I have fairly good experience with cars and being as this is my 5th cam, i noticed a diference in the numbers


As recomended by a board member, i order a comp cams custom grind. I ordered it via jegs and they asked me several question
what core.........."07-000-9" (billet LT1 style cam)
whats lobes......."3190/3192 lobes" Specifiys the XE lobes with lift and duration
What LSA............"114"

He said that was all i needed and he would call me if there were any questions. I thought i would maybe give hime more info. I believe i told him 110 intake centerlne were what all my past cams were on, but he did not seems to think that was important.

Well i got the cam, here is the cam card...
http://images.cardomain.com/member_i...3_184_full.jpg

If for some reason the pic goes dead...
Grind#: LT1 3190s/3192s HR 114.0
SPC INSTR1:
SPC INSTR2:

---------------------------Intake.......Exaust
valve adjustment........hyd ..........hyd
gross valve lift{1.5}.....531.........568
duration @ .006.......... 265 .........275
valve timing.............OPEN..........CLOSE
@.050............ INT:.. 7- BTDC.....41 ABDC
......................EXH:..46 BBDC......2- ATDC

These specs are for a cam installed at 114.0 Intake center line
.............................. Intake......... Exhuast
Duration at .050..........214 ...........224
lobe lift ---------------.3540---------.3790
Lobe sep angle ..........114


Now reason i am asking all this, reason for the post is all my previous custom and off the shelf cams have had a 110 ICL no matter what the LSA was. this one cam with a 114???
How will this affect me?
Should i return the cam and get it on a 110 ICL (114 LSA)?
Or does comp cam decided the ICL?


THANKS!!!

 

Any LT1 cam I have ever had always has 4* Adv ground into it. Which is 4* less ICL than LSA. So you having the same ICL as LSA would mean you have no advance ground in. Someone correct me if i'm wrong, it's monday.

 

You are right, but that cam will work fine "straight up".

Rich Krause

 

Intake centerline is not something ground into the cam by the manufacturers like the Lobe Seperation Angle. ICL is just a reference point of the valve events in relation of crank position. 110 ICL means the Intake valve reaches its maximum lift at 110 degrees BTDC. 114LSA means maximum exhaust valve lift is 114 degrees before maximum intake lift. If you advance or retard you valve timing you are changing the ICL. Someone correct me if I'm wrong.

 

so what would be the difference between THIS CAM above, and the same cam but with 110 ICL?? Or no difference at all?

I have a cloyes, but i believe that only alows me to go +2 or -2 or striaght up..


I was told by a friend that his cam motions cam say its is 110 ICL 118 ECL (exhaust centerline) and that the LSA was the avg, 114.
Least his cam sheet indicated that.


Im still confused.

 

On an LT1 any advance IS usually ground into the cam. The reason is that the distributor is driven from the pin on the end of the cam. The position of the pin relative to the ICL establishes the relationship between the valve and igntion timing as well as to the piston position. If you advance or retard the cam in an LT1 (impossible with the stock timing setup anyway) you will throw off the ignition (and injector) timing by a like amount.

You can install an adjustable timing set in an LT1. But to avoid throwing off the timing you need to make a compensating adjustment in the PCM ignition programming. The injector timing will still be off, but a couple of degrees there doesn't mean anything significant.

Rich Krause

 

No difference at all. If the cam card says 110 ICL and you advance it 2 degrees it ends up being on a 112 ICL, if you retard it 2 degrees then its 108 ICL

 

Cam cards list the timing of the valve events for the cam installed at the specified centerline. You can install it at any ICL you want, but that will change the timing of the valve events. For an LT1 cam, if the LSA and the listed ICL are the same, the cam is ground without any advance (or retard). If they differ, the difference is the advance that is ground in to the cam. Example: ths cam card says"LSA = 114 degrees" and lists the valve events for a "cam installed on a 110 degree center line". In that case, the cam has 4 degrees of advance ground into it.

The cam I am using was designed to work at a 105 degree ICL. It is on a 113LSA. There are four degrees of advance ground into the cam, which is the max amount the core would allow. I will degree the cam in at 105 degrees but will need to retard the timing 4 degrees. That 4 degrees is the difference between the ICL of the cam lobes relative to the distributor drive pin and the ICL of the cam as it is installed (109 degrees - 105 degrees).

Seems confusing, but not if you think about it for a minute.

Rich

 

Why do they do that on the LT1? Whats the point in installing the pin offset? The cam card for my GM847 didn't specify on what ICL to install it. It just gave max intake valve lift as 107 BTDC. When I installed it straight up and checked it, it was at 102 BTDC. Crane says their cams are ground with 5 degrees advance. I advanced mine 4 degrees to 106.5 which was the closest I could get it to 107. So technically I advanced the timing 4 degrees as well but the computer doesn't know it. I get 34 degrees spark at WOT minus 1 degree knock retard.

 

"Crane cams and 5 degrees of advance ground in"

So what exactly is the purpose of grinding some
amount of advance into the cam? I will be installing
a 210/224 very soon and have not quite figured out
why this is done. I understand that degreeing a cam
in an LT1 is not really possible due to the issues
described by rskrause:

That 4 degrees is the difference between the ICL of
the cam lobes relative to the distributor drive pin and the
ICL of the cam as it is installed (109 degrees - 105 degrees).

I still would like some clarification on what the 5 degrees of
advance accomplishes?

 

When you install an LT1 cam and line up the marks on the timing set, assuming the cam was ground to spec, the ICL as measured should be same as the specs in the statement "valve timing for cam installed at xxx ICL". If it is not, the cam was not ground to spec. That's why you might want to check the ICL. But not to actually install the cam on a different ICL, for reasons described above.

Why advance a cam (or have advance ground in)? With large cams, advancing them a few degrees (typically 4) slightly improves low end performance with a small loss at the top end. When the cam is advanced, the intake valve will open earlier during the exhaust stroke and the exhaust valve will shut earlier during the intake stroke. This will increase the DCR but may lead to more reversion. These effects are not large, especially with a smaller cam. I have done dyno tests with advancing and retarding cams 2-4 degrees and seen a difference, but it's very small. On the order of a few hp and a few lbs.ft. of torque.

As I responded to the initial post, the 214/224 cam will work fine with no advance. I have used it, so I am speaking from experience.

Rich Krause

 

Ok i will keep the cam


I just did not know if i was supose to get it on a 110 ICL like all the other was i have had/seen

I guess it doesn't matter. im sure this cam wll work great as long as i ordered it right