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Old 09-19-2020, 06:23 PM   #1
Scott52
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Default 8BA fuel pump pushrod diameter

I have 2 8BA engines. Both fuel pump pushrods are loose in their bushings. What is the diameter of the rod where it moves in the busing? Wondering if the rods have worn under size and/or the bushings have worn oversize. And is it common to have this type of wear. Just part of my education of Ford Flatheads. Thanks
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Old 09-19-2020, 07:22 PM   #2
51 MERC-CT
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Default Re: 8BA fuel pump pushrod diameter

The pushrods are 7/16 " dia. Unless you can get definitive dimensions on the bushing and the pushrod to get actual clearance, looseness is just a matter of perception.
Don't over think it.
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Old 09-19-2020, 07:27 PM   #3
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Default Re: 8BA fuel pump pushrod diameter

It's possible to wear, but I have never seen one in 20 years.
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Old 09-19-2020, 07:41 PM   #4
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Default Re: 8BA fuel pump pushrod diameter

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It's possible to wear, but I have never seen one in 20 years.
Yep, several years ago because of the perceived looseness in the bushing I ordered a new bushing only to find out that it was no better than the original one.
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Old 09-19-2020, 09:25 PM   #5
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Default Re: 8BA fuel pump pushrod diameter

I did notice that both rods measured the same and both seemed equally loose. That is without the fuel pump which holds the rod "straight"?
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Old 09-19-2020, 11:05 PM   #6
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Default Re: 8BA fuel pump pushrod diameter

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Be sure you’re using an 8BA pushrod.
The ‘48 earlier are thinner, but they will work.
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Old 09-20-2020, 02:50 AM   #7
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Default Re: 8BA fuel pump pushrod diameter

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Be sure you’re using an 8BA pushrod.
The ‘48 earlier are thinner, but they will work.
They will not work because they are too short.
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Old 09-20-2020, 05:00 AM   #8
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Default Re: 8BA fuel pump pushrod diameter

Scott. You can use the shank end of a twist drill bit to measure the bore of the pushrod bushing. Larger drill sets come in 1/64" (0.0156") graduations, so you can get pretty close on the bore size. Just don't drop the bit into the engine.
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Old 09-20-2020, 07:18 AM   #9
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Default Re: 8BA fuel pump pushrod diameter

I don't see this as an issue. The bushing is hardened and so is the pushrod, and there isn't any oil lost by this condition as the bleed hole is very small. Unless you have a New bushing and pushrod, you can't define "loose" aS THE PUSHROD IS A ROCKER ARM.
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Old 09-20-2020, 07:27 AM   #10
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Default Re: 8BA fuel pump pushrod diameter

Just checked 2 NOS 8BA push rods in some NOS bushings & they are quite loose. I have just fitted some of these parts in a 8BA I have just rebuilt & they are no tighter than the ones I took out.
Phil.
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Old 09-20-2020, 09:11 AM   #11
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Default Re: 8BA fuel pump pushrod diameter

I didn't think the looseness would be a problem but we all know about "ASSUMING". The pushrod diameters measure about .430 and 7/16 is .4375. The defection back and forth is over .060 at the top of the pushrod. I am satisfied the pushrods and bushings are fine. Since this is my first Ford Flathead, it's nice to have a one fully assembled as comparison to the one that has been torn down to just the block. Off the machine shop to check the block out.
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Old 09-20-2020, 09:36 AM   #12
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Default Re: 8BA fuel pump pushrod diameter

Scott, be sure to have the block pressure tested before investing in any machine work. Magnaflux may not find all the possible cracks, the block needs to be pressure tested.
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Old 09-22-2020, 12:28 AM   #13
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Default Re: 8BA fuel pump pushrod diameter

Yes, it will be pressure tested.
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Old 09-22-2020, 11:20 AM   #14
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Default Re: 8BA fuel pump pushrod diameter

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Originally Posted by Scott52 View Post
I didn't think the looseness would be a problem but we all know about "ASSUMING". The pushrod diameters measure about .430 and 7/16 is .4375. The defection back and forth is over .060 at the top of the pushrod. I am satisfied the pushrods and bushings are fine. Since this is my first Ford Flathead, it's nice to have a one fully assembled as comparison to the one that has been torn down to just the block. Off the machine shop to check the block out.
.060" deflection at the top of the rod is insignificant. In my opinion, unless the rod itself showed unusual side wear on the shaft I would not be concerned.
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