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Old 10-24-2021, 04:43 PM   #1
49 Jonesey
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Default Flathead won't idle

Looking for some insight on an issue I have been having with a 49 F-1.
So I inherited of sorts my Dad's 49 F-1. He built it from the ground up years ago but due to his health and mom's it didn't see much use over the last 5-6 years so he sent it to me. When it arrived it run rough and rich. I rebuilt the stromburg 97 and now replaced it with a new carb and while I can get it started after a bit I can't keep it running without feathering the gas pedal. It's set up as a tri-power but I am only running off the primary. Any thoughts? I did see a similar post here on the forum but I can't see to find it.
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Old 10-24-2021, 05:59 PM   #2
tubman
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Default Re: Flathead won't idle

When you say you are "only running off the primary", what exactly do you mean? Did you actually block them off, or just disconnect them. Since we don't know much about the end carbs, I think the best thing to do at this time is to completely eliminate the end carbs from the equation and try to get it running on one, either by temporally substituting a stock manifold or actually making block off plates to put under the end carbs.

It can be tough enough to get one of these to run right with a single carb much less trying to solve the problems that may be caused by a multi carb setup you know nothing about.

Also, what kind of distributor are you running? One of the first things you should know is that the engine will never run right with a stock distributor and multiple carbs, especially if you are using 97's.

Last edited by tubman; 10-24-2021 at 06:35 PM.
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Old 10-25-2021, 12:52 AM   #3
Tinker
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Default Re: Flathead won't idle

As tubman says. You don't know anything about the motor. Get it running on one carb and add.
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Old 10-25-2021, 08:07 AM   #4
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Default Re: Flathead won't idle

After getting it running on one carb.
Pick up a Uni-Sync from one of the vendors and learn hoy to properly balance the carbs. Are you using straight or progressive linkage? Chap
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Old 10-25-2021, 12:11 PM   #5
drolston
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Default Re: Flathead won't idle

Getting a tri-power setup to idle correctly depends on getting the linkage and associated return springs set up so that with foot off the pedal, the throttle butterfly valves in the end carbs are both exactly and perfectly closed. The idle jets on the end carbs also need to be completely closed. The only way to do that is to take the body of the carbs off, leaving bases still tightly bolted to the manifold, and the throttle linkage in place. Taking off the carb tops is easy with Stromberg 97s, as all screws are accessible from above. Then adjust the linkage joining the end carbs so that both go fully closed together.

But that alone is not enough, because there is always a little slop or flexibility in the linkage and throttle shafts. For me the key was having stout return springs on the driver side throttle shafts of both end carbs. If you look very closely at the left carb in the photo of the linkage side, you can see the spring that goes around the throttle shaft, between the linkage arm and the carb base. One end of the spring rests on the base of the carb, the other is hooked under the linkage arm, pulling it towards the closed position. The return spring on the accelerator pump tends to close the throttle, but that alone is not enough.

With the end carb butterflies tightly closed, all idle airflow and mixture is controlled by the center carb, making it possible to reliably tune the idle, and avoid stalling at stop lights due to vacuum leak past the secondary carbs.
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Old 10-25-2021, 12:28 PM   #6
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Default Re: Flathead won't idle

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Tubman's distributor info is crucial. Do you know what cam is in the engine?
Your problem can be figured out, there are lots of guys here with tri power and in the know.
I only have 2 with Dual manifolds, 1 with a 4bbl, and 2 stock so I don't have anything else to add.
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Old 10-25-2021, 08:52 PM   #7
49 Jonesey
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Default Re: Flathead won't idle

Quote:
Originally Posted by tubman View Post
When you say you are "only running off the primary", what exactly do you mean? Did you actually block them off, or just disconnect them. Since we don't know much about the end carbs, I think the best thing to do at this time is to completely eliminate the end carbs from the equation and try to get it running on one, either by temporally substituting a stock manifold or actually making block off plates to put under the end carbs.

It can be tough enough to get one of these to run right with a single carb much less trying to solve the problems that may be caused by a multi carb setup you know nothing about.

Also, what kind of distributor are you running? One of the first things you should know is that the engine will never run right with a stock distributor and multiple carbs, especially if you are using 97's.
Thank you all for your responses!! Yes I have the fuel shut off on the other two carbs to eliminate the extra trouble. Pretty sure the distributer isn't stock as he changed out the cam, intake and heads. I can confirm with him although he doesn't seem to remember much nowadays.

Just reading though various forums and threads it seems as though the problem may lay in the idle circuit? Although I feel I have thoroughly cleaned the carb I saw somewhere it could help to remove the air/fuel screws and blow air though them??

Thanks again for all your help!
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Old 10-25-2021, 10:54 PM   #8
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Default Re: Flathead won't idle

Do as someone else suggested and take the other 2 end carbs off the manifold and put a flat plate over each mount and with a new gasket, tighten them down. While you have no fuel going to those carbs they can be letting in too much air. If you leave the linkage working on all 3 make sheet metal pieces to go under the dummy carbs to assure no extra air is getting in to mix with the center carb's fuel.
Did the car sit for a few years since last run? the points that were open all that time can get oxidation to the point they are not working but the car will still run poorly on just 1 set of points. That will also happen when the spring breaks on one of the points.
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Old 10-25-2021, 11:10 PM   #9
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Default Re: Flathead won't idle

You said you replaced the carb. What did you replace it with? Another 97, a Holley 94, or maybe even a Speedway "9Super7". It would help to know, Also, more information on the distributor would help; does it have a label on it? Perhaps it's a Mallory or MSD. If no label, perhaps you can open it up (remove the cap) and tell us how many sets of points it has, or even if the condenser is on the inside or the outside of the distributor housing.

You have to approach these things in a systematic manner with all the information you can gather; just trying to throw random things at it seldoms has good results.
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Old 10-26-2021, 07:59 AM   #10
49 Jonesey
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Default Re: Flathead won't idle

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Originally Posted by deuce_roadster View Post
Do as someone else suggested and take the other 2 end carbs off the manifold and put a flat plate over each mount and with a new gasket, tighten them down. While you have no fuel going to those carbs they can be letting in too much air. If you leave the linkage working on all 3 make sheet metal pieces to go under the dummy carbs to assure no extra air is getting in to mix with the center carb's fuel.
Did the car sit for a few years since last run? the points that were open all that time can get oxidation to the point they are not working but the car will still run poorly on just 1 set of points. That will also happen when the spring breaks on one of the points.
It actually run just before I removed and replaced the carb, a bit rich but it run.
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Old 10-26-2021, 08:02 AM   #11
49 Jonesey
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Default Re: Flathead won't idle

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Originally Posted by tubman View Post
You said you replaced the carb. What did you replace it with? Another 97, a Holley 94, or maybe even a Speedway "9Super7". It would help to know, Also, more information on the distributor would help; does it have a label on it? Perhaps it's a Mallory or MSD. If no label, perhaps you can open it up (remove the cap) and tell us how many sets of points it has, or even if the condenser is on the inside or the outside of the distributor housing.

You have to approach these things in a systematic manner with all the information you can gather; just trying to throw random things at it seldoms has good results.
I replaced it with another Speedway "9super7". I will check the distributor and see what I can for information.
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Old 10-26-2021, 08:37 AM   #12
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Default Re: Flathead won't idle

While you're looking at the distributor, check and see if it has a vacuum can on it with a vacuum line going to a port on the manifold.

Just so you know, the "9Super7" carburetor has a spotty reputation and sometimes runs rich out of the box. Some people say they work fine, but there are plenty who have had problems.
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Old 10-26-2021, 08:58 AM   #13
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Default Re: Flathead won't idle

You say you have the fuel shut off. What a bout the air?
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Old 10-26-2021, 01:33 PM   #14
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Default Re: Flathead won't idle

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You say you have the fuel shut off. What a bout the air?
My point exactly. If the end carbs are not going to be used, the best solution is to use the block-off plate between the carb and manifold, as recommended in earlier posts.

If you do not do that, obviously linkage to the end carbs must also be disconnected so they do not open with throttle movement. Also disconnect linkage between the end carbs which might be holding one end open a little, creating a vacuum leak.

Back all the way off of of the idle adjust screws on the end carbs; that is the spring loaded screw on the passenger side of the carbs, not the idle mixture adjust screws in the base (which should be closed, finger tight). Then peer down into the end carbs with a flashlight to be sure the throttle plates are fully closed.
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Old 10-26-2021, 02:15 PM   #15
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Default Re: Flathead won't idle

Flatheads are not supposed to idle. They are intended to run wide open. (Grin)
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