Carbrator size help

[KB9GIB]

Hi just need some of your thoughts on carb size 69 b body 440 40 over factory heads comp 509/209 cam 323 gears Should I go Holley 770 or 870 I do appreciate your thoughts.Thanks KB9GIB

 

[Jcharger]

I have some thoughts but not an answer.

Given you have narrowed it to 770 or 870, it seems you are looking at the avenger series vacuum secondary. My experience with a 670 was that it cam jetted very lean, so you will want to pay attention to that. My car spit and backfired out the carburetor. I have used neither of the two you are considering so would wait to see what others say. My guess is that both may be comparable.

If it were me, I would consider something like a 750 double pumper (mechanical secondary) instead.

 

[hemidon1]

Hi just need some of your thoughts on carb size 69 b body 440 40 over factory heads comp 509/209 cam 323 gears Should I go Holley 770 or 870 I do appreciate your thoughts.Thanks KB9GIB

Since your only running a 3:23 gear your not going racing and if fuel mileage is of any concern at all both of these holleys are larger than you need--so go with the smaller unit--a much better carb for the street would be an Edelbrock 750 cfm as they are trouble free carbs once you set the mixture & idle speed--the holley will shine in a car set up to race as they're very fuelish but they're not the best on a street set up--you'll always be screwing around with keeping a holley adjusted. I own 3 Hemi B-body cars & 4 big wedge B-body cars right now & build 8 to 10 each year for other guys--Ive done a lot of experimenting & this was the result of 45 years of big block Mopar experience. also if you change those rear gears to a 3:55 you'll have a very quick & fast 69--all the best to you--Hemidon

 

[lewtot184]

you'll probably have a bigger issue with that .509 cam than any carb; especially with 3.23 gears. the cam may be a tuning headache for you if your not carb and ignition savvy.

 

[KB9GIB]

Thanks on your input on the carb I haven't tried a Edelbrock but I will go that way and on the cam I think I'm going to change it out this winter I should have done more reading on cams before I installed it. I do thank you guys I will check back later this fall to see what you would recommend on cam shafts and will be pulling the stall converter also. Thanks KB9GIB

 

[PRND21]

For what it's worth... I'd stick with a vacuum secondary carb on the street with an auto trans, especially with 3:23s. Good luck.

 

[dla4567]

I'm not going to say one is better than the other, but, my edelbrock has been very reliable and was easy to tune. More of a "set it and forget it " carb.

 

[747mopar]

I don't get where one says a Holley isn't the best for the street??? They're the most copied carb out there and do perfectly fine on the street. I've ran an 870 and a 750 back to back on mine and like the 750, you'll use all 4 barrels more often but idle and off idle performance is much cleaner making it a lot nicer around town. I like double pumpers but with those gears and an automatic you might be better off with the vacuum sec but like mentioned the Avengers seam to come very lean (if I remember correctly I went up 10 jet sizes). I prefer Holley's, Demons and Quick Fuels myself but that's just me. Good luck

 

[WileERobby]

Holley 3310.

 

[727]

Street demon!

 

[forphorty]

750 double pumper. You didn't mention what torque converter you have , but that .509 really needs 3500 plus stall.

 

[oldbee]

"PRND" has it right....Vacuum sec. on the street. Cam seems a little big w/o a higher stall converter though.