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

Subject: [Fot] Do(o)med or flat lifters?
From: fubog1 at aol.com (fubog1)
Date: Mon, 23 Jul 2018 08:40:15 -0400
References: <CAPrGtEPT+VALhduVjCNE=wBqtWThFb02hBAPh39fzYy=Veu1nA@mail.gmail.com>
 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>
To: fot at autox. team. net <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>:

 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>
To: 'fubog1' <fubog1 at aol.com>; rbtr3a <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
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