I have what I feel is a problem with a custom-ground cam. Stock ls1 w/ ported heads, 2.055int 67cc chambers and 10:1 cr. The cam was spec'd out to be max-effort n2o w/ stock pistons/no reliefs. The cam was installed and degreed by one of the best, and his readings were double-checked at the same time by someone even more ****.

The problem is the motor flatlines on the dyno at 5000rpm and goes in the toilet by 5800rpm. This cam was supposed to pull to 7k+. The springs were checked and found to be 125#seat and 400+ open. Below are the specs:

comp cams 3016r/3038r HR116+5
230/242 @ .050 .613/.613
116LS

valve events:
int. open@ 4 BTDC close 46ABDC
exh. open@ 62 BBDC close 0 ATDC

Can someone please tell me what it is about this cam? It made 370rwhp @5200 and went away from there making no power or climbing above 5800rpm

 

prob need to know a little more info than that

 

What else is there to know? The motor spun well past this w/ the stock cam?

 

Do you have enough injector?

Is your fuel pressure good?

 

Full racetronics system and 36# injectors, AFR not lean. New wire/plugs tr6

 

^^info like that lol

and did you run it on hp tuners or anything to check everything out?

 

car was drivability-tuned for an hour (driving around) w/ efi live by the tuner/cam spec person.

 

uhh-ohh.....

 

heres your sign.

 

What intake mani also? ls1s don't pull much past those types of rpms....A ported FAST, or even just a ls6, will pull out harder. If you are wanting to spin that high, maybe look into the Edelbrock Performer intake or something.

 

He has the ls6 intake, motor spun to 6100 no problem b4, stock cam and heads. His current set-up should be good to 7k+ rpm, heavily ported big-valve heads that spun 7250rpm on previous motor w/ 232/237 cam. This cam was spec'd for him by someone to use these heads and n2o w/ stock pistons/no reliefs. He is convinced it is the cam, someone else said it may be the generous exhaust duration coupled w/ the 116+5. All I know is the motor peaks at 5200rpm, don't go saying it's the intake LOL. We wish New cam should be here today, so it's gonna be fine. He does, however, want to know what it is about this cam. We have a cam card, but no cam doctor sheet. I degreed forward and backward, checking .006 and .050, as well as LS and got the intake opening @.050 dead nutts at 4* BTDC.

 

Yea, not the intake. It wasn't stated at first....was hoping it would some a simpled fix like that. I can't comment on the cam though...116+5 for N/A would be way to weak on the LSA (from my knowledge....I am still trying to learn about cams), but for a nitrous grind.....I honestly haven't a clue.

 

a 116 lsa would push the peak farther up in the band. got a dyno graph to post? it makes no sense that proper fuel, timing, and valvetrain setup would peak at 5k and nose over at 5800. ported heads and that cam would most likely peak closer to 6700 with use of a crossover style intake. something is definately wrong, but i don't think it's the cam. what valve springs are you using? what pushrods? lifters?

 

Hmm...... Cam profile or heads are going turbulent as hell maybe?

 

Finally a good question/comment. I would add, what seated spring load and what rockers and just for grins, where was the intake centerline actually set?

Initially it sounds like a valvetrain control issue with the XFI lobes, but unless you went to aftermarket roller rockers and dual springs with normal weight steel retainers with low seat loads and wimpy pushrods, 5200 sounds WAY low.

 

Texas Speed Pushrods 7.4, Comp replacement lifters 4-850-16, Stock rocker arms, Do'nt know the brand on spring but it is a big single spring with 130- 400 #. Springs where also checked for lift and I was told would be good to 650 lift. I seen it with my own eyes
Also heads have titanium retainers.

 

They are heads I used to own, they have 1.550 dia. springs and ti retainers, the new cam going in tommorow or monday, but he thought that someone here might have some insight as to what is going on w/ this cam. The heads are not going turbulent, and the lifter pre-load is fine.

 

I would find out what spring you have, spring loads alone do not tell the story.

The cam also may be advanced too far, making it peak way low. Ive seen that happen a few times. Did you degree the cam?

 

Yes, twice it was on the money.

 

XFI lobes may be the problem. You are not using the type of springs Comp recommends. If you really want to use that cam, get some help from a real cam guy who has done things sucessfully with these lobes.

I'm not a cam guy, but I listen to a couple of good ones.