Performer vs AVS Carb's

[Paul Keller]

Am considering upping from the current 500cfm to a 600/650cfm (yes, I am aware of the diff in low speed performance and smoothness). Has anyone tried both the Edelbrock Performer and the AVS? It would seem (that has got me into trouble several times) that the AVS, w/ its adjustable vacuum secondaries would potentially be more more tunable to specific driving conditions and engine.
Any experience and/or viewpoints would be welcome.
Paul K

[Gunslinger]

The AVS is more tunable, but for most driving...i.e., non-sporting, it offers little advantage. They're both excellent...the AVS is simply a somewhat more refined Performer. Unless you want maximum street performance, it offers little advantage. If you like tinkering for the little bit of extra adjustments, go for it.

[sbca96]

I never had any low speed performance or smoothness issues of any kind running 600
series Carters on Studebaker 289s. I am pretty darn sure the factory Carters were in
the 625 range. This is on stock engines and built ones.

A friend tried an AVS carb years ago, unfortunately data was hard to determine since
he had ongoing dealing (oops:sealing) issues with the "R3" aluminum intake he bought.

Tom

[bezhawk]

The old Carter AVS's didn't have secondary venturi boosters, just brass tubes angled into the airstream.
Probably not very good at fuel atomization.
I had one on a 64 Daytona and it worked well. Better than the worn out AFB that was on it. I couldn't say if a new AFB would have worked better.
The newer Edelbrock AVS's DO have secondary boosters.....probably more efficient and smoother transisition. However the secondary air valve has more and larger notches to clear the boosters, and might not be as responsive to airflow opening it .....It might have too much airflow even when closed and cause a bog when secondarys are open.
If it doesn't, then It would be a good choice for a carb.
The secondary air valve is adjustable if need be.

[Mike Van Veghten]

You're funny Tom..

Do you even have any experience with a 500 cfm carburetor..?
I'd suspect not from the way you talk.

Now....just how do you know if your engine might not just be a little peppier with a more proper carb. size...being that you have no experience to draw from ?

See...I do. And yea, even a 650cfm carb. On a stock engine...they are very noticable in the way they react to the throttle.
That's why my Lark engine has an Edelbrock....500cfm carburetor.

Now the hot rod engine I'm building for my Conestoga wagon...yes, I've got a new 650cfm carb. BUT...I bought the "annular booster" version so the booster signal is a bit stronger to help with the weaker signal the booster will receive from the slower airflow.
Plus, my heavily ported heads, one off intake manifold (well, I think there is about 5 of these manifolds out there..), R2+ cam.
Plus my loose converter, plus my 5.15 (about) gear ratio, plus the T-200-4R transmission.

Paul, Tom -

The above is what it will take to make a 600+ cfm carburetor....work "well" on a small engine, unless of course, a supercharger of some kind is bolted to the manifold.....

Will a 750cfm carburetor work on a 289....yes, it will....but.........

Mike

[leyrret]

It appears the many of older AFB's (at least aftermarket) have same size primary throttle bores and venturi. Not sure if it applies th the later Edelbrock. From this it seems there would be little or no difference in low end performance with properly control secondary

[sbca96]

You're funny Tom..
Do you even have any experience with a 500 cfm carburetor..?
I'd suspect not from the way you talk.
Now....just how do you know if your engine might not just be a little peppier with a more proper carb. size...being that you have no experience to draw from ?
See...I do. And yea, even a 650cfm carb. On a stock engine...they are very noticable in the way they react to the throttle.
That's why my Lark engine has an Edelbrock....500cfm carburetor.

How do you know your Lark wouldnt run better an elephant riding in the
trunk if you have never tried it? The way you talk, I would assume you
have absolutely no experience with elephants. Report back when youve
done considerable research on where the elephant is best positioned.

Thanks!

Tom

[Paul Keller]

Wondering if Mike V.V. has a 650 cfm Holley or similar design (Demon, etc.)? Yes, the 500 Edelbrock runs quite nicely on my old and very tired 289. However, moving up (hopefully) to a slightly mod'd engine, it would seem that possibly it could tolerate a bit more fuel/air. The question is then, try for Performer or an AVS.
Another question - Have been told that Holley carbs are a pain to fit (physically) to a Stude' engine. Any truth to this and if so, what is neededto adapt them to this fine automobile?
Thanks for all your info - extra minds often bring in extra info.
Paul K

[bige]

[QUOTE=Paul Keller;509185]Am considering upping from the current 500cfm to a 600/650cfm (yes, I am aware of the diff in low speed performance and smoothness). Has anyone tried both the Edelbrock Performer and the AVS? It would seem (that has got me into trouble several times) that the AVS, w/ its adjustable vacuum secondaries would potentially be more more tunable to specific driving conditions and engine.
Any experience and/or viewpoints would be welcome.

The biggest difference in the two is the adjustable secondary air valve. Edelbrock's and AFB's do not have vacuum secondaries they are mechanical opened by a spring as long as the choke is fully opened they will open all the way no matter what RPM the engine is turning. The air valve keeps your engine from bogging by limiting air flow until the engine needs it. You could say the air valve is vacuum operated but they are pushed open when air demand becomes more than the primaries can handle. It's rare that an Edelbrock even one too big for the engine, properly jetted, will bog an engine when the secondaries are opened. You would want a Thunder Series (AVS Style) if your engine could handle a faster opening secondary air valve without bogging. The only way to adjust a perfromer's air valve is to grind away some counterweight and if you over do it you need a new one but with the Thunder you can dial in a faster opening thus feeding the engine quicker and possibly improving acceleration.

The reality of it is that with any of the Edelbrock Carbs your engine will only get what it can use. You will not draw 650 CFM from the Thunder or 600 from the performer because the air valve on either will only open to a point that the engine can handle the incoming air and the CFM will be whatever that is.

I don't know your engine, trans, rear combo but I would say that you would gain nothing from a carb switch unless you had some very low rear end gears, a very low 1st gear ratio or very high stall speed converter hooked up to a quick reving engine.

Just to continue to beat this dead horse the only advantage in tuning is the air valve, the rest of the carb is basically the same as the Performer, and you would tune mainly for more air/fuel at lower RPM.

I have a Thunder 650 on my El Camino only because I was able to grab one on ebay for $75 ( long story ). I've had a 600 Performer on it as well as a vacuum secondary 750 Holley. Why it's on there has nothing to do with me trying to gain any performance and I won't bore you with the story but Performer and the Thunder perform exactly the same on my 350 el Camino. The Holley was just a placeholder and was set up for a 460 Ford so I can't give you a good comparison on Holley vs Edelbrock.

Save your money.

ErnieR

[sbca96]

Due to the location of the fuel bowls, Holleys tend to leak, they also are not a plug
and play carb, usually requiring adjustments from time to time. If you want to just
slam the hood and forget : a 600 series Carter or Edelbrock AFB will do you well.

Tom

[Gunslinger]

IMHO, Holley has been riding along on their past reputation for years. Not that they build a bad product, but I don't think they're the best...maybe in some applications. I've heard Demon carburetors called "Holleys that work".

While a Holley and Demon carbs might be good for full out high performance, I think the Edelbrock Performers are far better street carburetors. They're simple to adjust and hold their adjustments. Holleys are simple to adjust as well, and guys running Holleys do adjust them often...because they need to.

The one carburetor not mentioned which is the best of all for drivability, street performance, economy, etc., is one Studebaker never used since it hadn't been developed yet...the Rochester Quadrajet. The small primaries and huge secondaries made for a great carburetor. It's been so many years now it's difficult to find a good Q-Jet core and not many know how to get the best from them anymore and even fewer can rebuild one properly. Edelbrock made a clone of the Q-jet but discontinued them several years back.

Quadrajets notwithstanding since they're no longer available new and that Studebaker never used them, I think for the street, Edelbrock Performers are best, followed by Demon and Holley. Just my opinion.

[Mike Van Veghten]

Paul -

No, my new carburetor is a Quick Fuel version of the Holley. It's got the "annular" boosters that I mentioned. I've used that type in the past with a good outcome in slightly oversizing carburetors.
This type booster works well with the lesser airflow of an oversized carb.
And no....as a noted poster above states...in my past 45+ years of tuning many different style carburetors, the Holley (or the type) is my favorite...and according to..., well, I must be doing something wrong, because the only time my Holleys have leaked, is when I take a bowl off. Then...yea, they piddle a little. Nothing a rag won't quickly despense of.

As mentioned, by the math, even a good running engine of 290-300 inches, at 6000rpm, at .90% effency wants "less" than a 500cfm carb.
So...you've got to ask yourself..
1. What's my engines cubic inches?
2. What will be my maximum rpm (be TRUTHFULl !)?
3. What is my volumetric effency (most probably around 75% to .80%)?

I'd guess, you wont spend much time with the tach needle above 5500rpm...no need for a large carburetor.

Ok....lets look at the positives of a big carb. -
1. Bragging rights
2. may feed my engine enough air and fuel to turn to 6500rpm (most Studes won't).

...all I can think of

Ok..lets try this again (only shorter !).

Negetives of a large carburetor -
1. Poor, around town driveability (as compared to..)
2. Poor gas milage (as compared to)
3. Initial throttle tip-in will be...not as crisp or peppy as it could be, (as compared to...)
4. More time to correctly set up "properly". Meaning, not just ok, but properly.

If you really want a large carburetor, (but need a smaller one) !! Do this, it'll cost less, proove a point and you can pick the best method for you.

Buy a 500cfm carb. of your choice. Then buy a 2.00", "open" spacer (if the hood will allow !).
The engine will react very much the same as it would with the larger carb. That is, lower or less signal or air speed to the carb's booster ventury. A standard booster is designed to work at a specific range of airflow speeds. If it gets too low, it doesn't know that it's still supposed to still flow fuel. The airspeed isn't fast enough to pull the fuel out of the booster.
Can you tune this out,...yes...but milage will suffer greatly when done..."correctly". If done to just get by....milage will still suffer, but not as bad...and the performance will also suffer some.
With this method, you can play with things a bit without buying a 600 or 650cfm carb., then not being sure. You'll never REALLY know how the smaller carburetor will work...because you don't have one..!

On one hand, using a "slightly" larger carb. than the math tells us to use is fine. BUT, if you look at the math....the 500cfm carb. is already........larger than the math tells us to use.!

Back to the spacer....if your "seat of the pants" dyno is good, you can actually feel the difference with a 1/2" spacer, vs. without. So a 2.00" open...will really change things.

As I noted before...you "can" run a 750 carb. It will run, and if tuned well, will "almost" feel ok, as far as "driveability". Just not nearly as good as it could.

All in all...a too big a carburetor can be somewhat sucessfully used in a light, four or five speed (trans.), with a LOT of rear gear (4.56 or lower) car, that's used to most always go fast...not to be driven around town or to car shows.

For what it might be worth, I've been porting heads and intakes for "many" years, experimenting with carburetors, and spacers. It will get expensive and sometimes frustrating playing with all this stuff...weather on the street or on the track. I've learned that while the "math" isn't always correct, it's a very good starting point.

And the math says to use a 485cfm carburetor for 300 cubic inches, 90% volumetric effency, at 6000rpm.
You've got to ask yourself (and be honest)
1. how big is my engine?
2. how often will the tach needle be above 5000rpm?
3. what is the internal condition of my engine and what IS...its effency? Most street cars are in the 75% to 80% range if they've been on the street a while.

Good luck.

Mike

P.S. - please excuse any poor spelling...

[Felix Benet]

hey ya know what FoMoCo line mechanics called the late and not lamented VV carb??

Wondering if Mike V.V. has a 650 cfm Holley or similar design (Demon, etc.)? Yes, the 500 Edelbrock runs quite nicely on my old and very tired 289. However, moving up (hopefully) to a slightly mod'd engine, it would seem that possibly it could tolerate a bit more fuel/air. The question is then, try for Performer or an AVS.
Another question - Have been told that Holley carbs are a pain to fit (physically) to a Stude' engine. Any truth to this and if so, what is neededto adapt them to this fine automobile?
Thanks for all your info - extra minds often bring in extra info.
Paul K

[Felix Benet]

The 500cfm ECarb on my R-1 works well[QUOTE=bige;509477]

Am considering upping from the current 500cfm to a 600/650cfm (yes, I am aware of the diff in low speed performance and smoothness). Has anyone tried both the Edelbrock Performer and the AVS? It would seem (that has got me into trouble several times) that the AVS, w/ its adjustable vacuum secondaries would potentially be more more tunable to specific driving conditions and engine.
Any experience and/or viewpoints would be welcome.

The biggest difference in the two is the adjustable secondary air valve. Edelbrock's and AFB's do not have vacuum secondaries they are mechanical opened by a spring as long as the choke is fully opened they will open all the way no matter what RPM the engine is turning. The air valve keeps your engine from bogging by limiting air flow until the engine needs it. You could say the air valve is vacuum operated but they are pushed open when air demand becomes more than the primaries can handle. It's rare that an Edelbrock even one too big for the engine, properly jetted, will bog an engine when the secondaries are opened. You would want a Thunder Series (AVS Style) if your engine could handle a faster opening secondary air valve without bogging. The only way to adjust a perfromer's air valve is to grind away some counterweight and if you over do it you need a new one but with the Thunder you can dial in a faster opening thus feeding the engine quicker and possibly improving acceleration.

The reality of it is that with any of the Edelbrock Carbs your engine will only get what it can use. You will not draw 650 CFM from the Thunder or 600 from the performer because the air valve on either will only open to a point that the engine can handle the incoming air and the CFM will be whatever that is.

I don't know your engine, trans, rear combo but I would say that you would gain nothing from a carb switch unless you had some very low rear end gears, a very low 1st gear ratio or very high stall speed converter hooked up to a quick reving engine.

Just to continue to beat this dead horse the only advantage in tuning is the air valve, the rest of the carb is basically the same as the Performer, and you would tune mainly for more air/fuel at lower RPM.

I have a Thunder 650 on my El Camino only because I was able to grab one on ebay for $75 ( long story ). I've had a 600 Performer on it as well as a vacuum secondary 750 Holley. Why it's on there has nothing to do with me trying to gain any performance and I won't bore you with the story but Performer and the Thunder perform exactly the same on my 350 el Camino. The Holley was just a placeholder and was set up for a 460 Ford so I can't give you a good comparison on Holley vs Edelbrock.

Save your money.

ErnieR

[Paul Keller]

Thanks again for the clarifications and added info. As an aside, Holley makes a new replacement for the GM version of the quadrajet (it is listed in either Speedway or Summit's catalog - Had not realized that it may be a possibility.
Paul K