[Fot] Do(o)med or flat lifters?

Ron KRANTZ rkrantz77 at comcast.net
Mon Jul 23 09:32:59 MDT 2018 

The reason for a slight angel on the lifter is to keep it from digging into the ramp on the cam lobe due to an aggressive acceleration design.  Typical American (cannot say what European mfg. does) lifters have approximately a 60 inch radius.  I even have an additional edge radius put on the lifters.  The cam lobes have a slight taper side to side for rotating the lifter.  Lift on a cam is limited by base circle radius which in turn is limited by cam bearing diameter.  Then you get into duration and how fast you can get the valve open.  All the Triumph "flat" tappets I have ever seen have a slight radius.  The rules say you must retain the same type (flat, roller, mushroom) lifter as stock.  My question is "how flat is flat".  Rule does not say the lifter has to rotate.  If a lifter has a 0.75 inch radius across the lifter diameter and no taper on the cam lobe,you can keep the lifter from rotating and accelerate the cam opening very fast.  Think about that.

> On July 23, 2018 at 8:46 AM Christian Marx via Fot <fot at autox.team.net> wrote:
> 
>     This may be true for American engines.
> 
>     All European engines have no angel in the Cam shaft. And all the tappets, lifters, rollers, are flat. Dead flat. No light with an edge on it.
> 
>     So maybe this is just an American thing?
> 
> 
>     Cheers Chris
> 
>     fubog1 < fubog1 at aol.com mailto:fubog1 at aol.com > schrieb am Mo., 23. Juli 2018, 15:40:
> 
>         > >         This is well covered in many engine-building books & I've discussed it at length with several camshaft engineers over the years.
> >         It's my understanding that the lobe should have a very slight angle ground in, and the "flat" tappet really isn't, it's very slightly convex.
> >         This will give it rotation, if it doesn't rotate it will wear.
> >         There could also be spring pressure or lubrication issues?
> >         In any case I would discuss it with the tappet supplier before doing anything, at the least make sure that they are sufficiently hard to begin with and can be reground.
> > 
> >         Glen
> > 
> > 
> > 
> >         -----Original Message-----
> >         From: Christian Marx via Fot < fot at autox.team.net mailto:fot at autox.team.net >
> >         To: fot at autox. team. net < fot at autox.team.net mailto:fot at autox.team.net >
> >         Sent: Mon, Jul 23, 2018 6:04 am
> >         Subject: [Fot] Do(o)med or flat lifters?
> > 
> >         In the past we had this discussion.
> >         I've bought some high quality lifters from USA, made from tool steel I suppose. 400$ they've cost..... and started to fail. On 3 of them, the very center does show e few pittings. Also visible that only a small part of the Cam is used.. The cam is okay
> > 
> > 
> >         The machine shop will grind the lifters dead flat, as they should be, they say.
> > 
> >         Cheers
> >         Chris
> > 
> >         Am 18.07.2018 02:12 schrieb "fubog1 via Fot" < fot at autox.team.net mailto:fot at autox.team.net >:
> > 
> >             > > >             Yes, lacking access to a Cam Doc, you can use a set of V or bearing blocks, a degree wheel, dial indicator, and a bit of time, checked at 5 cam degrees, works fine.
> > >             I'm still old school though, I plot them out on graph paper!
> > >             That will give you the lobe profile but most folks don't have the full specs on the cam, usually just advertised lift and duration.
> > >             Since the tip of the lobe usually starts to go away first, a simple lift measurement will reveal the worst, best done with a dial indicator cuz some (cheap) cams are ground on different base circles.
> > >             Generally, ramp wear is unusual if the tip is still OK, although there can be exceptions.
> > > 
> > >             Glen.
> > > 
> > > 
> > > 
> > > 
> > >             -----Original Message-----
> > >             From: timmmurphh < timmmurphh at gmail.com mailto:timmmurphh at gmail.com >
> > >             To: 'fubog1' < fubog1 at aol.com mailto:fubog1 at aol.com >; rbtr3a < rbtr3a at cox.net mailto:rbtr3a at cox.net >
> > >             Sent: Tue, Jul 17, 2018 12:38 pm
> > >             Subject: RE: [Fot] Cams
> > > 
> > >             By degreeing the cam using increments of 10 crankshaft degrees (5 camshaft degrees) and then plotting the results in Excel, it is possible to get a very accurate picture of the profile of the cam.
> > >              
> > >             I’ve attached a spreadsheet showing an intake and exhaust lobe comparison two years apart of our Kastner G3 cam for reference.
> > >              
> > >             Tim Murphy
> > >             #317 TR4
> > >              
> > >             From: Fot <fot- bounces at autox.team.net> On Behalf Of fubog1 via Fot
> > >             Sent: Monday, July 16, 2018 6:31 AM
> > >             To: rbtr3a at cox.net; fot at autox.team.net
> > >             Subject: Re: [Fot] Cams
> > >              
> > >             Generally any obvious wear or pitting would make it unserviceable, but the wear isn't always so obvious.
> > >             You can measure the lift and compare to spec, that will show any worn lobes, but the best way is to find someone who has a "cam doctor". It's a machine that sets it up and measures the complete profile.
> > >             Usually if there is anything apparent that suggests that there may be problems, there are...
> > >              
> > >             Glen
> > >              
> > >              
> > >             -----Original Message-----
> > >             From: rbtr3a--- via Fot <fot at autox.team.net>
> > >             To: fot <fot at autox.team.net>
> > >             Sent: Sun, Jul 15, 2018 6:47 pm
> > >             Subject: [Fot] Cams
> > > 
> > >             How do I determine if a cam is good or bad. If there are any marks on it does that make it bad. I do know that two of the lifters has pitting on the surface.
> > > 
> > >             Ronnie
> > >             _______________________________________________
> > >             fot at autox.team.net
> > > 
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> > >         > > 
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