Conflicting carb advice

[six_sigma 12]

Hey folks, 

So I have rebuilt roller 302 with an RPM intake, B cam and Tri-y's. I have an Edelbrock 1406 600cfm performer carb and it's running quite rich. I was told, and had read in a few places that a 500 CFM carb is really the way to go, so I found a used on for a good price that was on a V6 chevy motor. I installed the carb and I can't get the car to idle below 1K RPM, previously is was idling around 750-800 with a nice burble. So I go to a specialist carb rebuilder to ask if they have a jet and rod kit for the carb and the old guy says that the 500 is too small and the engine is going to run lean. so now I have 2 carbs and more confusion. 

Any of you guys care to add to my store of conflicting knowledge?

Thanks in advance.

[mqu02 30]

A 600cfm carb is on the extreme high side of what a decent 302 will normally use unless it is absolutely screaming, and a 500cfm carb should be more than sufficient (actually ideally suited).  Are you sure your 500cfm unit doesn't have a tuning problem?  Also, I am not very familiar with the 1406, but you should be able to jet it down and keep it.

[barnett468 418]

what is your compression with a gauge?

auto or manual?

what type of driving do you do?

i would throw the eddy in the trash or give it to someone i dislike greatly.

 

 

 

 

[Rsanter 152]

BS

a carb too small will not make an engine run lean.

a carb too small will limit the top end of the engine because it can't get any more air into it. How often do you spend at wide open throddle?

too small of jets make an engine run lean. Typically if you have the carb jetted correctly for up to 75% throddle, it will typically run a but lean at the top. But it is better to run lean at the top than to burn rich at everything below 1/2 throddle.

 

do you know the carb is any good? Do you have the strip kit for the carb? It has all the small parts to make changes.

 

bob

[six_sigma 12]

2 hours ago, mqu02 said:

A 600cfm carb is on the extreme high side of what a decent 302 will normally use unless it is absolutely screaming, and a 500cfm carb should be more than sufficient (actually ideally suited).  Are you sure your 500cfm unit doesn't have a tuning problem?  Also, I am not very familiar with the 1406, but you should be able to jet it down and keep it.

I'm not sure that the 500 doesn't have a tuning problem that's why I had gone to that guys place to buy a metering rod and jet kit. The 1406 had been rebuilt and jetted down for use on my engine but it still runs too rich which is why I had been looking for the 500cfm unit. 

2 hours ago, barnett468 said:

what is your compression with a gauge?

auto or manual?

what type of driving d you do?

i would throw the eddy in the trash or give it to someone i dislike greatly.

2

Compression or vacuum?

Auto, AOD

Right now almost none, it's quite irritating. 

I'd rather not do that.

53 minutes ago, Rsanter said:

BS

a carb too small will not make an engine run lean.

a carb too small will limit the top end of the engine because it can't get any more air into it. How often do you spend at wide open throddle?

too small of jets make an engine run lean. Typically if you have the carb jetted correctly for up to 75% throddle, it will typically run a but lean at the top. But it is better to run lean at the top than to burn rich at everything below 1/2 throddle.

 

do you know the carb is any good? Do you have the strip kit for the carb? It has all the small parts to make changes.

 

bob

Bought the carb used, and was, of course, assured that it ran great when pulled, the guy I bought it off was installing a FiTech system

What do you mean by strip kit, you mean this?

https://www.summitracing.com/int/parts/edl-1486

If so, that is what I was trying to buy.

 

Thanks for your time guys.

[barnett468 418]

 

you did not answer all my questions, therefore, i can not help you.

you also said you did not want to throw the eddy carb away yet you already quit using it when you bought another carb that purportedly does not work and if that is also an eddy carb you should start to figure out by now that maybe you should do what i said and start with a carb that is easy to tune like a holley or quick fuel . it is obvious that tuning the eddy carb is beyond your ability otherwise you would have done it already and you may net even be able to tune a holley style, therefore, you might just be stuck having ti pay someone to tune any carb you get it if the carb is really the problem and if you can find someone that actually knows how which will likely be next to impossible.

 

you need to answer these questions also.

what exactly is the problem with how it runs?

what is the used carb you bought?

is your distributor vacuum connected to ported or manifold vacuum?

is there vacuum from that port at idle?

does the idle drop if you remove the distributor hose while it is idling?

does the idle drop much if you remove the pcv valve them plug it with your thumb?

what is your initial timing at idle with the distributor vacuum hose both connected and disconnected?

 

 

 

 

 

[six_sigma 12]

7 hours ago, barnett468 said:

you did not answer all my questions, therefore, i can not help you.

you also said you did not want to throw the eddy carb away yet you already quit using it when you bought another carb that purportedly does not work and if that is also an eddy carb you should start to figure out by now that maybe you should do what i said and start with a carb that is easy to tune like a holley or quick fuel . it is obvious that tuning the eddy carb is beyond your ability otherwise you would have done it already and you may net even be able to tune a holley style, therefore, you might just be stuck having ti pay someone to tune any carb you get it if the carb is really the problem and if you can find someone that actually knows how which will likely be next to impossible.

 

you need to answer these questions also.

what exactly is the problem with how it runs?

what is the used carb you bought?

is your distributor vacuum connected to ported or manifold vacuum?

is there vacuum from that port at idle?

does the idle drop if you remove the distributor hose while it is idling?

does the idle drop much if you remove the pcv valve them plug it with your thumb?

what is your initial timing at idle with the distributor vacuum hose both connected and disconnected?

5

Hey Barnett,

First off, thank you for taking the time to try and help me. I appreciate it. That said.

You asked me 4 questions. To the first, I responded by asking for clarification, to the second, I answered (auto), the third I probably responded with a little too much humor I'm just going to be cruising around town and some highway driving. As to throwing the carb away it's more than just the carb that would have to be replaced and I'd rather not incur that expense as well. As to your preference for Holly over Eddy I've heard just as much bad as I've heard good for both.

I readily admit I'm a novice and while it may, in fact, be beyond my ability to tune the eddy I was not asking for advice on how to tune it. I was asking about the appropriate CFM carb for my engine. Was it 500 which I had been told was the right size by a number of people and the online CFM calculators that I had used and 600 which the rebuilder at the shop I went to buy a calibration kit from insisted was more appropriate.

 

[barnett468 418]

i am an engine builder and tuner and have built over 1,000 carbs, therefore, i can tell you for a fact that you are asking the wrong questions.

you have also given us absolutely zero info as to EXACTLY what symptoms/behaviors the car exhibits, therefore, we have absolutely no idea what to suggest.

either answer all the questions or don't.

my questions do not need clarification.

if you don't want to buy another carb that is easier to tune then use the new 1406 eddy carb you have . it is NOT too big for your engine . if anyone says it is they have absolutely no idea what they are taking about, HOWEVER, you may need to adjust the air door on the secondaries so it opens later.

 

 

 

[MN69Grande 203]

I don't know a lot about Edelbrock Carbs, but what I read about them is that model doesn't allow more fuel into the secondaries until there is increased airflow even though the flap on top may open.  Not exactly like a vacuum secondary but not fully mechanical either.  Anyway the reason the 600 would not be over sized for you application is because the secondaries only provide additional fuel when needed so you aren't actually using the full 600 CFMs unless you need it.  The pull of air into the engine basically tells the carb how to operate.  That said you may need to tune this a bit to get it to run better.  And if you want help tuning it people would need more information about the symptoms.  However lots of people run those same carbs on 302s.  

[six_sigma 12]

29 minutes ago, MN69Grande said:

I don't know a lot about Edelbrock Carbs, but what I read about them is that model doesn't allow more fuel into the secondaries until there is increased airflow even though the flap on top may open.  Not exactly like a vacuum secondary but not fully mechanical either.  Anyway the reason the 600 would not be over sized for you application is because the secondaries only provide additional fuel when needed so you aren't actually using the full 600 CFMs unless you need it.  The pull of air into the engine basically tells the carb how to operate.  That said you may need to tune this a bit to get it to run better.  And if you want help tuning it people would need more information about the symptoms.  However lots of people run those same carbs on 302s.  

Thanks, I'll be looking at it more over the weekend after I pick up a calibration kit. 

[SWPruett 83]

On 6/30/2017 at 9:14 PM, barnett468 said:

HOWEVER, you may need to adjust the air door on the secondaries so it opens later.

 

1406 Eddy's are an AFB design.  No air door.  They are also a "lean-cal" economy setup, so one of these running rich is pretty unusual.

[six_sigma 12]

I had had the 600 rebuilt and tuned on a flow bench but was always told the 500 was a better fit that's why I got that one. When I did install it it and got the car running even 1000 RPM it smelled MUCH less like unburnt gas. Which I thought was a step in the right direction. Now I just have to get it dialed in.

[barnett468 418]

2 hours ago, SWPruett said:

1406 Eddy's are an AFB design.  No air door.  They are also a "lean-cal" economy setup, so one of these running rich is pretty unusual.

thanks, yeah i had their thunder carb in mind for some reason . the 1406 is a vacuum secondary a counterweight that can be altered to change the opening time but that's a pita.

 

[barnett468 418]

15 hours ago, six_sigma said:

I had had the 600 rebuilt and tuned on a flow bench but was always told the 500 was a better fit that's why I got that one. When I did install it it and got the car running even 1000 RPM it smelled MUCH less like unburnt gas. Which I thought was a step in the right direction. Now I just have to get it dialed in.

if your 1406 carb is too rich then it will smell less like gas also if you lean it out . it's really quite simple . its not like you have a behemoth 850 mechanical secondary carb on there . also, it is quite possible that the primaries on the eddy are the same size as the ones on your other carb it the other is a square bore.

also, a boss 302 is 302 cubic inches just like your is and it uses a 780 cfm carb . even if a 500 cfm carb is a slightly better match for your engine, like i said, a 600 is still not too big but since you haven't given us much info or answered many questions, you are completely on your own because it is simply absolutely impossible to help you based on your replies and lack of info in them.

 

 

 

.

[Bob & Sue 110]

10 hours ago, barnett468 said:

if your 1406 carb is too rich then it will smell less like gas also if you lean it out . it's really quite simple . its not like you have a behemoth 85 mechanical secondary carb on there . also, it is quite possible that the primaries on the eddy are the same size as the ones on your other carb it the other is a square bore.

also, a boss 302 is 302 cubic inches just like your is and it uses a 780 cfm carb . even if a 500 cfm carb is a slightly better match for your engine, like i said, a 600 is still not too big but since you haven't given us much info or answered many questions, you are completely on your own because it is simply absolutely impossible to help you based on your replies and lack of info in them.

 

 

 

.

I agree with Barnett you can use almost any size carb it's all about air/fuel mixture for your setup. 

Barnett can seem to be a bit grouchy gruff sort of guy ( so am I ) but he has a wealth of advise & knowledge everyone on here is just trying to give the best advise they can but without knowing or being able to know all the info needed it's just guessing at what solution is needed for any problem. I'm speaking just for myself a healthy discussion is the only way to get decent advise even if you disagree it's better to talk it through than waste money on throwing parts at a problem & ignoring questions being asked unless you want a garage full of spare parts. 

This post seems like what you've done has only confirmed that maybe the problem could be something else if 2 new carbs have the same symptoms, try giving step by step what you have, what you've changed & what the results are. From there people are here to help you there not here to just waste time on a forum well maybe some are most have a wealth of knowledge by learning the hard way doing it.

On another note after you've found a solution please post the results some threads can be pages long when someone else has a similar problem you get to the last post never knowing if the problem was found.

Please don't take this personally it's just a learning curve problems can get very frustrating.  

[SWPruett 83]

Might be worth it to start from scratch and understand what you've got:

An Edelbrock 1406 is a 600cfm "Performer" series carb that is based on the carter AFB.  Your 1406 _should_ have the following setup out-of-the-box:

Primary Main Jet = .098"

Metering Rod = .075" x .047"

Secondary Main Jet = .095"

Step-Up Spring = Yellow (4inHg)

Float Level = 7/16"

Float Drop = 1-1/4"

Pump Link Hole = Middle

Pump Shooter = 0.031"

I would suggest you buy a carb gasket kit (they're cheap) and a #1480 calibration kit (we used to call them Strip Kits in the Carter days) and rebuild the carburetor to the exact factory specifications.  If you've never done a carb rebuild, now is as good a time as any to learn.  This will give you a good starting point and answer a lot of questions as to what's "in there" and what the P.O. may have screwed up (hopefully nothing).  Otherwise, you will be shooting in the dark forever.

I don't hate Eddy's with the passion that Barnett468 has (but I understand it!), and the Eddy can be one of the most "driveable' carbs anywhere, but it ain't a Holley and it will require some study to get them to behave.  Start with the basics and let's see where we can get from there.

[six_sigma 12]

2 hours ago, SWPruett said:

Might be worth it to start from scratch and understand what you've got:

An Edelbrock 1406 is a 600cfm "Performer" series carb that is based on the carter AFB.  Your 1406 _should_ have the following setup out-of-the-box:

Primary Main Jet = .098"

Metering Rod = .075" x .047"

Secondary Main Jet = .095"

Step-Up Spring = Yellow (4inHg)

Float Level = 7/16"

Float Drop = 1-1/4"

Pump Link Hole = Middle

Pump Shooter = 0.031"

I would suggest you buy a carb gasket kit (they're cheap) and a #1480 calibration kit (we used to call them Strip Kits in the Carter days) and rebuild the carburetor to the exact factory specifications.  If you've never done a carb rebuild, now is as good a time as any to learn.  This will give you a good starting point and answer a lot of questions as to what's "in there" and what the P.O. may have screwed up (hopefully nothing).  Otherwise, you will be shooting in the dark forever.

I don't hate Eddy's with the passion that Barnett468 has (but I understand it!), and the Eddy can be one of the most "driveable' carbs anywhere, but it ain't a Holley and it will require some study to get them to behave.  Start with the basics and let's see where we can get from there.

Thanks for all the info it's good to have.

That was my plan all along. It was my trip to buy the calibration kit that sparked this whole thing! After I get it all sorted out I'll get back to you guys.

[barnett468 418]

unless your timing curve is optimal for your particular set up, it will never run as well as it could and may have burbles or flat spots upon acceleration that are impossible to fix by simply jetting the carb.

the carb is rarely ever the only problem, and since timing affects jetting to some degree, you must have the timing properly set to be able to jet it as best as it an be.

 

[six_sigma 12]

5 hours ago, Bob & Sue said:

I agree with Barnett you can use almost any size carb it's all about air/fuel mixture for your setup. 

Barnett can seem to be a bit grouchy gruff sort of guy ( so am I ) but he has a wealth of advise & knowledge everyone on here is just trying to give the best advise they can but without knowing or being able to know all the info needed it's just guessing at what solution is needed for any problem. I'm speaking just for myself a healthy discussion is the only way to get decent advise even if you disagree it's better to talk it through than waste money on throwing parts at a problem & ignoring questions being asked unless you want a garage full of spare parts. 

This post seems like what you've done has only confirmed that maybe the problem could be something else if 2 new carbs have the same symptoms, try giving step by step what you have, what you've changed & what the results are. From there people are here to help you there not here to just waste time on a forum well maybe some are most have a wealth of knowledge by learning the hard way doing it.

On another note after you've found a solution please post the results some threads can be pages long when someone else has a similar problem you get to the last post never knowing if the problem was found.

Please don't take this personally it's just a learning curve problems can get very frustrating.  

Hey Bob & Sue, 

I know it's all about air/fuel mixture and I suspect that the difference in carb bodies between the 1403 and 1406 is probably minor. It's more about the metering rods, jets and springs that it comes with out of the box. I'm all for discussion that's why I posted but the question wasn't "help me tune my carb" is was "500 or 600 CFM which is better" to which I've gotten 500 is better, 600 is fine or it doesn't matter. 

The calibration kits that Edelbrock sells are specific to each carb and then you can use their chart for rod and jet combos to get the desired mixture.

The two carbs do not have the same symptoms. The original 600 CFM carb idled nicely and ran fine around town but smelled and smoked a bit. The 500 that I bought USED and had been on a V6 previously would run but I'd have to to keep the idle up higher than I wanted. 

I am really glad you guys are here to help, even Barnett who is almost aggressively helpful. I picture him on his porch yelling at children to get off his lawn and every community needs one of those guys!

I'm not answering questions because I don't want too, it because I don't have the answers yet, when I do I will post them and I am thankful to Barnett for giving me the list of questions. Not having a home garage full of tools also means it takes some time to get the tools I need to get those answers.

I will absolutely post the results when I get it sorted.

I'm not taking this personally, this is a new hobby for me and everything has been a learning curve so yes frustrating but also satisfying when things finally work.

Now I'm off to replace my underdash harness with a refreshed one I just got from Randy at Midlife.

[Bob & Sue 110]

On 6/29/2017 at 5:38 PM, six_sigma said:

Hey folks, 

So I have rebuilt roller 302 with an RPM intake, B cam and Tri-y's. I have an Edelbrock 1406 600cfm performer carb and it's running quite rich. I was told, and had read in a few places that a 500 CFM carb is really the way to go, so I found a used on for a good price that was on a V6 chevy motor. I installed the carb and I can't get the car to idle below 1K RPM, previously is was idling around 750-800 with a nice burble. So I go to a specialist carb rebuilder to ask if they have a jet and rod kit for the carb and the old guy says that the 500 is too small and the engine is going to run lean. so now I have 2 carbs and more confusion. 

Any of you guys care to add to my store of conflicting knowledge?

Thanks in advance.

After reading thru your post again I can see why all the confusion on CFM sizing even the statement from your carb specialist is just an off the cuff type answer. For curiosity sake I looked at Edelbrocks calculation page even they aren't definitive on which one to run from their chart it seems like you can run either a 500 or 600 cfm, their FAQ's do go into a lot more detail on how to set it up. If it were me I'd get the tuning kit for whichever carb you want to run and set it up for your specific needs.

http://www.edelbrock.com/advertising/Literature/Misc/EDL_Carb_Application_Chart_03186.pdf

Summits calculator street 483 strip 625 CFM

https://www.summitracing.com/expertadviceandnews/calcsandtools/cfm-calculator

I've also had some tuning issues about ready to throw away the carb and dizzy to put on a Hilborn injection system ( non electronic, simple jetting ) with a Vertex Magneto. Already have the Hilborn from a trade I did just need to find the Magneto. 

[jholmes217 65]

Where are you located?  If you happen to be close to Fort Lewis, WA., I have a known good Holley 1850 600 cfm carb that I use for engine break ins.  It was last used in to a 302 a couple years ago, and seemed pretty dialed in to a mild 302 build.  Plugs were that nice light brown color when pulled after break in.  If your close, we can try that carb on your engine.

[Rsanter 152]

Yes, that is the kit you need if you are going to be messing with those carbs. 

 

While i I do agree with what was said about the 600cfm not being too big. There are advantages and disadvantages to what size carb you use depending on your usage.

the carb size is based on what the max RPM you will be using will be. If you have a 302 and will be road racing then you will need a bigger carb than a 302 cruzer 

 

if you have big ports (like a boss 302) and a single plane intake and big headers as well as the cam that can handle it, then you can use the bigger carb. 

If you have stock 302 then while you can make it run with the 750cfm carb. You will not get as good of throddle response or metering accuracy from that setup.

 

the 600cfm will work fine if properly setup. If you are getting gas smell at idle then I might suspect that you are not just on the idle circuit but perhaps the setscrew for the throddle blades needs to be backed off.

it is also possible that you have a float not setup right and you might be pushing too much fuel into the carb and have a little bit of overflow dumping int the engine.

if you are rich on running then you need a bigger needle or smaller seat, or both. Actually this what is often called the metering rods and seat.

 

I think I would try to get that 600 set up correctly before I tried someone's used 500

 

bob

[six_sigma 12]

10 hours ago, Bob & Sue said:

I've also had some tuning issues about ready to throw away the carb and dizzy to put on a Hilborn injection system ( non electronic, simple jetting ) with a Vertex Magneto. Already have the Hilborn from a trade I did just need to find the Magneto. 

No that is a cool looking set up! I'd like to see the install details on that one.

[six_sigma 12]

5 hours ago, jholmes217 said:

Where are you located?  If you happen to be close to Fort Lewis, WA., I have a known good Holley 1850 600 cfm carb that I use for engine break ins.  It was last used in to a 302 a couple years ago, and seemed pretty dialed in to a mild 302 build.  Plugs were that nice light brown color when pulled after break in.  If your close, we can try that carb on your engine.

That is a VERY generous offer thanks, but I'm a little out of the way. Toronto Canada.

[six_sigma 12]

2 hours ago, Rsanter said:

Yes, that is the kit you need if you are going to be messing with those carbs. 

 

While i I do agree with what was said about the 600cfm not being too big. There are advantages and disadvantages to what size carb you use depending on your usage.

the carb size is based on what the max RPM you will be using will be. If you have a 302 and will be road racing then you will need a bigger carb than a 302 cruzer 

 

if you have big ports (like a boss 302) and a single plane intake and big headers as well as the cam that can handle it, then you can use the bigger carb. 

If you have stock 302 then while you can make it run with the 750cfm carb. You will not get as good of throddle response or metering accuracy from that setup.

 

the 600cfm will work fine if properly setup. If you are getting gas smell at idle then I might suspect that you are not just on the idle circuit but perhaps the setscrew for the throddle blades needs to be backed off.

it is also possible that you have a float not setup right and you might be pushing too much fuel into the carb and have a little bit of overflow dumping int the engine.

if you are rich on running then you need a bigger needle or smaller seat, or both. Actually this what is often called the metering rods and seat.

 

I think I would try to get that 600 set up correctly before I tried someone's used 500

 

bob

8

Hey Bob,

This car is a total cruiser. I already have the 500 and I think that I'll work with that one both are going to require me buying a calibration kit and rebuild kit so I'd rather use the one that is right than the one I should be able to make work.