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primary and secondary break

Old 12-16-2018, 09:03 AM
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primary and secondary break

I recently installed a non cc carb on my 83 ta. It only has the secondary vacuum break. I have heard that it is not necessary but by name and pictures a primary break is usually on the carb. Is the primary vacuum break necessary? Car seems to run correctly accept for one issue I am having. Whenever I floor the gas pedal,high idle cam kicks in.

Last edited by Rich1374670x; 12-17-2018 at 11:00 AM.
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Old 12-16-2018, 03:36 PM
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naf
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Re: primary and secondary break

the forward vacuum break on third gens provides two functions. it cracks open the carb slightly once it is started with the choke on (the motor starts and vacuum is applied to the diaphragm). it also works in conjunction with the secondary air valve spring to delay opening of the secondary air valve. under high throttle vacuum decreases and the break's plunger comes out releasing the air valve linkage.

not sure which rear break you have. some provided a 'dashpot' function to delay, or slow, the closing of the throttles.
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Old 12-17-2018, 10:50 AM
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Re: primary and secondary break

If the choke comes back on when the vacuum goes low, then its electrical function isn't working right. It should be completely opened by the thermostat and then never come back on once the engine has been running for more than a few minutes. It should take quite a while after the car is stopped to cool back down enough to close the choke again.
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Old 12-17-2018, 11:02 AM
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Re: primary and secondary break

Originally Posted by sofakingdom View Post
If the choke comes back on when the vacuum goes low, then its electrical function isn't working right. It should be completely opened by the thermostat and then never come back on once the engine has been running for more than a few minutes. It should take quite a while after the car is stopped to cool back down enough to close the choke again.
could this be related to my oil pressure switch? Oil psi is always buried and I believe power for the choke comes from it?
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Old 12-17-2018, 12:16 PM
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naf
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Re: primary and secondary break

no

power from the choke comes from the alternator. when the alternator is not spinning the choke doesn't get power
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