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Edelbrock Carb tuning
I have an Edelbrock 1406 (600cfm) carb that I am trying to tune. I currently have .073 x .047 metering rods, .098 primary and .098 secondary Jets and the 4in Yellow Step-Up springs.
Heavy acceleration from a standing stop is very sluggish. I have moved the external setting for the Accelerator pump, and it does not get better (currently set on center hole). Rolling acceleration seems to be good. Timing is set to about 12 deg. before TDC and I just installed a Pertronix Ignitor. What changes can I make to help? |
remove carb, place in box, install holley.
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Put in your 8" step up spring and move accelerator pump to the innermost hole....Max squirt!!
This should help a lot!! If you have other metering rods try to go richer in the power mode. Email me and I'll share my experiences getting mine right!! It may not give the last HP the Holley will but it sure is less trouble once you richen it up!!! Do keep in mind that they are set up very lean from the factory for "smog" reasons. Good Luck, Jack :MECOOL: :MECOOL: |
I have the same carb on my truck and had the same problem.
I moved to the 7" spring, (heavier spring means more vacuum required to stay in cruise mode so the idle to WOT is quicker to power mode), went to the innermost hole on the pump, and richer power mode on metering rod and that cleared up most of it. It seemed to improve a little be retarding the timing a couple of degrees as well. I now run at an initial timing of 10 degrees BTDC and max out at 34 degress BTDC at 2400 RPM. Now it only chokes if it sits idling for a while just prior to jumping on it. Sorry Mr. Fixit I'd rather give up a few horsepower on the top end and not have to replace power valves every 6 months. |
Hmmmmmmm,
Just the reverse problem with my 750. Run so rich out of the box your eyes would water a block away with soot out the sidepipes. 2 buddies with 600's with the same symtom. Have leaned mine down 2 steps and then got the hesitation. I believe it has to do with the transition circuit. Am going to try an old trick after I pull the carb and check the butterfly position at idle. Two thirds of the idle opening should be exosed. If not a 3/32 hole through each butterfly is supposed to fix that. ** Someone stop me if they've been down this road. ** |
Quote:
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Mr. Fixit and TP:
I thought I was going to be a real a$$hole and say the same thing you guys did, but you beat me to it. :3DSMILE::3DSMILE::3DSMILE: http://www.uselessgraphics.com/plane44.gif |
The power valve myth is just that, a myth. Any holley made in the last 15 years has that problem solved, if it doesn't, than a quick check ball install to the baseplate is all it takes. How often does your motor backfire through the carb anyway?
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Hi,
Someone has changed the factory settings, go back to them. .098 primary jets .095 secondary jets .075 x .047 metering rod your secondaries are way too rich with the bigger jet . go back to the stock metering jet also. turn front air screws all the way in and back them out 1 1/2 turns to start, turning them out richens up the mixture. make sure you have decent vaccum or look for a leak. good luck, Perry.:cool: |
As it turns out (after a call to Edelbrock) I was close. All I needed to change was to the 7 in spring. Runs great now.
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C_forshaw,
Does the carb you have handle really aggressive throttling in 2nd and 3rd gear without stumbling? What intake are you running? Steven:) |
There is no stumble on agressive throttle in any gear. I am running a Weiand intake.
Chuck |
Me too....have to get up earlier in the morning to play the heavy these days......
Bill S. Quote:
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Now, with that said, tell us a little more about your motor....
year of the block year of the heads Compression ratio Cam profile Type of intake Automatic or stick shift All will play a factor in how your particular carb should be set up. However, I can tell you from experience that the Edelbrock carbs do not lend themselves to performance, but more to the "bolt on and forgetaboutit crowd".........I sell them (Holley, Edlebrock, Barry Grant, Dan Best, etc), and have seen far too many replaced with a generic (yet quite tunable) Holley 08777C (650 double pumper), tuned properly (usually on a chassis dyno), that make more power, with better reliability than the Edlebrock units............ Bill S. |
I have a 1980 302 block (EOAE) with a Weiand of intake and Toploader 4sp (RUG-E)- wide ratio tranny out of '67 Mustang. I don't know to much more about the engine. I have a date with the dyno is a few weeks. That will tell me a lot more about the engine.
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I suggest making sure that the dyno is equipped with a wife band O2 sensor, and that your bring along someone who can tune your carb while it is up there....You want as close to a 14:1 air fuel ratio as possible............
Bill S. |
Bill,
Can you elaborate a little on your experiences as to the Edelbrock carbs? I ask, because I have not been able to eliminate the stumble my friend's 347. I have tuned it per their book, experimenting to the extremes of the jetting and spring combos. We dyno tuned it to around 14:1 with good transitions. I suspect the carb is just not capable of handling really aggressive driving due to the combination of mechanical linkage to the 2ndrys and it having no 2ndry accelerator pump. (it just seems the air door design can not handle it) I posed this question to the tech rep at Edelbrock and he danced around the question. I have also noticed they now make a version of the AVS carb. Will they phase out the current offering due to it's limitations? Being in the business, what are you hearing? Thanks Steven |
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