carb. suggestions!!!!!!!!

[440nika]

Hey Guys,
I got a 70' Dart with a 440 and I'm looking for the best carb. that would be an easy install and get pretty good fuel mileage if that's possible. I currently have a 750 Holley and I can not get this carb. adjusted so that it won't miss while pulling out. After pull out it runs fine but while cruising at 10 or 15 mile an hour or pulling out it will miss every time (But no backfires). I've tried changing jets (up and down in sizes), re-adjusting float levels, checking and re-checking spring tension on secondaries, adjusting several times the air/fuel mixture screws. I just can't figure this carb. out.
I also need to know if I change my carb. (Holley) to say an Edelbrock will my Lokar Kickdown cable and accelerator (Gas pedal) cable still mount the same way on other carbs or will I need to buy different mounting brackets or stuff.

Thanks for helping out, Dave !!!!!!!!!!

Oh ya it's an automatic transmission

 

[pettybludart]

Could you post some pics. also you don,t mention anything about vacuum?gaskets,spacers,4 hole or spread-bore.Is it double pump or v.secondarys??

 

[416stroker]

If you decide to go with a Edelbrock, I have a 800 Edelbrock Thunder AVS with auto choke for sale.

Like new...$225.00 plus shipping. Your linkage should work okay with it.

 

[440nika]

Thanks for the quick reply, There is a pictures of the car (and motor) in the gallery section under 440nika: "1970 Dodge Dart 440". The only gasket would be carb to intake. There is no spacer. It is a spread bore and it is a double pumper carb. Oh ya the vacuum is off the distributor. I believe that should help out with the stuff that I forgot to mention at the begining.

Thanks again in advance and keep shooting me your suggestions, I appreciate them. Dave!!!!!!!!!!!

 

[demon seed]

Thanks for the quick reply, There is a pictures of the car (and motor) in the gallery section under 440nika: "1970 Dodge Dart 440". The only gasket would be carb to intake. There is no spacer. It is a spread bore and it is a double pumper carb. Oh ya the vacuum is off the distributor. I believe that should help out with the stuff that I forgot to mention at the begining.

Thanks again in advance and keep shooting me your suggestions, I appreciate them. Dave!!!!!!!!!!!

Are you sure that Holley isn't a square bore and if so the Edelbrock RPM wants a square bore. Also you mentioned "spring tension on the secondaries" which tells me you're running a vacuum secondary carb. Either way I'd put on a 750 double pumper Demon carb with that RPM manifold.

Terry

 

[2 Darts]

You may want to consider this formula in selecting carb size.

(CID x Max RPM)/ 3456 = CFM @ 100% efficiency.

Most engine run in 70% - 95% range. Rule of thumb is 85% for most high performance engines. Take the rating above and multiply by .85 to get the requirement for your situation.

What ever brand & size you decide on, make sure you get a Chrysler kickdown lever for it. It'll save time and irritation of having to adapt or fabricate a substitute.

 

[65Val]

You haven't mentioned playing with the accelerator pump circuit at all. Sounds to me like it could use a tweak.Make sure its squirting some fuel even with the slightest throttle opening.

 

[LXguy]

I'd stick with the Holley. More power, looks cooler!

I can't find the pic, but if you're changing vacuum secondary springs its a vacuum secondary carb rather than a double pumper.

It sounds like your problem has more to do with either pump cam or squirter size than anything else.

As you go from idle to part throttle, there is an interruption in the vacuum signal to the carburetor. Holley carbs crutch this by using an accelerator pump to squirt raw gas during the time that the engine isn't directly drawing fuel via vacuum.

You either have too much pump shot causing a stumble, or too little, causing a hesitation. With a 750 and a 440, I'd wager you don't have enough, either because the squirter is too small or because the pump cam is not ideal or on the wrong hole.

I'd find out what squirter you've got and either get one the same size with the brass tubes to increase the duration of the shot, or try a couple in larger sizes.

If you're interested in gas mileage, Id put the pump cam in the middle hole.

If you do by some chance actually have a double pumper you'll have two pumps, cams, squirters, etc. Double pumpers are not the way to go for fuel mileage. Their emulsion circuits are designed more for racing and are overly rich.

Last, having the vacuum hooked up to the dizzy will help fuel mileage immensely, *but* you have to be sure to hook it up to the ported vacuum on your carb *not* the engine vacuum.

Holley does sell a tuning DVD (or they include it with their Street Avenger carbs) that has a lot of helpful troubleshooting tips.

I don't believe the Lokar setup works with the Edelbrock carbs.

Good Luck!

Steve

PS If you can swing it, Id HIGHLY recommend getting a wideband 02 sensor. It is *very* helpful at getting idle mixture correct, and figuring out which way you need to go to adjust pump shot, jetting, etc. Also makes fuel economy tuning much easier.

 

[440nika]

Hey Guys, Thanks again for helping out. I'm sure it's a double pumper (NO DOUBT). When I said about adjusting the secondaries, what I meant was adjusting the tension of the springs that control the rear jets to .010. I'm not very savy on carbs. and I'm trying to list information that I remember from talking with my brother in law who's been trying to help me out also.
I agree that a double pumper is not a very good choice if fuel mileage is what your looking for which is why I'm trying to find out what carb. is my best bet. Not only for decent fuel mileage but a carb. that can just about be bolted on and it's ready to go without a day of tuning (if that's possible).
Is anyone running a 440 and if so what fuel mileage should I expect to get on mine. Currently I'm getting 11.4 mile at best on the highway and worse around town to a gallon, this I know because I check it every tank full.
Hey guys thanks again and please don't lose patience with me I really do appreciate all your help. Dave!!!!!!!!!!!!!!!!!!!!!!!!!!

 

[C130 Chief]

You have a 440 in a Dart and want gas mileage?!? All things are relative, and 11.4 is better than I would have expected knowing nothing about your cam, compression, gears, converter, etc...

Something also sounds odd about your description. You say you adjusted the spring tension on the rear jets? Jets have no springs, although vacuum secondaries do (and most Holleys had secondary metering plates). Holley did make some mechanical secondary spreadbore carbs as Quadrajet replacements. These were mostly designed to help GM applications pass smog while still running like a worn out Q-jet. Avoid these as they were NOT a performance carb out of the box. If you post the Holley part number for the carb you have, we can help you identify it. Carb number is stamped on the front of the choke horn.

If your 440 is basically stock, I'd say either an Edelbrock Performer 750 or a Holley 750 vac secondary (like a 3310). If you have a larger cam, headers, and are looking for a bit more performance, the 850 Thunder AVS will do nicely.

If you want gas mileage, and don't want to do a lot of carb tuning, you don't want a double pumper with an automatic on the street.

 

[LXguy]

The springs you're talking about are for the accelerator pumps, which control the shot to the squirters. That isn't an adjustment that is going to do anything for you. You need to adjust the size of the squirters themselves.

How much cam duration do you have? How much compression?

A double pumper carb isn't really for someone who's new to carbs. I did it that way and spent an entire summer kicking myself in the nads before I figured it out and got my car running half decent.

I'd highly recommend a vacuum secondary Holley 4150. Which one depends a lot on what else your combination consists of.

I'd also recommend picking up a book on tuning Holley carbs, and that wideband 02 sensor I was telling you about.

Steve

Hey Guys, Thanks again for helping out. I'm sure it's a double pumper (NO DOUBT). When I said about adjusting the secondaries, what I meant was adjusting the tension of the springs that control the rear jets to .010. I'm not very savy on carbs. and I'm trying to list information that I remember from talking with my brother in law who's been trying to help me out also.
I agree that a double pumper is not a very good choice if fuel mileage is what your looking for which is why I'm trying to find out what carb. is my best bet. Not only for decent fuel mileage but a carb. that can just about be bolted on and it's ready to go without a day of tuning (if that's possible).
Is anyone running a 440 and if so what fuel mileage should I expect to get on mine. Currently I'm getting 11.4 mile at best on the highway and worse around town to a gallon, this I know because I check it every tank full.
Hey guys thanks again and please don't lose patience with me I really do appreciate all your help. Dave!!!!!!!!!!!!!!!!!!!!!!!!!!

 

[demon seed]

Ya lost me Dave, cuss that picture in your photo album of the old engine is showing a Holley Vacuum Secondary which I've never seen with a secondary accelerator pump. How about posting a picture of the carb and intake setup and what rear gears are you running (are they still the 3.55's). Also what's your initial timing at 800 RPM with the distributor vacuum line removed from the distributor and line plugged. Once you're sure of your initial timing at let's say 800 RPM try to idle her back to 500 RPM and check timing again. Like C130 says forget mileage, at least for now, get the 440 running properly, which ain't no magic, and worry about mileage later.

Terry

 

[3404spdvaliant]

It sounds like you have the wrong shooter and the wrong power valve.
If there is a shooter in the front[primary] and the rear[secondary] then it's double pumper.
Automatic?
good size cam?
Go to kragen/shucks/checker and buy a manifold vacuum gauge then find out what the vacuum at idle is while in gear/foot on brake.
Install a power valve half to 1 size more than half the vacuum reading.
Then with engine still warmed up crack the throttle as fast/wide open as you can, you'll probably get a pop out the carb [cause there aint enough shot]
Go 2 shooters bigger then whats on there now[28-31-34 ect.]
Also what color pump cam? red? white? orange?
If this doesn't cure the problem completely then it will at least 'mask' it making it more drivable till you fix/change the air bleeds.
Let us know.
Buy new plugs also and go with 70-72 size pri jets to start[if 4779 holley]
80-82 sec[unless you have frnt & rear power valves then square it up 70-72 all 4 corners]

PS 830 annular would be what I'd use on a hot street or mild strip 440.

 

[72_Durstya]

I dont really know much about big blocks, but from talking to people Mopars dont really like Holleys, they're too touchy, I hear Edlebrock's are better for mopars. I know my Duster did not like the Holley 750 dbl pumper I had on it and it was jeted down to a 650.

 

[65Val]

I dont really know much about big blocks, but from talking to people Mopars dont really like Holleys, they're too touchy, I hear Edlebrock's are better for mopars. I know my Duster did not like the Holley 750 dbl pumper I had on it and it was jeted down to a 650.

AFB's ,whether Eddy's or Carter/Fed.Mogul are generally easier to adjust for the street. For an all-out race car, you can go with Holley.

That's been my experience, anyway.

 

[65Val]

I dont think carbs care which brand of engine they are on, just the application. What I dont understand is...How do you jet a carb from 750cfm to 650cfm? You can change jets from ie 75's to 72's or 71's,etc, but the cfm of the carb is pretty much unalterable...(is that a word?)

 

[Petzschler]

You may want to consider this formula in selecting carb size.

(CID x Max RPM)/ 3456 = CFM @ 100% efficiency.

Most engine run in 70% - 95% range. Rule of thumb is 85% for most high performance engines. Take the rating above and multiply by .85 to get the requirement for your situation.

the proper way to determine engine VE is as follows:

~ theoretical cfm = rpm x displacement / 3456
~ volumetric effciency = actual cfm / theoretical cfm x 100
this is only good if you have an access to an engine dyno.

otherwise,

this will get u in the ballpark much better then the .85 rule:

~ rpm x displacement / 3456 x .975

 

[3404spdvaliant]

I dont really know much about big blocks, but from talking to people Mopars dont really like Holleys, they're too touchy, I hear Edlebrock's are better for mopars. I know my Duster did not like the Holley 750 dbl pumper I had on it and it was jeted down to a 650.

Carburetors don't care what brand engine they are on.

 

[72_Durstya]

I dont think carbs care which brand of engine they are on, just the application. What I dont understand is...How do you jet a carb from 750cfm to 650cfm? You can change jets from ie 75's to 72's or 71's,etc, but the cfm of the carb is pretty much unalterable...(is that a word?)

1st As far as brand, every local mopar guy I've talked swears by the Edlebrock over Holley's and the way it sounded when they were telling me is that Mopars are more reliable with the Edlebrock's. 2nd I borrowed the Holley from a friend who said it was jetted down to run more like a 650cfm carb and since im not a mechanic and I'm learning new things everyday i just took that as it being jetted down to a 650cfm carb.

If you were just trying to help out by noting this so maybe me and other can learn something from it thanks! But if you were just trying to be a know it all I don't appretiate it. Hope it's the first of the two. Cheers!

 

[65Val]

1st As far as brand, every local mopar guy I've talked swears by the Edlebrock over Holley's and the way it sounded when they were telling me is that Mopars are more reliable with the Edlebrock's. 2nd I borrowed the Holley from a friend who said it was jetted down to run more like a 650cfm carb and since im not a mechanic and I'm learning new things everyday i just took that as it being jetted down to a 650cfm carb.

If you were just trying to help out by noting this so maybe me and other can learn something from it thanks! But if you were just trying to be a know it all I don't appretiate it. Hope it's the first of the two. Cheers!

It is most definitely the first! I apologize if it came across differently. I've just never heard of changing a carb's cfm rating by rejetting it. If it's possible,it's new to me. You can put jets from a 650cfm carb into a 750cfm carb, but that just changes the fuel mixture, not the cfm rating,as far as I know.

...and I agree totally with your first paragraph, but mostly the performance tends to favor one brand or the other by application. If you have race-only car, seems a Holley is preferred because of their adjustability. If the car is mostly street-driven, the Carter/Edelbrock is preferred for their easy "out-of-the-box" installation and "no-fuss" operation.

...but everyone will have their own opinions and experiences. The above are mine...whatever that's worth.

"your mileage may vary"

Take care....

 

[72_Durstya]

It is most definitely the first! I apologize if it came across differently. I've just never heard of changing a carb's cfm rating by rejetting it. If it's possible,it's new to me. You can put jets from a 650cfm carb into a 750cfm carb, but that just changes the fuel mixture, not the cfm rating,as far as I know.

...and I agree totally with your first paragraph, but mostly the performance tends to favor one brand or the other by application. If you have race-only car, seems a Holley is preferred because of their adjustability. If the car is mostly street-driven, the Carter/Edelbrock is preferred for their easy "out-of-the-box" installation and "no-fuss" operation.

...but everyone will have their own opinions and experiences. The above are mine...whatever that's worth.

"your mileage may vary"

Take care....

Cool, glad to here it's the first lol, I didn't think it was the second just sometimes its hard to gage how ppl are coming across on here when you can't here how they're speaking. No appology needed. Thanks for the info though, learn something new every day!

 

[65Val]

Cool, glad to here it's the first lol, I didn't think it was the second just sometimes its hard to gage how ppl are coming across on here when you can't here how they're speaking. No appology needed. Thanks for the info though, learn something new every day!

Yeah...that's what wrong with computer-chat...hard to convey emotions or feelings...and sometimes the wrong ones get conveyed!!:toothy10: