Hello,

Carb has been rebuilt, timed perfectly but car still get's awful gas mileage (around 10 mph). Runs good most of the time. Pops and stalls when cold. (fuel mixture too lean?). And when heat soaked and turned off for more than a few minutes, really had to start. Is this all due to the same carb issue? Any advice would be helpful, stumped at what to do next.

Thanks!

Dan

Firs tell us about the engine is it stock or modified, year of car, make and model of carburetor, static timing setting, and elevation car is operated at.

Lean and poor fuel economy are not bedfellows, but can both be present; in other words you may have several things not up to snuff.

Does exhaust stink when idling? (A sign of over rich condition)

Depending on which carburetor you have there are several problems that would contribute to poor fuel economy. I’ll list a few common conditions that cause rich condition:

High float level

Ruptured power valve, and / or mal adjusted and / or wrong rods.

Idle mixture screws out to far

Idle and or main jet air bleed plugged

Over size main jet

Choke not fully pulling off once engine is warmed up

Float needle valve not fully seating

Accelerator pump leaking

Heat riser crossover in manifold plugged, or stuck.

PCV valve stuck, and or not connected to manifold vacuum.

Fuel leak… smell dipstick for heavy gasoline smell, inspect all fuel lines and pump

Big vacuum leaks cause popping out carb, and dying or non-idle:

if power brake equipped check its vacuum circuit all the way back to diaphragm for leaks.

Intake to carb gasket, and or carb base warped.

Mechanical advance not free to move disallowing any advance, and or vacuum advance circuit not working for whatever reason

_________________
67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

Please give us more to go on. What car? What carburetor? Any modifications? To what specs has it been tuned? .... That sort of information helps.

Edit: wjajr is quicker on the trigger than I am.

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"When you find a big kettle of crazy, it's best not to stir it." - Pointy-haired Boss

1964 Valiant V200, 225/Pushbutton 904
BBD, CAI, HEI, LBP, AC, AM/FM/USB, EIEIO

It's a plain 'ol 1974 Custom 4-door with automatic transmission. Carb is the Holley 1945-R6724A. She's stock. I'm in the Seattle/Everett Area; altitude would be no more than 100ft. Not sure of the static timing, it had been timed by my mechanic actually. (covering head in shame) Exhaust does not stick when idling, no knocking or pinging either.

have you also checked the non engine related items
* brakes dragging
* low tire pressure
* tranny slipping
* fuel leak
* working the throttle like an on-off switch

Thanks for the advice. The popping and poor running when cold has been alleviated. The ignition ended up failing; replaced that, all the wiring to the coil and had to replace the distributor (again unfortunately) because it all shorted out. It's running much better since I had all that done. I was hopeful the fuel economy would improve but it did not. Still between 10-11mpg. But it runs good, that's what's baffling. New tires too. I did have to adjust the vaccum at the carb a bit; when it came back from the shop it was running really rough and kind of lurching at low rpms while at higher speeds. That has improved.
No bad smells like exhaust or fuel, I think the choke is working fine. She still starts a little hard when warm; but it's not flooding. If anything it's too lean, it's impossible to flood. So I'm back to scratching my head. Maybe check the vacuum more precisely. Heck, maybe the brakes are dragging. Thanks for all your help and suggestions!

Does it have a rebuilt carb? Does it have a rebuilt distributor?

When you get rebuilt stuff, god knows what you are getting. I would suggest that you take them apart and see what you got. Then you can go from there.

For example, I have found that initial timing on these engines starts at 15* btdc.

Sounds like you have some timing/carb issues, but maybe your gas line or tank is rusted through somewhere? 10 mpg sounds like a 440 tri-power or 426 with two 4 bbls type mileage...

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Have you pulled a couple plugs out to look at their color?

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2 Mopars come with Spark plug tubes. One is a world class, racing machine. The other is a 426 CI. boat anchor!

12.70 @ 104.6

Hi,

I have a 74 Swinger, and have driven it up to Everett from Black Diamond everyday for work for many years. It gets great mileage even with over 300,000 on the engine.
That is due to heat soak.....click on the red link below my name and look at the pictures. You can build a heat deflector for under the carb to stop that. Mine cost less than $5.00 but, larger ones would even be more effective and help a lot more with the mileage.

In 74 they make you do some goofy things like set the timing at zero....which I disregard and run it at 12 degrees instead, with 5 turns out on the 11X vacuum canister so it won't ping and run 55 degrees total timing. I re-curved the distributor but a 77 and up dist. are good replacements in stock form. The 74 distributor springs were way to sloppy and it would advance way to fast....and ping. Installing the stiffer springs did the trick. Read the recurve instructions in the FAQ. I have contributed some good info there....
Get rid of the EGR stuff and turn it back into a normal engine. You will be glad you did......you can see mine is very basic and clean. I do suggest keeping the charcoal canister hooked up. It is nice not having smell gas after shutoff. Years ago I ditched the 1945 after many hours trying to make it work well. I went with a 1972 Holley Economaster and never looked back. It is a great carb. You can clearly read the carb number in the close up pictures. "1920 Holley Economaster List# R-7585 68-72 Chrysler"

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Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG