BlackC3vette

I've been looking for a 650 CFM Holly for my 383, the Brawler 67256 has good features but down leg boosters. Actually it looks like all of the vacuum secondary carbs have the down leg. To me its like a coffee can with a hole in the bottom. Looking at the AVS2, it has the annular, but I don't know if I would be sacrificing performance with this Edelbrock? If you have the Brawler, input would be nice.

Please, don't respond with Q-Jet info.

4-vettes

OK, I won't reply with Quadrapuke info. The best thing I ever did, (At the time) was throw that Quadrapuke into the woods and never went back looking for it!
None the less. A 650 Holley on a 350 is a bit undersized. A 383 with any kind of cam at all and that 650 is REALLY undersized!
Think 750 - 800 CFM.
Just my 2 cents.

Jebbysan

Holley 0-90770 770cfm Truck Avenger or the Holley Street HP 750….
The truck avenger has annular primaries…..best out of the box carb Holley makes but the Street HP has removable air bleeds for fine tuning…..
Don’t get hung up on annular boosters…..the Street HP is a dedicated performance carb unlike the AVS2…..

Jebby

randallsteel

I had the edelbrock 650 AVS2 on my sbc for 4 years, I had it dialed in too. Started/idled/ran perfectly regardless of outside temp.
I switched out to a Holley for more flow at higher rpm’s.
Honestly the AVS2 did better with cold starts and cold idling. But maybe I just haven’t got the Holley dialed in yet.
no difference by seat of the pants feel at WOT.
I hit the dragstrip in two weeks so I should be able to see then.
So far I think the AVS2 is a better “all around” carb then the Holley, but I’m relatively sure the Holley is going to be faster.

Rescue Rogers

Ive owned all 3 general carbs...currently i would go with holley just because you can find parts for them pretty easily....but theres a lot of things you have to learn to tune them...

Edelbrock are fine but You have to buy all the jets and needles and do pretzel brain math

I switched from the quadrajet spreadbore to a holley and loved it.

Stick with a 750, the carb will use what it needs

Best thing you can do to make this all easier is to het an AFR gauge

Stormin_Normin

For street, I would stick a 800 CFM Edelbrock on it. You need at least 750 cfm on a 383, I ran a Holley 770 on mine and it was a bit too small.

Edelbrock carbs are easy to tune, every Holley I’ve run has been a battle to get squared away.

BlackC3vette

Thanks for the input, I am glad I don't need the carb right now so I can look at the suggestions. I had an Edelbrock on a streetrod 350, and I liked the easy cold start and the overall performance but it was a mild build. The 383 was put together for low end torque. Brodix 180 heads, intake valve lift =0.50, its not setup for racing just good street performance. Several of the techs at Holly told me that the 670cfm brawler would be more than enough carb. That's when I posted here to get real info.

BlackC3vette

Hello Jebby,
I did look over the two carbs and the Street HP looked great, I just don't think the choke situation would work for me. Anyway I think the SS-780-VS has the features I am looking for. Any thoughts on the SS-780?
Thank you for you input, I know you have helped many on the forum.
George

76strokervette

Here is old article on booster differences. I pefer the annular for throttle response and the improved signal, both work.https://www.motortrend.com/how-to/carburetor-showdown/

brentry

Depends if the carb is the restriction . My kids mustang went same ET with a 750 and a 650he had a very small duel plane on it at the time .

BlackC3vette

Thanks for the reply. I am very familiar with the advantages of the annular. I am just trying to narrow down choices on a holly carb.

BlackC3vette

Well if I believed my manifold was a restriction, I would of replaced it. I did have a 67 Mustang fastback with a 289, it had a 600cfm holly, cam, headers, intake, upgraded ignition on it and it was a animal.

brentry

What does matter is flow at valve lift, with intake and carb on. Fortunately I can test this

which one flows more Ported duel plane or the single plane. Tried many sspacers on both and 2 carbs

BlackC3vette

Wow, Please, I am just trying to narrow down Holly carb choices

brentry

Maybe fine with the 650

7t9l82

In what way is a 289 Ford comparable to a 383 Chevy? Everyone for the most part has said a 650 is too small. and the.cold start on an Edelbrock is. Better how?

JC 1975

I have a FST RT-X 750 cfm carb which is a Holley style carb AND I LOVE IT!!!!

I had a Holley 750 vacuum secondary with the choke horn milled off to aid in airflow. Anyway, it took more to start it and it would surge quite a bit before the engine finally warmed up. And insult to injury this carb was professionally rebuilt by a “reputable” carb builder. Right out of the box my FST starts the engine right up and immediately idles at 700 rpm. No surging, no fast idle then slowly settling down. Just rock solid idle quality.

It is a weird duck COVID carb as it came with 3 port billet metering blocks and you can only get 2 port with this specific version.

76strokervette

I don't know the power level of your 383 but I would say anything over 400 hp the 750 would be my choice. The edelbrock is a 4 circuit carb with loads of adjustibility and looks like a pretty good piece.

BlackC3vette

HP is about 420 to the flywheel. I originally posted 650 CFM pretty much knowing it would generate some comments , I agree with the 750 -800.
I was looking at the:
800 cfm Edelbrock - it does have the annular boosters
Quick Fuel SS-780-VS - Down leg boosters but it has the 4 corner, vacuum sec - screw adj., sight glass, changeable air bleeds, electric choke, etc. But much higher price to match the features.
750 Speed Demon (SPD) - down leg
770 Brawler BR-67258 - down leg
If anyone is current running one of these, please advise.

BlackC3vette

Is the version a vacuum secondary that only has 2 vacuum ports? Is there a port for power brakes?