Regards,

Dennis

Here's a pic of the broken lifter from JC 's engine .    Barry

Do you know who's tappet?  OEM Ford, aftermarket, off shore, part number, etc ... .

Regards,

Dennis

I’ll add that pushrod clearance issues at the heads and/or inadequate rocker arm to shaft clearance will destruct a lifter.

Although preferences for an undercut at the base of the lifter stem where it connects to the lifter foot seems to be divided, that undercut does allow the lifter to go up fully without jamming in the block at the bottom of the lifter bore.  The lifters I use all have this undercut.

With all that being said, I’m having no issues with either the Isky or Hylift Johnson tappets for the Y.  These lifters were used in the 2009 EMC engine with the over the nose pressures being right at 400 pounds and the camshaft suffered absolutely no wear.  Likewise, that same camshaft still looks good after being pulled from the 2010 EMC engine but the valve springs were changed up on the aluminum heads to provide only 330 pounds of over the nose pressure for that particular combination.

I’ve used Elgin valves without any issues but have no experience with Elgin lifters though. Although hardness testing would be a good indicator of the soundness of the lifter quality, it’s out of the realm of the home mechanic. Visually inspecting each lifter for defects such as voids or porosity and putting a straight edge across each lifter face insuring that each lifter is ground with a ‘crown’ is something that can be done by the home assembler.

What are the concerns with the Ford 5120 Steel tappets?  It appears Ford went from cast iron, to steel, then back to cast iron.  It appears the later (>1962) Ford induction hardened cams specified cast iron tappets.

I would guess that more YB engines were originally equipped with cast iron than steel tappets.

Regards,

Dennis

I've been using this stuff called "ToughMet" for sleeve bearings in unbelievably bad conditions. It commonly comes in a hardness of about 30 Rc - and absolutely resists being "welded to" or scored by iron based materials. Brush Wellman invented it to replace the Berylium Copper used since WWII for aeronautical engineering purposes (ball screws, etc.). This link will show you the engineering properties:

http://www.matthey.ch/fileadmin/user_upload/downloads/Fichiers_PDF/Toughmet_Engin_Guide.pdf

My contact for using it in the mining machines is Dave Krus - he may be able to tell us if it has been tested or used in a similar service to the cam lifter. Even if the iron or steel lifter body simply was fitted with a shrunk on bronze mushroom "foot" and upper pushrod socket, it might be able to do the job - maybe aluminum bar housing to change the weight?

I gotta admit that I"m a little concerned.

Got a fresh engine here waiting for Mummerts heads that have Vern"s "white box" lifters inside.

Now I am considering changing those out for some old N.I.B. Wohlert Johnson tappets that I was saving.

Wadduya think folks.Safe with Verns products?Or change them out to be safe?

Oldmics

Mike, saving the good lifters for what? use the good ones while you pursue the others, thats my thoughts. regards bill.

The lifter would have to be jammed extremely hard to create an issue at a rocker arm.  Valve spring pressure by itself is expected to be more than adequate to free up a stuck lifter.  The lifter foots have an 1/8” or more clearance between the top of the lobes and being in a position to be jammed at the bottom of the block so for a lifter to get jammed on an engine that has already had the valves set, something else is going to be out of kilter.  But improperly set valves (way too much clearance) could increase the propensity for jammed lifters.  Assuming the radius at the base of the lifter stem is not excessively high, it’s improbable that a jammed lifter is the root of the problem for a broken rocker arm.  Having only used the undercut lifters in recent times though, I haven't had an opportunity to examine the radius on the other lifters that are available.

On the flip side of all this,  I have checked blocks where core shift did have lifters on one side of the block having less clearance in regards to jamming than what the clearance was on the other side of the block.  I’ve ended up having to check some of these oddball clearances only because of using camshafts in the Y engines with a 1.150” base circle which has the lifter coming out of the bottom of the bore just enough that if core shift is evident, one lifter bank can be a problem in that the lifters are coming too far out at the bottom of the lifter bore.

But back to the undercut.  Undercutting is another way to allow for an increase of pressure at a joint before experiencing a failure just as including a generous amount of radius at the same joint does the same.  The undercut simply has the advantage of allowing the lifter to go all the way up without allowing the lifter to stick in the lifter bore whereas a radius at the lower end of the lifter stem will allow the lifter to wedge itself at the bottom of the lifter bore if pushed up too high.

Ted,

On the undercutting, do you have a picture of how they are undercut? in my world of large machinery, normally when a head shaft failure occurs, its because it was locally made and they did not radius them properly, rather cut square corners on the steps of the shafting. I understand how the radiuses strengthen the joint but not clear how the undercut strengthens them?

Bear with me on this as I put some various thoughts together.

An undercut removes the potential for a stress riser similarly as does having a generous fillet.  You’ll find undercuts used extensively in the gear industry as an undercut will allow more flexibility or ‘bend’ in a given section of material that’s under load than is seen with a radiused fillet.  It’s that particular flexibilty that allows a machined part to last longer without a stress related failure.

Square corners or the lack of any radius or fillet does increase the propensity for stress risers.  That’s why when grinding crankshafts it is  important the the stone being used is properly dressed so that at least the factory radius is being maintained in the corners or at the fillets.  Likewise aftermarket performance crankshafts are supplied with an even larger radius than what the oem’s use.  But with those larger radii comes the need for narrower bearings as those radii shorten up the available machined surface that the bearings can ride upon.

But the option of restoring usable bearing width to a crankshaft journal comes by using undercuts at the journal edges or fillets.  This is not new as many of the older oem Mopar performance crankshafts comes to mind when discussing journals with undercut fillets.  These undercuts allow the crankshafts to not have sharp riser points at the journal edges while also eliminating the need for an offset bearing in the connecting rod in which to clear a radiused fillet.  Here’s a picture showing undercut fillets on a crankshaft.

But here’s getting back to lifters.  When talking about a radius or generous fillet at the junction of where the lifter stem meets the foot, it’s critical that this be as smooth as possible.  Any irregularities in this fillet promotes stress risers which in turn just gives the lifter a place to ‘break’.  A majority of the Y lifters do have some kind of undercut at the base of the stem as opposed to having a generous fillet or radius.  Here’s some pics of various Y lifters.

A late tool shop machinist friend of mine referred to those undercuts as "protected radius".  I don't know if this his his term or a commonly used shop term in tool shops.  Any toolmakers on thi forum?

Doesn't appear to be a standard "feature" term.  It doesn't appear in the ANSI Standards book on GDT (Geometric Dimensional Tolerancing),  ITW Gear books, and others.  Perhaps addressed in a Machinery Handbook (I don't have a copy)? 

"Protected", may have to do with being below the functional diameter and in theory not in contact with anything. 

The tappet stem has a diameter tolerance of .0006" and a finish of 12 micro.  I would expect this would have to be ground and polished to achieve.  The radius is .06 and the minor diameter of it is around .013" to .014" below the major (stem) diameter.  Probably there for tool clearance when finishing the stem diameter.

Before "reinventing the wheel", are there any known concerns with the Ford tappets, early or late cast iron, or 5120 steel?  I assume the other tappets on the market were developed by reverse engineering a Ford tappet. 

Regards,

Dennis

All good points there, I do think some of the undercuts are in things for tool clearance, and yes it may give more flexibility before fatigue occurs, but actually strengthening the joint, I am having a hard time with that one.

As Tim does, I have used resurfaced Ford lifters with no problems, I almost don't dare to use anything else with all the horror stories.

   In simple terms, so I can understand it. If you flex a 90 degree, sharp inside radius, all of the motion, and therefore stress, is concentrated at the sharp edge. With the undercut it is spread out over the entire radius of the undercut. Metal, especially cast metal, does not flex well. Very low elongation, and the yield strength is very close to the ultimate. It won't bend, it just breaks. clear as mud? 

The other (2) are:

(1) To avoid a design factor called "Notch Sensitivity" - the harder a part is, the less tolerant it is of grooves, corners and changes of section. A soft mild steel bar is therefore less sensitive to a "notch" than a quenched and tempered chrome/moly bar.

Anyone who has cut glass or seen it cut knows about the effect of the scribed notch on the hard unmarked surface. Or maybe "don't ever leave scratches in a hardened rod or crankshaft journal".

(2) To mitigate design factors called " Stress Concentrations" - where the internal stresses of a loaded part are forced to travel around geometric features or be forced into a smaller section. This chart shows the "old school' way of estimating this effect and sizing the parts accordingly. There are times when necking down the intersection - to provide the increased radius of the undercut is just enough to make it work - and last.

Today - my engineering tech's use a computer design aid called FEA (Finite Element Analysis) to get similar (and more accurate) information when designing parts with very complex geometrical shapes - changes of diameter, corner radii etc.

As can be seen in these graphical representations - just about any technique that allows increasing the radius that the internal load or stress must "flow" around - is good.

Good thread guys!  Steve, Thanks for the engineering graphs.  Great stuff !

A question for Barry or Royce.  Was the lifter badly worn on its face before it shattered?  Any wear factor simply makes the lifter face thinner and brings a breakage issue to the forefront.

This doesn't sound like a wear problem, but I wasn't there. Like to see photos of the cam and lifter to see the truama.

You and me both.  Steve, although it hurts my little brain I love the stuff you share with us.

I thought Royce mentioned there were no evident marks on the cam other than scratches from after the lifter failed. They are not amature builders and I am sure they used the proper assembly and break in lubes. It just looks like the lifter shattered.

Royce, Since Jerry doesn't visit here, ask him to look for marks on the bottom of the rocker where that particular lifter failed to see if there is any evidence that the rocker that broke didn't get jammed under there.

A lot depends on the type of guide used in the head as to the required stem clearance. I never use stainless valves in iron guides so no need to talk about correct clearance there. Iron guides can destroy stainless valves even with chrome plated stems. If using a thin wall bronze guideliner we shoot for .002" clearance on the intake valves and .0022" on exhaust. Some people will tell you that is too loose but experience has shown that guides with .0015" clearance will likely cause trouble in iron heads.

If you are using .502" OD bronze guides I would recommend even more clearance. .0022-.0025". The bronze is not dimensionally stable until many heat cycles.

When it comes to sizing valve guides my motto is: If the guide has a couple 10,000ths more clearance than might be required the customer will never know it. If it has a couple 10,000ths too little he will hate you.

I think that Jerry should disassemble his heads and have someone carefully check the valve guide clearance!!!!

BTW, he was not using the aluminum heads I sent him.

It is too easy to blame the broken part for a failure. How often is a broken connecting rod really an oiling problem?  A broken ring or pounded out rod bearing a detonation problem? In other words, a rod bearing failure could be caused by an ignition or A/F problem. If Jerry had only broken a lifter it would be tempting to blame the lifter but with a broken rocker arm also, something in the valve train was binding up.

I have sold 1000s of the Schumann lifters and lifters from the same manufacturer (Vern does QC for the other vendor) with an extremely low failure rate. I did replace 2 for a shop that broke during engine assembly! I suspect the "mechanics" broke them by beating a tight cam gear on and using a lobe/lifter for a back stop.

Also, if you are rotating the crank without the full cam assembly bolted on allowing the cam to slip back while rotating, 2 lobes can be forced between lifter heads. I would guess that some lifters have been broken this way.

Now you have my 2 cents worth.

John.  Thanks for the input.  I have never seen a flat tappet lifter failure here in the shop on any engine that was a result of cam/lifter metalurgy or the oil.  When there have been failures, it’s always been another factor such as lifter bore clearance, valve spring pressure, coil bind, retainer to seal clearance, rocker arm geometry, inadequate pushrod clearance, valve stem clearance, camshaft end play, rocker arm to shaft clearance, inadequate prelube, connecting rod to cam lobe clearance, and the list goes on.  Because I do get to run in engines built by other shops or individuals on the dyno, I remain cognizant on how easy it is for the simple failures to take place.  It typically takes overlooking a single detail among a myriad of items that must be thoroughly checked to propogate a failure.

As far as bushed rocker arms, I’ve had repeated breakage problems with those on the FE engines.  The bushing reduces the wall thickness of the aluminum around the shaft and just makes the rocker more prone to breaking.  Because of this, it’s difficult to just assume that the rocker and the lifter are automatically related.  Age of the rockers is also a player and any aluminum rockers that are eight years or older automatically become suspect also.

Bronze wall guide clearance has been a topic in the past and it will be interesting to see what Jerry’s and Royce’s final assesment is of the heads once they are pulled apart and examined if not already done so.  I still see bronze wall guide clearance problems cropping up in the circle track engines and this is normally traced back to an inexperienced shop or new personnel doing the head work.  Learning curves can be expensive to say the least.

Now I am wondering if it wouldn't be wise to break in an engine with the weaker push rods, just in case there is binding this weakest link would be an easy change, rather than broken lifters, rockers etc.

A definate fatigue break with the FOMCO stamped on the reverse side.

That break does look too clean.

No one to blame except me.  Hopefully my last mistake.

Thanks

Dale

On another note, I don't know if the cast lifters are anything like railroad rail material but I have had an instance where assembling machinery a piece of rail was dropped 6-8' and it broke in half. I have also heard in the old days they could scribe rail where they needed and break the rail there, I have not seen it done personally but beleive it since seing that rail break. Trains ride on that rail and it flexes seriously and takes all kinds of abuse but if scoured shatters like glass.

Could Jerrys lifter, or many lifter failures for that matter be caused by a scratch on the surface?

Hopefully everythings works out better when its put back together.

Royce.  Pass on to Jerry that I worked on an early model Austin Healy 4 cylinder early last week that had stuck the two center exhaust valves due to being too tight on valve stem clearance.

Here’s the full story.  I’m involved in this as I had originally recommended and milled the heads 0.055”.  This was just prior to the heads going to another shop for new valves, bronze guides, and a valve job.  Once that freshly machined head was reinstalled on the engine, the center exhaust valves banged the pistons after 25 minutes of running.  This engine was never under a load and simply started missing prior to it being shut off.  Not only did the valves whack the heads hard enough to bend, the pushrods also wadded up.

The customer then took the removed head back to the shop that did the guide installation and the valve job.  That shop said the problem was in the valve to piston clearance which they pointed the problem back to the head milling.  When the customer called me on this, I simply told him to bring the engine to me and I would go to the trouble of checking those clearances.  Upon doing the checks, I found that the valve to piston clearance was 0.155” on the intakes and over 0.200” on the exhausts; this was more than adequate.

Because I now had the cylinder head apart, I checked the stem to guide clearance on the valves that banged the pistons and found them on the tight side at 0.0011” and 0.0016”.   Although the hole size in the guides were the same, the two valves in question varied 0.0005” on the stem diameters.  And to compound the problem, the exhaust valves stem diameters were slightly larger than the intake valve stem diameters.  Final analysis is that both of the center exhaust valves share the same exhaust port so these two valves naturally get hotter than the valves on the end cylinders; subsequently they just ‘seized’ in the guides first due to inadequate clearance to compensate for expansion when hot.  In looking at the stems and the guides on the two that bent, there is no evidence of any galling.

This isn't Daytona and there isn't a million dollar prize for winning. Tight guides are all risk and no reward.

I would rather be down 3 horse power due to loose guides than be down 3 cylinders when the guides sieze up.