[Fot] Oversize lifter bore

[Kas Kastner]

I can't agree with you Joe or maybe I just misunderstand your meaning. The lifter is the object of attention when doing up a new cam.  Every engine I did and had cams made, ( all the Triumphs for 12 years) first requirement from the cam guys was "what is the diameter of the lifter", from this dimension we did the camshafts.
---- Joe Curry <spitlist at cox.net> wrote: 
Bill, 
The lifter diameter is typically sized for the amount of lift on the cam's
lobe.  If it is too small, the lobe will run off the edge and cause damage
to the cam.  So you must have a lifter properly sized for the cam itself.
This was the case with early Spitfire engines.  They had very small lifters.
Later when the cam was upgraded, they had to increase the size of the lifter
to keep pace with the cam upgrade.  Anybody who has an early Spitfire 1147
engine and wants to upgrade its performance would have run into this issue,
(Right Cary?)!

Joe

So, the cam itself dictates the lifter size not the other way.  It would be
like the tail wagging the dog.

-----Original Message-----
From: fot-bounces at autox.team.net [mailto:fot-bounces at autox.team.net] On
Behalf Of Bill Babcock
Sent: Saturday, February 05, 2011 1:06 PM
To: Larry Young
Cc: fot at autox.team.net
Subject: Re: [Fot] Oversize lifter bore

Okay, that one confused me. How do you get more lift using a cam designed
for
a larger lifter. When the cam is at full lift on any lifter it is in the
center of the lifter. Are you saying you can use a higher lift cam that runs
off the edge of the lifter to get more lift?
Bill
On Feb 5, 2011, at 6:22 AM, Larry Young wrote:

> Chip, could you explain this?  How does a larger diameter lifter change
the
valve timing?
>
> For the TR3/4 I've found that 99% of the available cams are designed using
the lowest common denominator for lifters.  In the US, the smallest common
lifter is the SBC at 0.842.  I've often wondered whether some of these
grinds
find their way into Spitfire and TR6 engines with the 0.800 lifter.  The
result would be a cam that would run off the edge of the lifter. One can
always get more lift by using a cam designed for a larger lifter.
> Larry Young
>
> On 2/4/2011 6:45 PM, Chip Collingwood wrote:
>> This mod will open and close the valve sooner but will
>> not effect maximum lift...
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