Edelbrock AVS2 650 vs Holley 600 Vac Sec (1850) - Track Shootout

[66 Sat]

Well the results are in from my Edelbrock AVS2 650 vs Holley 600 Vac Sec (1850) - Track Shootout, and the results aren't what I was hoping for.

My car in full street trim, 3.23 rear, "street" take-off (i.e. no burnout, slow) ran the following fastest times:

14.104 @ 99.80 - Holley
14.418 @ 98.54 - Edelbrock (down 0.314 sec / 1.26 mph)

Avg times as follows (3 runs each):

14.262 @ 99.44 - Holley
14.558 @ 97.65 - Edelbrock (down 0.296 sec / 1.79 mph)

Now I should say that after some teething troubles the Edelbrock is a great carb on the street, easy to tune, sharp throttle response and "feels" fast, but it doesn't do the numbers of the Holley.

The only tuning the Holley has is some 68 primary jets in lieu of the 66 jets it came with.
The Edelbrock has bigger secondary jets and thinner metering rods (I bought the tuning kit and have been playing around with it for optimum response).

The numbers are in line with conventional wisdom but still a bit disappointing as the Holley is the most bland 600 they make. Single fuel feed, side hung floats, not really a performance carb, but it still outperformed the Edelbrock.

It's also disappointing as 0.11 second / 0.20 mph will get me into high 13 secs / 100mph and my target has always been 13.5 @ 105 mph so it would be nice to move in the right direction, not the wrong direction.

 

[DanielSlocum]

A breakdown/analysis of what portion of the 1/4 mile you were slower [if not every segment] might shed some light on the reason. For example....sometimes a smaller carb will produce better torque resulting in better e.t.s at 60 ft, 1/8th etc. . I think using an air-fuel ratio meter to tune both carbs perfectly before testing them against each other would be much better. If one is richer or leaner than the other....using them on a larger or smaller or more radical engine could easily give the opposit reults i.m.o. .

 

[Rebelrouser]

I agree never seen that much difference. I ran NSS for years and was way down in the 9's with AFB style carbs, and so were a lot of other guys.

 

[Rusty knuckles]

I find I hard to believe your A/F ratio was right or something else in the carb tune. I'll buy the AVS is a touch slower. I'm not buying 3/10ths slower apples to apples.

 

[Bee1971]

I was going to ask you this very question when I saw your post the other day on another thread about your Edelbrock when you mentioned it

Did you pop the top on the Edelbrock AVS2 and look it over , brand new out of the box before you installed it - Quality control is horrible on floats , jetting , baffles

Anyways I was watching this video a few weeks ago - Not apples to apples , but

 

[66 Sat]

I saw that video in the lead up to buying the AVS2. I've got nothing against the AVS2 - in fact I've come to love it. I pulled the top off before installation and set the floats. It ran like crap at part-throttle, contrary to what these carbs are meant to do with the smaller primaries and annular boosters. I pulled the top off again, removed the boosters and soaked them and blew them out. Low speed response was transformed, carb felt sharp. There must have been flashing or something partially blocking the tiny holes in the boosters. Pulled the top off again a few months later and did the same with the secondaries (should have done it the first time), nothing was wrong with it at this stage but I was just tinkering.
This winter I noticed some detonation on medium acceleration up hills etc. Timing was fine, thought the carb was leaning out. Bought the tuning kit and followed the chart. Did 3 different trials with metering rods, springs and secondary jets. No A/F ratio, just sound, smell and feel.
Detonation cured after Trial 1 (Secondary Jets 1 stage richer, different metering rods, different vacuum springs), but was too rich.
By Trial 3 I had it nailed, no detonation, no smell, feels very sharp.

The only Cons I have for this carb is that the fuel evaporates out of the bowls much quicker than the Holley when parked for a few days, and it's track performance. Other than that I love it.

For simplicity I've only listed the averages in the below - I've been doing my own analysis with a spreadsheet as:

Holley
60ft - 2.350
330 ft - 6.188
1/8 mile - 9.307
MPH - 79.127
1000 ft - 11.993
1/4 mile - 14.262
MPH - 99.440
1/8 to 1/4 mile time - 4.976
1/8 to 1/4 mile MPH - 20.31

Edelbrock
60ft - 2.332
330 ft - 6.230
1/8 mile - 9.391
MPH - 78.130
1000 ft - 12.119
1/4 mile - 14.424
MPH - 98.235
1/8 to 1/4 mile time - 5.033
1/8 to 1/4 mile MPH - 20.11

You'll notice the averages have improved for the Edelbrock - I've only averaged 2 of the runs (which were very close) as the 3rd was out by a bit and is throwing off the figures.

There's really not much in it and it's mostly in the first half of the track.

I'll be out again in 2 weeks so will see what figures I get then and update for anyone that's interested.

 

[Geoff 2]

I read the AVS2 owners book, & unless I missed it, I could see no reference to the Air Valve tension/adjustment. I would tighten it, & a significant amount; not 1/8-14 turn, but 1/2 to a full turn.

 

[70bigblockdodge]

Air valve adjustment. As mentioned tighten it up, too much then start loosening it till it falls on its face at launch then tighten back up a little. Should get you closer to Holley, maybe better depending on how well vacuum pot is working on Holley.

 

[lewtot184]

I use the old factory avs air valve adjustment on the newer carbs. I turn the adjuster to where the air valve touches the top of the carb and then go 2 1/2 more turns as a starting point. I've found that the 2 1/2 turns to be close to ideal in my cars.

 

[qkcuda]

This is not news to me. When I was racing Holleys always beat similar Carters, and did not have the heat soak/hot start problems on the street. I was running 12.9's on a fairly stout 360 with a 750 Holley DP. I sold the car and the I met the guy who bought it at the track several months later. I asked him how it was running and he said the first thing he did was replace "that POS Holley" with a 750 AFB. I watched him run 13.4.

I recently did a dyno test on my new mild 400 build, and I ran three carbs back to back. The dyno operators 650 Holley DP with stock jetting made 419.2 lb/ft of peak torque and 340.4 peak horsepower. The 625 AFB was 400.4/325.5 and my 625 Street Demon was 407.1/335.3. Before you ask, the A/F ratios on the AFB and SD were very close. That said I am still going to be running my Street Demon on the car because of its small primaries.

 

[lewtot184]

Back in the day I used to beat on my 383 road runner. A 4618 avs and a 780 holley ran identical times, 13.22. I think there is more to the story with the OP's results. There shouldn't be a big spread with those two carbs.

 

[Geoff 2]

A friend bought a 'Chinese' 600 cfm AFB. Other than sight glasses added to the sides of the float bowls, it looks like any Carter/Edel AFB. It also came with three sets of jets, largest being 0.110".

Hmm, 0.110?

The AFB sec bores are 1 11/16". The 650 AVS2 is 1/16" larger, at 1 3/4". I always thought the sec jets of 0.098" were on the small side for that size bore. So I would also try larger sec jets such as 0.106", even if you have to drill them.

 

[66 Sat]

A friend bought a 'Chinese' 600 cfm AFB. Other than sight glasses added to the sides of the float bowls, it looks like any Carter/Edel AFB. It also came with three sets of jets, largest being 0.110".

Hmm, 0.110?

The AFB sec bores are 1 11/16". The 650 AVS2 is 1/16" larger, at 1 3/4". I always thought the sec jets of 0.098" were on the small side for that size bore. So I would also try larger sec jets such as 0.106", even if you have to drill them.

The tuning kit comes with different size jets. I've already gone 1 stage richer in the secondaries (to 0.100). The biggest ones in the kit are 0.104 which is 3 stages richer). Why would I want to go larger than this again?
Also the air door spring was the first thing I tightened 6 months ago, to get rid of the huge bog when I opened up the throttle fully at speed.
The carb is set up perfectly for the street now. I'm loathe to make changes just to match the Holley at the track. I was just hoping it would do both.
I also have a 700 Holley Double Pumper. I might put that on before my next outing and see what it does.

 

[Geoff 2]

The reason you play with jetting......is because every combo is different. And you do not know until you try......
Many people think that [ erroneously ] a carb taken from a small engine & used on a bigger engine will need bigger jets. Maybe. Maybe not. Anybody who has the MP engines book can see an example of this. In the BB carb section is jetting for a TQ on a 400 engine uses a 0.137" sec jet. The same carb in the same book on a 340-360 has a 0.169" sec jet!!! That is a huge increase in fuel flow area.
I am just including this to show.....sometimes things ain't always as they seem...

 

[lewtot184]

What I've noticed looking at edelbrock catalogs is the difference in primary jetting. I think the ootb jetting on the power circuit of the avs2 primaries is too rich. I do the math on that stuff and the avs2 has over 10% more jet area than 1405 and they both have the size primaries. 10% on a gasoline engine is a big deal. I'd try a 70x47 rod. Too much jet will slow'em down as well as not enough. Edelbrock taking over the Carter afb carb is a mixed bag and sometimes I think Edelbrock has been a curse for that platform. Keep in mind that edelbrock won't produce any universal parts unless they're a good fit for a small block chevy.

 

[Bee1971]

So what would flow more fuel
Edelbrock AVS2



Secondary Jet .104 and .068 X .047 Rod

Or

Secondary Jet .107 and .068 X .052 Rod

And for mid to wide open throttle , are you better off concentrating on primary circuit or secondary circuit

Take those two examples above

 

[RemCharger]

The 700 DP should be interesting. If I had the choice I'd try the 4779.
You're 60' is quite down, should be easy to get that 13 with a good launch

 

[lewtot184]

So what would flow more fuel
Edelbrock AVS2



Secondary Jet .104 and .068 X .047 Rod

Or

Secondary Jet .107 and .068 X .052 Rod

And for mid to wide open throttle , are you better off concentrating on primary circuit or secondary circuit

Take those two examples above0

Mid to wide open should be the power circuit, if the proper step up spring is used. For this carb I'd do .100 primary jet with a 70x47 rod with a .101 secondary jet. The wild card with edelbrocks is the clusters main emulsion tubes and the fact that those dummies have down sized the fuel passages between the jets and main wells. This makes it very difficult to make meaningful changes. Holleys have about 25% more fuel passage area; otherwise you can't starve an engine running gasoline.

I think edelbrock just screwed up a good design just to fit a damn chevy.

 

[BSB67]

Were the tests done on the same day? Do you have the time slips to post? Did you adjust them to standard conditions to help assure you have minimized atmospheric variables that can present noticeably on the time slip.

 

[Bee1971]

Mid to wide open should be the power circuit, if the proper step up spring is used. For this carb I'd do .100 primary jet with a 70x47 rod with a .101 secondary jet. The wild card with edelbrocks is the clusters main emulsion tubes and the fact that those dummies have down sized the fuel passages between the jets and main wells. This makes it very difficult to make meaningful changes. Holleys have about 25% more fuel passage area; otherwise you can't starve an engine running gasoline.

I think edelbrock just screwed up a good design just to fit a damn chevy.

Meaningful changes , like fuel starvation , no matter what jet changes - That’s why I posted those two scenarios above

Anyways apples to oranges 650 AVS2 with original poster


I have now had friends return on separate occasions with Stroker big blocks , two 800 AVS2 carbs that I have worked on personally


I talked about it in another post weeks ago - Primary circuit , start , idle , off idle , cruise , all work and perform perfect honestly


Secondary power circuit is another story

No matter what float levels , air door adjustments , even going with .110 Needles and Seats

Try richening up the secondary circuit short of no jets at all , fuel starvation , engine stops building RPMs , like it’s running out of gas - Changing secondary jets richer did absolutely nothing

My tried and true Carter Competion Series 750 cfm all stock , just bolt it on and go confirmed the problems with those 800 AVS2 s - Zero issues on the top end RPMs with the Carter , other then the fact I hate the weighted air door , but that carb just flat out works