So i have been trying to do some research on the topic of what carb is best to run. Currently i have a 500 avs edelbrock. Ive done some readings that a 390 is slightly more responsive and is worth a mph or so. I also have been looking at the 450 cfm carbs. What do you guys think?
Thanks

Well, this is up to the individual.Kind of like, some people like green apples and others prefer red. I first started with a 390 Holley but soon switched to a Edelbrock 500.Not a big fan of Holleys.I felt (to me) that the car ran better with the AFB.

If you are worried about overcarburetion, try locking out the secondaries by removing the throttle linkage. See if that feels any better to you.

_________________
Casually looking for a Clifford hyperpak intake for cheap.

The 450 cfm Holley carb I'm aware of is really stripped of features like a choke and a secondary accelerator pump.

If you want to get a fair idea of how a carb will respond in normal use look at the venturi diameter. Smaller being more responsive and economical in most all cases. For high speed output you want to minimize the pressure drop across the carburetor consistent with good mixture preparation (not too large a fuel droplet and not too small, but too large is usually the case). A 500 CFM carb will give a lower pressure drop all else being equal, but in reality it comes down to the function of the secondaries.

I would work with the 500 AVS before buying something else. The adjustable secondary air door is very much like the vacuum secondary of a Holley, but you don't have to change springs or replace torn diaphragms.

_________________
Joshua

I know that there are people selling venturi restrictors on eBay for the edelbrock performer that drop the CFM from 600/650 don to 500. maybe research if those will fit your carb and lower the CFM?

_________________
Casually looking for a Clifford hyperpak intake for cheap.

Personally, you couldn't give me an Edelbrock carb.

I prefer Holleys. Simple to tune, easy to get parts for, but also easy to screw up if you have no clue what you are doing.

I tested a 390 Holley against a 500 Edelbrock back to back, same day, same fuel, etc.. The Holley was a touch quicker and faster, but the Eddy was out of the box. If I had tuned on it it may have gone faster, but I don't like them so I quit on it.

That being said, you will see more street cars with Eddy carbs and more race cars with Holleys. Either one will work well if you know what you are doing, just as both will be heinous turds if you don't.

Do yourself a big favor and buy a good tuning book for whichever one you choose. It will make life much easier.

_________________
Official Cookie and Mater Tormentor.

Hey Big D! You can give me that 500. I'm lookin for a good one.

I couldn't tune a Holley to save me. And then by the time I got it close it would be time to tune it all over again! And again, And again!

_________________
2 Mopars come with Spark plug tubes. One is a world class, racing machine. The other is a 426 CI. boat anchor!

12.70 @ 104.6

Every four barrel Holley I have ever worked on leaked. Some more than others, but every single one leaked. I greatly prefer carter/edelbrock carbs. No leaks. No engine fires. Dead simple.

_________________
Casually looking for a Clifford hyperpak intake for cheap.

Here's the rub....

If you are not carb savvy and just want set and forget, you will be looking at the Edelbrock; AFB if you want to set the mechanical secondaries, or the AVS if you want the vacuum response... they can be tuned well up to a certain point... (Josh did a good job on the essentials)

Holley is for a person that has a good understanding of carburator function, is looking to dial the tuning in better (but they don't have as many items to tune in as a weber though...).

Overall, if you are looking for a naturally aspirated build, and for best compromise between mpg and power are the Holley 390 or the Edelbrock 500 are the choices here.

If it is strictly a track car then Holley 450 or 600 are fine (or 570 in some flavors), or the Edelbrock in 500 or 600 are good choices too, depending on what the build is...(a 600 on an 8.4:1 stock build is just not going to work so well...)

I can tell you on the holley side that out of the box, it's great for a V-8, but needs some rejetting, change the accelerator cam, change some of the base settings, and the power valve to put it on the 6 cylinder...(mostly because of the lack of 100 cubes...)

If you get a Holley at a swap meet and it was made before 1992 your will need to install a backfire protection valve, as they didn't make carbs with them up to that time, and one backfire without it will wipe out the power valve membrane and cause a nice rich leak. So that scores one back for the Edelbrock fans...but is easily remedied by a $8 kit and 15 seconds with a cordless drill and pump pliers duringyour carb rebuild...)

Having run a few different Holleys and a few different levels of slant builds:...on a mild engine the 390 is great, the 450 is too big (you will get all the power of the 390 and the gas mileage of a stock mopar 360 in a truck...)...
On a hi-po engine the 390 can still be used, but will be restrictive...so you will lose some power, but when tuned right, it will give you good mpg...
The 450, and 600 will give a lot less mpg, but if tuned for the power level they will give you the top power the engine could make.
(we should also assume that you have dialed in a good timing curve to support the style of build or driving you intend).


Going back to other comments....two barrels are simple, but they only flow X amount, the advantage on the 4 barrel is the primaries are usually smaller, so on the daily driver you will be able to save some gas sipping out of the smaller primaries...and only use the secondaries when passing aggressively, racing, or trying to be James Bond... As stated in many cases the primaries on the 4 barrel are smaller than the bores on the relatively equivalent 2 barrel (i.e comparing the Holley 350 vs. the Holley 390, and the 500 vs. the 600/625/650)

When tuning the primaries you can in most cases lock out the secondaries so you only run those for tuning....one item to note especially on holley is that you will save gas if you just turn the 4 barrel carb into a 2 barrel carb...especially if you have a lead foot...(if you added a quick change secondary spring pod during your rebuild...changing the spring to block will effectively lock out the secondaries on the daily driver engine and lighter hi-po builds.. and with the use of a phillips screw driver you can change it back if you need the other 2 barrels)

This is essentially true if you are one of those guys that has to tip into the secondaries to show Mr.Honda what you can do out of the driveway, and light to light... but when you look at it from the off pedal and idle perspective...the 4 barrel still has to have all 4 plates indexed to get the correct air into the manifold when not in the mains, and you have both primary and secondary idle circuits that still need gas, vs. the 2 barrel that just has one circuit to feed... so on the low end of the rpm scale not much savings there.

The AFB and AVS are essentially the same. The AFB air valve operates with a weight, the AVS with a spring. While the secondary butterflies are mechanically operated, the air valve controls whether the secondary comes in or not.
I've run both Holley's and Carters. You can only measure the difference at the track. The Holley can deliver a couple hundredths over a like sized AFB. This is negligible on a street/strip level build. The Holley can deliver a big punch on a race engine. If you drive it on the street, don't bother with a Holley.
The AFB is generally a better choice than the AVS on a slant. Getting the secondary spring right is exacting, and it will run best at the factory setting anyway. Just get the AFB. The only things that had to change on my build were the pump shot and metering rod springs. Everything else went full circle back onto the base calibration. This was true with the Carter set up as a 500, or as a 600. (Change the primary boosters, swap the primary jets and metering rods.) I run the heaviest springs on the metering rods that are available. This pulls enrichment in sooner.

My car runs 3/10ths faster with the Carter AFB set up as a 500 rather than as a 600.
It starves for air running the 390 Holley, and the Holley 600 doesn't run as quick as the Carter 500 by, you guessed it, 3/10ths.

Trust time slips, not your butt-dyno.

CJ

_________________
Part of Tyrde-Browne Racing