I have used the bushed rockers and have had no problems either. I like the groove in the bushing for good rocker oiling. I have found the clearances usuallytighter to the shafts than a new no-bushed rocker so less oil pours down the stands.

It is very interesting to see what the professional engine builders on this site who do it for a living, not us occasional weekend engine builders, use for lifters. The common thread I see is that none of them use the "no name" white box lifters when doing an engine build. I am always suspicious whenever a company will not put their name on their product it is almost as if they don't have the confidence in their product or want to be "inrecognito" as they used to say in the kids cartoons.

Here is another link to a list member who had a failed lifter problem awhile back.
http://forums.y-blocksforever.com/Topic31169-3-1.aspx
marv

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.

   

  

  

Lorena, Texas (South of Waco)

Ted:

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?

John - "The Hoosier Hurricane"

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

Ted, 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.

55 Vicky & customline

58 Rack Dump, 55 F350 yard truck, 57 F100

59 & 61 P 400's, 58 F100 custom cab, 69 F100, 79 F150, 82 F600 ramp truck, 90 mustang conv 7 up, 94 Mustang, Should I continue?

Not strength, flexibility. It essentially makes the part tougher, meaning it can take more before it fails. Tougher is not always stronger.


Lawrenceville, GA

"Flexibility" is a good term, many things that are made "tougher" break just as easy but as with the radius there is a little give with a smooth transition.  I wonder if the term "protected" radius is because it is protected from high production shops that will not radius their stones before grinding a crank.  A "rolled" or "relieved" radius/fillet can't be ground out.  (most Chrysler products and a lot of the later Ford and GM cranks have this)  I'm very leery of Y cranks that have been ground not because undersize cranks are bad but because most of the time the radius has been removed.

   God Bless.   Tim                           http://yblockguy.com/

350ci Y-Block FED "Elwood", 301ci Y-Block Unibody LSR "Jake", 312ci Y-Block '58 F-100, 338ci Y-Block powered Model A Tudor

tim@yblockguy.com  Visalia, California    Just west of the Sequoias

Bill/ Charlie,

   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? 

Frank/Rebop

Bristol, In ( by Elkhart) 

I understand. I should rephrase. Flexibility, per Ted's explanation, makes the part tougher but it does not necessarily make it stronger. I would define strength as the amount of force it can withstand and toughness as how long it can withstand a given force before failure.

For instance, we know that a Chevy can be built to meet Y-Block power levels but the Chevy will fail far sooner. In this scenario, the Y Block is tougher. The Chevy has to be built to a lesser power level in order to survive. In this scenario, The Y Block is stronger.


Lawrenceville, GA

Great analogy,Charlie!

 

Paul,

Boonville,MO