fuel pump pushrods

dsd1967

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RC had a worn part checked, and it was still hard.

He had the surface checked. That will not tell you if it is through hardened. Unfortunately to check for through hardening you must destroy the part by sectioning the area you want to investigate. If the surface shows Rc60 and the core is Rb85 then it is case hardened low carbon steel. If it reads high on the Rc scale all the way through, then it is through hardened medium or high carbon steel.

The reason I was saying to check a worn part was that once you check it....there is no going back. You can also check a new one, but it will be a sacrificial lamb. You would have to buy a new one if the original checks good.
 

padam

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If the surface is hard, it should wear properly.
I agree it would be interesting to know if it was through hardened, but it shouldn't matter.
 

Richard Cranium

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He had the surface checked. That will not tell you if it is through hardened. Unfortunately to check for through hardening you must destroy the part by sectioning the area you want to investigate. If the surface shows Rc60 and the core is Rb85 then it is case hardened low carbon steel. If it reads high on the Rc scale all the way through, then it is through hardened medium or high carbon steel.

The reason I was saying to check a worn part was that once you check it....there is no going back. You can also check a new one, but it will be a sacrificial lamb. You would have to buy a new one if the original checks good.


That's like breaking a shatter resistant window to see if it really is shatter resistant.
 

dsd1967

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That's like breaking a shatter resistant window to see if it really is shatter resistant.

Yup....you got to break a few eggs to make an omlet.

I worked 18 years on a product line that we used both case hardened and through hardened parts. The only way to know you were getting what you paid for on the hardness was to section parts and test them....and assume the rest of the batch was following suit. We usually pulled random parts throughout the batch to ensure consistency through the entire run.

Padam.....On a case hardened part, if the base material can't handle the load stress, it doesn't matter if the surface is hardened. The case hardening offers very little structural integrity...it's just a wear surface. It's just like an egg shell over a hard boiled egg underneath....crack the shell and the mush underneath won't support much load.

The through hardened parts are robust through and through and have extremely high tensile strength. The tradeoff is that they can be extremely brittle at the Rc60's hardness. For a fuel pump rod....a through hardened part will survive. For an impact type application, it will probably snap or chip.
 

padam

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I know a through hardened part would probably be better, but case hardened would seem fine for a push rod.
But I'm no engineer.
 

dsd1967

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Padang

If you look at post 5 the fifth picture down it looks to be case hardened. It appears to have a axial crack that is only about .015” deep from the surface. The pushrod wore significantly in length once the case was compromised.
 

padam

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Padang

If you look at post 5 the fifth picture down it looks to be case hardened. It appears to have a axial crack that is only about .015” deep from the surface. The pushrod wore significantly in length once the case was compromised.
If you say so.
i cant see the pictures that well.

my point is that it should not even wear through the case.
If your lifter wore .002" it would be flat and wipe the cam.
 

Richard Cranium

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This thread may be of interest. It is concerning the massive springs that are in many mechanical fuel pumps made today and the overly high force it takes to work them. Also the crappy assembly of the Carter pump's diaphram assembly. It may not be the problem but it could be part of it.

Mechanical Fuel Pump 101
https://www.forbbodiesonly.com/moparforum/threads/mechanical-fuel-pump-101.194336/#post-911570724



The business mentioned in that thread is not far from me.
 

Nate S

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It’s a different application. Seems lifter-ish but doesn’t have the crown or spin of lifters, nor the surface area. When designed it was made for the mild factory fuel pumps you could pump with the arm in the palm of your hand. .. and that was with the good factory rods.

The higher volume pumps would push a hole through your hand! A whole different deal. Still ok with the good, thru-hardened rod but use the crappy rods and the show is over. More reason people seek out actual factory parts, the engineering is almost always better, when you can spread that research over hundreds of thousands of cars you can donit better.
 

khryslerkid

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It’s a different application. Seems lifter-ish but doesn’t have the crown or spin of lifters, nor the surface area. When designed it was made for the mild factory fuel pumps you could pump with the arm in the palm of your hand. .. and that was with the good factory rods.

The higher volume pumps would push a hole through your hand! A whole different deal. Still ok with the good, thru-hardened rod but use the crappy rods and the show is over. More reason people seek out actual factory parts, the engineering is almost always better, when you can spread that research over hundreds of thousands of cars you can donit better.

I was thinking the same thing when using the heavier pumps and it might have been the contributing factor in wearing the one that I encountered but there have been several individuals who had the same failure using a stock pump with aftermarket rods. It's junk like half the stuff on the market today. We the consumers take the hit and like this part we find out the hard way. Pass on the info and hope no one else buys these inferior products.
 

RemCharger

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It’s a different application. Seems lifter-ish but doesn’t have the crown or spin of lifters, nor the surface area. When designed it was made for the mild factory fuel pumps you could pump with the arm in the palm of your hand. .. and that was with the good factory rods.

The higher volume pumps would push a hole through your hand! A whole different deal. Still ok with the good, thru-hardened rod but use the crappy rods and the show is over. More reason people seek out actual factory parts, the engineering is almost always better, when you can spread that research over hundreds of thousands of cars you can donit better.
I have never been inclined enough to measure fuel pump lobe taper.. but they are designed to spin by simply looking at enough of them. I would say it's when they stop spinning that they will start to get trashed.
 

hunt2elk

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I have never been inclined enough to measure fuel pump lobe taper.. but they are designed to spin by simply looking at enough of them. I would say it's when they stop spinning that they will start to get trashed.
Didn't know that, but it would make sense.
 

Nate S

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What is wrong with the stock ones that go 200k miles
Kinda nothing. It doesn’t always work out that people have a good one on hand though so we’re discussing the flaws with replacements that often do fare too well.
 
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