Author Topic: BJ/BK Carbs Will Not Idle Down  (Read 786 times)

Drew Pojedinec

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Re: BJ/BK Carbs Will Not Idle Down
« Reply #15 on: August 03, 2020, 05:39:27 PM »
If nothing else, that reply was entertaining :P

shelbydoug

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Re: BJ/BK Carbs Will Not Idle Down
« Reply #16 on: August 03, 2020, 07:19:53 PM »
If nothing else, that reply was entertaining :P

I know...my fly was probably open while I was talking? :o
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JWH

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Re: BJ/BK Carbs Will Not Idle Down
« Reply #17 on: August 04, 2020, 12:27:18 AM »
First off, thank you to everyone for thoughts on this.
>the primary idle screws are backed all the way out
>the secondary idle screws have been completely removed to make certain they are not the issue
>the choke is not hanging up on the fast idle cam so I am certain that is not causing the issue
>the BJ/BKs worked great on the previous engine but after sitting for 4-5 weeks, decided not to idle down
>the second set of Holley carbs I have idle beautifully on the new engine. Which leads me to the conclusion the problem is somewhere in the BJ/BKs.


Question-- this seems like it could be a vacuum related problem. Like extra air is coming into the engine from the carbs and raising the idle. Am I off track?
>is it possible the diaphragm that opens the vacuum secondaries would cause a higher idle if they are torn or worn?
>is there anything else inside the carbs that would introduce more air and increase the idle speed?
>would the cork gaskets around the idle mixture screws cause a higher idle if missing? (I need to go check them closely)

It is a mystery these carbs worked well on the old engine and now won't idle down. Again, thanks for your thoughts.
Jeff
PS - I have the secondary idle screws removed and plan to install the screws Drew suggests to make it easier to adjust the secondaries.

shelbydoug

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Re: BJ/BK Carbs Will Not Idle Down
« Reply #18 on: August 04, 2020, 07:12:17 AM »
You need to verify that the power valves are not leaking. If even one is a little, it will drip into the vacuum chamber and provide un-monitored fuel.

You just can't say, well I put new ones in. They need to be tested and shown that they hold vacuum.

It is the only item that I see missing from your list .
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Drew Pojedinec

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Re: BJ/BK Carbs Will Not Idle Down
« Reply #19 on: August 04, 2020, 09:20:08 AM »
Leaking PV would slow idle.

Yes I think you have a vac leak.
Vacuum leak check.
Most folks spray fluid or use a torch, etc.
I never do that, If you have no vacuum leaks, you should be able to shut the engine off by putting your hand over the choke horn.

If your choke air inlet drawing air?


shelbydoug

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Re: BJ/BK Carbs Will Not Idle Down
« Reply #21 on: August 04, 2020, 11:17:36 AM »
https://www.ebay.com/itm/EVAP-Smoke-Machine-Diagnostic-Emissions-Vacuum-Leak-Detector-Tester-USA-MADE/282241437563?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m1438.l2649

I did a smoke test on mine and foiund several leaks in the vaccum hose system. However you are going to need to adapt it to a carburetor system. Smoke systems are really intended for FI cars.

Take the throttle plates off of the main body and check the gasket orientation. It is possible to put it on backwards and block one of the vacuum ports.

Many of the carbs from Holley use only 6 mounting screws for the throttle plate. It's also possible to pick up a vacuum leak there. Put two more screws in if they are missing. It can't hurt.


I would also highly recommend disconnecting the pcv while you are doing this so not to fight a leaking pcv or system.  That I recommend from experience.
« Last Edit: August 13, 2020, 10:06:57 AM by shelbydoug »
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