Question about Edelbrock carbs

Joined
May 23, 2016
Messages
50
Reaction score
19
Location
Warrenton, VA
. I have an Eddy Performer 750 cfm with electric choke. It has the original jets both primary and secondary. I changed the metering rod and the spring however. Went with a rod that keeps the cruise mixture the same but makes the power one stage richer. I guess it had the orange spring in it and I changed it to the silver spring to make the power stage come in sooner. I have the original pump shooter with the setting at the top (I think) hole.

It generally runs OK but does have some issues. When the engine is cold, it kind of sputters a little at light throttle. Sometimes it backfires! It also kind of surges at steady speeds leading both my mechanic and I too think the cruise setting may be too lean. I tried the metering rod that was one stage rich both cruise and power. Although it didn't surge, mileage was terrible (bout 8 -9 mpg) and performance was no better than with the stock metering rod.

I have two calibration kits (for both Performer and Thunder carbs) and I have the entire set of pump shooters.

Couple of questions:
Which hole is the top hole in the accel pump rod? The one nearest the carb (where its set now).
I know the springs bring the metering rod up to the power stage at certain vacuum readings. It had the orange spring in the carb stock....Edelbrock says it stages at 4 or 5 inches of mercury. Isn't that when the throttle is almost floored?? My car has a vacuum guage. That's why I put the silver spring in. Supposedly stages about 8" of Hg. Is the vacuum reading given by Eddy when the spring starts to release or is fully released??
Which spring should I use?

Sorry bout the lack of specific part numbers. My Eddy books are downstairs and someone is sleeping and I don't want to disturb.

Ok, my car is a 67 300, stock 440 TNT with electronic ignition conversion and TTI exhaust. Its and automatic with 3.55 rear gears
 

sczuylevch

New Member
Joined
May 13, 2016
Messages
24
Reaction score
12
Location
mopar alley
have you checked your fuel pressure? i changed out my stock fuel pump for a stock replacement from napa over the winter, and rebuilt my stock carb. It would surge at hwy speeds stall making left turns or braking, flood after i shut the car off, vacuum gage flutter while tuning, and bog off the line or somtimes backfire. i adjusted the floats to the wrong spec the first time i had the carb apart. Reset it still ran like crap, then i decided to try a fuel pressure regulator, solved all my problems. If you have changed your original pump out your replacement could be feeding to much pressure to the carb. think those edelbrocks like 5.5 psi! I mean in all the old mopars ive had i never had to use a regulator before, and ive replaced the fuel pumps on all of them. but i swear to you she runs GOOD now!
 
Joined
May 23, 2016
Messages
50
Reaction score
19
Location
Warrenton, VA
Fuel pressure regulator??

But previous carbs worked OK.

No one has explained the effects of changing the springs satisfactorily... Seems the springs Edelbrock has in there don't stage until the throttle is nearing full throttle...Is that the way it should be?? Doesn't the engine need More fuel BEFORE the secondaries start to open??
 

70bigblockdodge

Old Man with a Hat
Joined
Jan 19, 2013
Messages
13,157
Reaction score
10,563
Location
Avonmore Pa.
Surging at cruise is usually a lean condition. Power pistons/ springs are connected to manifold vacuum, so any time the manifold vacuum is above the springs rating it is pulled down. I have a surging condition on a 440 with same carb and it turned out the vacuum advance was pulling in like 65 degress at 3000 rpm, I tightened the spring up in the canister and it helped, just something to check especially if you changed the dist/reman
 

Kelgar50

New Member
Joined
Jun 25, 2015
Messages
40
Reaction score
23
Location
Bakersfield
I had to dial in the same carb on my 383.
I ended up with changing the nozzle to the largest one in the kit .043 (the nozzle kit comes with 3 nozzles). I also used my vacuum gauge to find out the engine vacuum then divided that in half to get the correct spring. Then I jetted the primary side up to if I remember right a 110 can't remember what rods I used and last I stepped up secondary jets.

No hesitation at all now.
 

Fury440

Member at Peace
Legendary Member
Joined
Jan 15, 2011
Messages
2,619
Reaction score
3,536
Location
Calgary, Alberta
When my 440 was built we used an Eddy Performer 750 cfm with electric choke on an Eddy intake. It ran but surged, leaked, had starting issues and otherwise was a PITA to tune. After discussions with the experts at Eddy, they told us that our basically stock built 440 would be much happier with a 600 carb and a fuel regulator to hold the fuel pressure at around 4.5 psi. Well, they were right, even though I still really would have liked the larger 750 carb.
 
Joined
May 23, 2016
Messages
50
Reaction score
19
Location
Warrenton, VA
When my 440 was built we used an Eddy Performer 750 cfm with electric choke on an Eddy intake. It ran but surged, leaked, had starting issues and otherwise was a PITA to tune. After discussions with the experts at Eddy, they told us that our basically stock built 440 would be much happier with a 600 carb and a fuel regulator to hold the fuel pressure at around 4.5 psi. Well, they were right, even though I still really would have liked the larger 750 carb.
 
Joined
May 23, 2016
Messages
50
Reaction score
19
Location
Warrenton, VA
Interesting Bill. I had a 600 Eddy Performer on the car at one time. It ran great with NONE of the choke, surge, etc issues I had with all the other carbs. My car did not have the crisp, effortless performance it had with the Eddy Thunder 800 cfm carb I had on it (that carb had lots of other issues with it though) so I thought I needed a bigger carb. Sort of a compromise.
 

Fury440

Member at Peace
Legendary Member
Joined
Jan 15, 2011
Messages
2,619
Reaction score
3,536
Location
Calgary, Alberta
I guess its a function of how fast the engine can breath or move fuel/air mixture through the engine from the base of the carb all the way to the far tip of the exhaust pipe. Any obstructions will cause the system to load up. However a carb that puts out a fuel/air mixture in too high a volume will surely cause all sorts of problems no matter how well the engine flows.

At least that's how I justify having a dinky little 600 cfm carb instead of a macho 750 cfm or bigger. I do have to admit, the engine has never run better.
 

commando1

Old Man with a Hat
FCBO Gold Member
Joined
Mar 10, 2011
Messages
36,435
Reaction score
36,960
Location
Sebring, Florida
The Eddy 600 and 750 come from the factory tuned differently. Most times the 600 runs perfectly out of the box vs the 750 which seems to always require further diddling with.
 

Fury440

Member at Peace
Legendary Member
Joined
Jan 15, 2011
Messages
2,619
Reaction score
3,536
Location
Calgary, Alberta
The Eddy 600 and 750 come from the factory tuned differently. Most times the 600 runs perfectly out of the box vs the 750 which seems to always require further diddling with.
Even so, Paul spent a lot of time trying to get the 750 set right without success. Paul doesn't throw in the towel until he's beat!
 

WorkerBee

Active Member
Joined
Dec 25, 2014
Messages
326
Reaction score
283
Location
Norfolk County, Ontario
Ive read that the 340/383 AVS was 480 CFM and the 440 AVS was 580CFM. I'm pretty sure that was done by Chrysler.
Isn't the 6bbl carbs 350 CFM X 3 .....1050CFM???
 

tallhair

Rufus "Mod Hair" Firefly
Staff member
Joined
May 12, 2013
Messages
10,280
Reaction score
4,604
Location
Mascoutah, Illinois
Ive read that the 340/383 AVS was 480 CFM and the 440 AVS was 580CFM. I'm pretty sure that was done by Chrysler.
Isn't the 6bbl carbs 350 CFM X 3 .....1050CFM???

No the center one is 350 cfm and the two outers are 500 cfm = 1,350

caveat diff carb manf flow and rate their carbs differently and I've read that the 2 BBL holley's are flowed and rated differently than the 4 BBL holley's and just from a weak memory that the true comparable flow of a 440 six BBL set up was really around something like 980 cfm .. but memory is not always accurate
 
Top