Quality Flat Tappet Components

[BCjohnny]

I'm sure someone with more understanding will correct me, but .....

In engineering terms the notion of putting a radius against a taper makes absolutely no sense ..... all you are creating is tangential point contact

But in a manufacturing environment theory is often nonsense, you have to make things happen ....... and striving to match tapers might be a production managers nightmare

So tangential point contact is the best of a bad job, tolerance wise, and you run with it

This is why you have to 'bed' a FT cam in ..... and as such 'tool steel' lifters take one variable out

[CamKing]

I'm sure someone with more understanding will correct me, but .....

In engineering terms the notion of putting a radius against a taper makes absolutely no sense ..... all you are creating is tangential point contact

But in a manufacturing environment theory is often nonsense, you have to make things happen ....... and striving to match tapers might be a production managers nightmare

So tangential point contact is the best of a bad job, tolerance wise, and you run with it

This is why you have to 'bed' a FT cam in ..... and as such 'tool steel' lifters take one variable out

With most overhead cam engines, that run bucket type followers, the followers are flat, and the cam lobe faces are flat and parallel to the lifter face. To get those lifters to spin, the centerline of the lifter is offset from the centerline of the lobe, either to the front of the head, or towards the back. This gives you line contact, instead of point contact. The only issue with this, is that it makes the effective diameter of the follower act smaller, so you can't design the lobe velocity curve for the actual lifter diameter.
This has been tried on pushrod engines, but with the lifter bores not being perfectly true, and the cams flexing, you no longer end up with the lifter face, and lobe face being parallel. With all the machine tolerances you end up with in a pushrod engine's valve-train, the tapered lobe, and crowned lifter is more forgiving.

[BCjohnny]

With all the machine tolerances you end up with in a pushrod engine's valve-train, the tapered lobe, and crowned lifter is more forgiving.

Yes, of course ....... I was referencing exactly this, in this particular context

[hoffman900]

I'm sure someone with more understanding will correct me, but .....

In engineering terms the notion of putting a radius against a taper makes absolutely no sense ..... all you are creating is tangential point contact

But in a manufacturing environment theory is often nonsense, you have to make things happen ....... and striving to match tapers might be a production managers nightmare

So tangential point contact is the best of a bad job, tolerance wise, and you run with it

This is why you have to 'bed' a FT cam in ..... and as such 'tool steel' lifters take one variable out

With most overhead cam engines, that run bucket type followers, the followers are flat, and the cam lobe faces are flat and parallel to the lifter face. To get those lifters to spin, the centerline of the lifter is offset from the centerline of the lobe, either to the front of the head, or towards the back. This gives you line contact, instead of point contact. The only issue with this, is that it makes the effective diameter of the follower act smaller, so you can't design the lobe velocity curve for the actual lifter diameter.
This has been tried on pushrod engines, but with the lifter bores not being perfectly true, and the cams flexing, you no longer end up with the lifter face, and lobe face being parallel. With all the machine tolerances you end up with in a pushrod engine's valve-train, the tapered lobe, and crowned lifter is more forgiving.

British engines like Triumphs are like this, and it’s just better to defer to cam grinders like yourself to match taper to tappet diameter.

[Mummert]

what makes a tool steel lifter superior to some other alloy? for instance the 4140 that spring retainers are made of? do they have the same crown as iron lifters?

I'm not a metallurgist but from what I take from is that the material can achieve high surface hardness, while still having excellent toughness. Many metals that can achieve the 63 rc don't have good toughness or dont get through hard. Other metals like many different versions of chromalloy can have excellent toughness but struggle to get harder that 55ish rc.
Tool Steels are easy to heat treat, through hard and have good toughness. There are many versions of tool steel ,some can have tungsten, carbide, and vanadium which makes the material expensive and harder to machine.

[BCjohnny]

The through hardness of 'tool steel' lifters is important, mostly to avoid the deformable 'pie crust' catastrophe, but they also have a higher wear resistance ...... lower abradability ...... than plain chilled Iron

The contact area between the lobe taper and lifter crown radius is obviously a controlled wear interface, and where experience has dictated that the cam is the sacrificial partner

The conclusion being it's the rate of lobe sacrifice where TS lifters apparently excel, the ability to maintain their own form (radius) and allow the cam to bed in without prematurely wearing out

I did ask before if anyone knew the specific 'tool steels' used in lifter manufacture, but not sure I received a definitive reply ........ the assumption being M2/D2/H13 or something similar ?

[frnkeore]

M2 (HSS), I would think would be a over kill and H13 would be to soft. A2 is a good all round TS & D2 is very good at long run abrasive applications but, is more brittle than A2 and harder to machine.

I think A2 would be my choice, at least as a place to start, for making lifters.

I never got a answer to my earlier question, of what should the difference in hardness be, between the lifter and lobe, if any.

[BCjohnny]

I never got a answer to my earlier question, of what should the difference in hardness be, between the lifter and lobe, if any.

The reality in practice is the cam lobe is slightly softer than the lifter, hence the former being the 'sacrificial' part ....... but I guess historically it's all been tried and mostly settled on this ....... they simply can't be the same hardness as predictable wear ('bedding') would go out the window

The Powell Machine video is interesting, and in line with what I've measured myself, cams around 50+ Rockwell and lifters usually 4-6 points higher ....... ultimate hardness all being equal would mostly govern component lifespan

Having the lobe around a few points softer on HRC seems to be were the sweet spot lies, at least with chilled Iron parts ...... but hardness is not the only consideration, hence the interest in the actual alloys used in TS lifters

In the absence of specific information, I'd be happy to use D2 and anneal it back to the hardness needed, but that's probably because I'm familiar with it and I have suitable bars lying around, lol ....... it's stable and annealing it back to 56-58 HRC would take virtually all the brittleness out of it

H13 could be a little soft granted, but can go up to over 50 HRC so, if the cam is ~ 48 HRC, there's no apparent reason why it wouldn't work

Fascinating subject, and also thanks to the real Pros who've chipped in with info so far

[CamKing]

I never got a answer to my earlier question, of what should the difference in hardness be, between the lifter and lobe, if any.

When we started making our own "Flat Follower" cams for IndyCar, in the 90's, I talked with a few metallurgists, and the consensus was, you should have a difference of 4 points of hardness, on the RC scale. On those, the followers were 4 points less then the cams, and the followers would wear quicker then the cams. Later on, we had the followers DLC coated, and that solved the wear issues.
In the 2000's, we were making all the cams for the Indy Pro Series, and we made the cams about 8 points harder then the followers they were using. They were bucket type followers with a puck on the top of the follower. Those pucks would wear, and have to be replaced every season, but they were only about $8.00 each, so it was much cheaper and easier to replace them, then it would be to replace the 4 cams.

[Walter R. Malik]

I never got a answer to my earlier question, of what should the difference in hardness be, between the lifter and lobe, if any.

The reality in practice is the cam lobe is slightly softer than the lifter, hence the former being the 'sacrificial' part ....... but I guess historically it's all been tried and mostly settled on this ....... they simply can't be the same hardness as predictable wear ('bedding') would go out the window

The Powell Machine video is interesting, and in line with what I've measured myself, cams around 50+ Rockwell and lifters usually 4-6 points higher ....... ultimate hardness all being equal would mostly govern component lifespan

Having the lobe around a few points softer on HRC seems to be were the sweet spot lies, at least with chilled Iron parts ...... but hardness is not the only consideration, hence the interest in the actual alloys used in TS lifters

In the absence of specific information, I'd be happy to use D2 and anneal it back to the hardness needed, but that's probably because I'm familiar with it and I have suitable bars lying around, lol ....... it's stable and annealing it back to 56-58 HRC would take virtually all the brittleness out of it

H13 could be a little soft granted, but can go up to over 50 HRC so, if the cam is ~ 48 HRC, there's no apparent reason why it wouldn't work

Fascinating subject, and also thanks to the real Pros who've chipped in with info so far

I remember testing lifter faces years ago and anything under 61Rc was not used in our own engines.
Later ... flat lifters used to come in the tray with that little testing dot in the face.

[PRH]

Anyone know how hard the Schubek lifters were?

The Trend website says their tool steel lifters are hardened to 64c.

[PackardV8]

Hi, Mike,

You see more of the cam-lifter interface than any of us, but what I've seen is:

1. From the first days of post-WWII OHV8s, OEM lifters varied widely from highly crowned, i.e. 30-degree spherical radius, Packard and Mopar, to flat, Buick for one. The SBC solids were ground with a much larger radius, that is more nearly flat, than the OEM hydraulics.

The Operator's Manuals which came with the cam grinder or tappet grinder specified the lobe taper and the lifter face radius for each engine family/years.

2. Today's lifters, including most we see from Johnson HyLift, are ground to much greater radius than the OEMs of the 1950s. I've asked Johnson about this, but the promised reply came crickets. The one thing I know from observation is they're not coming through to OEM spec. We've worried about this, but thus far, the larger radius lifters seem to be OK with the limited miles today's hobby cars see.

So question is, has the cam/lifter industry found a happy mean and grinding most of the lobes to the same taper and the lifters to a matching radius?

[CamKing]

So question is, has the cam/lifter industry found a happy mean and grinding most of the lobes to the same taper and the lifters to a matching radius?

That's a good question, but I don't know the answer.
I don't really get into those older, less popular engines.
Almost all the lifters I sell, are one of these part#'s: 817, 900, 992, 998, 2000, or 2011.
I really haven't studied the other lifters.
Next time I talk to the Hylift Johnson engineer, I will ask him about the crowns.

[frnkeore]

Can I assume that the lifter radius and the lobe taper, should meet in the center of the cam lobe?

How important will it be?

[PackardV8]

Next time I talk to the Hylift Johnson engineer, I will ask him about the crowns.

Hi, Mike,
Thanks for the offer to ask the question. Specifically, what radius are the #812 and #879s being furnished today?