I replaced my Holley 750 with a Street Avenger 670. My milage has improved 25%, as well as improving the power. My primary use is daily driver, but still wanted to run a high to mid 12 ET. In addition, the electric choke really makes the big cam motor easier to start in cold weather.

400HP 350, .30 over, 10.4:1, Comp Cams 278/284 .500 high energy cam, MSD ignition, etc... I have ben very happy with the balance.

Was your 750 a DP?
I have a 750DP and hate watching the gas needle. I too feel a different carb would be best.
Did you go with the Holley Part 0-80670 (http://www.holley.com/HiOctn/ProdLine/Products/FMS/FMSC/0-80670.html) ? How much did you pay? $359 at summit

I like the idea of square bore and vacuum secondaries. What I don't understand is the 670 says up to 400HP, well my 465HP engine I would have to probably go with a 770 version instead, but do I really need too? If I go with the 670 am I just going to lose a little HP? Or would I risk hurting the engine at full throttle?

I certainly don't want to start any arguements, but it is no surprise to me that your milage went up... that 750 carb was too big for that motor. I think we are all guilty of over-carbing the motor at one time or another, but I have seen very few 350 motors that NEED a 750, but yes, many are run with them! Some of the items you have listed are the results of a properly sized carb that keeps the air velocity up and metering circuits working correctly.

Brian,
Your 383 motor looks to be about on the edge as to which carb to use. I think you could go either way, but you might fall off just a hair on the top end if you go with the 670. It won't hurt the motor, it might just limit the power the motor can make at higher rpms. One thing to remember is that you can put whatever jets you want in there, so you can dump as much fuel as you want, but it's getting the air in that might be a problem. For that reason, I'd say you probably want to go with the 770 carb. Then you can jet it down a bit and be ok.

Best of luck guys,
Bill C.

I also changed my Edelbrock 600 for the street avenger 670. I am pleased with the unit with the exception of the high idle when you first start it up. It runs around 1800 for a bit until you give the accel a kick and then it drops to around 1400 and then eventually to 800. I haven't paid much attention to gas mileage but that problem is due to my heavy foot. I did replace the springs to the lower pressure for the secondaries to open sooner. I paid $305 through ebay and it was brand new. I did have a minor gas leak at the rear input but it appears to be ok now.

Mister G there's a fast idle adjustment on that carb. You should be able to dial it down to 1200 or so you don't have to worry about grenading that cold motor. graemlins/beers.gif

i have a mild 327 with 218/218@0.050" cam, headers, intake and holley 4150 DP 600cfm. A friend gave me a 4160 vacuum sec 600cfm. I'll install it on the car to gain mpg.

i'm mostly cruising the car on w-e and sometimes i enjoy reving it up. oh i have a M21 with 3.73 gears.

i' d like you tell me the driving differences (throttle response) and mpg differences between a holley street avenger, holley 4160 vac sec , and edelbrock 600 cfm.

does a street avenger has 2 accelerator pumps?

thanks to tell me .

Marc

Originally posted by Mister G:
I also changed my Edelbrock 600 for the street avenger 670. Were there any other positives or negatives with the Holley over the Edelbrock?

Fuel ecomomy or lack of, is more the result of proper tuning and driving habits than carb size.

Obviously you don't really want to over carb, but if you have a larger vacuum sec carb don't run out and buy a new smaller one just for better mileage. Remember the flow rating is the carbs max potential. Learning to tune your carb properly can save you the expense of a new carb and net you the same results. I run an older vacuum sec 780 on my 383 and have seen 23-24 mpg keeping my foot out of it. I ran the same carb on a 350 before the stroker and chevy put the 780 on several SBC's back in the day.

If your running a double pumper that's another story as the secondary side of the carb is mechanical and isn't as flexable.

If you are in the market for a street carb the "Street Avenger" series is building a very solid following!

please tell me ..

Originally posted by Marc:
i have a mild 327 with 218/218@0.050" cam, headers, intake and holley 4150 DP 600cfm. A friend gave me a 4160 vacuum sec 600cfm. I'll install it on the car to gain mpg.

i'm mostly cruising the car on w-e and sometimes i enjoy reving it up. oh i have a M21 with 3.73 gears.

i' d like you tell me the driving differences (throttle response) and mpg differences between a holley street avenger, holley 4160 vac sec , and edelbrock 600 cfm.

does a street avenger has 2 accelerator pumps?

thanks to tell me .

Marc i think Marc wtill would like to know if it has 2 accel pumps,
I have no clue as i have not seen this carb yet

Holley web site does not mention the accelerator pumps at all.
http://www.holley.com/HiOctn/ProdLine/Avenger2.html

I am no carb. guy by any stretch but will say...

I have read where the old 3310-, 750/780 vacuum secndary Holley carb's. are right out of the box for the 375/hp396!!

So, yes, I would say tuning to go on any other engine that isn't like that is in order!!!

And as Honest Charlie used to say, "the 3310- is the runninest carb. ever.!!"

Sure I like the new and improved carb's. but NOT their costs!!! As for the big carb's, the old, 950cfm three-barrel gets my vote when she's tuned right!!

I bet for the majority of mild 327/350 motors, a good old 600cfm, 1850 Holley vacuum secondary carb. will do fine unless you rpm you motor above its rating...

As always, jmho... pdq67

No vac sec carb has 2 accel pumps because the sec's open gradually. The accl pump is needed to supply additional fuel when the throttle blades is opened because air throught the throttle bore moves faster than fuel through the carb. Without the squirt the engine would go lean and fall on it's face. Same when mechanical sec's are used, hense the double pumper...

Vac sec carbs are a demand system and very forgiving, unless the primary side of the carb is too big for your engine you can run one without the effects of being over carb'd.

I just replaced a Bary Grant 750dp with the 770 Street avenger.
What a big change, so much easier to drive.
Easy starts and runs a little smoother.
Now, it doesnt dump quite like the dp did when ya stomp it to the floor but thats ok.
I am very pleased with the unit.

"I bet for the majority of mild 327/350 motors, a good old 600cfm, 1850 Holley vacuum secondary carb. will do fine unless you rpm you motor above its rating...

As always, jmho... pdq67 "

>>
Well that's OK then , as my 4160 is a 1850holley.

I hope i will improve my mpg a lot 'cuz now, i get about 12 mpg. while still having smooth funny driving.
In Belgium, 12 mpg this is insane ! thankfully i don't drive it much.

Thanks guys for the info smile.gif

Marc

Marc,

What does gas cost over there, $5.00 a gallon?

today at the pump it was 0.94 € for 1 liter. for 95 octane gas (the lowest here). It is less expensive then what you thought.
98 octane is 1€ / liter.
Diesel is 0.75 € /liter.