A tale of 2 cams

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Ironmike

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I've attached a pic of specs from 2 cams. 2 different companies. As you can see, they are damn near twins. Except for the lobe separation angle and intake centerline.

I was hoping someone could REALLY tell me how these 2 cams might be so different.
Which one has more overlap?
Which one would have a higher reversion tendency?
Which would build more cranking compression?

I never did quite get the LSA and ICL thing. At least how they would change the characteristics of the cam...

Given the choice of these two, which would you run?
20181212_215529.jpg
 
Ironmike said:
I've attached a pic of specs from 2 cams. 2 different companies. As you can see, they are damn near twins. Except for the lobe separation angle and intake centerline.

I was hoping someone could REALLY tell me how these 2 cams might be so different.
Which one has more overlap?
Which one would have a higher reversion tendency?
Which would build more cranking compression?

I never did quite get the LSA and ICL thing. At least how they would change the characteristics of the cam...

Given the choice of these two, which would you run?
View attachment 1715261210
Click to expand...
106 vs 108 LSA
And
100 vs 104 Intake center

The LSA is ground into the cam,
can’t change that. Just being realistic, I very much doubt that anyone would be able to tell the difference of a 2 degree shift.
Both are on the narrow end of the LSA spectrum, so both would have some overlap. For reference a LSA of 110 and up would be on the wide end of the overlap spectrum.
The Intake centerline can be adjusted when the cam is installed.
Called ‘degreeing a cam’ so either cam could be installed at either ICL.
 
Very close. The 106° cam might idle a bit rougher. Both will be pretty nasty especially in a smaller cube engine.
 
Holy crap Mike! Dang!

How about a brief reminder of the engine build as it sits today and what is the idea of the cams/cars useage.

The cams appear to be drag related. With only 33*’s between advertised and duration @.050 except cam right having 31*’s on the exhaust.

If it were a drag only car trying to take advantage of its build (and IIRC about your build) this would be a hard call on which one makes more power, acts, performs better than the other one because as you said, there very close to each other. Cam left will idle the worst being all the way down on at 100. Not that cam right is a peach for smooth idling ether.

Cam on the right has more overlap And a higher tendency to have more reversion I believe. However, with these cams, I don’t think that’s really an issue to be concerned with considering what I think they’re designed for.

We’re missing the cams timing event numbers for intake and exhaust opening and closing points. That would help as well. Are they a solid? Solid roller?
 
Ironmike said:
I've attached a pic of specs from 2 cams. 2 different companies. As you can see, they are damn near twins. Except for the lobe separation angle and intake centerline.

I was hoping someone could REALLY tell me how these 2 cams might be so different.
Which one has more overlap?
Which one would have a higher reversion tendency?
Which would build more cranking compression?

I never did quite get the LSA and ICL thing. At least how they would change the characteristics of the cam...

Given the choice of these two, which would you run?
View attachment 1715261210
Click to expand...

The overlap should be listed.

Can't answer the reversion tendency.

The 106 LSA cam will have higher cranking compression.

THe LSA affects the power curve, cranking compression and idle quality.

Lower LSA will give you more cranking compression, choppier idle and build power faster and power will fall off faster (a peak instead of broad band)
 
You can make life easy for this type of thing by downloading the program at the bottom of this page on your Windows based PC:
Dynamic CR
Just enter the advertised parameters on tab 2 and it will spit out the numerical answers.

ICA for #1 is 64* ABDC
ICA for #2 is 70* ABDC

These are based on the advertised durations. That assumes that the advertised measurements are at the same value of lift... we don't know that for sure, unless you have some detail that you can share on that spec, IM. So just based on ICA, you would think #1 would build compression better.

BUT, the actual intake closing angle is based on the real closure to some value of lift, and that is modified for a solid by the intake lash and the lash ramps. Intake lash is smaller for #2 than for #1 so that should cause the intake closing to be even later for #2 relative to #1.

Cylinder filling and compression building at the lower RPM's (below the torque peak) is also effected by how fast the valves open up the opening ramps, and both these cams have equal opening rates based on the advertised versus .050" lift durations. So no apparent difference there.

I tend to associate reversion with overlap and how early the exhaust closes; not sure that view incorporates everything. Overlap is not much different between the 2:
80* for #1
78* for #2

ECA (exhaust closure angle) is identical between the 2:
36* ATDC for #1
36* ATDC for #2

The tighter lash for #2 should mean that its actual exhaust closure would be a bit later than #1. (Again, this assumes that the lash ramps are close to the same.) So, #1 would appear to have less actual overlap and reversion.
 
nm9stheham said:
I tend to associate reversion with overlap and how early the exhaust closes; not sure that view incorporates everything. Overlap is not much different between the 2:
80* for #1
78* for #2
Click to expand...

Same here. How is it you got these specs for the cam but not others?

Another spec that is worth taking a look at is the duration @.020.
 
If you could install the cams with a degree wheel and set up to watch and measure valve lift....

Oh you could really nail this thing down all over the place.

We could use some engine specs and intentions!
 
roccodart440 said:
How is it you got these specs for the cam but not others?
Click to expand...
I just picked out what seemed pertinent to the questions IM posed.

Here is a complete list of timing events, taken from the program listed above. These are in order of #1cam/#2cam and are based on the advertised duration numbers and the published ICL's:
Intake open BTDC: 44 / 42
Intake close ABDC: 64 / 70
Exhaust open BBDC: 80 / 80
Exhaust close ATDC: 36 / 36
Overlap: 80 / 78
Ground in cam advance: 6 / 4
 
Intake close ABDC: 64 / 70

so the intake valve will close 6 degrees sooner on the cam 1,
and the intake valve closing point is considered to be the most
important cam characteristic, so cam 1 has the potential to have slightly more dynamic compression. Do you want more or less dynamic compression?
But it is only 6 degrees, that is not much difference. If it was double that
12 to 15 degrees, you would have something to really consider.
As all other cam events are with 2 degrees of each other, or identical
I still contend that one would be pressed to find a performance difference.
 
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Are the advertised numbers from the same starting point?
Are the .050s after lashing?
What happens after lashing?
IMO the the 292 will be a full size bigger, after lashing, with perhaps a 7* later ICA. I see a lil higher operating rpm, a lil more lift left over,and you can run a lil more compression with it, and so all that adds up to, a lil more absolute power.
The .050s are saying nearly the same thing, the 292 is a lil better than a half size bigger.
However, the possible 7* earlier closing intake of the 288, could be useful, because it makes the compression cycle also 7* greater.
The power and exhaust cycles are a wash because at the listed ICLs, the advertised are identical.

I was hoping someone could REALLY tell me how these 2 cams might be so different.
Which one has more overlap?
Which one would have a higher reversion tendency?
Which would build more cranking compression?
Click to expand...

Overlap difference is only 2*, a wash
Reversion might be a few degrees greater on the 292,probably not worth 50 rpm
The 288 will make perhaps 10 psi more, depending on the accuracy of your install. Doesn't sound like much does it? But it will take the 292 cam about 6/10s of a point in Scr to make it up.
 
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Cam 2 is a Bullet solid roller I'm running now. Cam 1 is a Lunati.
Last year I had to choose between the 2 and I chose the Bullet. It finally ended up making 576 at 6400, but some guys here didn't really like the cam. (Missed on this combo?). Don't read the thread unless you're prepared....it's loong.

I now find I MAY have to pull my engine and wondered about changing cams while its out. Might not pull it, but just thinking....

On a whole OTHER subject, I think the Super Victor may be better than the Victor 340.

Hey. It's that time of year. My brain starts working overtime...
 
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Oh hell yea, brain in overdrive time and no outlet!

Ahhhhhhh-uuuuughhhhh!!!!!

From what I have read a few times, the SV will need serious porting.
 
rumblefish360 said:
Oh hell yea, brain in overdrive time and no outlet!

Ahhhhhhh-uuuuughhhhh!!!!!

From what I have read a few times, the SV will need serious porting.
Click to expand...
Hey I'm no genius, wouldn't think of going anywhere near a head with a grinder, but I've done several SV's now. They all work great. It's pretty simple, but time consuming. Match em up to your heads and go for it. About halfway up the runners. I never touch the plenum, though. That's for the experts.

Man, around 3000 in 4th gear......stomp it and that shiftlight comes on FAST. Which is very stupid and dangerous, but a REAL rush. I sold one on here last year that I wish I hadn't. This Victor 340 made good power, but for me, the seat of the pants ain't near the Super Victor. Hell I may change that too.
 
I agree! Some smart peoples here!

Hell! I just try them out and see what they do.
I don’t mind changing parts just to see what happens... or doesn’t.... LOL!
 
They are so close, just pick one and go.
 
As you are running cam 2, if you do pull the motor and swap in cam 1, after you have some experience with cam 1 revive this thread. It would be interesting to hear how the two compare performance wise.
 
106 in at 100 with street type closed exhaust?

No thanks.

For a car that’s primarily driven on the street, and from the sounds of it not “optimized” for track use....... I’d give up 15-20hp to have the car drive better.
 
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