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How to straighten out warped fuel pump flange?
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dennis 356
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Location: Malmö, Sweden
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PostPosted: Sat Jan 06, 2018 6:07 am    Post subject: How to straighten out warped fuel pump flange? Reply with quote

I have four early fuel pumps and all of them have more or less warped base flange from the eternal rod knacking or being overtightening, is there any way to level this pot metal material out so they´ll be straight again and if yes, will it last or will they get warped again after a while with running motor?

Dennis
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Last edited by dennis 356 on Sat Jan 06, 2018 9:09 am; edited 1 time in total
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hazetguy
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PostPosted: Sat Jan 06, 2018 7:54 am    Post subject: Re: How to straighten out warped fuel pump flange? Reply with quote

Can you post better pics of the flange on your pump? It looks like there is gasket material between the flange and the pump base, giving a false reading. Can you remove the flange, gasket material, and lay the pump base on a straight edge?

Others are going to say "machine the flange surface to make it flat again", and I know many people do this and sell many that have been machined.

I do not agree with that method for a couple reasons.

-The flange is a certain thickness and over time it has obviously warped. Machining that surface will remove material from the outer part of the mating surface, which is an already stressed area. I feel that when you tighten it again after machining, with a "thinner" outer (where the stud holes are and where the compression and warpage take place) and "thicker" center area, you really haven't solved anything and now you're working with less flange thickness, especially at the outer edges.
I have seen a few (rebuilt, never installed) pumps over the years that had machined flanges, and I guess the initial warpage was so significant, that there was a noticeable "bowl" shape to the base (as seen in the "before" pic below), even though the flange was machined "flat". Those bases went to the scrap, as there simply was not enough material remaining to tighten the pump securely without major warping happening right away.
-Another problem which can happen is that over the years, depending on how the pump had been attached to the case, there could be washer or nut gouges in the pump base, so machining flat will make that area even more "thin" and vulnerable to warping, or even cracking.
-Depending on what year pump you have, there are different internal reinforcements. Earlier pumps will have less reinforcing, later ones will have more. I'm sure this was a factory addressed issue, as earlier pumps do tend to warp more. Removing material from an earlier pump is weakening an already weak area. See pics below.
-The base will warp again, even during initial tightening to the case. That is one reason I press them 'past flat', so that during initial tightening, as the flange seats, it gives nice, firm compression around the entire base/gasket, rather than having more in the center versus the outer edges/ears of the base. Although these cars are not being daily driven as they have been in their earlier lives, warpage will happen.

A long time ago, I read in an automotive restoration magazine (Skinned Knuckles) about people repairing warped flanges on fuel pumps and carbs that are made of Unobtanium. I have used that method ever since, and have had excellent results and only one mishap, which was totally my fault to begin with.

I use the factory diaphragm preload tool, put some large washers on the two posts, so the ends of the pump base are supported, put the bare fuel pump base on the tool, use some wood on the opposite end from the tool (snout of the pump base) for soft cushion type support, and GENTLY evenly clamp it in a bench vise. Then I CAREFULLY AND SLOWLY heat the fuel pump base with a LOW FLAME torch to get it warmed, then SLOWLY AND CAREFULLY tighten the vise, keeping a careful eye on base positioning, flange movement, etc, making any necessary adjustments. Once the flange is pressed SLIGHTLY past flat, I keep everything secured in the vise and let it cool off naturally. One reason I like to press it slightly PAST flat is that it will compress again when the pump is installed on the engine, sealing tightly on the gasket.
This process took a little trial and error in the beginning (on junk pumps obviously), but I have the process down very well now and would not consider machining a pump base flange.

Granted, this method is rather time consuming, but for me, and the quality level I try to achieve, it is well worth it.

Again, I have had excellent success with this, and I have had no complaints from people who have installed my rebuilt pumps.

Internal pump reinforcement example. Early style:
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Later style internal reinforcements (this pump base has been 'reshaped' using my method):
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Basic demonstration of how I initially set up the base for straightening. This is a much older pic, and my method is slightly different, but you can get the general idea from this picture:
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Before:
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After. If you look very carefully at the outer edges, you'll see a slight gap where the flange has been pressed slightly past flat. This will compress during initiall installation.
Image may have been reduced in size. Click image to view fullscreen.


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Image may have been reduced in size. Click image to view fullscreen.

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dennis 356
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Joined: January 09, 2009
Posts: 100
Location: Malmö, Sweden
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PostPosted: Sat Jan 06, 2018 9:31 am    Post subject: Re: How to straighten out warped fuel pump flange? Reply with quote

Hi Don,

Thanks so much for your input, great help.....I definately wouldn´t consider machining the flange either and actually share many of your ideas on how to proceed to straighten it, although initially have planned to make a small jig instead of using vice, which of course is a much smarter idea. Same with the warming and cooling process.
The pumps I have, have all the 6 small reinforcement wedges like in your pic #2, but apparently it didn´t help much.
I have taken that photo deliberately in order to underline the warping, making it more noticeble, but its definately warp, probably as much as the #4 pic you´re showing.
One of the pumps I have has a slightly cracked base at the side, assuming = scrap, so I´m going to experiment on that one.

Dennis
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