409 Running Rich

[DonSSDD]

My 409 is running rich and I’m trying to understand the possible causes.

I have my timing set at 12, does backing it to 10 or 8 help my problem?

I am learning this stuff gradually, so bear with me. I set my mixture screws using a vacuum- 21 degrees and pretty steady. My stock distributor with Pertronics pulls vacuum from a carb mounting post- I teed my vacuum guage off that. The idle is set at 750. If I turn my screws in a quarter turn, it won’t idle. I have my carb wired open to eliminate that variable, it starts very easy, idles good, but blows black smoke and my plugs are black as well. No big chunks, just black.

I get no pinging, run premium gas, new plugs, wires, and engine is freshly rebuilt, maybe 500 miles. Throttle response is excellent, no hesitation, but has a bit of a miss/loses oomph at about 4500RPM or so.

It is a 63 340HP 409 with stock intake, heads, valves, manifolds, cam, bored 30 over, Carter AFB #3783. The carb I bought, rebuilt to stock specs I am told. It’s a 4 speed as well. The carb works so well, even idles not bad cold without the choke, I haven’t touched it.

Is timing likely to cure my rich problem?

Don

[bobs409]

When you find out, let me know. :) I asked about mine being the same way a long time ago and pretty much sum it up to being normal for big engines aka; big blocks, etc. My tail pipes are constantly sooty. I don't even use my choke, it's starts in 20 degree weather without it!

My plugs run light brown/light tan in the centers with black soot on outer rings.


Bob

[oldskydog]

Something that been coming up lately on other sites is supposedly stock new replacement fuel pumps putting out way too much pressure...like 15-17 psi. Might be worth a check.:dunno

[WENGINE]

Check that fuel pressure If it's OK I'd look at that carb. Have had similar problems with many a rebuilt carb dumping fuel. Bad idle circit or a leak. I don't use them anymore and unless your going for a all original " numbers matching" application I'd think about getting a new carb. Do you have another carb or can you borrow one to see if it clears up you problem?

[Ronnie Russell]

Don, The guys are right of course. Check fuel pump pressure , if that checks out it would have to be the carb. Timing change will not help. Just a suggestion,,, Pay the $280 for a new Edelbrock #1404 500cfm and sell the 3783 on e-bay. It will bring a decent amount to offset some of the expense of the new carb. It might seem that a 500cfm is too small for the 340hp engine, but if you are not going to be racing, the 500cfm will be a good dependable carb and will not blow out the black smoke like you are doing now. The problem you have with the 3783 can be fixed, but it would be hit and miss , trying to chase the culprit causing the problem. Just my opinion. Good luck...

[fatride]

Good carb tuners are like good friends, if you find one treat them really good and try and keep them close. ;) Ronnie has some good advice., bigger is not always better. A lot of so called "bolt on carbs" are a myth. If you get lucky your engine will match the so called out of the box carb. Carbs are to be matched to engines not the other way around. A new Edlbrock carb will come with a complete set of instructions, yes I have to read them too, make your step up spring selection/float setting place a good filter before and after the fuel pump and get cruising!

[DonSSDD]

So what you are all saying is- too much fuel? Either fuel pump or carb? Nothing in my timing or carb tuning is too far off base to cause the rich problem?

How much fuel pressure is acceptable?

Thanks for the advice.

Don

[Ronnie Russell]

Don, 4 to 8 psi is in the ballpark for fuel pressure. Not enough vacuum would cause that symptom. Metering rods not being pulled down . But you have plenty of vacuum, if you plan of repairing the 3783 , you would start by identifing jet and metering rod size. If theyare indeed stock size, you would have a different problem , maybe improper float setting. If you have a buddy that is experienced in rebuilding and tuning carbs, good, he can probably find the problem. If not, you are stuck . Fight the black smoke or buy a new carb. It is still my opinion to save yourself a lot of problems and buy the new carb. I just bought a new #1404 for $237 including shipping. Price has just been raised $12, but still fair for a brand new carb.

[fatride]

Ronnie is the "Go to guy" for setting up a AFB style carb for your engine, too bad going to his house involves a major road trip. Then again there would be a waiting line around the block at his house. :eek:

[Tom Kochtanek]

Looks like I will be heading to Michigan the weekend of July 25th to hang out with old high school buddies and hit some golf balls. Haven't bought an airplane ticket as yet, might just drive out and visit Mom in Cleveland afterwards (Monday the 27th). That's not too far from you, Fatride. Might just have to zip out and visit you and Marcia if you are in town. Can I bring my tripower setup and a lot of adult beverage?

Not sure if I will be driving my SS or not, but I haven't had a good road trip yet this year. I missed Bowling Green, missed a Nostalgia weekend in St. Louis, it's just been one thing after another. I think I need a road trip to lighten my spirits :).

I might try to connect up with Loren in central Ohio on the way home, who knows?

Cheers!
TomK

[bobs409]

Someday I might try a new carb myself. I've tried everything; float setting, mixture settings, timing, metering rods/jets, you name it. Nothing helps. I have plenty of vacuum too. Can't find any vac leaks anywhere.

So, what's a good replacement # for my 3499S? It's a 63 400hp 409, stock except .030 over.


Bob

[dq409]

I would listen to the others suggestions about the fuel pump then recalibrate the carb.
IMO,, if the fuel pressure was high you would over rode the nettle and seat and flood out the engine and it would die.

Go to a leaner idle/cruse setting (meter rods and or jets) and see if that helps.
It is cheaper then another rebuild or carb.
From what you have said it seems to run fine but on the rich side at idle and I would guess at light cruse also.
Because of the "If I turn my screws in a quarter turn, it won’t idle" I would say that indeed you are running to rich.
This should be an easy fix as you sound like you are close.
,,,dq

[fatride]

I run Carter Competition series 600 cfm carbs on top of my 09, I would chose them over an Edlbrock carb, but that's just me :dunno

[larry t]

I run Carter Competition series 600 cfm carbs on top of my 09, I would chose them over an Edlbrock carb, but that's just me :dunno

Is Carter still making AFB's? For some reason, I thought they had discontinued their Carb line.
Larry T

[fatride]

Is Carter still making AFB's? For some reason, I thought they had discontinued their Carb line.
Larry T

I think your right, I buy Ebay or the like.

[DonSSDD]

Carter I think went out of business in the 70's and Edelbrock bought the patents or copied them. I have a Carter in a 63 Corvette, it works perfect. I will see what I can sort out with this one. Maybe I should not have upgraded my fuel line to 3/8".

The car works very good, I am just concerned the extra fuel will cause a problem. Maybe the solution is keep the RPM's up and burn more fuel.

I found a Sun analyser today- it is the size of a suitcase, with 4 instruments. The one for vacuum and pressure only goes to 7lbs. I guess that was all that was needed then. A friend inherited a building full of stuff, this was there and he doesn't know how to use it.

One other question, when idling, I get a squeak from the drivers side exhaust- no obvious noise in the motor, just out the exhaust. A fellow who listened to it said he thought it might be a noisy valve guide- said to run some auto tranny fluid through the gas tank. What do you think of that?

Don

[jester]

Be carefull when u lean those puppies out. You don't want then running any hotter :dunno

[fatride]

Looks like I will be heading to Michigan the weekend of July 25th to hang out with old high school buddies and hit some golf balls. Haven't bought an airplane ticket as yet, might just drive out and visit Mom in Cleveland afterwards (Monday the 27th). That's not too far from you, Fatride. Might just have to zip out and visit you and Marcia if you are in town. Can I bring my tripower setup and a lot of adult beverage?

Not sure if I will be driving my SS or not, but I haven't had a good road trip yet this year. I missed Bowling Green, missed a Nostalgia weekend in St. Louis, it's just been one thing after another. I think I need a road trip to lighten my spirits :).

I might try to connect up with Loren in central Ohio on the way home, who knows?

Cheers!
TomK

Tom

I am on vacation in that time period, call me, I may just be home sitt'in around. You can spend the night if you've a mind to. Or stop for dinner and put your feet up, how's pizza and a beer sound?

[Ronnie Russell]

Don, all the suggestions you have recieved are good. The problem is that you must disassemble the carb. to make changes. If you are comfortable doing that, jump into it. As I suggested earlier, you first must identify the jets and rods you have before you can determine if that is the problem. You can then lean it out with smaller jets, put it back together and maybe you fixed it maybe you didn't . Bob, normally I would say a 750cfm would be correct for your 400hp engine , and it would be good for maximum performance,,, personally I would go with a 600cfm for better drivability and economy. Oh, by the way , Don, automatic trans fluid should go in the automatic transmission, not in a gas tank. Just my opinion.

[DonSSDD]

Ronnie, I have put a kit in a Rochester 4jet, haven't had a Carter apart yet. The Rochester worked very good.

Are the Carters the same as the Edelbrocks, so if I find the schematics/manual for one, it works for both? I think I have the specs for the carb I have.

Is the fuel pump pressure supposed to be the same on all Chevy mechanical fuel pumps, SB, BB, and W?

Any suggestions on my squeak?

Thanks for the help.

Don

[skipxt4]

I had a similar problem with a Carter AVS on a 340 mopar, back in the 70's. Same deal. Crappy idle with black exhaust smoke. Adjusted everything over and over. Idle, mixture, float setting, choke pull off. Nothing helped.:dunno Had erratic vacuum reading with a gauge on it. Finally had enough, and pulled the carb off. I opened the butterflies and noticed the mixture slots, weren't slots anymore. They looked twice their normal size and now were round. The mixture screws also were damaged. Apparently someone turned them in, way TOO TIGHT. :eek:The fix, in this case was a 1850 Holley. :clap Skip:)

[larry t]

[QUOTE=DonSSDD;99898].... I have a Carter in a 63 Corvette, it works perfect. I will see what I can sort out with this one. .............


Don,
How about trying the Corvette carb on the 409? It should tell you if you have carb problems or something else (fuel pressure, etc.).
Larry T

[Ronnie Russell]

Don, I have many instructions that comes with kits. Exploded views of the carb. If you have rebuilt a Rochester, the AFB will be simple. Be glad to mail you those instructions if you need. Just PM me your address. Sorry, I have no idea what the squeak could be. I would guess an exhaust manifold gasket leak, but that is a wild stab. Fuel pressure for stock pumps is about the same. Anything over 9 gets a little iffy about over riding needle and seats. You might want to take the car around the block and get it up to temperature, park it , take air cleaner off and see if you are getting smoke back up through the carb. A simple way to tell if carb is leaking fuel ( flooding ) . Skip, bought an e-bay carb a few months ago and the idle air mixture slots were broken out. Much the same as you described. e-bay carbs are always a gamble. Sometime you when, sometime you lose.

[johnnyrod]

I have a 348 300 hp with an Edelbrock AVS 650 vac secondarries is that too big for what I have? Turbo 350 3.55 posi. 29 inch tall tires. John

[Ronnie Russell]

johnny, That's pushing it. The AVS is a great carb. I would go two stages lean on both primary and secondary. Should work out good.

[DonSSDD]

Don, I have many instructions that comes with kits. Exploded views of the carb. If you have rebuilt a Rochester, the AFB will be simple. Be glad to mail you those instructions if you need. Just PM me your address. Sorry, I have no idea what the squeak could be. I would guess an exhaust manifold gasket leak, but that is a wild stab. Fuel pressure for stock pumps is about the same. Anything over 9 gets a little iffy about over riding needle and seats. You might want to take the car around the block and get it up to temperature, park it , take air cleaner off and see if you are getting smoke back up through the carb. A simple way to tell if carb is leaking fuel ( flooding ) . Skip, bought an e-bay carb a few months ago and the idle air mixture slots were broken out. Much the same as you described. e-bay carbs are always a gamble. Sometime you when, sometime you lose.

I'll send you my address Ronnie and check out the smoke.

Don

[DonSSDD]

On the Corvette carb, I checked out that carb, it is a 300HP 327, it has this gasket:

http://images.corvette-paragon.com/840_standard1.jpg

My 409 carb has a similar gasket, but without that horseshoe cutout.

This is my intake (before I cleaned it up):
http://pic20.picturetrail.com/VOL164/2040090/3952594/323293878.jpg
The gasket I have lines up over those 2 holes.

The base of my carb looks like this (one I found on ebay, not the one I bought):
http://pic20.picturetrail.com/VOL164/2040090/3952594/323293872.jpg

Show Cars have a different gasket #3320A, see here for a pic.

http://www.show-cars.com/01%20Fuel%202.htm

Is the gasket I am using correct?

Don

[gearhead409]

Don, i see your problem. you are boiling the gas out of your AFB. you need to plug the two exhaust crossover holes in that 340 manifold or use the steel shim gasket that was used under the 300hp AFB

[larry t]

Don, i see your problem. you are boiling the gas out of your AFB. you need to plug the two exhaust crossover holes in that 340 manifold or use the steel shim gasket that was used under the 300hp AFB

I agree, look at part number 3320 that Show Car sells. Your Corvette should also have the same setup.
This might not fix all of your problems, but it would eliminate one of them.
Larry T

[DonSSDD]

The Corvette does have that plate. Is that a cause of running rich?

Don

[dq409]

The Corvette does have that plate. Is that a cause of running rich?

Don

Don, Rather then keep hashing over what could cause this you need to start somewhere,,

Pull the meter rods and jets to see what you have and go from there, use a carb gasket that will isolate the heat from the manifold after you block the cross over.

You can use the Edelbrock calibration book if you change over to the Edelbrock jetting numbers and parts. Easy to follow and use,,

http://www.edelbrock.com/automotive_new/mc/carbs_acc/pdf/carb_owners_manual.pdf

[MileHiSS]

That Carb gasket is just like the one that is stock for a Carter AFB. I just rebuilt one on my 63 Cadillac. The openings are for the heat risers to heat the carb, but it also uses a flat metal spacer.

[models916]

I had an idle rich problem with the Edlbrooks 600's on mine with the HP Carter pump. I switched to offroad needle and seat and all cleared up.

[DonSSDD]

Don, Rather then keep hashing over what could cause this you need to start somewhere,,

Pull the meter rods and jets to see what you have and go from there, use a carb gasket that will isolate the heat from the manifold after you block the cross over.

You can use the Edelbrock calibration book if you change over to the Edelbrock jetting numbers and parts. Easy to follow and use,,

http://www.edelbrock.com/automotive_new/mc/carbs_acc/pdf/carb_owners_manual.pdf

DQ- pulled metering rods, they are stamped 16-202 C- what's that translate into?

Don

[Ronnie Russell]

Don, The metering rod size tells nothing without knowing the jet size. You can use dial calipers to measure metering rod. Two measurements, one ,, the tip ,the other,, move up the rod until size changes to larger. The rod is a shaft that partially fills a hole. You have to know what size hole it is filling.

[DonSSDD]

Thanks Ronnie. I measure the rods as 0.081 and 0.059. The jets, the closest drill I have to fit the hole is 0.096, and it being a little loose, I'm guessing they are 0.098.

Seems big based on the Edelbrock specs.

I appreciate the education, the fellow who worked on my carbs died last fall, cancer, 58.

Don

[Ronnie Russell]

Don, It is good that you have identified sizes. It would be good if someone could supply the original 3783 sizes. Sorry, I don't have those. A 600 Edelbrock uses .100 and 70x47 rod,,, the 500 uses much smaller primaries, I believe .086, so there is a big difference between the two, but that has nothing to do with the 3783. You have a .098 to .100 jet and a .081 rod so that seems in the range. I sure would not call that rich. In fact, I don't see how you can go leaner and have the engine run at all. I guess we will have to hope the new metal gasket will make a difference. Boiling fuel makes since, unless you show black smoke with a cool engine. Well, hope you track it down. Sometimes these things can drive you nutty. The main reason I suggested picking up the phone and ordering a new one. :rofl

[dq409]

Have you checked the fuel pressure yet ?:doh

[DonSSDD]

Haven't- have to get a fitting.

Thanks,

Don

[gearhead409]

Don, i see the boys over on chevytalk are helping you out. good luck with your project.

[DonSSDD]

Actually, I didn't ask about my rich problem there, somebody must have seen my question here.

I find very helpful people on both sites, where do you hang out there gearhead? I see many people from here over there.

Don

[gearhead409]

Don, i was just jerking your chain! i spend time over there too.

[bobs409]

You two are now banned from this site.

Just kidding! :rofl


Bob

[DonSSDD]

You two are what makes this site such a sweet place to visit.:hug:takethat:evil:stooges:D

[DonSSDD]

Have you checked the fuel pressure yet ?:doh

Well I did it- my gauge reads to 10 lb and it pegged out.

I haven't done this before- I disconnected the fuel line before the inline filter and blocked the line there to the carb. I hooked my gauge to the line coming out of the fuel pump and started the car, using the fuel in the carb. Or should I have teed off the fuel line with the gauge while leaving the connection to the carb?

Don

[dq409]

Well I did it- my gauge reads to 10 lb and it pegged out.

I haven't done this before- I disconnected the fuel line before the inline filter and blocked the line there to the carb. I hooked my gauge to the line coming out of the fuel pump and started the car, using the fuel in the carb. Or should I have teed off the fuel line with the gauge while leaving the connection to the carb?

Don

Either way you found your problem !!
Too much pressure !!
Now get your self a fuel regulator and start enjoying that car !!

[DonSSDD]

What PSI would work?

Don

[oldimpala]

What PSI would work?

Don

I would run 4-7psi. I keep my pump 5.5-6.....

-Andy

[Old School]

Someday I might try a new carb myself. I've tried everything; float setting, mixture settings, timing, metering rods/jets, you name it. Nothing helps. I have plenty of vacuum too. Can't find any vac leaks anywhere.

So, what's a good replacement # for my 3499S? It's a 63 400hp 409, stock except .030 over.


Bob

Bob: I had the same problem on my 400HP… I went through 3 AFB’s and never had one that would run correct. I purchased an Edlebrock Performer 1406 600 cmf carb and converted it. The stock 3783 takes fuel from the driver’s side and the 1406 has the fuel inlet on the passenger side. Instead of re plumbing all the fuel lines, I swapped the tops and used the 3783 top with the driver’s side inlet on the 1406. It worked perfectly while retaining the stock appearance.

Also, I took off the 1406 electrical choke and replaced it with the original AFB heat choke.

I used the stock metering rods and jets because that is way above my level of expertise. This is the first carburetor I have had on this motor that has had no issues. No longer runs rich, no pinging, easy starting even when hot and the choke actually works..

I think I may have lost a little performance but am willing to live with that for the smooth running and drivability.
Mick

[DonSSDD]

Don, I have many instructions that comes with kits. Exploded views of the carb. If you have rebuilt a Rochester, the AFB will be simple. Be glad to mail you those instructions if you need. Just PM me your address. Sorry, I have no idea what the squeak could be. I would guess an exhaust manifold gasket leak, but that is a wild stab. Fuel pressure for stock pumps is about the same. Anything over 9 gets a little iffy about over riding needle and seats. You might want to take the car around the block and get it up to temperature, park it , take air cleaner off and see if you are getting smoke back up through the carb. A simple way to tell if carb is leaking fuel ( flooding ) . Skip, bought an e-bay carb a few months ago and the idle air mixture slots were broken out. Much the same as you described. e-bay carbs are always a gamble. Sometime you when, sometime you lose.


Thanks Ronnie, received the book yesterday, very nice of you to go to that trouble.

Haven't got new gaskets yet- later this week maybe.

Don

[gearhead409]

i have been thinking about your carb problem some more after you said you had 10 plus psi fuel pressure. if you are still using the stock 340hp pump on your engine, it is rated at 7.5-8.5 lbs. if you are not using the fuel filter return line, this pressure could even be higher. your AFB may not be able to handle this and for sure will not hold back the fuel if it has been rebuilt using the larger .120" needle and seats. get yourself a 5 lb. pump and use the base gaskets that we talked about earlier and you should be fine.

[DonSSDD]

I got a regulator and new gasket and spacer, it seems cured. Been busy and haven't been driving it much but it is not putting out a lot of black smoke now.

Thanks again.

Don

[johnnyrod]

Is that vacume line off the front of the carb ported for your Distributor ?
John

[DonSSDD]

My distributor runs off a vacuum line hooked to the driver side rear carb mount bolt. I used the same bolt from my 59 El Camino 283 PG.

Don