The Ford Barn

sunshine · 07-28-2018, 03:21 PM

Thank you drolson for your advise I installed the recently professionally rebuilt carb . Check for vacuume leaks ,found none .I checked compression on all cylinders all at 100 PSI. I have strong spark at all cylinders. Can this be ignition? Every thing in this engine is new about 500 miles on rebuild . 59 ab 39 pkp. Tonight in the dark I am going to run it to see if there is any spark where it should not be. Thank you all for any help SUNSHINE

drolston · 07-28-2018, 11:48 PM

At 500 miles that engine is barely broken in. Could be still tight, which means you may need to set the idle speed higher for a while.

Hmmm? At what rpm does the engine smooth out. If the engine has a modified cam shaft it will not idle smoothly at 500 rpm. I have a pretty mild cam in 59A/B and the idle is set just over 600 rpm to idle smooth and not stumble.

Ignition? if you have a good spark at the plugs the only other aspect is timing. Pretty unusual for timing to be far enough off to mess with the idle. But, to be sure, check where the timing is set on the distributor. The big screw on the side of the distributor near the top on the driver's side. The scribe on the distributor should be near the center scribe on the sliding plate under the screw. Loosen the screw and tap the sliding plate down (retard) two lines, about 4 degrees. That is a lot, but should tell you if your spark is too far advanced for a smooth idle. If that does not help, or makes it worse, go the other way - up to advance. If it takes a big adjustment either way, something is messed up and your distributor is a candidate for overhaul.

sunshine · 07-29-2018, 08:17 AM

Drolson thank you again for your help I will try the timing check. As soon as I am able .The disturb. Was rebuilt by Bubbas about two years the coil by skip same time frame I have not put much mileage on the truck , but it has run great in that time . It started to have a hesatitation in 2nd. Gear , using a carb . That. I had rebuilt myself , so I thought I would get a spare carb. I had rebuilt by someone recommended on the Ford barn.I don't think it is the rebuilt carb because it does the same bad idle with the old carb.I am going to look at maybe bad fuel . But accelerates fine. It does have a mild cam . But has not had this rough idle. Thanks SUNSHINE

supereal · 07-29-2018, 01:55 PM

The best tool to diagnose rough idle is a vacuum gauge. If you need a "how to" use one, I can post it.

FlatheadTed · 07-29-2018, 03:22 PM

Sponsored Links (Register now to hide all advertisements)

If it smokes a the exhausted check fuel pump pressure /needle valve

07-28-2018, 03:21 PM	#1
sunshine Senior Member Join Date: Feb 2011 Location: SUNSHINE MD. Posts: 318	Rough Idle Thank you drolson for your advise I installed the recently professionally rebuilt carb . Check for vacuume leaks ,found none .I checked compression on all cylinders all at 100 PSI. I have strong spark at all cylinders. Can this be ignition? Every thing in this engine is new about 500 miles on rebuild . 59 ab 39 pkp. Tonight in the dark I am going to run it to see if there is any spark where it should not be. Thank you all for any help SUNSHINE

07-28-2018, 11:48 PM	#2
drolston Senior Member Join Date: Jun 2014 Location: Williamsburg, VA Posts: 1,627	Re: Rough Idle At 500 miles that engine is barely broken in. Could be still tight, which means you may need to set the idle speed higher for a while. Hmmm? At what rpm does the engine smooth out. If the engine has a modified cam shaft it will not idle smoothly at 500 rpm. I have a pretty mild cam in 59A/B and the idle is set just over 600 rpm to idle smooth and not stumble. Ignition? if you have a good spark at the plugs the only other aspect is timing. Pretty unusual for timing to be far enough off to mess with the idle. But, to be sure, check where the timing is set on the distributor. The big screw on the side of the distributor near the top on the driver's side. The scribe on the distributor should be near the center scribe on the sliding plate under the screw. Loosen the screw and tap the sliding plate down (retard) two lines, about 4 degrees. That is a lot, but should tell you if your spark is too far advanced for a smooth idle. If that does not help, or makes it worse, go the other way - up to advance. If it takes a big adjustment either way, something is messed up and your distributor is a candidate for overhaul.

07-29-2018, 08:17 AM	#3
sunshine Senior Member Join Date: Feb 2011 Location: SUNSHINE MD. Posts: 318	Re: Rough Idle Drolson thank you again for your help I will try the timing check. As soon as I am able .The disturb. Was rebuilt by Bubbas about two years the coil by skip same time frame I have not put much mileage on the truck , but it has run great in that time . It started to have a hesatitation in 2nd. Gear , using a carb . That. I had rebuilt myself , so I thought I would get a spare carb. I had rebuilt by someone recommended on the Ford barn.I don't think it is the rebuilt carb because it does the same bad idle with the old carb.I am going to look at maybe bad fuel . But accelerates fine. It does have a mild cam . But has not had this rough idle. Thanks SUNSHINE

07-29-2018, 01:55 PM	#4
supereal Senior Member Join Date: Jul 2014 Location: Iowa Posts: 1,634	Re: Rough Idle The best tool to diagnose rough idle is a vacuum gauge. If you need a "how to" use one, I can post it.

07-29-2018, 03:22 PM	#5
FlatheadTed Senior Member Join Date: May 2010 Location: Auckland Posts: 4,705	Re: Rough Idle Sponsored Links (Register now to hide all advertisements) If it smokes a the exhausted check fuel pump pressure /needle valve __________________ http://www.flatheadted.com Flathead Ted brake Floaters ,