Im looking at carbs to finish my swap on my 383 this winter and im curious what the rest of you guys believe in. Im a big fan of holley and thats what im planning on going with unless you change my mind, im looking at the 850 DP.



thanks guys,
-john

 

We like ethier the trusty HOLLEY or the DEMON carb from BARRY GRANT!

 

i agree

 

850 is too big dont go over a 650 but i like the edellbrock

 

I agree. Somewhere (in a mag) there was a calculation to determine what size carb you'd need based on the maximum volume of airflow through any sized engine. It was dependant on displacement and maximum RPM, and even then, they said most engines only run ~85% efficient at best (I mean airflow capabilities) and for a 355 running 6500 RPM, I think that ~687 CFM is what it called for? So for a 383, you could probably get away with a properly jetted 750 CFM carb, but a 650 would probably work just fine.

FWIW, we currently have a 650 Holley mechanical double-pumper on my Dad's '73, and it seems to work really well. We had a 750 Edelbrock on it before, and it runs much smoother (and was easier to drive with the 4-speed) after swapping to the Holley. I'm sure it's all in the setup though?

 

Those formulas are good for making a safe choice so you don't over carburate, especially on stock and mild buildups. But aggressive engines make more hp with carbs that are supposed to be too big for them. Probably has something to do with airflow quality and not quantity.

My favorite carb is the 780 vacuum secondary Holley. Convert the secondary to metering block for jets, use a quick change kit for the secondary spring and tune it for your application.

The 750 Edelbrock is an air valve secondary, comparable to the vacuum secondary Holleys. Both will tend to be more driveable than double pumpers on street cars. Holley's ability to pull the needles out the top for cleaning, and tune the secondary opening, are 2 advantages over the Edelbrock/Carter.

 

For one of my motors, I decided to try a custom built carb. The motor was a 355, aluminum heads, 10:1, a fairly agressive hydraulic cam, all the usual crap. The shop wouldn't even consider anything over a 650. I really worked the guys over, but they wouldn't budge. He said they build custom carbs for maximum performance in all areas, including throttle response and driveability - the carb they spec'd out was a Holley 650HP - and that size was more than enough to supply a healthy 355. When they finished working it over, they flowed it, and it flowed 685cfm. I was extremely impressed with it, it was by far the best carbed motor I've ever had in terms of starting, throttle response, WOT, etc. From my experience, I'd say do not go over 750.

 

I used to be a diehard Q-jet man. However since going with a Holley 700 DP on our 350HO crate motor I'm a changed man.

 

My Holley performed a little better than the Edelbrock I have now, but it was an older Holley so one backfire ate the power valve up. I'd say go with Holley, they have better warranties than Demon and work a little better than Edelbrock. Plus, the new Holleys don't blow out powervalves. I'm going to run a Holley 750 on my 383.

 

An 850 DP is WAY to much carb for anything other than an all out race 383. I have a 750 on my 427 big block and it may be a little too small. But not by much. You need a 750 vacuum secondary carb MAX. Unless you are a carb wizard you will NOT get an 850 DP to run well.

Rich

 

http://www.bigsperformance.com/

 

I have run 850 dp, 830 annular dp, 800 dp, 780 VC, 750 dp, 700 dp, 650 dp
750 vc, 600 vc on my street 350 and the fastest at the track was the 850 dp, best all around was the 800 dp or 750 dp, everything smaller left alot of acceleration on the table, i even carried multiple carbs with me to the track
and made back to back runs, the 850 required alot of tunning out of the box it would not work well on my little 350, Id say go with the 750 dp if your not planning on tunning much and drivability is main concearn with little sacrifice of ET, those charts for calculating cfm are for stock motors, when you modify a motor correctly ve goes up and ultimatly the faster the air goes in and out the faster youll rev and the faster youll run

 

My dad's camaro has a holley spreadbore double pumper kinda rare but it works really good. I had a holley 750 on my old 396 bb and it ran great someone tried to sell me an edelbrock 750 and i tried it first....ran like crap. Go with holley or demon(little pricy though).

 

Im also a demon fan (and owner) but what is your 383 like? 850 sounds too big for a mild stroker, they tend to make better power with a slightly undersized carb then oversized... but that does depend on how radical the 383 is..

 

Large SR (havnet specd it yet cuz I havent got that far, lol) AFR CNC 210s, Converted Super Vic, 12:1 CR.


-john