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wkilleffer
Jedi Knight
Offline
Hi everyone,
I am trying to adjust the carbs on my 1974 MGB, with a 1972 engine and HS carbs. Just about the time I think I've got it right, it seems like I've done nothing right. The part that's really throwing me for a loop is the part where you're supposed to push up on the piston lifting pins to determine whether or not the mixture is correct for each carb. This will be my third try, it's getting late and I need to be able to drive the car in the morning.
The vacuum advance for the distributor has been connected the whole time.
I started out by disconnecting all interconnections and adjusting the throttle stop screws 11/2 turns in, raised the jet even with the bridge and backed it down 12 flats. I started the car and it got to NOT quickly. Then, I backed the idle speed down to just under 1000.
After that, I used a carb balancer to check the airflow into each carb. The rear always seemed to be higher than the front, so I'd tweak the idle screws to bring both carbs to the same place on the balancer.
Then, I started turning the jets flat by flat until I got the fastest running speed with an even fire and exhaust sound. This necessitated adjusting the idle speed and re-checking the airflow with the balancing tool. The airflow was never the same with either carb at that point.
At that point, the directions say to push up on the piston lifting pin first on the front carb and then on the second. If the speed rises, the carb is too rich, if the engine tries to stall, it's too lean, and if it briefly goes up and comes back down, it's just right.
What if I get none of the above? Well, sometimes it's obvious that it's trying to stall. But otherwise, I might get the slightest quick blip upwards, and then an attempt to stall. A few times have brought no change at all.
All the books seem to give a different amount as to how far up one should push the pin. Trying to push it up 1/32" and keep it steady is almost impossible. It's really difficult to push it anywhere but all the way up with any consistency.
Part of me just wants to stop before I get to that point and hope for the best. But that just doesn't seem right. I'm trying to use less gas while still having fun and retaining reliability. But it's no fun if unsuccessful attempts to adjust the carbs use 1/4 of a tank.
The carbs have been reshafted and rebushed in the last three years, and don't show any signs of leakage around the shafts.
There probably haven't been too many times that I've had the carbs adjusted all the way right, so I'm trying to do it this time. Any suggestions would be appreciated.
Thank you,
I am trying to adjust the carbs on my 1974 MGB, with a 1972 engine and HS carbs. Just about the time I think I've got it right, it seems like I've done nothing right. The part that's really throwing me for a loop is the part where you're supposed to push up on the piston lifting pins to determine whether or not the mixture is correct for each carb. This will be my third try, it's getting late and I need to be able to drive the car in the morning.
The vacuum advance for the distributor has been connected the whole time.
I started out by disconnecting all interconnections and adjusting the throttle stop screws 11/2 turns in, raised the jet even with the bridge and backed it down 12 flats. I started the car and it got to NOT quickly. Then, I backed the idle speed down to just under 1000.
After that, I used a carb balancer to check the airflow into each carb. The rear always seemed to be higher than the front, so I'd tweak the idle screws to bring both carbs to the same place on the balancer.
Then, I started turning the jets flat by flat until I got the fastest running speed with an even fire and exhaust sound. This necessitated adjusting the idle speed and re-checking the airflow with the balancing tool. The airflow was never the same with either carb at that point.
At that point, the directions say to push up on the piston lifting pin first on the front carb and then on the second. If the speed rises, the carb is too rich, if the engine tries to stall, it's too lean, and if it briefly goes up and comes back down, it's just right.
What if I get none of the above? Well, sometimes it's obvious that it's trying to stall. But otherwise, I might get the slightest quick blip upwards, and then an attempt to stall. A few times have brought no change at all.
All the books seem to give a different amount as to how far up one should push the pin. Trying to push it up 1/32" and keep it steady is almost impossible. It's really difficult to push it anywhere but all the way up with any consistency.
Part of me just wants to stop before I get to that point and hope for the best. But that just doesn't seem right. I'm trying to use less gas while still having fun and retaining reliability. But it's no fun if unsuccessful attempts to adjust the carbs use 1/4 of a tank.
The carbs have been reshafted and rebushed in the last three years, and don't show any signs of leakage around the shafts.
There probably haven't been too many times that I've had the carbs adjusted all the way right, so I'm trying to do it this time. Any suggestions would be appreciated.
Thank you,
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