Holley Truck Avenger 470cfm

[amajor]

i've got a 78 w/ crate 350, accel HEI, edlebrock alum intake, & headers, i'm trying to make it as efficient as possible and was woundering if you guys think the Truck Avenger 470cfm would give it enough juice. maybe it'll need to be re-jetted? i talked with a guy who ran the 670cfm on his 454, and i'm not sure i need that much juice. i'm trying to get gas mileage out of this old girl aswell as a little off road umph. only pushing 31's so i don't need a WHOLE lot.


thanks for the input

 

[79k20350]

they make a 470????? i thought it was 670 and 770?

 

[amajor]

yep check out summit or the holley web site, 470, 670, or 770.
holley says the 470 will work on a v8 to 338cubes, an extra 12 isn't THAT much, right?

 

[SUPER'BURB]

More information about the motor would help make the determination of what type of cfm numbers are required.

Things like compression ratio, cam dimmensions and the advertised horse power of your crate motor.

I have known poeple with raced out 350's that required 1050 dominators to make good #'s and guys with mild motors that a 470 would have been perfect for.

WE WANT INFORMATION, INFORMATION, INFORMATION.........

 

[mrk5]

Personally I would contact Holley and ask them. That would be the safest.

I feel like you should run the 670.

I'd be more inclined towards the 470 if you were running a 305.

 

[beater_k20]

i'll agree, 670 minimum

 

[amajor]

it's just a crate motor straight form GM, basic internals. i was trying to go for the 470 for mileage purposes.
i have found a formula for finding ballpark cfm it is:
cfm= [(engine discplacement x max RPM's)/3456] x Volumetric Efficiency

so given a 350 turning 5000 max, and a generous VE of 85%
that would be
CFM= ~430

does any of this check out with you guys?

 

[diesel4me]

leaner=meaner!

I've run holley 450 CFM "economaster" carbs on 2 different 454's with excellent results on the street--lots of guys said "you'll melt the pistons",or "the valves will burn" because they thought it was too lean..they never pinged,or ran hot..and both ran much peppier than the ailing Q-jets they replaced..got 2-3 more mpg too..

To those who say a 470 CFM is "too small",I say "Bull"!..they made GM motors as large as 455 cubic inches with rochester TWO barrel carbs,that flowed only about 390 CFM's,and you don't hear of them having any troubles..Of course a larger carb WILL give more fuel and air,and consequently more power--but there is a limit to how big you can go as well..many of those 2 bbl motors not only gave better gas mileage--they also made more tourque than the 4 bbl versions!..

If you go TOO big,you can flood the motor with too rich a mixture--however,I've seen 1150 Holley "Dominator" carbs re-jetted that run well and deliver decent mileage--those huge barrels let lots of AIR in too,and by cutting back on the amount of fuel,mileage can be improved--at the expense of some ponies,but with those huge barrels you can get a lot of "bogging" if you open the throttle quickly..

Smaller CFM carbs keep the mixture velocity fast,and thats important for complete combustion and quick throttle response..I would not be one bit afraid to try a 470 CFM carb..many older AFB's were 425 CFM,and Holley makes a 390 CFM 4 bbl too..I've seen them on everything from 4 cylinder corvairs with aftermarket manifolds,to big block chevy's,and they run quite well with them..you won't get the same HP as a bigger carb,but close,and much better economy.. bigger isn't always better when it comes to carbs...

 

[mrk5]

This is from Holley Tech FAQ:

QUESTION How do I tell what size carb I need?
ANSWER You take the engine cubic inch and multiply by the maximum RPM and divide by 3456. If you have an automatic transmission you will need a vacuum sec. carb, a standard transmission can use a Double Pumper carb.

That comes out to 506.

Is the number based on wet flow or dry flow?

I know that Demon carbs cfm rating is based on wet flow, meaning that they flow rate it with a gas and air mixture. This results in a lower cfm rating because the gas displaces some of the air.

Where as most other companies use air only resulting in a higher cfm.

Hence a 650 Demon is roughly the equivalent of a 750 Holley.

So, that is why I would recommend contacting Holley. It's their carb, they know what it will work on.

You can make a carb that is too big or too small work, but it's going to take a lot of tuning.

My set up with 670 avenger is getting better than 11mpg, and that is running over the divide @ 11,000' + elevation.

 

[SUPER'BURB]

amajor,

The motor sounds like it is basic.

If you are not going to be spinnin the heck out of it go with the 470.

Just my thoughts.

 

[trailblazr81]

I would call Holley. But if its the base 190-240 HP crate motorthan a 470 would be fine. If it never see's over 5000 RPM, and you never plan to add intake, headers, cam than there would be no problems. I dont know that it will increase your mileage.

I run a Speed Demon 650 on a 383 thats pushing 425-450 HP. Thats what BG told me to use.

 

[dyeager535]

A q-jet is either 250 or 300CFM on the primary side, keep your foot out of it and your economy will be just as good as any smaller carb. Q-jets were used from the small sixes up to the 455's.

If anything, the one and 2 barrel carbs were used by GM to save money, nothing else. (hence the dualjet or whatever, the Q-jet with the secondaries cast shut)

I highly doubt that carb size, within reason, is going to net you any savings in economy. If anything, a properly tuned carb is going to make more of a difference than the flow rating.