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Discussion Starter · #1 · (Edited)
I'm putting this in the M8 section, but it also applies to Twin Cams.

There seems to be a lot of mistaken information out there about Harley tappets as to source and how they work.

Lets start with what style of tappet they use. Harley uses a Delphi designed hydraulic self adjusting roller tappet. It called a Delphi tappet because Delphi produced them for GM back in the 80's when the small block Chevy transitioned over to roller tappets. It was designed to be a drop in replacement for the existing flat tappets and only required an anti rotation devise to work in existing castings. And it was a pretty slick idea when looked at beside the existing roller tappets of the period. The two flats on the upper body are what prevents rotation. They ride in a guide on the M8 or against a pin in the Twin Cam. The M8 guide was used to make the engine quieter, as the pins were known to chatter. Internally, the Delphi tappet used the same parts as the existing hydraulic flat tappet. Now, while Harley uses a Delphi (GM) style tappet, they do not buy them from Delphi. Fact is GM didn't use Delphi as a sole source. The other big player in the tappet business is Eaton. And Eaton builds Delphi style roller tappets, but they uses Eaton internal parts. And since GM used Delphi and Eaton to supply tappets, they needed a way to tell them apart. The clip on top of the tappet is how you tell them apart.

The left tappet is a Delphi and the right is an Eaton. Notice snap clips that hold the seats in.



Now here is a tappet from a Harley M8. Twin Cams are the same. It has an Eaton style clip.



Here is another difference, Delphi on the left Eaton on the right. The Delphi oil port is above the roller axle the Eaton is rotated 90 degrees from the axle.



And the tappet from an M8



It should be noted that the location of that hole has no effect on the function of the tappet, despite what some resellers will tell you. Its whats inside that makes a differance.

Insides of a Delphi, same as your 71 Chevy.



Insides of an Eaton, note the check valve on the bottom.



And here are the guts from an M8 tappet.



So its not Delphi Tappets that are in Harley's, its actually Eaton tappets.

BUT.....................They may or may not be built by Eaton. These tappets have been around since the 80's and lots of companies make them all over the world. I suspect that tappets are an item that the MoCo puts out on bid.

Next I'll describe how the Eaton tappet works.
 

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Discussion Starter · #2 · (Edited)


The way an Eaton tappet addjusts is like this.

The tappet body fills with oil through the hole in the side of of the tappet body (A). It fills the tappet body and the valve section (C). Any air either leaks out the top or is pushed up the push rod. This is what you are filling when you prefill a tappet with a pump can.

In the engine, the spring (B) pushes the valve body (plunger) and push rod seat (D) upwards until the free travel is gone, or it runs up and hits the retaining clip. When the plunger rises up in the tappet, oil moves freely into the tappet past the check valve. When the plunder moves down, the check valve prevent oil from moving from the tappet body into the plunger. This is what sets the tappet at zero lash and holds it. It is not a perfect seal, as oil can still move past the plunger body. This is what is happening while you wait for your push rods to spin freely after adjusting them. The range of travel is set when the tappet is built, and not all tappets have the same travel. When you adjust your threaded push rod, you are basically centering the tappet guts in the middle of their travel. That way they can account for increases or decreases in valve train span.

When the tappet tries to open the valve, the check valve in the bottom of the plunger prevent oil from moving from the tappet body into the plunger, so the valve opens. Each time the valve closes, the tappet readjusts to 0 lash. The tappet can adjust for increased lash a lot faster than it can adjust for decreased lash. That's why the motor will run poorly when you exceed the ability of the valve springs to keep up with the cam. The valves are late to close and the tappets take up the lash, then hold the valves open while they bleed off the oil used to adjust that excess lash out. The cause of the valve float is the valve spring, not the tappet.

The amount of oil metered to the top of the valve train is a function of metering hole size and oil pressure. The Eaton metering hole is in the side of the push rod seat (D)



Oil flows between the seat and the tappet body, enters the metering hole and flows up the push rod. And contrary to the internet, this is not something that is changed for the MoCo. They flow the same oil to the push rods as a GM tappet. But with that said, the same can not be said of all aftermarket GM tappets. Some race use tappets restrict the flow of oil to the push rods.

So you can see how the oil already in the tappet does the adjusting. And the oil only needs enough pressure to enter the tappet through a hole. No valves or anything to overcome. And no need for or advantage to having high oil pressure to the tappets as far as lash is concerned. But with that said, air is another issue. Because it is compressible, any that finds its way to a tappet will cause some ticking until it works its way out. And because of the design of Harley's pump and cam plate, there tends to be some air in the oil at start up.

So what is the issue with using automotive tappets in your Harley? Basically there are three issues.

1) Quality. A stock low end GM engine will run a long time with low quality roller tappets. And there are companies that produce budgets tappets just for that market, the budget re-builders. The springs are soft and the cam profiles are not aggressive, so they last a few 10's of thousands of miles. Put that tappet in a Harley and you will see roller issues. Harley found that out the hard way.

2) Plunger travel. Not all tappets are the same on the insides. Some GM tapped used in performance engines have reduced plunger travel. This allows them to reduce the piston to valve clearance on their performance motors. So if you use GM high performance tappets, and adjust them like oem Harley tappets, you might have issues.

A standard GM tappet has an adjustment range of about 6mm. Tappets for High Po LS's up to about 2010 have an adjustment range of about 3mm. So if you adjust out the normal 3mm to center the plunger, and do it on a hot day, you might have valves hanging open when you try to start it on a cold day. And many aftermarket suppliers just rebox tappets. So while this works fine in a LS Chevy, it could be and issue in your Harley.

3) Oil flow to the push rods. As said above, some tappets are setup to reduce the flow of oil to the pushrod. And while this is a good thing for your hot rod small block, its a bad idea on your Harley.

With that said, if you push the oil pressure up, you increase the amount of oil that flows up the push rod. So when setting oil pressures, that should be a consideration. But oil pumps and pressures is another issue.
 

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And just out of curiosity what about 18538-99 and 18538-99A lifters? Third revision for the twin cam and sportster were 18538-99b, a Delphi lifter. Exactly what part number were these Eatons? When a source or design change is incorporated Harley does revise the part by letter designations. Agree with your definition of air being an enemy but unfortunately by the nature of the dry sump system the scavenge side will suck air and that just means it is doing its job. The oil does have entrained air to some extent, a whole new discussion.
 

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Discussion Starter · #4 · (Edited)
The tappets in the first photo with the white back grounds are a (L) Delphi out of a GM parts bin. And a (R) Eaton out of an 11 twin cam, and the last one's are of an Eaton out of a M8, so its a -99c. Or I should say it would be replaced with a -99c. Service parts and assembly line parts may or may not be from the same source. There have been rumors of the MoCo buying spot market tappets for years. And I would suspect that the flaking rollers we saw back in the early teens were not made by Eaton or Delphi.

Chinese tappets can be had for less than $3 a pop in lots as small as 20. And retail for as little as $5. I have been told that the Mexican tappet plants that were set up to service the American auto industry after NAFTA, just assemble Chinese tappets now. By shipping in parts only, they avoid tariffs, and can then ship the assembled part to the USA tariff free.

You can buy these Chinese tappets on Alibaba. And I'd bet more than a dollar that the MoCo ended up with some of them.

Chinese roller tappets
 

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Yes, same here.
Although this will take me more than one read through to begin digesting. haha
 

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Johnson was the source of the original and -a harley lifters. They are now split into two companies, not connected. Hylift Johnson, Chicago and Johnson Lifters Michigan, both still made in the USA. Before we go down the everything is made in china junk there are still several quality aftermarket companies producing lifters in the USA and Canada, parts all manufactured there, not sold by Harley.
 

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Good post. Personally I use the Hylift Johnson when I have the choice but whether they are really better... at least they are made in the US.
 

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Excellent thread, thanks for a well written explanation!
 

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There are other USA sources not discussed which I will leave alone, I personally use Morel, USA made lifters. Only lifter I have found that is true to size .842 +or- .0002 and the roller axle is clipped in rather than crimped which is what causes OD distortion. They are slow bleed and properly heat treated.
 

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I wish I had retained this info the first time around.

Sent from my captainhook455 clone device
 

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I own a 13 CVO. They have 18572-13 lifters. The lifter wheels were frosted at 6500 miles. That isn't going to shut you down but it is an indication that the heat treat was not done properly or the alloy of steel is suspect.
 

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Discussion Starter · #16 ·
I own a 13 CVO. They have 18572-13 lifters. The lifter wheels were frosted at 6500 miles. That isn't going to shut you down but it is an indication that the heat treat was not done properly or the alloy of steel is suspect.
Some things never change.

2019 tappets with 1000 miles on them.

270015
 

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Still reading this over again. It's very informative. But, I'm just a bit confused. If the HD 18538-99C Lifters are junk, why is HD still selling and using them? Also FYI, I went to CYCO Gaskets to buy some parts and noticed they are selling a C18538-99C Lifter. When I asked them if they were HD's the rep said they were their own brand. When I pressed him further asking if they made them he told me they were made in China.
 

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Discussion Starter · #18 ·
Still reading this over again. It's very informative. But, I'm just a bit confused. If the HD 18538-99C Lifters are junk, why is HD still selling and using them? Also FYI, I went to CYCO Gaskets to buy some parts and noticed they are selling a C18538-99C Lifter. When I asked them if they were HD's the rep said they were their own brand. When I pressed him further asking if they made them he told me they were made in China.
On average, Harley only needs the tappet to last 10K miles, after that its someone else's problem. So they don't have much incentive to use higher quality tappets. And the letter behind the part number used to change when the vendor of the part changed. That is no longer the case. Hasn't been that way for quite a while. Based on packaging, Harley is using more than one supplier for tappets at this time. From what I have seen from 18's and 19's, Harley is using a very low end tappet.

I recently saw a tappet that had worn the roller down to were the cam was lifting the tappet by the body. How soft does a roller have to be to wear that much without wiping the lobe off of the cam?
 

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On average, Harley only needs the tappet to last 10K miles, after that its someone else's problem. So they don't have much incentive to use higher quality tappets. And the letter behind the part number used to change when the vendor of the part changed. That is no longer the case. Hasn't been that way for quite a while. Based on packaging, Harley is using more than one supplier for tappets at this time. From what I have seen from 18's and 19's, Harley is using a very low end tappet.

I recently saw a tappet that had worn the roller down to were the cam was lifting the tappet by the body. How soft does a roller have to be to wear that much without wiping the lobe off of the cam?
Thanks Thermodyne, yeah that's weak on that roller. And HD wonders where their loyal riders went. The statement that on average they only expect them to last 10,000 miles and after that it's someone else's problem is disheartening for sure. Lots of riders buying bikes with extended warranties. Don't they take those failures into consideration?
 

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Thanks Thermodyne, yeah that's weak on that roller. And HD wonders where their loyal riders went. The statement that on average they only expect them to last 10,000 miles and after that it's someone else's problem is disheartening for sure. Lots of riders buying bikes with extended warranties. Don't they take those failures into consideration?
4 lifters at their cost is worth what 10$ maybe plus couple $ for gasket? For the time mothership does not pay full labor rate any way! Trust the bean counter if they were to loose money the would go for better quality parts.
 
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