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My recently acquired 1959 245 hp 2 X 4 is running very rich, especially at idle and low rpm.
After thoroughly warming up (not just water temp), and getting into city driving, the idle will deteriorate gradually until she will not idle at all. I believe the plugs are becoming fouled, as to restart the car, I sometimes have to open the throttle fully. There is usually a raw gas smell and plenty of smoke. Around town, this is a really stinky car.
If I shut the car down for a few minutes, or get out on the open road, she will idle OK again (800 rpm), but then the same gradual deterioration will occur. Revving the motor will improve things temporarily. I'm guessing that this cclears some of the raw gas from the system.
At the provincial emissions test I failed miserably: the car had 9% CO at 2500 rpm in 2nd gear at a simulated 25 mph. This reading might be somewhat higher I would get normally as it followed a few minutes of idling. Idle readings were also up around 7%. Hydrocarbon emissions were at 275 ppm at 2500 rpm, and 1050 ppm at idle.
Gas mileage around town is very poor, probably south of 10 mpg.
On an extended highway run, I got 15 mpg at 65-70 MPH with 3.70 gears. Does this gas mileage sound reasonable, or should I be expecting more? In other words, does the gas mileage indicate that the rich problem is persisting at high rpm’s?
Initial timing has been set at 8 degrees.
Spark plugs are R45.
Compression is 170-175 all around, except #2 which is 160.
On the open road the water temp shows a consistent 175-190 depending on outside air temperature, but will go up to 210-220 in stop and barely go “border line-up” traffic with the poor idle. Comes down again nicely after getting back up to speed.
The carbs have just been completely rebuilt to stock specs (they needed it anyway) by Gary Hodges without resolving the problem. Given Gary’s reputation, I’m pretty sure that the carbs are working in the way they were designed.
I not sure that this is a straight carburation problem, although it has been suggested that reducing the size of the jets might be a cure. It’s difficult for me to question people with decades of experience, but it would seem that if Chevrolet designed this set-up with the stock jets, then it should at least function marginally well with the stock jets.
The previous owner put a more “aggressive” cam into the car in place of the stock unit. Is it possible that my problems are stemming from a mismatch between the carbs and the cam? In reading the archives, I’m not sure whether a problem of this magnitude can be caused by a simple mismatch, or whether there are other issues at play. Perhaps the plugs? Or the cam, timing, and plug combination?
Should I consider switching out the “aggressive” cam for a stock unit anyway? I’m guessing that this would improve low end driveability and as I’m not really a “foot to the floor” kind of guy, perhaps the overall performance might be more satisfying.
Sorry for being so long winded and presenting so much information. As a newbie, I’m struggling to understand how the various pieces of the puzzle fit together and am not sure which info is important to consider and which is not.
Any feedback or advice would be greatly appreciated.
Dave
NCRS #42719
After thoroughly warming up (not just water temp), and getting into city driving, the idle will deteriorate gradually until she will not idle at all. I believe the plugs are becoming fouled, as to restart the car, I sometimes have to open the throttle fully. There is usually a raw gas smell and plenty of smoke. Around town, this is a really stinky car.
If I shut the car down for a few minutes, or get out on the open road, she will idle OK again (800 rpm), but then the same gradual deterioration will occur. Revving the motor will improve things temporarily. I'm guessing that this cclears some of the raw gas from the system.
At the provincial emissions test I failed miserably: the car had 9% CO at 2500 rpm in 2nd gear at a simulated 25 mph. This reading might be somewhat higher I would get normally as it followed a few minutes of idling. Idle readings were also up around 7%. Hydrocarbon emissions were at 275 ppm at 2500 rpm, and 1050 ppm at idle.
Gas mileage around town is very poor, probably south of 10 mpg.
On an extended highway run, I got 15 mpg at 65-70 MPH with 3.70 gears. Does this gas mileage sound reasonable, or should I be expecting more? In other words, does the gas mileage indicate that the rich problem is persisting at high rpm’s?
Initial timing has been set at 8 degrees.
Spark plugs are R45.
Compression is 170-175 all around, except #2 which is 160.
On the open road the water temp shows a consistent 175-190 depending on outside air temperature, but will go up to 210-220 in stop and barely go “border line-up” traffic with the poor idle. Comes down again nicely after getting back up to speed.
The carbs have just been completely rebuilt to stock specs (they needed it anyway) by Gary Hodges without resolving the problem. Given Gary’s reputation, I’m pretty sure that the carbs are working in the way they were designed.
I not sure that this is a straight carburation problem, although it has been suggested that reducing the size of the jets might be a cure. It’s difficult for me to question people with decades of experience, but it would seem that if Chevrolet designed this set-up with the stock jets, then it should at least function marginally well with the stock jets.
The previous owner put a more “aggressive” cam into the car in place of the stock unit. Is it possible that my problems are stemming from a mismatch between the carbs and the cam? In reading the archives, I’m not sure whether a problem of this magnitude can be caused by a simple mismatch, or whether there are other issues at play. Perhaps the plugs? Or the cam, timing, and plug combination?
Should I consider switching out the “aggressive” cam for a stock unit anyway? I’m guessing that this would improve low end driveability and as I’m not really a “foot to the floor” kind of guy, perhaps the overall performance might be more satisfying.
Sorry for being so long winded and presenting so much information. As a newbie, I’m struggling to understand how the various pieces of the puzzle fit together and am not sure which info is important to consider and which is not.
Any feedback or advice would be greatly appreciated.
Dave
NCRS #42719
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