What's the correct shape and finish for tappet faces?

[MacGyver]

I need to have my tappets resurfaced, and I'm wondering what the correct shape is for the tappet face?

Most engines I'm familiar with have a very slightly convex shape to the face. If you take 2 lifters and put the faces together they should "rock" slightly against each other. Once they've worn flat, they're usually considered to be worn out.

These lifters seem to be very slightly concave.
 Is that correct?

If I take my lifters to a machine shop for refacing, what should I have them do?
Convex? Concave? Flat?

[mobile_bob]

a proper flat tappet should always be convexed, but
that is predicated on the cam lobe also being off parallel by a .001" or so to match the convex
the two work together to assure rotation of the tappet.
i have no idea whether or not the indian cam lobe has this offset, but one could mic it out
and find out easy enough.

you can have the machine shop grind the tappet flat and finish the convex quite easily on an oil stone
by hand.

the convex will result no matter how careful you are to try and keep it flat against the stone
if you work it in a rotational figure 8 pattern across the stone,
no matter how hard you try to keep it flat it will by nature of the process generate
a convex face.

that is why one needs three surface plates to hand lap and get a perfectly flat surface
if you only use two plates one will end up convex and the other concave.

this is the one time that a problem in lapping is used to your advantage.

not very common to get a problem to actually work to your favor.

also it is not likely you will find a local machine shop that can properly grind and polish the lifters
with a convex anyway.

you can use the stem of the other lifter as a staight edge to determine the "rocking" and get
and indication of convexity of the lifter you are generating.

even if the indian cam is parallel on the lobe i would still go to the effort to convex the lifter
over time the cam will wear in to match the lifter anyway.

good luck
bob g

[Tom]

Here is a bit from Georges site:

7/11/06:  Stopped by my friend’s machine shop yesterday afternoon.  I chucked the tappet stem in the lathe and turned it on.  Both tappets spun true.  No runout.  I also placed a straight edge across the tappet faces and was able to fit a 0.003” feeler gauge between the center of the tappet face and the straight edge.  My other engine had tappets cut the same way.

[M61hops]

Hmmm, concave tappets?  I don't think that sounds right, I also thought they were supposed to be convex.  I would look into buying new ones as that might cost less than paying someone to resurface them, and it would be interesting to see the shape of the face on replacements.  If a person were to reface tappets wouldn't they need to be re-hardened ?      Sorry to hear your tappets aren't square MacGyver.                        Leland

[xyzer]

I'm goin with flat. The camshaft is offset so it always works on one side of the lifter to cause it to rotate. I just mount mine in a V block and surface grind them. Even doing that I still have haseled with the rotation issue. Things I have found that will give you headaches include the guide bore is not bored straight to outside, I sometimes loosen the clamp and rotate the guide till I see rotation, then clamp. I also have an engine that the block was bored over for the guides (if you don't need a lifter guide puller it's loose) and allowed the lifter guide if loose to tilt when clamped. The problem with those sheetmetal clamps is they deform with almost any pressure and the soft gaskes they use doesn't help either.  When you tighten down the clamp it deforms and tightens on one point at a point on the inside of the guides and if it is loose in the case it will tilt contributing to a no spin condition. I made a solid aluminum clamp that gives good preasure on opposite sides so the clamping force is straight down. Concave or convex will give you a small contact area on the cam and cause premature wear issues with no oil film to lubricate. IMO there are several reasons to cause the no spinning lifter to happen.  You fix may vary
Dave

[MacGyver]

Thanks guys for the info!

I guess "flat" sounds like the way to go.
Concave definitely seems wrong, but that's what they were like to start with .

I did a little test yesterday. I removed the pushrods and set up a dial indicator over the top of the tappet. I rolled the engine over until a tappet was on top of a lobe, zeroed the dial indicator then rotated the tappet in it's bore by hand. The exhaust tappet showed .006" of up and down movement as it was rotated. The intake tappet showed .004" of up and down movement, but most of the variation was in a fairly narrow area like someone had carved a ditch across part of the tappet face.
So I'm pretty sure the problem is with the tappets themselves, and not issues with the tappet bores being crooked. I emailed George B this morning and it sounds like he can probably help me get some resurfaced ones.

Dave, I didn't use the paper gaskets under my tappet holders. I just put a small bead of silicone sealant under them and clamped 'em down. I just didn't like the look of the paper gaskets. They were thick and spongy and they didn't look like a very stable surface for the tappet holder to sit on...

[ronmar]

When I was speccing mine, I first spun the tappet in the lathe to measure face runout.  I chucked the tappet holder in the lathe, and aligned the holder so the lip that sets on the engine case had 0 runout. then I inserted the tappet into the holder and rotated them both together to see what the combined error was from holder lip/flange to face.  This showed me how true the holder bore was.   

MacGyver.  You might be able to get an idea of how true the holder bores are by re-creating your tests and see what happens when you rotate the tappets with the holder in different positions.

Ron

[spike]

MacGyver

You might run your engine a bit more to see if your tappets don't free up and start rotating. I've got a 6/1 which had non rotating tappets, that now has about 450 hrs on it, and one of the tappets starting rotating after 50-100 hrs of use. I just haven't gotten around to working them yet but it would be nice if the other tappet would also start turning.

Tim

[MacGyver]

Well, I guess I took care of my tappet problem...

At first I was just going to send them off to one of George B's buddies and have them reground, but yesterday I got into one of those "DIY moods" (what causes that anyway?) and took care of the problem myself.

I've got a small "Cheap-ass Chinese Lathe". It's about the same ugly quality as a 'roid but a several hundred pounds lighter.
I welded up a couple chunks of steel and made a "Cheap-ass MacGyver Syle Holder" to mount my Dremel tool on the lathe cross slide.

I put a stone in the Dremel tool, chucked up the tappet in the lathe and spent a *lot* of time getting the tappet square and the Dremel tool centerline lined up the way I wanted it.  Once all the angles looked good I just spun up the lathe and the Dremel tool and "went at it" and worked the stone back and forth across the face of the tappet until I thought it was reasonably flat and square.

I'm sure that I would have got a better job done by letting "the professionals" do it, but even with my crude methods I was able to get them reasonably square. The total runout on the face ended up at much less than .001" (instead of the .004 - .006" I had before)
When I got them as flat and square as I could I finished the faces by hand with a piece of 400 grit sandpaper on a piece of glass.

I reinstalled them in the 'roid and started it up and now the tappets spin like crazy in their bores instead of being "stuck" in one place.
The exhaust tappet goes around about once per second (or a little faster) and the intake tappet goes maybe 50% faster than the exhaust. Tappet rotation is no longer an issue!

Another low tech solution for a low tech engine.   

I took a few photos of the tappets when I was done, but they came out all fuzzy and unfocused.    Sorry...

[Tom]

Sigh, I WANT a lathe!

[MacGyver]

Sigh, I WANT a lathe!

Well you've got a credit card, right?   

Mine is just a tiny lathe... (7 x 14)
It was cheap (*way* less than a 6/1) and it's not a very rigid or high precision device, which is severely compounded by the fact that I'm a terribly inexperienced operator.

But it is handy when I need to make or fix small "round stuff", and it doesn't eat up much space on my workbench and I can pick it up and move it myself (on a good day) if really in the way.

It was certainly handy for fixing 'roid tappets once I figured out how to attach the dremel tool to the cross slide. 

[rbodell]

Sigh, I WANT a lathe!

I know where you are coming from. I saw a Harley Sportster with 66 miles for $6K this afternoon. If the bank had not been closed I would have baught it.

[Tom]

I'm actually a fairly experienced operator, I used to manufacture video pipe inspection cameras and associated winches and stuff. Even made a mill for the company that worked pretty good for years. And my cards are MAXED out as we finished building the house on the cards. I'm sure a lathe will find its way into the basement sooner or later.

By the way I believe that lathes are sized by the diameter of the chuck, length of swing (aka diameter of of part that will fit) and length of travel on the bed.

[MacGyver]

I'm actually a fairly experienced operator, I used to manufacture video pipe inspection cameras and associated winches and stuff. Even made a mill for the company that worked pretty good for years.

Maybe this summer you need to come over for food and beverages and teach me some of what you know. A crash course in grinding HSS tool blanks would be a good start...

And my cards are MAXED out as we finished building the house on the cards. I'm sure a lathe will find its way into the basement sooner or later.

Well, I've seen your off-grid place, and it's beautiful. And as energy costs skyrocket you are going to be plenty glad that you spent the $$ for those panels and batteries.

By the way I believe that lathes are sized by the diameter of the chuck, length of swing (aka diameter of of part that will fit) and length of travel on the bed.

Yep. diameter and travel = 7 x 14.
This is pretty much the same beast here, although I see the price has gone up substantially in the last year or so. And mine's red...
http://www.ares-server.com/Ares/Ares.asp?MerchantID=RET01229&Action=Catalog&Type=Product&ID=82710

[jimdunne]

Well McGyver, wasn't sure at first you would do it. But you stayed with it, and now have a decent engine.

See, it doesn't do a bit of good to fuss, or belly-ache about an issue, but THAT energy can sure be well-used for DOING something!

Congratulations, and don't pay any attention to those who give you a bunch of sh** about how you do repairs, etc.

Instead, pay attention to folks like Quinn, and hotater, and xyzer, who help you find the correct path to head down.

What we all need more practice doing all our lives is what  you just did with your 6/1; decide what you need to do, and do it.

Well done!