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

[Geoff 2]

I also wondered about the jetting 'strategy' of the E carbs. There is also the very low fuel level in the bowl resulting from the 7/16" setting. I have seen a few Carter AFB/AVS carbs with a 3/8" float level setting, never 7/16", more common is the 7/32 - 5/16" range.
The low fuel level might explain the big jump between the cruise step & the power step on the met rods. Doesn't explain the relatively smaller sec jets, also being fed from the same low fuel level. Edel may have changed the main air bleed sizes as a way of changing the fuel curve.

 

[lewtot184]

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

First, I think the old sand cast carter's are superior to what edelbrock is doing. Second, I think the edelbrocks run better in pairs on larger engines due to the down sizing of the fuel cicuts. And lastly, try to get a 750 edelbrock to work properly on a larger engine. I remember reading some stuff on moparts a few years ago about the problems to get them to work. My first thoughts were the guy just didn't know how to work on them. I've got three 750's and singulary or as duels they will not cruise. I don't think they're properly moving fuel on the cruise circuit. I've got two of them apart on the bench looking for issues and compared to the factory avs everything is obvious. It's not carter that's a problem it's edelbrock.

 

[lewtot184]

I also wondered about the jetting 'strategy' of the E carbs. There is also the very low fuel level in the bowl resulting from the 7/16" setting. I have seen a few Carter AFB/AVS carbs with a 3/8" float level setting, never 7/16", more common is the 7/32 - 5/16" range.
The low fuel level might explain the big jump between the cruise step & the power step on the met rods. Doesn't explain the relatively smaller sec jets, also being fed from the same low fuel level. Edel may have changed the main air bleed sizes as a way of changing the fuel curve.

Start measuring the depth of the emulsion tube's in the main wells. Notice the inconsistencies and lack of depth. Notice how some of the main feed orifices on the secondary clusters are only .076" but there's a .107" jet. Find some old jet specs and compare them to the new " equilivent crabs. It's crazy.

 

[66 Sat]

Were the tests done on the same day?

I was wondering when someone was going to ask that question...
No the tests weren't done on the same day. They weren't even done in the same year. The Holley was this time last year. The Edelbrock was last week. Same time of the year, same weather, same track, same driver. No other changes to the car. If you know the weather in SE Queensland you'd know what I mean. Clear winter night, cold (45° F), no humidity.
I could (should maybe) have mentioned this at the start but I knew the reaction it would give from the Edelbrock fans. Invalid data etc.
I believe in the comparison. I know my car and have tracked it many times. It's always very consistent. This time is was consistently slower. I also know the changes in the way the car feels on different days. Some days it feels great, others less so. Same as the Holley and probably every carburetted car. Mostly weather dependent. After the initial teething troubles with the AVS2 (poor quality control?) I thought it was running great, and it was...on the street. But it just didn't feel as strong at the track. Felt great on the 70 mile trip there and the 70 mile trip home, but didn't produce the numbers to match.
I really wanted this carb to work - I paid $800 AUD for it, plus another $100 or so for the wooden spacer, plus another $150 or so for the tuning kit and it hasn't lived up to expectations. Maybe it's a dud. I don't know, and it's too late to prove it in order to return it.
This afternoon I put the 700 Holley Double Pumper on there. This is a reconditioned carb that was on the car when I bought it and has sat in a box for most of the last 10 years. I pulled it out today (it was last on the car September last year for a chassis dyno test) and whacked it on. It fired up after a little priming and runs great. Took it to the beach for a test and it feels so much livelier, smooth and powerful.
I'll be testing it at Mopar Sunday next weekend to see what numbers it runs. I'd like to test all 3 carbs on the day but I'm not like Uncle Tony swapping carbs on the side of the road in 10 minutes, fuel spilling everywhere. I like to take my time and do it properly, and then the day becomes a mad rush working over a hot engine and isn't enjoyable.

 

[Bee1971]

First, I think the old sand cast carter's are superior to what edelbrock is doing. Second, I think the edelbrocks run better in pairs on larger engines due to the down sizing of the fuel cicuts. And lastly, try to get a 750 edelbrock to work properly on a larger engine. I remember reading some stuff on moparts a few years ago about the problems to get them to work. My first thoughts were the guy just didn't know how to work on them. I've got three 750's and singulary or as duels they will not cruise. I don't think they're properly moving fuel on the cruise circuit. I've got two of them apart on the bench looking for issues and compared to the factory avs everything is obvious. It's not carter that's a problem it's edelbrock.

Thank You

You couldn’t give me a Edelbrock 1407/1411 today other then for a door stop or paper weight
Those carbs drove me crazy on the street for years back in the day until I went with the factory Carter AVS and learned how to rejet making my own flat metering rod covers and using Edelbrock hardware then of course Edelbrock came out with there version Thunder Series AVS

And if someone tells me it’s the same carb one more time as the Carter Competition Series , they haven’t run them side by side on the same motor or taken them both apart , Dyno and Track confirmed the differences back then

Yes there is a great article on Speed Talk about the design flaws of the 1407/1411
And Dyno #s comparing the carbs on Moparts

 

[66 Sat]

OK so here's another question and a possible explanation for the poor showing from the AVS2, but I'm not sure.
I have the 700 double pumper on now and it feels so much stronger, especially from idle. I'm running MVA and it just powers away with a touch of the throttle. It honestly feels so much stronger it's not funny.
When I got the AVS2 the PCV hose connects to the front of the carb, not the rear like the Holleys. My hose was too short so I got a longer piece of hose. I just grabbed some radiator overflow hose I had, quite weak walled, but it worked OK. When I swapped in the Holley on the weekend I used that same longer hose as I was rushing to finish the swap. As soon as I started the car the vacuum was sucking the hose flat and the idle was irratic. I swapped a shorter, more rigid walled hose in and all was fine. But the hose was never sucked flat by the AVS2. WHY? Could that port on the front of the carb be blocked or partially blocked somehow? I haven't had time to check but if that was the case would it cause poor performance?
I know the annular boosters were partially blocked when I first got the carb - maybe I got a Friday afternoon carb?

 

[lewtot184]

I don't have an answer to your question but would like to know what your engine build is.

 

[66 Sat]

I don't have an answer to your question but would like to know what your engine build is.

It's a 318 poly that's now a 354 with a 3.58" forged crank, forged rods, Ross pistons, 1.94"/1.60" valves, mild-ish 264 solid lifter cam (Schneider Racing Cams), factory 4 barrel intake and custom stepped headers (1 5/8" to 1 3/4").
It's a nice torquey engine, will run with stock big blocks. It made 341 hp at the wheels on the chassis dyno at the height of summer - as a comparison a stock Shelby Mustang with a 428 cobra jet made 290 hp that same day.

 

[kiwigtx]

I haven't had time to check but if that was the case would it cause poor performance?
I know the annular boosters were partially blocked when I first got the carb - maybe I got a Friday afternoon carb?

Possibly all those years of sitting in a box on a shelf had gummed something shut or partially shut.

Only a complete tear-down and rebuild will validate that reason....or some Redex carb cleaner or something similar - then go for a decent drive to loosen things up.
I know my A100 doesn't start performing until there's a few hot miles under its belt.

 

[66 Sat]

No, it was the Holley sitting in the box for years...and ran fine. The AVS2 was brand new last November, ran like crap from day one, until I removed the boosters and cleaned them out.

 

[kiwigtx]

Having been a 14-15 second dweller for most of my racing days, I can assure you @66 Sat that when you break out a mid to low 13 time, you'll be absolutely stoked how good it feels.
The best I did in my GTX was a 13.3 at 107mph. Felt good too. First run OOTB for my new engine in the A100 was a 13.07 at 103mph.....pretty fast in that thing with all the aerodynamics of a brick.

 

[kiwigtx]

No, it was the Holley sitting in the box for years...and ran fine. The AVS2 was brand new last November, ran like crap from day one, until I removed the boosters and cleaned them out.

My mistake. So the AVS2 is all freed up now?

 

[66 Sat]

My mistake. So the AVS2 is all freed up now?

Yes and no...it felt great on the street, but now I've switched to the double pumper it feels better again. When I first changed from ported to manifold vacuum advance (before the AVS2) it had a much stronger idle and initial take off. I'd forgotten that feeling with the AVS2, until I switched back to the Holley. The throttle response from idle is terrific now, feels like it just wants to rev and go. I'm convinced there's some passage not drilled properly in the Edelbrock carb, I just haven't had time to check.
Mopar Sunday at that track this weekend with the 700 D/P on there will be revealing. Feel on the street often doesn't equate to times at the track (at least in my case). So many times I've said to my son "it's gotta run 13's, it feels so strong"...and then it doesn't.
But this weekend will be different - it's gotta run 13's, it feels so strong haha.

 

[Geoff 2]

There is a significant difference in pri throttle bore size between the H & the E carb: 1 11/16" v
1 7/16". All else being equal, cracking the throttle off idle on the H is going to admit more & fuel; the E carb would need more throttle opening to admit the same amount of air. So this might explain 'the livelier' feel of the H carb off idle.

PCV hose. It can go front or rear, makes no difference. Some engines, like Pontiacs the PCV goes into the intake runners, not the carb.
PCV hose collapsing suggests more idle vacuum with the H carb. Was the base of the E carb, & it's passages sealed by the base gasket? Engine heat might have an effect. Rubber gets softer when heated, more likely to collapse. Could the hose have been cooler when fitted to the H carb?

 

[66 Sat]

There is a significant difference in pri throttle bore size between the H & the E carb: 1 11/16" v
1 7/16". All else being equal, cracking the throttle off idle on the H is going to admit more & fuel; the E carb would need more throttle opening to admit the same amount of air. So this might explain 'the livelier' feel of the H carb off idle.

PCV hose. It can go front or rear, makes no difference. Some engines, like Pontiacs the PCV goes into the intake runners, not the carb.
PCV hose collapsing suggests more idle vacuum with the H carb. Was the base of the E carb, & it's passages sealed by the base gasket? Engine heat might have an effect. Rubber gets softer when heated, more likely to collapse. Could the hose have been cooler when fitted to the H carb?

The hose I used with the Edelbrock, in hindsight, was way too weak. I've also had a fuel type grade hose on there in the past, but for the longer hose I used on the Edelbrock I used this soft rubber hose...but it worked fine for 9 months.
Immediately on firing up the car with the Holley the hose collapsed - way too much vacuum..which is unsurprising if you felt how soft the hose was. My mistake. But somehow it worked on the Edelbrock, which leads me to believe there was no vacuum or very little, coming through it.
The carb was installed properly on the Edelbrock wooden spacer / gasket, no vacuum leaks. It ran fine eventually..sort of. If I hadn't taken it to the track I wouldn't have even swapped it out for the Holley. It's only now after comparing them back to back that I realise how down on power it felt with the Edelbrock.

Also with regard to your first comment I thought the smaller primaries on the Edelbrock were meant to give it that great low speed, off idle response? I think I may have a dud carb.

More investigations needed on my part.

 

[lewtot184]

When I seen you're earlier pics I thought " is that a poly?". My next thoughts are "you're doing pretty darn good with it" ! Another thought was we're concentrating on the carbs but not the intake. What are the intakes limits? Are you at that point to where more carb isn't the answer? My first attempt at hot rodding was a 58 Plymouth with a 318 and I never got it to work; i was18yrs old. Did you open up the throttle bores in the intake? Something designed in 50's isn't going to meet modern expectations but I'd rather have old iron than one of those aluminum intakes.

 

[66 Sat]

When I seen you're earlier pics I thought " is that a poly?". My next thoughts are "you're doing pretty darn good with it" ! Another thought was we're concentrating on the carbs but not the intake. What are the intakes limits? Are you at that point to where more carb isn't the answer? My first attempt at hot rodding was a 58 Plymouth with a 318 and I never got it to work; i was18yrs old. Did you open up the throttle bores in the intake? Something designed in 50's isn't going to meet modern expectations but I'd rather have old iron than one of those aluminum intakes.

The intake is holding it back and I need to remove it and open up the center plenum as per Gary Pavlovic's advice but I haven't got around to it yet.
This is unrelated to the issues with the AVS2 carburetor though. If the intake was an issue it would be an issue with the 700 Double Pumper too.
If I didn't have so much work to do I could investigate what is going on, but if I didn't have so much work to do I wouldn't be able to afford all these carburetors in the first place.