Failed bronze tip fuel pump pushrods

[540 RAT]

From time to time, over the past couple of years or so, folks have been posting threads on some of the Forums about failed bronze tip fuel pump pushrods. There has of course been some discussion about all that, but no real wind-up as to what is actually going on here.

Since there has not been a solution, some folks have switched to composite fuel pump pushrods in an effort to get out from under this problem. However, that may not be the best choice either, since it is not that uncommon for composite fuel pump pushrods, or for that matter composite distributor gears, to break inside a running engine. And that can leave you with quite a task to clean all the broken pieces out of the engine, not to mention having a running failure when you least expect it. For that reason, I don't believe composite engine internal components are a good idea in our traditional SB and BBC's.

I think it is much better to get to the root cause of what the problem may be with the metallic parts in question. Because bronze fuel pump pushrod tips and bronze distributor gears won't generally ever break on you, in a running engine, even if they may have some wear issues. Bronze parts such as those, are softer material and are expected to wear, thus preventing wear on your steel cam. They are maintenance items, much like solid roller lifters. You can't expect to install them and permanently forget them. At the very least, you should periodically inspect them to see how things are going.

In any case, I think it is about time to do a failure analysis of bronze tip fuel pump pushrods to get to the bottom of the failures some folks are experiencing. To accomplish this, I'm in the process of gathering as much information as I can about this issue.

So, if you'd like to be part of this failure analysis, please share the details about your bronze tip fuel pump pushrod failure, by answering the questions below:

NOTE: Just as important to this overall failure analysis of what did NOT work, is what DID work. So, if you've run a bronze tip fuel pump pushrod, and have had no issue with it, please answer the questions below as well.

1. Did your bronze tip fuel pump pushrod fail on you, or has it been fine?

2. If your bronze tip fuel pump pushrod failed on you, what brand was it?

3. If you experienced a failure, would you consider it excessive wear, or did the bronze tip mushroom to the point that you could not get it out of the block?

4. How many miles did you get out of it, or have gotten out of it so far, if it was primarily a street car?

5.How many passes did you get out of it, or have gotten out of it so far, if it was primarily a drag car?

6. What percentage of the time was this engine operated on the street, and/or what percentage of the time was this engine operated on the track?

7. What rpm did this engine most commonly see?

8. What is the psi rating of the mechanical fuel pump used with this pushrod. The psi is determined by how stiff the diaphragm spring is, which in turn, determines the load applied on the bronze tip.

9. What specific oil or oils, and what viscosity version of that oil or oils, did you use or are using with this pushrod?

10. Did you use any aftermarket oil additives in the oil used with this pushrod?

11. I'd like to get my hands on as many failed pushrods as I can for evaluation. So, would you be willing to send me your failed bronze tip fuel pump pushrod for that purpose? If you really want to keep the pushrod, I'd be happy to return it to you after the evaluation.

After gathering as much information as possible, including physical evaluation of failed parts, I'll post the results of the analysis. And hopefully, we'll have a workable go-forward plan at that time.

Thanks for any information you are willing to share.

540 RAT

Mechanical Engineer

U.S. Patent Holder

Member SAE (Society of Automotive Engineers)

Member ASME (American Society of Mechanical Engineers)

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[JoePorting]

I don't think very many people use mechanical fuel pumps anymore. Analysis on bronze distributor gears might be more useful since just about everyone has one of those.

[Greenlight]

I think another important factor is the maximum engine RPM. I suspect that some failures (excessive wear) can be attributed to impact loading of the bronze tip against the cam lobe when it experiences something similar to "valve float", due to the pump spring load and related component weights.

[novadude]

Cam material is a big variable, and a question you should be asking (SADI core, Billet core, etc). I wonder how many of the failures are from people trying to use bronze on an incompatible cam core?

[wyrmrider]

Thanks for looking into this

[cottonwood green]

Changed one out last year during a CV products fuel pump diaphragm change on a billet pump. It was a SBC Comp cams bronze tip model. Mostly street use, billet cam with an iron distributor gear. Had been in the car for about 3,000 miles. Pump had blue spring ( pretty stout ). Was slightly mushroomed over to a point where a pair of vise grips were needed for removal, but not too tough to remove. Compared to replacement, wore about .025 (WAG), threw it in trash so I can't send it to you for inspection

Dave

[540 RAT]

I think another important factor is the maximum engine RPM. I suspect that some failures (excessive wear) can be attributed to impact loading of the bronze tip against the cam lobe when it experiences something similar to "valve float", due to the pump spring load and related component weights.

Hi Greenlight, long time no talk. I completely agree with that, and that is one of the things I would be gathering info on. That is what question number 7 is intended to capture. For a race car, the answer would be the shift point rpm, or the max engine RPM. For a street/strip car there would be a street RPM answer as well as a track RPM answer.

540 RAT

[Belgian1979]

1000 km's and my bronze tip was worn pretty bad for the amount of miles. Since I went to FI, I threw it out. Still have it lying somewhere though.