Carb Tuning?

[zupanj]

I thought I would see if any of you guys with more carb tuning experience had any ideas about this issue. My 526 ci hemi has a stumble when I step on it from light cruise. I have twin Edlebrock 750's (1406) on it. The accelerator pump linkage was set in the middle hole. I set both linkages on the hole that gave the biggest squirt figuring with that much displacement I wasn't getting enough fuel in transition. That didn't seem to improve anything. Next I went to the hole that gave the smallest squirt. That also didn't offer an improvement but it wasn't the same kind of stumble. In this case it seemed the car went flat and then picked up.

I am not sure what the next step should be. Go with different metering rods maybe?

Any ideas?

 

[mac]

no experience on this type of carb but did find some info that may help you get closer. it does say that you should put the accel pump back the way it was and try using this as reference:

So here's the simple fix, toss your 1406 tuning chart, and use the Performer 1405 tuning chart.
For a mild/hot 302 engine, just start with the stock Performer 1405 tuning spec as your baseline tune;
That be, 1428 (.100) main jets, 1451 (070 x 047) metering rods, and orange springs.

Set your accelerator pump back to the stock middle position.

Set your mixture screws to 2 turns out (this is a good starting point)

Start the car and adjust the idle stop until you get it to idle between 800-900 RPM

With the air cleaner on, adjust the mixture screws until the RPM drops 50 (don't use a vacuum gauge).

Now take the car out for a test and tune.

The rest of your fine tuning can now be done accurately using the 1405 manual.

The 1406 on my built 302 runs like a champ now with 1405 tune #8 (1 step rich in cruise mode) with
pink springs. Which gave me confidence to share this revelation with you.

Good luck and happy tuning! ;)

 

[ACME A12]

Nice Mac, you'll have his dual quad 526 running like a 302 single quad in no time... :basketcase:

Honestly Jack, buy the calibration kit and follow the instructions. You may just need to change the springs.

 

[mac]

you probably have this but i thought i would throw it in.

http://www.edelbrock.com/automotive_new ... manual.pdf

 

[mac]

Nice Mac, you'll have his dual quad 526 running like a 302 single quad in no time... :basketcase:

Honestly Jack, buy the calibration kit and follow the instructions. You may just need to change the springs.

i saw that too, but tuning any engine you will have to go through the same process. :yesnod:

 

[zupanj]

Thanks guys. I did a little reading after I wrote that post and came to the same conclusion. So I will order a pair of tuning kits and go from there.

 

[69hemibeep]

I have a competition 750 Carter I can work on in my sleep and they tend to have a slight secondary bog. But two of them, Im thinking you better have some RPMs even my standard hemi with AFBs will bog below 1800 rpm.

 

[ACME A12]

i saw that too, but tuning any engine you will have to go through the same process. :yesnod:

Well of course, but you didn't really expect me (or one of the other resident smart-a$$es on here) to just skip over that now did you...? :devil:

:jester:

 

[mac]

i saw that too, but tuning any engine you will have to go through the same process. :yesnod:

Well of course, but you didn't really expect me (or one of the other resident smart-a$$es on here) to just skip over that now did you...? :devil:

:jester:

never. i know how the game is played here. :jester:

 

[moparchris]

I am not going to be very popular with this statement, but here I go anyways. The Edelbrock 1406 is not a good choice in carbs. I have found in my experience that they are lacking a properly engineered intermediate circuit. The original Carters seemed to have the perfect transition. Edelbrock is somehow missing the boat on proper fuel dynamics. If I were in your shoes I would find a pair of early competition series carters (AFBs) or even two factory AFBs for it and toss the Edelbrocks. Or this would be my favorite thing to do, buy a Stage V intake and put two holley 650 Double Pumpers on it and never look back. Except to look at the really long burnout marks you just left.

 

[zupanj]

I have 426-1 Indy heads so I am not sure that the Stage V intake would work. I can't remember if you can just bolt up Holleys to an intake that has Edelbrock carbs on it. Do you guys know?

I have to say I am intimidated by Holleys as I never seemed to understand them well enough to tune them.

I would be open to Holleys if my high dollar air cleaner would fit but I think the openings are different sizes.

 

[moparchris]

The stage V intake will fit but the carb spacing is different and the carb neck is bigger on a Holley. Holleys are very easy to tune and rebuild. Much easier than any other carb.