[Fot] Oversize lifter bore

[Kas Kastner]

I remember well the tiny lifter in the first Spitfire engines.  I had to deal with it, successfully I might add. 



---- Joe Curry <spitlist at cox.net> wrote: 
I think I said the same thing you did Kas.  The lifter size is directly
related to the lift of the cam lobe.  Yes, cam manufacturers ask about the
lifter size so they know how far they can go with the cam development.  But
as with the early 1147 engine, there are other work-arounds.  Triumph
increased the diameter of the lifter in order to go with a more radical cam
design.  Early engines have to have the lifter channels bored out to accept
the later (larger) lifters.  The Mk1 lifters were 11/16" and when the Mk2
came out with the improved cam, Triumph increased the size to 13/16".

Maybe my wording was not clear.

Joe

-----Original Message-----
From: Kas Kastner [mailto:kaskas at cox.net] 
Sent: Saturday, February 05, 2011 4:16 PM
To: 'Bill Babcock'; Joe Curry; 'Larry Young'
Cc: fot at autox.team.net
Subject: Re: [Fot] Oversize lifter bore

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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