Camshaft Discussion Part III
Why do we see soo much exhaust duration on LS1 cams? Usually longer exhaust durations are used to compensate for poor exhaust flow on cylinder heads, which might make sense for stock heads, but not ported heads.
This thread should be made a "sticky"
I personally love this quote "You can run a 216/216 @ .050" cam with a 106 lsa and it will shake like Katherine Hepburn in a paint shaker."
I agree that bigger isn't better and duration is more important than lift.
lots to learn here. I feel like I'm back in Engineering class.
jrod do you mind if I pm you to see what your opinion of the ideal blower cam would be for my setup?
again, great thread!
I personally love this quote "You can run a 216/216 @ .050" cam with a 106 lsa and it will shake like Katherine Hepburn in a paint shaker."
I agree that bigger isn't better and duration is more important than lift.
lots to learn here. I feel like I'm back in Engineering class.
jrod do you mind if I pm you to see what your opinion of the ideal blower cam would be for my setup?
again, great thread!
TECH Apprentice
Joined: Aug 2003
Posts: 335
Likes: 0
From: Vacaville, CA
I just put the TSP 228R in my car, and it seems just from driving it that my dynamic compression has gone down a little in the midrange. I know this is because it has 5 degrees of overlap at .050". What would be the best compression to run with this cam? Right now its on stock heads at 10.1 - 1. Its set up at 111.5 + 1. Which is like this:
IVO 3.5 BTDC
EVC 1.5 ATDC
IVC 44.5 ABDC
EVO 46.5 BBDC
With those valve events where do you experts think this cam will peak? It feels like it needs higher compression somewhat. I know tuning will probably make a night and day difference. I was just wondering what else I can do to get my car best setup for this cam. thanks for the advice
IVO 3.5 BTDC
EVC 1.5 ATDC
IVC 44.5 ABDC
EVO 46.5 BBDC
With those valve events where do you experts think this cam will peak? It feels like it needs higher compression somewhat. I know tuning will probably make a night and day difference. I was just wondering what else I can do to get my car best setup for this cam. thanks for the advice
On The Tree
Joined: Jul 2003
Posts: 139
Likes: 0
Why do LS1 cam makers seem to love the fast ramp rates?. I know it helps idle but I like to springs on the car more than tune the idle more. Is there a slow rate cam for ls1 with long duration? Seems like heads like the ls1 that flow well over a wide range would like this. 
Launching!
Joined: Jan 2003
Posts: 238
Likes: 0
From: Apollo Beach, FL
my brain hurts, but i think i have a good understanding of how cams work. going back to matching the cam to a set of ported heads to make the most power, how do you go about doing that? could somebody start an example - making up an imaginary set of ported heads w/ flow numbers and we could calculate a great cam to match. it would help me understand and im sure it would help many others too.
Staging Lane
Joined: Jan 2004
Posts: 72
Likes: 0
From: Price, UT
Wow, I'm glad I decided to check out this thread. After reading through all 3 of these threads I now feel much more knowledgeable about cams. Thanks guys; these threads definitely served their purpose.
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Originally Posted by DrkPhx
Why do we see soo much exhaust duration on LS1 cams? Usually longer exhaust durations are used to compensate for poor exhaust flow on cylinder heads, which might make sense for stock heads, but not ported heads.
Originally Posted by 66deuce
i would like to know this as well.since the heads are "intake restricted" and have a good exhaust port,why the extra dur. on the exh.?
Thread Starter
6600 rpm clutch dump of death Administrator
Joined: Dec 2001
Posts: 4,983
Likes: 13
From: Texas
Originally Posted by VINCE
Well IMO some of the old school thought still works when it comes to more exhaust than intake. Just in the case of nitrous.. We have seen many reverse split cams not perform as well as traditional split cams on the ls1. I have tried many cams as well and the reverse split cams did help in the hp dept, but never gave as much tq as the traditional split cams in my test. If you want to rev to the moon then you can reverse my cam and spin higher, but I think the tq would be lower and the hp would be a tad higher. I currently run a 250/257 lsa 112. If you were to reverse it to a 257/250 lsa 112 I think my hp #'s would be slightly higher, but my tq would be lower.
Nitrous is a different animal than just strictly N/A. Look at what you've done. You've taken a port (the intake) and increased the ammount of oxygen it sees from ~18% to 33% of total volume. That means a bunch more air and fuel. Once you've done that via an artificial means, then you have to look at how to get rid of that extra exhaust.
Now you end up needing more exhaust lobe.
I saw a dyno sheet of a SBC. It made X Hp optimized for N/A. Then sprayed the car and it made Y HP. They tehn swapped to a nitrous specific grind that had a bunch more exhaust lobe to it. This time in a N/A state it made 5-10 less HP. ON dope it made 50 more HP than the N/A grind.
It all about optimizing your combo...
TECH Senior Member
Joined: Mar 2004
Posts: 14,620
Likes: 17
From: BFE
True, I agree, J-Rod, and this is from personal experience.
I run a "small" XE-R reverse split now and compared to the stock cam (traditional) the power gain under nitrous was a bit higher with more exhaust on it. But I found that to be affected over ~125 rwhp shots.
Anything lower and it was meaningless.
You can also offset this situation with bigger exhaust runners, but that also has parameters and limits.
Also one point that we tend to ignore in any cam's performance is "Fuel" used, spark delivery & intensity and plug heat range..
I run a "small" XE-R reverse split now and compared to the stock cam (traditional) the power gain under nitrous was a bit higher with more exhaust on it. But I found that to be affected over ~125 rwhp shots.
Anything lower and it was meaningless.
You can also offset this situation with bigger exhaust runners, but that also has parameters and limits.
Also one point that we tend to ignore in any cam's performance is "Fuel" used, spark delivery & intensity and plug heat range..
TECH Addict
Joined: Dec 2001
Posts: 2,298
Likes: 2
From: new england
Originally Posted by VINCE
Well IMO some of the old school thought still works when it comes to more exhaust than intake. Just in the case of nitrous.. We have seen many reverse split cams not perform as well as traditional split cams on the ls1. I have tried many cams as well and the reverse split cams did help in the hp dept, but never gave as much tq as the traditional split cams in my test. If you want to rev to the moon then you can reverse my cam and spin higher, but I think the tq would be lower and the hp would be a tad higher. I currently run a 250/257 lsa 112. If you were to reverse it to a 257/250 lsa 112 I think my hp #'s would be slightly higher, but my tq would be lower.
Has anyone tried the new comp lobes, they look super agressive. I am trying the new 239 on the intake side of my new cams. This lobe has 164 degrees of duration at .200" of lift if I remember correctly and .649" lift. The 242 XE-r lobe is only 163 I believe. I'll let you guys know how it turns out.
Originally Posted by Dracus
Wow, I'm glad I decided to check out this thread. After reading through all 3 of these threads I now feel much more knowledgeable about cams. Thanks guys; these threads definitely served their purpose.
11 Second Club
Joined: May 2004
Posts: 226
Likes: 0
From: Va. beach,Va
Originally Posted by black_knight
DenzSS, your posts support a position that most people "over-cam" on this board. It seems like you mean not just the question of "will this cam idle/work," but more along the lines of "is the powerband of this cam useful at all?" Do I get your jist correctly?
So, I guess the natural question is:
What cam specs or cam would you recommend for someone who wanted to make maximum power from 2000RPM to the stock rev limiter, without any particular concern for idle quality or gas mileage or spring life or pretty much anything else? (I assume you would have two differant answers for stock heads and aftermarket heads) This is without Nitrous or any power adders, and for stock cubes.
I'm talking about the cam that would get such a car down the 1/4 as quickly as possible, whether that's with a good peak # or with power "under the curve."
~230-240 duration, high lift, is what I assume you mean when you say "over-cammed." If not, please do specify what you mean.
Basically, I'm asking that if you are going to trash the cams on this board, then please offer what your idea is of what people SHOULD be running.
So, I guess the natural question is:
What cam specs or cam would you recommend for someone who wanted to make maximum power from 2000RPM to the stock rev limiter, without any particular concern for idle quality or gas mileage or spring life or pretty much anything else? (I assume you would have two differant answers for stock heads and aftermarket heads) This is without Nitrous or any power adders, and for stock cubes.
I'm talking about the cam that would get such a car down the 1/4 as quickly as possible, whether that's with a good peak # or with power "under the curve."
~230-240 duration, high lift, is what I assume you mean when you say "over-cammed." If not, please do specify what you mean.
Basically, I'm asking that if you are going to trash the cams on this board, then please offer what your idea is of what people SHOULD be running.
I deliberately read and absorbed this and other threads(cam discussions) to avoid the proverbial" over cammmed" issue and to get it right the first time.
Sooo still looking for an answer. Btw for my combo(which is somewhat typical) would the c.c.224 be a good cam considering where I am at now?I liked the t.r.224 but from my new found knowledge there aggressive lobes might not be necessary.Let's bring this back alive....it's the off season for most of us.
TECH Senior Member
Joined: Mar 2004
Posts: 14,620
Likes: 17
From: BFE
I am not sure but I don't think TR 224 lobes are more agressive than XE-R.
What is TR's ramp rate variation at lifts?
XE-R are 49 or lower and XE 53.
I believe TR lobes fall somewhere in between.
anyone has TR 224 duration at .006?
What is TR's ramp rate variation at lifts?
XE-R are 49 or lower and XE 53.
I believe TR lobes fall somewhere in between.
anyone has TR 224 duration at .006?
Originally Posted by LS1derfull
Vince are you able to run your set up with a maf sensor? Sounds like you would need speed density tuning.What intake manifold works well with your set up?