay for shipping back & forth, i'll do it for 75.00, just something to think about, you can reach me at 417-334-1447.

Now if you decide to go with another carb, i would look at the Quickfuel carbs, they are reasonally priced & there fully adj. with screw in air bleeds, IFRs & PVRChannels, they come with aluminum bowls & they are light weight, they are super nice & of top quality IMO, before you buy, let me know, a friend of mine is a QF distributor, his prices blow summit/jegs out of the water

[471_Magnum]

Problem is the factory calibration on the Avenger series pretty much sucks for use on a big block, particularly the 770.

Get a LM-1 hooked up and start opening the PCVRs and they really perk up. After that, you can adjust them for better cruising and fuel economy. I don't think there was a jet, bleed or orifice left on my 870 that was the factory size after I was done with it.

DP calibration is much more forgiving out of the box, but the fuel economy generally suffers because of it.

[aifilaw]

I don't think there was a jet, bleed or orifice left on my 870 that was the factory size after I was done with it.

ditto, and it still wasn't running the way I wanted.

[Purple440]

Thanks for the feed back guys!  I'm going for the DP, just need to convince my business partner (father)...he's worried about gas mileage    I'll remind him that he also owns a toyota 

One more question:  we're being told that holley's leak to beat hell out of the fuel bowls and float holes.  Anyone experience that? 

- Doug

[aifilaw]

use good quck-change gaskets... mine have lasted years and years without leaking...
You can get the same gas mileage out of a double pumper with tuning

[471_Magnum]

use good quck-change gaskets... mine have lasted years and years without leaking...
You can get the same gas mileage out of a double pumper with tuning

The blue Holley gaskets. Not the rubber ones from Mr Gasket.

Mileage... maybe on the highway, but probably not around town. Tuning the accelerator pump(s) for economy is probably one of the more challenging aspects of carb tuning, even with a wideband O2. Easy to set up a pump for a nice fat shot, but leaning it out just right is tough. A DP is 2x as tough.