Edlebrock 1406 600 cfm tuning problems

[RR383]

Gentlemen,
My '70 383/727 roadrunner still has performance/tuning issues that to date haven't been resolved. Two specific things are going on...First, after a lengthy warm-up the car falls on its face when I put into drive. I mean it just peters out and dies. Secondly, at cruising speed say 50 mph when I nail throttle to open the secondaries...the car wants to backfire then accelerate.
What in the idle circuit would be causing the car to die after placing it in gear and just feathering the throttle...you can almost tell when its about to happen.
Further, is the carb leaning out at higher speeds causing this stumble/backfire?
FYI, the engine is Edlebrock at the intake and carb.
Edlebrock has an extensive tuning format on their website...not sure what direction I need to go in.

 

[Ranger]

What in the idle circuit would be causing the car to die after placing it in gear and just feathering the throttle.

Vacuum leak?

Secondly, at cruising speed say 50 mph when I nail throttle to open the secondaries...the car wants to backfire then accelerate.

Have you tried different step up springs?

 

[RR383]

What's the best location to check for engine vacuum...?

Would you go richer next size up...not positive which color according to the 1406 mixture chart.

What do think about more pump shot...to richen things up during transition from cruising speed to WOT.

I read where the 1405 is more of a performance carb vs. the 1406 w/electric choke. Where do the performance differences lie?

 

[RR383]

Also recently found an interesting article tuning the 1406 using 1405 guidelines with GREAT success. Note... I bought the car with the 1406 set-up...scrabbling now to correct it. The 1406 is more of an economy carb...not for my 383!

 

[Ranger]

Are you using the Edelbrock manual? It explains things pretty well.
http://www.edelbrock.com/automotive/misc/tech-center/dl/carb-owners-manual.pdf

Would you go richer next size up...not positive which color according to the 1406 mixture chart.

The springs control how fast the metering rods react to transitioning from cruise mode to power mode. Not how rich the mixture will be. That is controlled by the different metering rods and jets.
See the CALIBRATING THE POWER MODE STAGING section for step up spring selection. Further up (page 3) explains the principle behind the step up pistons & springs.

What's the best location to check for engine vacuum...?

Check engine vacuum at the full time vacuum port (right side). Diagram on page 21 (Part #51)

What do think about more pump shot...to richen things up during transition from cruising speed to WOT.

Try it and see if it helps. It's easy enough to go back if it doesn't.

Also recently found an interesting article tuning the 1406 using 1405 guidelines with GREAT success. Note... I bought the car with the 1406 set-up...scrabbling now to correct it. The 1406 is more of an economy carb...not for my 383!

I believe that the only difference between the 1405 & 1406 is a manual vs automatic choke. Both are 600 CFM carbs which is about for a 383. Mine has a 1411 (750) on it. That's what was on it when I bought it. I just leaned it down to about what a stock 600 is (rods & jets). It was running quite rich and I think it was over carb'd.

 

[RR383]

Ranger - I plan on ordering a tune-up kit from either Summit or straight from Eldebrock ASAP! BTW, I'm using the full time vacuum port...for advance. But for tuning that's the port to use....CORRECT?

 

[Ranger]

Correct. The "ported" port is an early emission control. It provides no vacuum (thus no advance) at idle.

 

[RR383]

Correct. The "ported" port is an early emission control. It provides no vacuum (thus no advance) at idle.

Edlebrocks website states the 1405 is designed for performance and the 1406 for economy. They even offer the electric choke as an option. I plan on contacting Eledbrock tech dept. tomorrow afternoon to discuss my particular issues and before I jump out and buy a 70.00 dol. kit that I may or may not need.

 

[Ranger]

Look at the carb descriptions on this page. http://www.edelbrock.com/automotive/mc/carburetors/performer.shtml

Note the difference in the description between the 1405 (calibrated for performance) & 1406 (calibrated for economy). The difference (aside from the choke) is the jets and metering rods. The "performance" model has a larger jet & smaller metering rod, thus more fuel, while the economy model uses a smaller jet and larger metering rod, thus less fuel. They also use a different step up spring, all of which are interchangeable.

P.S.
I think I bought a set of springs for about $14. The jets and rods where also much less than $70. No need to buy a full set you'll never use. Figure out what you want and buy one set of jets rods and/or rods on Ebay or Amazon.

 

[RR383]

Look at the carb descriptions on this page. http://www.edelbrock.com/automotive/mc/carburetors/performer.shtml

Note the difference in the description between the 1405 (calibrated for performance) & 1406 (calibrated for economy). The difference (aside from the choke) is the jets and metering rods. The "performance" model has a larger jet & smaller metering rod, thus more fuel, while the economy model uses a smaller jet and larger metering rod, thus less fuel. They also use a different step up spring, all of which are interchangeable.

P.S.
I think I bought a set of springs for about $14. The jets and rods where also much less than $70. No need to buy a full set you'll never use. Figure out what you want and buy one set of jets rods and/or rods on Ebay or Amazon.

Yes, sir will do exactly that. Alright out with old and in with the new. If I can mimic the 1405 factory set-up by simply swapping a couple of jets, springs and metering rods...that will be a good start and hopefully in the right direction.
There are allot of derogatory articles on the web about the displeasures of those who bought the Edelbrock 1406 and expecting GREAT things straight out of the box. But all the BIG brand names have there individual shortcomings.

 

[RR383]

Ranger - Edelbrock list both 1405 and 1406 carbs with the orange 5" hg step-up spring. And the primary jet being .002" larger and the metering rods being .003" smaller. Its all voodoo to me but I really appreciate you taking valuable time on this memorial day to communicate with me.

 

[Ranger]

We must be looking at different carbs.
In the link I sent, 3rd from the top is the 1405.
600 CFM, MANUAL CHOKE
(CALIBRATED FOR PERFORMANCE)
Designed and calibrated for optimum street performance in small-block and some big-block engines. Match with a variety of manifolds that include Edelbrock Performer, Performer EPS, Performer RPM, RPM Air-Gap, Torker II or other brands of similar design. Includes both timed and full vacuum ports for ignition advance. Electric choke #1478 can be added if needed. Comes with: Metering Jets - Primary .100, Secondary .095; Metering Rods - .070 x .047; Step-Up Spring - orange (5" Hg). Use Carb Studs #8008 or #8024 if needed.


4th from the top (in black) is the 1406
600 CFM, ELECTRIC CHOKE
(CALIBRATED FOR FUEL ECONOMY)
Designed for small-block and small displacement big-block engines, these carbs are recommended only for stock to Performer level applications. They are not recommended for use on RPM or Torker II intake manifolds. Match with an Edelbrock Performer or Performer EPS manifold or other brands of similar design. Calibrated 2% leaner than #1405. Includes both timed and full vacuum ports for ignition advance. Comes with: Metering Jets - Primary .098, Secondary .095; Metering Rods - .075 x .047; Step-Up Spring - yellow (4" Hg). Use Carb Studs #8008 or #8024 if needed.


You can also see the difference for an easier comparison on page 9 of the manual in the link in post #5.
Also see the calibration reference chart on page 12 for guidance in choosing the jets and rods to achieve your desired goal.

There are allot of derogatory articles on the web about the displeasures of those who bought the Edelbrock 1406 and expecting GREAT things straight out of the box.

Ahh, THAT I was not aware of.

 

[RR383]

There are (2) references to the 1406 electric choke models...one cadium plated and one black anodized. Look closer they advertise different springs one orange and one white. Now whether or not that's correct or a typo I'll be calling Edlebrock today... and hopefully get to the bottom.

 

[Ranger]

I see three 600 CFM carbs shown, but see the 1406 listed only once. That is the one pictured in black.

 

[droptop]

I have a 1406 on my '75 RR and had a plug and play experience right out of the box. What you are describing to me sounds like vacuum leaks.

 

[RR383]

Edelbrock tech stated I need to be pulling distributor vacuum from the timed port (passenger side) vs. the straight manifold port. Agree/disagree????????

 

[Ranger]

He is pretty much preaching the party line (clean air) and can't advise otherwise. Choice is yours. Timed port aka ported vacuum means no vacuum advance at idle. Like I said, that was an early emission control. I keep mine at full time vacuum.

Here is a somewhat lengthy article that may explain it better than I. It is written about/for Chevelles, but the principle is the same.
http://chevellestuff.net/tech/articles/vacuum/port_or_manifold.htm

 

[RR383]

Full time it is and btw...thanks for article...great read and certainly stands on its own merit. Bought a vacuum gauge this morning...will update you with a reading after I warm things up.

 

[RR383]

UPDATE Out with the old and in with the new. I opted to just replace the 1406 Eddy with a new 1806 Thunder series 650cfm and man what a difference. I mean straight out of the box performance. And I'm very pleased...just took it out for a shake-down cruise about 40 miles worth and the engine just came to life like it was missing this all along. I also adjusted my kick-down linkage and that comes in under hard acceleration very well. Now for the summer run!
Thanks for all your help...as always!:applouse:

 

[quikbird]

Glad to hear you are out having fun with the rr