I am running 2 500 CFM Edelbrock carbs on my 1st Gen 392 Hemi. They are running so rich, they are eating up spark plugs like they were pop corn.
A mechanic friend of mine says nothing can be done, it's the natuer of running 2 4's. I don't want to accept that. Any suggestions to improve, or eliminate this situation?

Number on the carbs??

Edelbrock sells a set calibrated for dual quad setups. I bet you don;t have that.

http://old.edelbrock.com/automotive/mc/carburetors/thunder.shtml

Calibrations are listed verify what you have.

Will check to confirm, but I am almost positive mine are the Performer series? I've had them for about 4 years?

Both are 8867, but one has electric choke? On the base plate of each, is stamped F 2 X 4.

my eddy 1406 was lean & the choke came off way too fast. check your needle/seat(s). waterlogged float(s). float hanging up. fuel psi

When adjusting fuel/air mixture, should both carbs be excatly the same, or adjust as individual carbs?

Both carbs HAVE to be synced or you will never get them to work right. It take patience and a bit of trial and error to get right. This Guide will help you and save me from typing it all out. Running rich is bad and your buddy should feel bad for that mistaken advise. Having one carb rich and another lean is worse. A broadband a/f gauge is a very good tool, but you should be able to get close without one. YouTube has vids to help out as well. HTH, Steve

Thanks a ton. I have a Hemi with a cross ram that is way out of tune. I was looking for a document like this as doing some tuning is first thing on my list this spring. I was pretty good at tuning a single four and did a pretty good job with the 6 pack (found the guide from someone here). Moparts comes through again.

Great info. Something I think even an idiot (that would be me) can understand, and do. Thanks.

Are you running them with both working at the same time, one to one linkage, or with progressive linkage?
You probably need to lean down the metering rods on the primary step, the bigger step up high, to get it to run good at light part throttle cruise
I would adjust the primary idle mixture screws so it is as lean as possible and still start and idle okay with no stumble from driving away from a idle.
What spark plugs brand and part numbers are you using now and how much compression on your motor?
The new Eddy carbs are not as good as they use to be
You can get them to work excellent with enough tuning, so good they should knock the tires off at will at WOT

One to one, come in together.
NGK plugs/Autolite 65.
The car runs and idles good. Exhaust tips black as coal, exhaust will burn your eyes, and foul the plugs. I just replaced the Autolite 65 with the NGK equivalent, but I don't remember the number.

i'm running two 600's on a ch28 and they work great. the 500's have a very restrictive primary booster, and you could be getting too strong of a vacuum signal to them. you might try a 68x52 rod; also do a fuel pressure and float level check. long cams will screw up the metering system too. in my opinion those 500's belong on small engines only. that primary cluster is just too screwed up to put on anything that will flow air. back in the day carter had a properly done small afb. instead of using the carter model, that required more part changes, edelbrock got cheap and just restricted the front half. I believe it is possible to put 600 clusters in those carbs. be careful of bad advice!!!!!!!!!

I started with 650's. Too much carb, switched to 600's. Too much carb, went to the 500's. Runs much better. 2 X 500 = 1000, that's a lot of cfm's. The engine is mild, only bored 30 over to clean up the block, and mild cam. Stock iron heads, stock exhaust manifolds, factory Weiand intake. I built it to drive, not to race, or win trophy's or burn out contest.

Try tuning the primary rods on the large step by making it larger in diameter by .002 to .006 or so and see if that helps, keep tuning it until your happy
How much timing at idle and how much total timing?
I cut my teeth( a long time ago back in the early to mid 1960s) on tuning the first gen Hemi Chrysler Firepower motors, 331,354 and 392 300 letter series motors
Good luck

Fuel psi is critical. IIR Edelbrocks cannot have more 6 psi.

I'm running 4 psi, Holley electric pump, Moon Eyes gauge. I lean toward the old stuff, moon eyes, stewart warner, etc. I also name my cars (car now). It's a 48 DeSoto, named Odd rOd. The O's are capital letters, and they are painted (no decals) like the moon eyes.

a carb cannot make 0ne cfm. cfm ratings are for dummies. you've got something wrong besides the carbs.

I had once bolted a Marine dual quad intake on a 440 with 2 brand new 625cfm Carter carbs, and that engine was a blast to drive.
Just some tweaking of the idle mixture screws was enough to get them to idle nicely. No issues whatsoever.




Many years later I installed two 650 used but otherwise equal Carter/Edelbrocks on a 354ci Chrysler poly-engine with a 392ci Hemi dual quad intake, and the engine ran very rich and backfired at the same time occassionaly. The carbs where jetted equally and checked for vacuumleaks but none were found. Something was not happy in that setup. After a while I switched back to a single carb as I just wanted to drive the car at the time.

8867 isn't the carb number.

the carb number is stamped as below

Only number. I checked there first, only numbers there was the F 2X4. The 8867 was stamped on top plate, left rear (driver side).