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Just go our 64BJ8 running after sleeping for almost 30 years. Everything rebuilt and motor seems to run fine. But have questions on the fine tuning of the SU HD8s.
I have been reading for several days the various threads and other available documentation on how to set these things. I have followed them and have gotten great results. Started out with a little backfiring and after some tweaking there is not longer any backfiring when blip the throttle and have a smooth 600 RPM idle. Timing, dwell, etc all spot on.
But all of the directions say to balance the front and rear carbs with the slow run adjusting screw the same amount to get 500-600 RPM. Supposedly you are to balance the air flow using a listing tube or in my case I want to use a Uni-Syn balancing tool. I tried this and cannot get them to exactly balance. For those of you familiar with this tool there is a little indicator that floats up and down in a tube that is about 3" long. Without any separate fine tuning of the slow running adjustment screw (meaning both are adjusted the same amount) they are within about 1-1/2" of each other but not exact. But then by fine tuning one or the other of the screws it does not seem to make any difference on the tools indicator, it is what it is. Using a listening tube simulating a stethoscope both carbs sound about the same.
Then I read a post where it says using such a tool does nothing because the slow running adjustment is done with the throttle plates close. If so why do all the instructions tell you to balance the air flow. So how does one actually balance the air flow? In the same post referenced above the claim is made that by default the air flow through each carb must be the same because the throttle plates are closed and the geometry is the same, UNLESS there is a major leak in the carb somewhere, such as the shaft bushings. Some instructions say to use the pointing wire setup which I have not tried.
Bottom line is the car seems to run terrific after a very brief road test. The only observation is the rear carb does not seem to be sucking as much air as the front as when the uni-syn is placed on the front it starves that carb a little. When placed on the back it has no effect.
Sorry for the long post, just trying to get it right, or maybe as long as the car runs right, should I not worry about it?
So question again is - how does one balance the air flow on these carbs?
Thanks,
jjs64bj8
PS, dumb question, would the rear carb maybe not be sucking as much because of the brake booster vacuum take off is at that end of the manifold? Told you this was dumb, but could it be?
I have been reading for several days the various threads and other available documentation on how to set these things. I have followed them and have gotten great results. Started out with a little backfiring and after some tweaking there is not longer any backfiring when blip the throttle and have a smooth 600 RPM idle. Timing, dwell, etc all spot on.
But all of the directions say to balance the front and rear carbs with the slow run adjusting screw the same amount to get 500-600 RPM. Supposedly you are to balance the air flow using a listing tube or in my case I want to use a Uni-Syn balancing tool. I tried this and cannot get them to exactly balance. For those of you familiar with this tool there is a little indicator that floats up and down in a tube that is about 3" long. Without any separate fine tuning of the slow running adjustment screw (meaning both are adjusted the same amount) they are within about 1-1/2" of each other but not exact. But then by fine tuning one or the other of the screws it does not seem to make any difference on the tools indicator, it is what it is. Using a listening tube simulating a stethoscope both carbs sound about the same.
Then I read a post where it says using such a tool does nothing because the slow running adjustment is done with the throttle plates close. If so why do all the instructions tell you to balance the air flow. So how does one actually balance the air flow? In the same post referenced above the claim is made that by default the air flow through each carb must be the same because the throttle plates are closed and the geometry is the same, UNLESS there is a major leak in the carb somewhere, such as the shaft bushings. Some instructions say to use the pointing wire setup which I have not tried.
Bottom line is the car seems to run terrific after a very brief road test. The only observation is the rear carb does not seem to be sucking as much air as the front as when the uni-syn is placed on the front it starves that carb a little. When placed on the back it has no effect.
Sorry for the long post, just trying to get it right, or maybe as long as the car runs right, should I not worry about it?
So question again is - how does one balance the air flow on these carbs?
Thanks,
jjs64bj8
PS, dumb question, would the rear carb maybe not be sucking as much because of the brake booster vacuum take off is at that end of the manifold? Told you this was dumb, but could it be?
