Carburetor Selection

[FridayGt]

Ok, I've been reading through some threads on carb selection and I want to see if I can ween some knowledge from the folks on here with more experience. I've read this thread and many others here; http://www.forbbodiesonly.com/moparforum/showthread.php?t=29056. However, I'm still left a tad curious. Maybe I can preface this with my set-up and then pose my questions.

1972 Road runner
1969 440 HiPo
Hedman Headers, to 3" all the way back through flowmaster mufflers
Edelbrock performer intake manifold
MSD Ignition and coil
Tan cap distributor
Initial timing around 14.5 dedgrees
727 Trans, highway stall at around 2300
Stock cam & heads presumably
2.73 open rear - Really trying to pinch pennies so I can pick up a 3.55 Sure Grip
It seems to love 750CFM

Ok, the reason I ask is because the carb that is on the engine now was pretty shot when I bought the engine. It was rebuilt and within weeks is giving me troubles again. The mechanic that did the engine swap for me said that I really needed a new carb, but with the unexpected cost of a new engine, I couldn't afford it. Well, he tried to rebuild, didn't get it working right. Tried one of his Holley's on it and that was worse, but he was able to get the Eddie working after that. When it was working, it was amazing, but it seems to be flooding now so I'm starting to research a new carb.

Fuel pressure is good. I was at one point pushing too much as I had a non-vented gas tank and a non-vented gas cap which apparently = bad. Lol. Vented the cap and all has been good. But lately, weeks after the succesful swap, it's been running stinking rich, literally. It's funking up the garage and house and it's fouling out plugs running so rich.

So, on to the questions I have. One, anyone had a problem like this before that can reccomend things to check? My float levels are where they should be per the manual, but apart from that, I don't know much else. Looking over it I found a few things I was curious about. The fast idler cam does precisely nothing it appears. As soon as the throttle is actuated, it just dangle there the rest of the time unless it's put back. Abnormal? Also, the metal flappy thing (technical term) that is supposed to cover the front two barrels just hangs open at all times.

Next, why do you pick the carb you picked? My plans for this car are primarily to be the once or twice a week nice weather driver to work. I will more than likely continue to drive it like I stole it at all times, but track time will be extremely limited, if at all. Any suggestions?

Oh, and I would prefer a manual choke. I'm thinking 1407 from Eddie, thoughts?

 

[67 coronet]

the"floppy thing that covers the front 2 barrels sounds like your choke,which would also explain why you high idle cam just dangles(part of the choke)you may want to get another tech to look at the carb,sounds like your guy is not that good.other wise with your set up a 750 edelbrock would work great.why the manual choke preference?electric choke is soo much easyer.
if you choke is just floating it could be cutting off air flow at upper rpms,thereby causing your over rich problem.

 

[Cranky]

Not sure if rebuild kits for these things include rubber parts that will hold up to ethanol laced gas. I do know that many years ago, they did not and I found out the hard way when the station I was using started buying E10 fuel and my Holley DP didn't like it. A rebuild kit didn't last more than a few months! My E58 360 with aftermarket intake and headers and 3.91 gears would scream after freshening up the carb but would start running crappy after a short while and doing tweaks didn't do much. I drag raced my cars etc and wanted the carb that made it go the quickest. I have a nice stock of carbs on the shelf and would just keep going bigger until it didn't go any faster. A 650 DP did the trick for the 360. A 750 DP on a mild 383 worked very well. The largest setup was 2 750's on a tunnel ram but it was a race only deal. Some preach using the chart to match the perfect carb with your engine but I've always gone faster with a larger carb than the chart suggests...and to me, the chart is only a suggestion but everyone drives differently and the needs are never the same.

 

[demonram]

I've got a a 1407 on my 451 stroker, in my 72 satellite. I changed it to an electric choke for ease of operation. I did rejet and rod it after the build It was a mild 400 250-300 horse and it was great. The only thing now is the hesitation when I mash the go peddle to pass. I've got the pump rod set at its peak but still can't get enough fuel to stop that hesitation. It's super easy to work on and actually gets decent milage when I stay out of it.

 

[ykf7b0]

The Edlebrock 1407 is a pretty good carb if your are not into performance. I ran one for a short while on my mostly street 440 and used every combination possible with their calibration kit and never got rid of the slight bog under hard excelleration. I was hitting the strip regularly and the bog was unacceptable. I now have a Holley 850 DP and it is really tuned in and the 440 really was awakened compared to the Eddy 1407 750.

 

[FridayGt]

the"floppy thing that covers the front 2 barrels sounds like your choke,which would also explain why you high idle cam just dangles(part of the choke)you may want to get another tech to look at the carb,sounds like your guy is not that good.other wise with your set up a 750 edelbrock would work great.why the manual choke preference?electric choke is soo much easyer.
if you choke is just floating it could be cutting off air flow at upper rpms,thereby causing your over rich problem.

Yes, the choke, the choke is not actually hooked up at the time. The car is already set-up for a manual choke from the last carb on the previous engine. The current carb, however, I believe was originally an electric choke, with the choke mechanism missing. It does not have the lever's and clasp for the manual choke line. The choke cable is currently just tied back. Also, that choke doesn't move when I actuate the throttle, it just hangs open.

Not sure if rebuild kits for these things include rubber parts that will hold up to ethanol laced gas. I do know that many years ago, they did not and I found out the hard way when the station I was using started buying E10 fuel and my Holley DP didn't like it. A rebuild kit didn't last more than a few months! My E58 360 with aftermarket intake and headers and 3.91 gears would scream after freshening up the carb but would start running crappy after a short while and doing tweaks didn't do much. I drag raced my cars etc and wanted the carb that made it go the quickest. I have a nice stock of carbs on the shelf and would just keep going bigger until it didn't go any faster. A 650 DP did the trick for the 360. A 750 DP on a mild 383 worked very well. The largest setup was 2 750's on a tunnel ram but it was a race only deal. Some preach using the chart to match the perfect carb with your engine but I've always gone faster with a larger carb than the chart suggests...and to me, the chart is only a suggestion but everyone drives differently and the needs are never the same.

I'm not certain that my station uses ethanol gas as I don't remember seeing the sign, but then again, which gas company isn't pumping the stuff now a days. Come to think of it more, when I start it up initially, it spews out enough liquid gas from the tail pipes to put a decent spray pattern on the front of the vehicle behind it. It also sputters and pops quite a bit in a vacuum. Primarily without touching the peddle after just getting into it.

I've got a a 1407 on my 451 stroker, in my 72 satellite. I changed it to an electric choke for ease of operation. I did rejet and rod it after the build It was a mild 400 250-300 horse and it was great. The only thing now is the hesitation when I mash the go peddle to pass. I've got the pump rod set at its peak but still can't get enough fuel to stop that hesitation. It's super easy to work on and actually gets decent milage when I stay out of it

Hmmm, that's good to know, but hopefully if I do wind up going with it I won't have the same issue with bogging. Well, at least not one that can't be adjusted out.

 

[Cranky]

I've got a a 1407 on my 451 stroker, in my 72 satellite. I changed it to an electric choke for ease of operation. I did rejet and rod it after the build It was a mild 400 250-300 horse and it was great. The only thing now is the hesitation when I mash the go peddle to pass. I've got the pump rod set at its peak but still can't get enough fuel to stop that hesitation. It's super easy to work on and actually gets decent milage when I stay out of it.

Could be a timing issue.....

Yes, the choke, the choke is not actually hooked up at the time. The car is already set-up for a manual choke from the last carb on the previous engine. The current carb, however, I believe was originally an electric choke, with the choke mechanism missing. It does not have the lever's and clasp for the manual choke line. The choke cable is currently just tied back. Also, that choke doesn't move when I actuate the throttle, it just hangs open.


I'm not certain that my station uses ethanol gas as I don't remember seeing the sign, but then again, which gas company isn't pumping the stuff now a days. Come to think of it more, when I start it up initially, it spews out enough liquid gas from the tail pipes to put a decent spray pattern on the front of the vehicle behind it. It also sputters and pops quite a bit in a vacuum. Primarily without touching the peddle after just getting into it.

Hmmm, that's good to know, but hopefully if I do wind up going with it I won't have the same issue with bogging. Well, at least not one that can't be adjusted out.

It's a federal mandate to blend 10% ethanol into the nations fuel supply.

 

[FridayGt]

I guess another question would be, between the most popular carbs out there, what the differences be? I hear sometimes heated debates go back and forth with some people who love one or the other, but what are the specific material differences? I hear that Holley's are better performance but harder to maintain and the opposite for Eddie's.

On a side note, performance is very sluggish and the pavement behind the exhaust tips is litterally wet on start up.

 

[oldbee]

From the setup you have--I would recommend a 780CFM Holley with vacuum secondaires or close to the same for a Carter AVS style...Over-carbureting is just as bad or worse than being a little under..The vacuum secondaries will compensate a little for a low-gear rear-end & less flow thru the heads&exhaust. They won't open up quite as quick..Hope this helps.

 

[FridayGt]

From the setup you have--I would recommend a 780CFM Holley with vacuum secondaires or close to the same for a Carter AVS style...Over-carbureting is just as bad or worse than being a little under..The vacuum secondaries will compensate a little for a low-gear rear-end & less flow thru the heads&exhaust. They won't open up quite as quick..Hope this helps.

Wow, 780 sounds like a lot for mostly stock. Have you seen or had any experience with the Street Avenger's by Holley? I'm fairly certain they have a 770CFM one.

 

[jteran2006]

Carburetor

my car died out last week and my uncle told me the carburetor was no good and i could either get it fixed or replace it with a better one. my friend told me that a Edelbrock 1805 Thunder will do the trick. I have a 1973 satellite/roadrunner clone 5.2L 318 v8 will this be compatible? Would I have to replace some parts or make major adjustments if its compatible?

 

[oldbee]

at "Friday"--seems to me a stock AVS was about 650cfm or so..A Holley 780 is pretty close and with the secondaries opening up when need be, it should work pretty good.Vacuum sec's only open as fast as "need be",you have to have the rpm's,etc. to let them open up. Kinda the same on an AVS. Nobody says they WILL open all the way every time.

 

[Meep-Meep]

I'll agree with the folks that say you can be having problems with your existing carb or other areas, but all that aside, my preference for a street driver is to focus on a carb that is designed for street driving. For example not all Holley's are created equal. Some have the circuits modified for high overlap cams (i.e. race engine) and some don't. There is a lot more to a carb than jets and metering rods. The emulsion circuit plays a huge roll in how fuel is metered throughout the RPM range and at various loads and vacuum levels. Carbs rely on vacuum in order to work properly so rounding down to a smaller carb is the best approach for a street engine that will rarely see 6000 RPM. The only thing more CFM does is allow for higher RPM potential at the expense of everything else. I'm running a 750 Eddy on a very mild but high compression 440 and it is fantastic.

 

[FridayGt]

at "Friday"--seems to me a stock AVS was about 650cfm or so..A Holley 780 is pretty close and with the secondaries opening up when need be, it should work pretty good.Vacuum sec's only open as fast as "need be",you have to have the rpm's,etc. to let them open up. Kinda the same on an AVS. Nobody says they WILL open all the way every time.

I suppose you're right. The difference between 750 and 780 really isn't all that much. Do you think that with a set-up like this though that I would find myself in a position where I might need to be jetting down the primaries? I do tend to really get into the peddle quite a bit, but a majority of the miles this car sees are the nice weather rides to work and occasional trips to the parts store.

I'll agree with the folks that say you can be having problems with your existing carb or other areas, but all that aside, my preference for a street driver is to focus on a carb that is designed for street driving. For example not all Holley's are created equal. Some have the circuits modified for high overlap cams (i.e. race engine) and some don't. There is a lot more to a carb than jets and metering rods. The emulsion circuit plays a huge roll in how fuel is metered throughout the RPM range and at various loads and vacuum levels. Carbs rely on vacuum in order to work properly so rounding down to a smaller carb is the best approach for a street engine that will rarely see 6000 RPM. The only thing more CFM does is allow for higher RPM potential at the expense of everything else. I'm running a 750 Eddy on a very mild but high compression 440 and it is fantastic.

Yeah, there's defenitely a problem with my current set-up. I suppose I could have been less confusing with the diagnostic information though. When the engine was swapped in mid December, there was an issue with excess fuel pressure causing issues. We then vented the gas cap, and the issue was solved. 5 -6 PSI I believe is the new pressure. All was running fine for a bit until a mangled connector on the spark plug wire that the shop cut for the car got corroded and scorched to hell. They apparently mangled it so much that it wasn't making a good connection at all and it was constantly fouling the plugs out. I fixed this with some pliers, wire brush and a can of WD-40. After this, all was running fine once more for a while and I was pulling little one wheel peels to my hearts content... lol. Until I started noticing that I was runnung extremely rich. I was dumping fuel out of the exhaust at start up, my plugs are fuel fouling out on me constantly and I'm getting those nice little sputters and pops when I let go of the peddle after partial to full throttle acceleration. The fumes are now noticably stronger in the garage and now defenitely can be smelled in the house.

The current carb has defenitely seen better days. It's an Edelbrock 1411 750 CFM carb that used to be electric choke. The electric choke was long gone before I got, but I already set my car up for manual choke anyway. It's been weather rotted and then cleaned up and rebuilt multiple times. The shop tried to get me to buy another, but after the unexpected cost of the engine, I just couldn't afford it so they rebuilt it again and had it running just fine for weeks. There used to be a Holley 750 Vac sec on the old engine, but this new engine just wasn't liking that one as much. On top of that I believe with all of the excess fuel pressure causing flooding before start up, carb backfires kept blowing out the power valves on it before they figured out to vent the gas cap.

I would love to rebuild it, but without knowing what could be wrong, I have no idea if this would help at all. Ultimately, if I get a new one, this old one will be torn down and rebuilt anyway because that's just how I learn best. There's nothing quite like a tear down and rebuild to show you exactly how something works and why it doesn't.

 

[FridayGt]

You know, come to think of it, any of you guys think this could be a loose air valve screw issue? Maybe it vibrated loose and backed out enough to just have the thing flapping open. This could explain the rich running, but would it explain the flooding carb when not running? Thoughts?

 

[FridayGt]

Also, looking at new carbs I think I've pretty much narrowed it down between two. I'm looking between the Edelbrock 1407 and the Holley 0-3310S. Both 750CFM, both manual choke, both square bore, both new. I see two main differences. The Eddy has only one fuel inlet, and for my purposes, I don't really care. The other difference I see is in the operation of the secondaries. While Holley incorporates a vacuum secondary, Edelbrock uses an air valve instead. I understand that the differences may be minimal in how the affect my uses, but can anyone explain the diffrerences a little more clearly than wikipedia for me? I'm curious as to how this would affect bottom line useage.

 

[dryheat]

According to some math that I just did given a stock 440 running at 6000 RPM the "maximum" CFM the engine can eat is around 670.

 

[FridayGt]

According to some math that I just did given a stock 440 running at 6000 RPM the "maximum" CFM the engine can eat is around 670.

I showed Street CFM at 649.31 and Racing at 840.28. I figured 750 CFM would be a good par for the course, especially considering that it slurped up everything the previous 750 had to offer and loved it when things were running right.

I used the CFM calculator on Summit's site;
http://www.summitracing.com/expertadvice/popup.aspx?Control=CFMCalculator

 

[dryheat]

I used the CFM calculator on Summit's site;
http://www.summitracing.com/expertadvice/popup.aspx?Control=CFMCalculator

Geez ... I went and made my own Excel worksheet ... :laughing1: ... well at least I remembered some basic geometry from the 70's ... Mr. McKeon would be so proud.

 

[67 coronet]

750 is a great street 440 cfm.the edelbrock uses"air flow"to actuate the secondaries,with a regulating weighted flapper.the holley uses a vacuum signal to regulate the opening of the secondaries.for the most part they work about the same.the edelbrock is a bit easyer to work on,the holley is far more adjustable.both should work great with minimal adjusting.