300 inline bucking
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300 inline bucking
I am working on a 66 f-100 with a 300 inline 6. I am having trouble with the truck "bucking" intermittently. It appears to drop one ore more cylinders sometimes to the point that it dies. It might drive 10 miles with no problem or act up several times in less than a mile. Happens at all driving speeds, engine temperatures, rpms, and loads. The only time it doesn't happen is when it's idling and not moving.
Engine is professionally rebuilt with less than 200 miles on it, new distributor wires and plugs, new fuel tank, lines, and new original style fuel pump. I have tried two different rebuilt carbs. Adjusting the float level didn't help, although I took it from being very rich to very lean and many points in the middle.
Please Help!
Engine is professionally rebuilt with less than 200 miles on it, new distributor wires and plugs, new fuel tank, lines, and new original style fuel pump. I have tried two different rebuilt carbs. Adjusting the float level didn't help, although I took it from being very rich to very lean and many points in the middle.
Please Help!
Lead Gopher
Joined: Aug 2012
Posts: 10,014
Likes: 1,565
From: Seattle
Gas cap? Is it vented in both directions? You might laugh but it's not entirely uncommon for a non-vented gas cap to be in use and they can cause fuel starvation issues.
Just ask Steve...
https://www.ford-trucks.com/forums/1...-for-long.html
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Just ask Steve...
https://www.ford-trucks.com/forums/1...-for-long.html
.
Post Fiend
Joined: Apr 2002
Posts: 19,311
Likes: 97
From: Waterloo, Iowa
Well it's worth trying knowing their history. What torques me, is there's no way the **********s selling these POS don't know they are almost all defective. But all up and down the supply chain right down to the retail level, no problem.
Lead Gopher
Joined: Aug 2012
Posts: 10,014
Likes: 1,565
From: Seattle
Cheap to try, too. Like others I tend to go NOS on those. I suppose I should go Pertronix but I've just never had any big issues.
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Senior User
Joined: Mar 2007
Posts: 481
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From: Deep River, CT.
Did you the have problem from the git-go of installing the engine? Has all you put on new been done to resolve your problem? In the dizzy there is a small ground strap from one of the points mounting screws to the dizzy body, make sure it's there and hooked up on both ends and not interfering with anything as the vacuum advance moves the point breaker plate. You can rotate the breaker plate with your fingers and went you let go it should spring back to it's original position.
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Laughing Gas
Joined: Dec 2010
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From: Tucson, Arizona
Another point to consider - your coil may be going bad. My truck went from running well, to an occasional buck, then to severe bucking (backfiring), and finally to where it wouldn't run at all. This happened in the space of about three trips out in it. A new coil solved the problem. Good luck.
Senior User
Joined: Dec 2003
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Happens at all driving speeds, engine temperatures, rpms, and loads. The only time it doesn't happen is when it's idling and not moving.
The Ford Loadamatic Advance system debut with the 8BA era flatheads and was used on some early Yblocks. Most six cylinders used this system until about 1970.
In the Loadamatic system timing advance is 100 percent vacuum controlled. The distributor and carburetor are a matched pair. Only a Loadamatic carb will work with a Loadamatic distributor.
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Put on a new condenser over the weekend, cured the problem. I've never seen had a condenser fail that way before, live and learn.
The trouble began from the get-go of installing the engine, nothing had been changed yet to try and resolve the problem except for a new coil (I had seen a bad coil cause symptoms like this before). The second carb had been borrowed from another truck. This is a restoration project; the engine was worn out so when we replaced the engine we just replaced everything else that ties into it because in most cases it was bad also. I had already looked into the things IICAP and F-ONE said.
As a side note this truck was purchased new in 1966 and driven by the same man untill 1995 when medical issues prevented him from diving any more. The mileage is unknown but is a lot. The engine had never been rebuilt, on dissemble the bores were worn about .040 over and about equal wear on the pistons making total clearance 1/16 inch or more between the piston and cylinders. Most of the bearing inserts were worn into the steel. I don't know what kept it going.
Thanks a million for all the help!! It was about to drive me crazy.
The trouble began from the get-go of installing the engine, nothing had been changed yet to try and resolve the problem except for a new coil (I had seen a bad coil cause symptoms like this before). The second carb had been borrowed from another truck. This is a restoration project; the engine was worn out so when we replaced the engine we just replaced everything else that ties into it because in most cases it was bad also. I had already looked into the things IICAP and F-ONE said.
As a side note this truck was purchased new in 1966 and driven by the same man untill 1995 when medical issues prevented him from diving any more. The mileage is unknown but is a lot. The engine had never been rebuilt, on dissemble the bores were worn about .040 over and about equal wear on the pistons making total clearance 1/16 inch or more between the piston and cylinders. Most of the bearing inserts were worn into the steel. I don't know what kept it going.
Thanks a million for all the help!! It was about to drive me crazy.
Elder User
Joined: Oct 2012
Posts: 772
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300 Sixes are virtually bulletproof when taken care of. I worked at a place that there were a fleet of them. Plus my own personal experience. My '91 had 190,000 miles on it and the oil was still clean brown after 3000 miles. It was the transmission that went out that ended that chapter.
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