[automotive breath]

Originally Posted by Rick WI

...If it was as easy as reading a PHR article we'd all
be designing camshafts and building championship winning engines.
After spending a few years playing around with combinations on the
dyno, track, with the flow bench, cam doctor it's not quite as easy
as picking up a $5.00 magazine to look up the answer. I am sure you
know that AB ....

Rick, you are missing the point of this tread. You continue relating
to designing the ultimate camshaft for a very specific application.
IMO that’s not what this is thread is about at all. It's more about
being able to read a cam card and have a basic idea what performance
characteristics the grind has to offer.

I don't claim to be a camshaft designer, but I do have a basic understanding
of camshaft design. When I need ultimate performance I go to an expert.
When I do, he sends me a camshaft with a tight LSA because that’s what
best for my application.

[Rick WI]

The point I am trying to make is you don't look at a camshaft catalog and say I want a 230/236 duration camshaft with .490 lift I/E ground at 108 LDA. You want to think about where the 4 cam timing events need to occur and the LDA falls where it may. Where the 4 cam timing events need to occur may be far different than the camshaft with a 108 LDA out of the catalog.

One HUGE variability in LDA is just the exhaust.

I think in trying to understand camshafts this is not the area to start in or even make generalizations. I think you need to start with reading the theorys and dynamics on the 4 timing events the camshaft is controlling.

[automotive breath]

Originally Posted by xntrik

2 cams. Identical symmetrical lobe shapes, durations, lift, etc.

One ground on 108* LSA one ground on 112* LSA.

This is not exactly what xntrik had in mind but close enough. Both
examples the same intake lobe and the same exhaust lobe, the
difference being LSA (lobe center). Same lobes two different camshafts.
What would be the differences if installed in otherwise identical engines?

****************************************
LOBE CENTER: 108 deg. OVERLAP: 59 deg. g.
THE ABOVE TIMING IS CHECKED AT .007

The following timing is taken at .050"
INTAKE DURATION: 221 deg.
OPEN: 2.5 BEFORE TDC
CLOSE: 38.5 AFTER BDC

EXHAUST DURATION: 232 deg.
OPEN: 44 BEFORE BDC
CLOSE: 8 AFTER TDC

**************************************
LOBE CENTER: 112 deg. OVERLAP: 51 deg.
THE ABOVE TIMING IS CHECKED AT .007”

The following timing is taken at .050"
INTAKE DURATION: 221 deg.
OPEN: -1.5 BEFORE TDC
CLOSE: 42.5 AFTER BDC

EXHAUST DURATION: 232 deg.
OPEN: 48 BEFORE BDC
CLOSE: 4 AFTER TDC

[killerformula]

I agree with Rick, and to be honest I think the tone of this thread has been pretty suspect from the beginning but that's another discussion

[automotive breath]

Looking at the valve timing events the differences in the two camshafts
become evident. Basically what the cam grinder did with the 112 LSA cam
was retard the intake lobe 4 degrees and advance the exhaust lobe 4 degrees.

Using identical lobes the cam grinder was able to tune the engine for different
performance characteristics. Studying the events of each camshaft will
illustrate the differences. To mention a few; the camshaft ground with 112 LSA
has the overlap reduced by 8 degrees, this will improve idle vacuum.
In addition the 112 LSA cam has a intake valve closing point 4 degrees
later, this will reduce dynamic compression to make the engine a
little more detonation resistant.

Killerformula, this is basic camshaft design, remember what xntrik said ”This is
a learning exercise”. We don’t think twice about advancing or retarding a
camshaft to achieve desired engine performance. This is much the same, the
difference being we can degree a cam at any time but once the LSA decision
is made and the cam is ground it is set in stone.

****************************************
LOBE CENTER: 108 deg. OVERLAP: 59 deg. g.
THE ABOVE TIMING IS CHECKED AT .007

The following timing is taken at .050"
INTAKE DURATION: 221 deg.
OPEN: 2.5 BEFORE TDC
CLOSE: 38.5 AFTER BDC

EXHAUST DURATION: 232 deg.
OPEN: 44 BEFORE BDC
CLOSE: 8 AFTER TDC

**************************************
LOBE CENTER: 112 deg. OVERLAP: 51 deg.
THE ABOVE TIMING IS CHECKED AT .007”

The following timing is taken at .050"
INTAKE DURATION: 221 deg.
OPEN: -1.5 BEFORE TDC
CLOSE: 42.5 AFTER BDC

EXHAUST DURATION: 232 deg.
OPEN: 48 BEFORE BDC
CLOSE: 4 AFTER TDC

[406 ss monte]

Originally Posted by automotive breath

The following timing is taken at .050"
INTAKE DURATION: 221 deg.
OPEN: -1.5 BEFORE TDC
CLOSE: 42.5 AFTER BDC

how can it have a -1.5 btdc? wouldn't that be after tdc?

[curtis73]

Originally Posted by 406 ss monte

how can it have a -1.5 btdc? wouldn't that be after tdc?

Yes. Different ways of saying the same thing.

[automotive breath]

Originally Posted by 406 ss monte

how can it have a -1.5 btdc? wouldn't that be after tdc?

Yes like curtis73 says it's the same thing. To the cam grinder is just
a math problem. That's the kind of things that makes this confusing.

[Guy Hiltz]

Well why dont you just tell us what you know ??

[xntrik]

Originally Posted by Guy Hiltz

Well why dont you just tell us what you know ??

Post #1

K I S S

2 cams. Identical symetrical lobe shapes, durations, lift, etc.

One ground on 108* LSA one ground on 112* LSA.

What is the difference when installed in an engine?
*************************************************

OK forget in the engine.

What's the difference lying on the table like I said in post #6.

quote= These 2 chunks of bumpy cast iron are lying on the table..... what's the difference between them?

[Guy Hiltz]

I dont know !!

[xntrik]

Originally Posted by Guy Hiltz

I dont know !!

There is lots of good information coming forth so far.

Sometimes "the way you look at it" makes it seem totally different.

It is pretty hard to distinguish between what is IS and what it DOES.

Hang on.

[automotive breath]

Originally Posted by 71C10

I wonder how many HBB members have been lured into sending you PM's, followed by their heads and money....

Zero. When someone is interested, my preference is to teach them how.

[xntrik]

Originally Posted by killerformula

I agree with Rick, and to be honest I think the tone of this thread has been pretty suspect from the beginning but that's another discussion

post # 1 , or # 6?


http://en.wikipedia.org/wiki/Subterfuge
Subterfuge can be any deceptive stratagem or manoeuvre designed to take advantage of an opponent.

[engineczar]

Well this thread has gone into the toilet. I'm going to lock it, edit out the personal stuff, and leave it visible for the technical value.