Poor engine performance and ugly MPG
09-18-2013, 09:32 PM
#1
Mopar Fanatic
Thread Starter
Poor engine performance and ugly MPG
Hi everyone!
Today I get my fury 74 back from some brake work, the mechanic try to tune up my holley 2245 but now the car has disastrous performance and disastrous mpg. Today I get around 5 MPG in city when it was used to make between 10 and 12 MPG in city. Since I buy this car I have never noticed a good performance from the 360 V8 maybe due to carburetor problems and engine problems (now the engine is rebuilded and has less than 30 miles on it). But now the performance is horrible! I hit the throttle but nothing happens there's no a great RPM change and the engine suddenly stops. Now the car easily starts but turns unstable when is idling and I must shift to Neutral
What can I done to correct this meanwhile the new carb arrives to home?
Today I get my fury 74 back from some brake work, the mechanic try to tune up my holley 2245 but now the car has disastrous performance and disastrous mpg. Today I get around 5 MPG in city when it was used to make between 10 and 12 MPG in city. Since I buy this car I have never noticed a good performance from the 360 V8 maybe due to carburetor problems and engine problems (now the engine is rebuilded and has less than 30 miles on it). But now the performance is horrible! I hit the throttle but nothing happens there's no a great RPM change and the engine suddenly stops. Now the car easily starts but turns unstable when is idling and I must shift to Neutral
What can I done to correct this meanwhile the new carb arrives to home?
09-19-2013, 02:55 AM
#2
Did he remove the carb? I'm thinking wicked vacuum leak. Check your idle mixture screws too, gently run them in all the way and then back them out 1 turn and see how it runs, 1 to 1.5 turns out should be ballpark.
09-19-2013, 05:04 AM
#3
Find someone who actually knows how to work on a carb !!! It is becoming a lost art with the advent of fuel injection
Check Fuel pressure, Check floats and float level, check that the mixture screw work. This is not the first problems you have had with your carb. I would get an adapter and buy a NEW Holley two bbl carb
Check Fuel pressure, Check floats and float level, check that the mixture screw work. This is not the first problems you have had with your carb. I would get an adapter and buy a NEW Holley two bbl carb
Last edited by TVLynn; 09-19-2013 at 05:08 AM.
09-19-2013, 06:21 AM
#4
Mopar Fanatic
Thread Starter
Find someone who actually knows how to work on a carb !!! It is becoming a lost art with the advent of fuel injection
Check Fuel pressure, Check floats and float level, check that the mixture screw work. This is not the first problems you have had with your carb. I would get an adapter and buy a NEW Holley two bbl carb
Check Fuel pressure, Check floats and float level, check that the mixture screw work. This is not the first problems you have had with your carb. I would get an adapter and buy a NEW Holley two bbl carb
I'll check the idle mixture screw and modify it, I expect a little change on my car performance
09-19-2013, 08:56 AM
#5
Also, throw the factory timing settings in the garbage can.
Plan on either recurving the distributor or buying a performance curve dist (with vacuum advance)
Most factory smog era distributors have a long slow advance curve which is not the best for either performance or mileage.
Lots of initial advance---more than 12TDC even on a fairly stock engine, and up to 15--20 BTC with a hotter cam.
This dictates a shorter mechanical advance so that you can still come up with an upper limit of 34--38* depending on the engine and fuel.
Be sure the vacuum advance is hooked up and working.
As for the carb, unfortunately there ARE problems in a carb that old (sometimes) that you just can't fix---tiny amounts of corrosion, etc in some of the small air bleeds and other passages. But the great majority of the time, just cleaning the carb PROPERLY and getting it back to original specs should result in a decent running car. As above, sounds to me like this guy just doesn't know carbs.
Plan on either recurving the distributor or buying a performance curve dist (with vacuum advance)
Most factory smog era distributors have a long slow advance curve which is not the best for either performance or mileage.
Lots of initial advance---more than 12TDC even on a fairly stock engine, and up to 15--20 BTC with a hotter cam.
This dictates a shorter mechanical advance so that you can still come up with an upper limit of 34--38* depending on the engine and fuel.
Be sure the vacuum advance is hooked up and working.
As for the carb, unfortunately there ARE problems in a carb that old (sometimes) that you just can't fix---tiny amounts of corrosion, etc in some of the small air bleeds and other passages. But the great majority of the time, just cleaning the carb PROPERLY and getting it back to original specs should result in a decent running car. As above, sounds to me like this guy just doesn't know carbs.
09-19-2013, 10:29 PM
#6
Mopar Fanatic
Thread Starter
Also, throw the factory timing settings in the garbage can.
Plan on either recurving the distributor or buying a performance curve dist (with vacuum advance)
Most factory smog era distributors have a long slow advance curve which is not the best for either performance or mileage.
Lots of initial advance---more than 12TDC even on a fairly stock engine, and up to 15--20 BTC with a hotter cam.
This dictates a shorter mechanical advance so that you can still come up with an upper limit of 34--38* depending on the engine and fuel.
Be sure the vacuum advance is hooked up and working.
As for the carb, unfortunately there ARE problems in a carb that old (sometimes) that you just can't fix---tiny amounts of corrosion, etc in some of the small air bleeds and other passages. But the great majority of the time, just cleaning the carb PROPERLY and getting it back to original specs should result in a decent running car. As above, sounds to me like this guy just doesn't know carbs.
Plan on either recurving the distributor or buying a performance curve dist (with vacuum advance)
Most factory smog era distributors have a long slow advance curve which is not the best for either performance or mileage.
Lots of initial advance---more than 12TDC even on a fairly stock engine, and up to 15--20 BTC with a hotter cam.
This dictates a shorter mechanical advance so that you can still come up with an upper limit of 34--38* depending on the engine and fuel.
Be sure the vacuum advance is hooked up and working.
As for the carb, unfortunately there ARE problems in a carb that old (sometimes) that you just can't fix---tiny amounts of corrosion, etc in some of the small air bleeds and other passages. But the great majority of the time, just cleaning the carb PROPERLY and getting it back to original specs should result in a decent running car. As above, sounds to me like this guy just doesn't know carbs.
If some of this parts isn't recommendable to use in my fury 74 please notice me, I can sell those parts to some friend and buy a more recommendable parts:
http://www.ebay.com/itm/MOPAR-DODGE-...0ca496&vxp=mtr
http://www.summitracing.com/parts/msd-8200/overview/
http://www.summitracing.com/parts/ms.../make/plymouth
Last edited by josehf34; 09-19-2013 at 10:32 PM.
09-20-2013, 09:39 AM
#9
Mopar Fanatic
Thread Starter
why? I too ordered a Carter AFB carburetor with a rebuild kit
I'm not sure but I think the brakes aren't dragging because if I shift to neutral the car doesn't inmediatly stop, it continues running for a long distance
New brake work ? Also Make sure the brakes are not dragging !
09-21-2013, 10:23 AM
#10
Mopar Fanatic
Thread Starter
Yesterday I change the carburetor jets and now the car runs better. The carburetor had jets size 62 number and I swapped it to a 58 number. The car still making black smoke when I accelerate but is less than with the jets number 62, a friend tell me this carburetor came from factory with a jet number 55 but I've been searching on google about it but I don't find so much information.
When I was checking the carburetor I noticed something: If I entirely close the mixture screws or I entirely open them nothing happens is like if them weren't working
When I was checking the carburetor I noticed something: If I entirely close the mixture screws or I entirely open them nothing happens is like if them weren't working
09-21-2013, 12:08 PM
#11
josehf34
You would be well off to get a book something like this and study it !
http://www.ebay.com/itm/How-to-Rebui...a#ht_192wt_679
You would be well off to get a book something like this and study it !
http://www.ebay.com/itm/How-to-Rebui...a#ht_192wt_679
09-21-2013, 01:57 PM
#12
Ok, now we're getting somewhere. If the corner idle screws don't affect anything your throttle plates are likely open too far, or there is a wicked vacuum leak. Where does the engine idle in gear with brakes applied? Where is the base ignition timing with vacuum advance disconnected?
09-24-2013, 07:35 PM
#13
Mopar Fanatic
Thread Starter
josehf34
You would be well off to get a book something like this and study it !
http://www.ebay.com/itm/How-to-Rebui...a#ht_192wt_679
You would be well off to get a book something like this and study it !
http://www.ebay.com/itm/How-to-Rebui...a#ht_192wt_679
Ok, now we're getting somewhere. If the corner idle screws don't affect anything your throttle plates are likely open too far, or there is a wicked vacuum leak. Where does the engine idle in gear with brakes applied? Where is the base ignition timing with vacuum advance disconnected?
I haven't check the ignition timing but I think the vacuum advance is broken because if I disconnet the hose coming from the vacuum port to the vacuum advance and blown on it nothing happens but this will be fixed when the new distributor arrives.
09-24-2013, 09:34 PM
#14
I would not lose the original carb jets. Assuming that "it previously ran right" it follows that the jetting used to be OK.
I would guess some other problem.............
Float level too high
Floats damaged or if "foam" floats are "waterlogged" and sinking
Junk in the needles/ seats or sticking
Fuel pressure too high.
You need to find out "what he did." How did it run BEFORE this guy "improved" it and why did it change?
I would guess some other problem.............
Float level too high
Floats damaged or if "foam" floats are "waterlogged" and sinking
Junk in the needles/ seats or sticking
Fuel pressure too high.
You need to find out "what he did." How did it run BEFORE this guy "improved" it and why did it change?
09-30-2013, 07:30 PM
#15
Mopar Fanatic
Thread Starter
Yesterday I got my car back from the mechanic, it runs good but now the MPG are even worse!! I'm getting 3.5MPG in city and 5.5MPG at highway. I live in a city with a few hills but I don't know if this is reason enough to get this kind of mpg
Can I check something else? If I don't get better MPG I must wait until the new carb arrives because I can't afford 3.5MPG
Can I check something else? If I don't get better MPG I must wait until the new carb arrives because I can't afford 3.5MPG
10-01-2013, 09:00 AM
#16
Did you get the AFB yet ?? I have said it before !! Find another mechanic !!!! IF you continue flushing that much fuel though the motor you will ruin it !! Washes all the oil off the cylinders & rings
Where do you live ?
Where do you live ?
Last edited by TVLynn; 10-01-2013 at 09:08 AM.
10-01-2013, 04:27 PM
#17
Mopar Fanatic
Thread Starter
yes I already bought the AFB and yes I already change the mechanic to a old man that only works with carburetors. I think will be a better option to leave the car in the garage while the AFB arrives from EE.UU. I live in Colombia, South America
Last edited by josehf34; 10-01-2013 at 04:30 PM.
10-01-2013, 04:42 PM
#18
Disco the vac advance and check the initial timing. Seriously. A lot of good advise has been posted here for you, are you trying any of it? Are you in New England by any chance? I would love to take a whack at this first hand.
10-01-2013, 08:15 PM
#19
Mopar Fanatic
Thread Starter
Thank you for all the help, is good to have some help in this hobby. When I finish the carter installation and timing adjustment I'll feedback on this post about the results
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