240 full throttle bog

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Blairsville Ed
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240 full throttle bog

Post #1 by Blairsville Ed » Sat May 05, 2018 4:58 pm

1968 F100 240 Carter YF, 3 on the tree
Recently rebuilt with 030 Oversize intake valves, standard exhaust valves, mildly ported, Chevy rockers
Modified intake by milling off the carb boss down to the top of the plenum and made an adapter to transition the carb to the plenum with a 45 degree angle. Plenum opening is 4” across. Carb sit 2-5/8” above the plenum.

Question: is it normal for these motors to bog at full throttle?
I’ll start out in 1st gear with the engine at a rolling idle. I’ll put the pedal to the floor and it bogs for about 3 seconds then goes. If I give it 1/2 choke, there’s no bog.
Did I open the plenum to much or do I need more fuel.
All other driving conditions are good.
The accelerator pump seems to be working well.

Blairsville Ed
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Joined: Sat Apr 22, 2017 3:39 pm
Location: North Georgia

Re: 240 full throttle bog

Post #2 by Blairsville Ed » Tue May 08, 2018 1:55 pm

UPDATE:

Last year I put a 1” spacer between the carb and air cleaner can. I thought the spacer would help with air flow.
I removed the spacer and ran it with the air cleaner can mounted to the top of the carb exactly as Ford had it.
The fuel throttle bog disappeared!

How did a 1” spacer create the bog?

Blairsville Ed
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Posts: 77
Joined: Sat Apr 22, 2017 3:39 pm
Location: North Georgia

Re: 240 full throttle bog

Post #3 by Blairsville Ed » Sun May 20, 2018 9:58 am

UPDATE

After studying this a bit, I realized that removing the air cleaner can spacer didn’t solve the problem. What actually happened was the engine was completely warmed up, but when I turned it off, the heat from the exhaust manifold rose up and heated the intake manifold. ( I had separated the intake and exhaust manifolds a while back by milling off the lower section of the intake manifold to fix the carb percolating ) when I restarted the engine the warmed up intake solved the bog.
I search the internet and found that Carter carbs had issued a fix for Jeep vehicles that did not have a heated intake. First they suggested that the thermostat should be checked for proper engine temperature.
Second, open up the accelerator pump discharge. Going from .026 to .031.
They also had different pump plunger springs available.

Has anyone tried these mods.

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bubba22349
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Re: 240 full throttle bog

Post #4 by bubba22349 » Sun May 20, 2018 1:25 pm

Blairsville Ed wrote:UPDATE

After studying this a bit, I realized that removing the air cleaner can spacer didn’t solve the problem. What actually happened was the engine was completely warmed up, but when I turned it off, the heat from the exhaust manifold rose up and heated the intake manifold. ( I had separated the intake and exhaust manifolds a while back by milling off the lower section of the intake manifold to fix the carb percolating ) when I restarted the engine the warmed up intake solved the bog.
I search the internet and found that Carter carbs had issued a fix for Jeep vehicles that did not have a heated intake. First they suggested that the thermostat should be checked for proper engine temperature.
Second, open up the accelerator pump discharge. Going from .026 to .031.
They also had different pump plunger springs available.

Has anyone tried these mods.


Do you have any pictures of your intake mods? Yes I have done semular mods to a carb's accelerator pumps to fix bogs, this is to either increase the pump shot volume and or the shots timing. Anytime you mod or change parts from the orginal intake design it can effect the tuning. Having carb heat is usally best for any street use car or truck and gives the best performance and economy. Good luck on your tuning. :thumbup: :nod:
A bad day Drag Racing is still better than a good day at work!

I am still hunting for a project car to build but with my current low budget it's not looking so good. My Ex- Fleet of Sixes these are all long gone! :bang: 1954 Customline 223 3 speed with O/D, 1963 Fairlane project drag car with BB6, 1977 Maverick 250 with C4, 1994 F-150 a 300 with 5 speed.

Blairsville Ed
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Location: North Georgia

Re: 240 full throttle bog

Post #5 by Blairsville Ed » Sun May 20, 2018 3:57 pm

How do I post a pic?

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bubba22349
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Re: 240 full throttle bog

Post #6 by bubba22349 » Sun May 20, 2018 4:49 pm

This is the way I have done it over the years however you need to pick the right free hosting site as some like photo bucket now want to charge you. I don't know which to recommend at the moment.

viewtopic.php?f=47&t=48863

Perry our site IT guy did some work on a fix for this problem that allows a direct attachment and this is the latest info (in the below link) on posting pictures. Good luck :thumbup: :nod:

viewtopic.php?f=71&t=76906#p592748
A bad day Drag Racing is still better than a good day at work!

I am still hunting for a project car to build but with my current low budget it's not looking so good. My Ex- Fleet of Sixes these are all long gone! :bang: 1954 Customline 223 3 speed with O/D, 1963 Fairlane project drag car with BB6, 1977 Maverick 250 with C4, 1994 F-150 a 300 with 5 speed.

Blairsville Ed
Registered User
Posts: 77
Joined: Sat Apr 22, 2017 3:39 pm
Location: North Georgia

Re: 240 full throttle bog

Post #7 by Blairsville Ed » Sun May 20, 2018 6:33 pm

Intake mod

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bubba22349
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Joined: Sun Jan 03, 2010 4:46 pm
Location: Flagstaff, Az. 86005 near the old Route 66

Re: 240 full throttle bog

Post #8 by bubba22349 » Mon May 21, 2018 4:16 pm

:?: we're is it!

Also something new on posting pictures ths month you can now drag and drop photos into your posts see below link. Good luck :thumbup: :nod:

viewtopic.php?f=21&t=78327
A bad day Drag Racing is still better than a good day at work!

I am still hunting for a project car to build but with my current low budget it's not looking so good. My Ex- Fleet of Sixes these are all long gone! :bang: 1954 Customline 223 3 speed with O/D, 1963 Fairlane project drag car with BB6, 1977 Maverick 250 with C4, 1994 F-150 a 300 with 5 speed.

Blairsville Ed
Registered User
Posts: 77
Joined: Sat Apr 22, 2017 3:39 pm
Location: North Georgia

Re: 240 full throttle bog

Post #9 by Blairsville Ed » Mon May 21, 2018 6:07 pm

I’m having trouble getting the pics to transfer

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