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Old 08-29-2020, 03:18 PM   #1
farmerdick
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Default Can Not Get Idle Down on Flathead

Started the flathead yesterday. Got the timing on TDC and 30 degrees of dwell but the idle will not go below 1800 rpm. The idle screws are are backed all the way off. If I turn the distributor before TDC it wants to stall. The temperature wants to go above 220 degrees but thats another issue because of the high idle(I do have thermostats in the system). Any ideas?
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Old 08-29-2020, 03:30 PM   #2
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Default Re: Can Not Get Idle Down on Flathead

My first thought is your carburetor. Check the linkage. It sounds like the idle circuit is not working and you are only running off of the power circuit.

You could have a dirty carburetor.

A vacuum leak will do this too.
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Old 08-29-2020, 03:48 PM   #3
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Default Re: Can Not Get Idle Down on Flathead

My first thought would be a air leak in the manifold/carb area. Check any rubber hoses for loose or cracks, There must be an air leak if you need to have the idle mix screws out to get enough fuel for it to run. One way to check for leaks is, with the engine running, using an unlit propane torch, pass the nozzle around the intake manifold and carb base in close proximity to see if the engine speeds up. An increase of engine speed indicates an air leak. Connect a vacuum gauge, and refer to the attached chart.
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Old 08-29-2020, 04:42 PM   #4
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Default Re: Can Not Get Idle Down on Flathead

Ok. Both stromburg 97s have been rebuilt by Uncle Max. J just replaced the intake manifold gasket because the aluminum intake had stripped threads on the generator support on the front of the intake and had to insert a helicoil. Torqued to 28 ft lbs. The idle was still at 2000 rpm with that gasket. I put the gasket on dry without any contact adhesive? I will check for leaks tomorrow, been a long day dealing with this. Thanks guys. I may start a new thread for an update.
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Old 08-29-2020, 04:45 PM   #5
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Default Re: Can Not Get Idle Down on Flathead

Make sure your dist advance is moving properly
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Old 08-29-2020, 05:04 PM   #6
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Default Re: Can Not Get Idle Down on Flathead

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Are the two carbs linked together? The only way it will run that fast is if one of the throttles is not going back to idle position or you have a big air leak.
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Old 08-29-2020, 07:16 PM   #7
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Default Re: Can Not Get Idle Down on Flathead

Yep, has to be getting air from somewhere. Might try blocking off one carb at a time and see if that makes any difference.
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Old 08-29-2020, 09:46 PM   #8
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Default Re: Can Not Get Idle Down on Flathead

Air leak somewhere !
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Old 08-29-2020, 09:54 PM   #9
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Default Re: Can Not Get Idle Down on Flathead

Another possibility is an off center throttle plate. If the throttle plates were removed, there's a slim chance one was not centered in the throttle bore when reinstalled and is hanging up.
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Old 08-29-2020, 10:00 PM   #10
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Default Re: Can Not Get Idle Down on Flathead

sync the carbs, one carb has the throttle plates open more than the other one making it run like that. second thing I would look for is bound up throttle linkage which is holding the plates open
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Old 08-30-2020, 02:41 AM   #11
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Default Re: Can Not Get Idle Down on Flathead

definitely sounds like its got a leak quick tip to find get some spray start [ether] and gently squirt away throttle shafts, carb base and work your way out could save you lifting a manifold for a base gasket or a leak at the wipers [often overlooked]
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Old 08-30-2020, 04:37 AM   #12
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Default Re: Can Not Get Idle Down on Flathead

Will be going out to the garage in a few minutes and will check those carbs. On top of all this my electric fan stopped working!!! Problems comes in bunches. OH, by the way, did I mention I have antifreeze coming out of the left exhaust pipe. No antifreeze in base. thank God. Stay tuned for updates.
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Old 08-30-2020, 10:49 AM   #13
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Default Re: Can Not Get Idle Down on Flathead

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Originally Posted by 40 Deluxe View Post
Another possibility is an off center throttle plate. If the throttle plates were removed, there's a slim chance one was not centered in the throttle bore when reinstalled and is hanging up.
Slim left town. Great care was/is taken with throttle plates, including use of factory mandrel when tamping the screws!
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Old 08-30-2020, 03:49 PM   #14
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Default Re: Can Not Get Idle Down on Flathead

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Slim left town. Great care was/is taken with throttle plates, including use of factory mandrel when tamping the screws!

Good to know Slim was not involved! I was just throwing out a suggestion based on my experiences. While a Chevrolet mechanic, a new '67 right off the transport was idling too fast. Cause was a throttle plate off-center. Have since seen it on reman carbs.
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Old 08-30-2020, 04:07 PM   #15
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Default Re: Can Not Get Idle Down on Flathead

Could it be a head/gasket problem? Being there is coolant coming out of the exhaust? Just a thought.
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Old 08-30-2020, 04:27 PM   #16
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Default Re: Can Not Get Idle Down on Flathead

Oops
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Old 08-30-2020, 04:27 PM   #17
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Default Re: Can Not Get Idle Down on Flathead

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Could it be a head/gasket problem? Being there is coolant coming out of the exhaust? Just a thought.
Again as I said in the other thread : probably not. I hate to be the one to break the news to you, but you probably have a cracked block. It certainly bears further inspection.
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Old 08-30-2020, 04:29 PM   #18
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Default Re: Can Not Get Idle Down on Flathead

Just saw the other thread
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Old 08-30-2020, 05:16 PM   #19
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Default Re: Can Not Get Idle Down on Flathead

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Originally Posted by farmerdick View Post
Will be going out to the garage in a few minutes and will check those carbs. On top of all this my electric fan stopped working!!! Problems comes in bunches. OH, by the way, did I mention I have antifreeze coming out of the left exhaust pipe. No antifreeze in base. thank God. Stay tuned for updates.
Was the block pressure tested prior to the machine work?
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Old 08-30-2020, 06:03 PM   #20
farmerdick
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Default Re: Can Not Get Idle Down on Flathead

Pulled head off and it was ok. Not sure if it was pressure tested but was checked for cracks. If I had a fiber optic camera I could check out the bolt hole that was leaking water. Will check with the engine builder tomorrow and get some thoughts on what I need to fix problem.
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