fuel pump pushrods

Nate S

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Hardness is only one material quality and not representative of good or bad with these. If the maker didn’t select the right steel it’ll wear away regardless. Hardness can also be “through” or “case”. Case is cheap, in both respects for a part like this.

Seems like the originals are good enough and plentiful enough to get the job done. If that’s not the case I can make up a print for a good one and we can get it quoted in qty 20 and divvy it up evenly. Could make it as indestructible as needed.
 

toolmanmike

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Hardness is only one material quality and not representative of good or bad with these. If the maker didn’t select the right steel it’ll wear away regardless. Hardness can also be “through” or “case”. Case is cheap, in both respects for a part like this.

Seems like the originals are good enough and plentiful enough to get the job done. If that’s not the case I can make up a print for a good one and we can get it quoted in qty 20 and divvy it up evenly. Could make it as indestructible as needed.
Makes you wonder if they didn't make them soft to prevent cam wear. May be a roller is in order. LOL
 

Jeremiah

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Did we put any assy grease on the pushrod upon installation? I have used several Comp pushrods without issue.
 

Daves69

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When I refreshed my engine about 15 years ago I used a Comp Cams pushrod. it failed within a year, luckily in my driveway, could not figure out why I wasn't getting fuel until I read a thread about the push rods. Shure enough thats what it was! I had a hell of a time getting that thing out because it mushroomed.
Luckily I found somebody on eBay with New Old Stock, I bought three of them.
No prob since, if I recall correctly they where like 30 bucks each.
Bitch is my builder tossed my old one becouse I provided him with the new one, oh well.
Find old original or a good used one
 

Richard Cranium

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Take both to a heat treat shop. Have them do a rockwell test on good end. Then ask them how much harder they recommend. And have harden it. Think induction hardening is the way to do it, you only harden near the ends. You don't want it glass hard. If you have several maybe have them do them to different hardness.
It only takes a few minutes to induction harden those pieces.

Hardness is only one material quality and not representative of good or bad with these. If the maker didn’t select the right steel it’ll wear away regardless. Hardness can also be “through” or “case”. Case is cheap, in both respects for a part like this.

Seems like the originals are good enough and plentiful enough to get the job done. If that’s not the case I can make up a print for a good one and we can get it quoted in qty 20 and divvy it up evenly. Could make it as indestructible as needed.




Well, I went to a local metal heat treating shop this afternoon and they did a Rockwell test on my new Comp Cams pushrod and a used one that I have (no idea whose it is). Both came out at 60.4, which I was told is very hard. I told him the issue of wear & he said that if there is a problem with wear, it's made of low-carbon steel. I asked about heat treating the tips and he said that it wouldn't do any good if the steel is cheap. So, I guess this leave me with a trial and error method.


IMG_1625.jpg
 
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khryslerkid

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Looking at some of the pictures of the ones that have failed, it looks like just the outside is hardened and the inside is soft (mild steel). Like stated in the last post if they're using cheap steel there's not enough carbon to create the hardness needed. It's the world we live in today.
 

Fran Blacker

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Well thanks for finding out hear treating isn't the answer. Did he say what steel alloy you should use? Would it need to be heat treated if you had one made?
 

Turboomni

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hunt2elk

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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
Thanks for posting that link. Made me remember that Mike from Then and Now has some original pump rods. He sold me a couple. Don't think he had to many left, but it would be worth asking him for you guys needing one.
 

Nate S

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Makes you wonder if they didn't make them soft to prevent cam wear. May be a roller is in order. LOL
Well thanks for finding out hear treating isn't the answer. Did he say what steel alloy you should use? Would it need to be heat treated if you had one made?
If you want good wear properties I’d make it out of A2 or D2, harden it to Rc 60 ish. Those are easy to get. Many other alloys that might be a little better but most will be a nuisance, like CPM 420V.
 

padam

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Well, I went to a local metal heat treating shop this afternoon and they did a Rockwell test on my new Comp Cams pushrod and a used one that I have (no idea whose it is). Both came out at 60.4, which I was told is very hard. I told him the issue of wear & he said that if there is a problem with wear, it's made of low-carbon steel. I asked about heat treating the tips and he said that it wouldn't do any good if the steel is cheap. So, I guess this leave me with a trial and error method.


View attachment 1208626

I don't think it would be 60 Rc if it was low carbon, unless it was carborized. I wouldn't think that would be much cheaper than using high carbon steel.

It would tell us a lot of the worn ones were tested.
 

Richard Cranium

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I don't think it would be 60 Rc if it was low carbon, unless it was carborized. I wouldn't think that would be much cheaper than using high carbon steel.

It would tell us a lot of the worn ones were tested.


The used one I brought in had some slight wear on the cam end & that’s the number the machine came up with when that end was tested.
 

Cranky

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I've had a couple that have worn, but who else has been having trouble with them wearing? What do youz guys attribute it to; the rod being made of Chinesium, the camshaft, or using oil with no zinc?

I just bought a Comp Cams hardened one.

https://www.summitracing.com/parts/cca-4626

Thoughts?
I have a old original.....last time I measured it, it was in spec so don't think it worn down any sitting in the container. And>>>>>>>was going to mention the file test too but like mentioned, it may not be hardened enough. During my machinist apprenticeship we took some 1020 cold roll steel and hardened it after grinding it into a center punch and that thing did dang well but don't know if it would last as a pump plunger. Whenever I installed a new cam, I would polish the lobe that the plunger ran on..... http://www.matweb.com/search/DataSheet.aspx?MatGUID=10b74ebc27344380ab16b1b69f1cffbb&ckck=1

Curious.........Do you know if that rod was full heat treated or induction hardened on the ends?
FILE HARDNESS TEST (tpub.com)
 

padam

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The used one I brought in had some slight wear on the cam end & that’s the number the machine came up with when that end was tested.
Steel doesn't get much harder than that, very interesting.
Maybe hardness isn't the issue.
I'm sure the factory put a lot of engineering into that little part. Some materials are not compatible in a sliding interface. I'd love to know the material of the original factory parts. Too bad I don't work at the metallurgical lab anymore.

Maybe the spring pressure on pumps is just too high.
 

padam

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I think the next thing to examine is the surface finish of the camshaft pump lobe.
I have noticed a trend in recent years, with cnc machining almost universal, to turn surfaces that in the past would have been ground.
While the surface finish may register the same on a gage, you have a different pattern, or lay.
With turning you have what amounts to very small threads that could have a cutting action in the direction of the cam centerline.
A ground finish has the lay in the radial direction.
This is the reason you never want a turned finish riding on a seal.
Not sure how they are done now or then, but since Comp seems to be mentioned often it's definitely something we should check out.
 

dsd1967

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The problem if it is carburized low carbon steel is that the first .008"-.015" will be Rc60, but the remainder of the part will be around Rb85 which provides no wear properties. If you break through that thin egg shell of hardness....there is nothing to stop the wear.

The medium carbon and high carbon steels can be through hardened which means it is the same hardness all the way through.

Low carbon steel is way cheaper than medium and high carbon steel and the carburization process is relatively inexpensive in a production atmosphere. The easiest way to check would be to take a used worn part, section it and take a hardness reading at the core.
 
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