I need to hear from anyone running an Edelbrock 650 on their 440, please!

[moparedtn]

Haven't checked in for a while...
For those unfamiliar, I have a '68 GTX with a bastardized 440 in it (built by someone now deceased).
It is basically a '75 block with all the internals from the stock '68 440 magnum in it. Least, that's what I'm told and I can verify at least some of that is true. Forged crank, 906 heads, etc. are present and accounted for.
It has less than 500 miles on this "rebuild" and seems mechanically sound.

I have replaced a Mopar 484 cam that was in it because it wiped 2 lobes. Cam is now a Comp Cams Magnum series 270/270 .470/.470. Pretty mild, in other words, just a tick or two above stock.

Exhaust is Hedmans and a whacky 3" all the way back dual system with Flowmasters. She's a tad loud.

Ignition is the usual Mopar electronic ignition conversion. Actually, right now the car has a new A-1 electronic stock unit in it, the result of past troubleshooting with the Mopar one.
Stock control box as well.
Timing is now CONFIRMED (AMEN!) to be set at the stock 5BTDC, thanks to getting rid of the original balancer (which wound up having slipped a ton and was giving erroneous timing readings). Vacuum advance is hooked up, although this motor has demonstrated it doesn't like that too much.

Oh, car is a 4-speed if that matters. 3.55 SureGrip in a 742 punkin.

I have just installed a new Edelbrock Thunder 650cfm, the result of conferring with folks here as well as at the Edelbrock tech line. The formula says this is enough carb, right?
I put a 1/2" spacer under the carb in anticipation of avoiding heat sink.
Intake is the factory 440 one.
I set the idle mixture screws for maximum vacuum/best idle (wound up 3 turns out each). I set the secondary door spring just like the instructions said to do, then set idle at about 750RPM.
She holds a real nice solid idle and revs freely over 5000RPM sitting still.
I have made no other changes or adjustments to the carb yet.

Results of maiden voyage today:
Under light acceleration, things seem fairly normal. She definitely sounds different than when the Holley 750 was on there. I want to say it sounds "cleaner"?
She seems to lean out under moderate acceleration on up; there's a little hesitation, not so much like a bog, just like she needs to "catch up" to what I'm doing with the throttle.
Brisk acceleration (just shy of flooring it/activating the secondaries), as well as when I first pull out (she tries to nose over a tad unless I give it more beans/slip the clutch some), is telling me it's pretty lean there as well.
When I floor it, there's a familiar old "quadrajet" momentary bog, then she takes off quite well.

Long-winded way to ask for help, but is anyone else running this carburetor on a fairly mild 440?
If so, what rods/jets did you wind up with? What hole do you have the accelerator pump set at?
Looking for some sage wisdom to get her in the ballpark. She's a street car, never will see the strip.

THANKS!

 

[terzmo]

I never run a 440...stock or otherwise with less than a 750 cfm...650 is for a stock 383 as far as I'm concerned...a 750 holly or edelbrock,new,should run fine on your engine unless there are other issues.

 

[5.7 hemi]

Could a power valve change help?

 

[KarNut46]

Try to locate an E-brock track tuning kit and play with jet size and/or metering rod size. Sounds like it's running a tad lean. A 750 will perform a bit better but your street performance will suffer. The smaller carb will give crisper throttle response on the street. I think the tuning kit is called a Trak Pak. I had one when I was running a 500 cfm E- brock and it helped. Has different jets (pri & sec), different metering rods, and different metering rod piston springs. Not very costly and worth it.

- - - Updated - - -

Not to be a wise guy but Holleys have power valves, E-brocks and AFBs have metering rods.

 

[moparedtn]

Try to locate an E-brock track tuning kit and play with jet size and/or metering rod size. Sounds like it's running a tad lean. A 750 will perform a bit better but your street performance will suffer. The smaller carb will give crisper throttle response on the street. I think the tuning kit is called a Trak Pak. I had one when I was running a 500 cfm E- brock and it helped. Has different jets (pri & sec), different metering rods, and different metering rod piston springs. Not very costly and worth it.

- - - Updated - - -

Not to be a wise guy but Holleys have power valves, E-brocks and AFBs have metering rods.

Yep, counting on buying the kit...but was hoping someone else is running an Eldebrock on a 440 who has some ballpark jetting sizes for me to start with.

 

[moparedtn]

Anyone? Ferris?

 

[KarNut46]

I was running a 500 cfm on a hi-perf 318 in an A body. Out of the box the carb was running lean on pri circuit but ok on sec. First thing I did was to go to a smaller metering rod. Solved the problem on the first try. It's a trial & error thing. Part of hot rodding. Jets are labeled as to size and the kit has the dimensions listed. I generally go about 2 to 3 sizes big on jet sizes to make it a bit rich then drop back one size at a time to get a good tune. Easy if you have the car set up w/ O2 sensors but most of us don't so we have to do it the old way. Read the spark plugs and shoot for a light brown to tan color after a bit of highway cruising.

 

[moparedtn]

Ok, let's try this:
Is anyone running ANY Edelbrock AVS carb on a 440?

 

[Dreamcatcher]

I tried one on my 440HP and it just would not run at all power wise. I tried bigger jets too. I went with a competition carter with 72 primaries and it runs awesome.

 

[moparedtn]

I tried one on my 440HP and it just would not run at all power wise. I tried bigger jets too. I went with a competition carter with 72 primaries and it runs awesome.

Ok, that's a start. 72 primaries, check. What rods?

EDIT - ok, not actually seeing this. I assume you mean 72 rods?

 

[lewtot184]

try one step heavier step-up springs. with that little carb and short cam there may be too much vacuum to release the step-up piston and enrich the main circut. those carbs come with an orange 5"hg step-up spring. probably ok for a small engine. try a pink 7"hg spring. read the instruction manual that comes with the carb.

 

[SlinktRR]

I use 98 mains 101 sec jets. 7047 rods, 5" springs. Secondary air door 1 1/2 turns out, middle setting on acc pump. Get the 1813 kit for the 800 avs, it has most of the parts you will need. You can also buy rods/jets separately.

 

[furyus]

I know you didn't ask, but I would try more timing. That 5* seems way too little. I would try 12-15*. It helps with bog/ hesitation issues. Your engine is modified, and will have different needs from stock.

 

[moparedtn]

I use 98 mains 101 sec jets. 7047 rods, 5" springs. Secondary air door 1 1/2 turns out, middle setting on acc pump. Get the 1813 kit for the 800 avs, it has most of the parts you will need. You can also buy rods/jets separately.

Thanks!
Can you give a brief description of your motor? Is it comparable to mine?

Ok, for comparison sakes, this 650 AVS has Primary .095, Secondary .098; Metering Rods - .068 x .047; Step-Up Spring - Orange (5" Hg). Your suggestions for slight increases in jets and rods therefore makes sense, at least to me.
EDIT: It appears the kit #1840 has the exact jet sizes you're recommending.

- - - Updated - - -

I know you didn't ask, but I would try more timing. That 5* seems way too little. I would try 12-15*. It helps with bog/ hesitation issues. Your engine is modified, and will have different needs from stock.

Yeah, it's been a long struggle with timing on this engine - apparently most of it caused by a harmonic balancer that had slipped and was giving me erroneous readings.
New Summit balancer on there now, so hopefully that cures that.
The engine has never liked the vacuum advance hooked up, either, but it is right now.

I'm sticking to baseline while I get the new carb dialed in - what's happening right now is definite flat spots in the fuel delivery, as opposed to it not picking up as quickly as it should (timing).
Once I get this carb close, I'll definitely start playing with the timing.

You know, now that you mention it, I've had some hellaciously advanced timing on this engine before, yet never heard it knock or ping. Weird. Sucks, because this shadetree likes advancing initial until I get a little spark knock, then back off a hair.

 

[Moparsmitty]

I'm running an old Eddy 750 on my mild 440. Even with a mild cam and a low compression motor I had to richen up the carb with smaller metering rods to get the mid throttle hesitation out of it. Like Furyous suggests, you probably need more timing advance at idle, I'm running about 12*

 

[SlinktRR]

Thanks!
Can you give a brief description of your motor? Is it comparable to mine?

Ok, for comparison sakes, this 650 AVS has Primary .095, Secondary .098; Metering Rods - .068 x .047; Step-Up Spring - Orange (5" Hg). Your suggestions for slight increases in jets and rods therefore makes sense, at least to me.
EDIT: It appears the kit #1840 has the exact jet sizes you're recommending.

Hi Ed, it's a 383 but with the 650 carb the fueling requirements will be very similar for any mild big block. In your owners manual for the AVS there will be a metering chart. Try to stay in the upper right region of the chart (richer cruise/power modes) to start and then fine tune from there. Tune the secondary jet according to how the car feels at WOT as it only comes into play when the AVS door opens. Lewtot184's suggestion to go to a 7" spring is right, if you have a lot of vacuum with a stock cam then you may want to try the 7".

Fine tuning will involve changing rods to get the best cruise performance once you get a good base setting for WOT. First 2 digits of the rods...higher is leaner cruise. Last 2 digits of the the rod number...lower is richer power mode.

 

[drobertson]

I have a 318... but it makes much more power with a 600cfm than a 500cfm. Weird, huh? I have seen 950cfm on 440s and they seem about right.

 

[moparedtn]

Hi Ed, it's a 383 but with the 650 carb the fueling requirements will be very similar for any mild big block. In your owners manual for the AVS there will be a metering chart. Try to stay in the upper right region of the chart (richer cruise/power modes) to start and then fine tune from there. Tune the secondary jet according to how the car feels at WOT as it only comes into play when the AVS door opens. Lewtot184's suggestion to go to a 7" spring is right, if you have a lot of vacuum with a stock cam then you may want to try the 7".

Fine tuning will involve changing rods to get the best cruise performance once you get a good base setting for WOT. First 2 digits of the rods...higher is leaner cruise. Last 2 digits of the the rod number...lower is richer power mode.

View attachment 292705

Thank you very much!
It took me a bit to get out of "Holley mode" thinking-wise and to grasp what's happening here, but thanks to your explanation, I'm starting to get it now.
The chart I have for the 1805 is much like yours:

As the car seemed to be sort of in the neighborhood on the secondaries (I'll be easing off a half turn on the air door, though, to get rid of a little bit of that "Quadrajet bog" it's exhibiting now), I'm thinking I'll shoot for #8 on the chart to begin with.
I think that means rod change only in my case?
Time to fetch some parts, I reckon. Thanks!

 

[moparedtn]

I'm fetching the Edelbrock #1840 calibration kit for my 1805.
It has this assortment:


By the way, are there other springs in the carb other than the ones on the metering rods?

 

[Tempest 455]

Change to a larger squirter. You will need a larger one than it came with because of the ci of the 440.