CHRISPY

Couple of cam comparisions for your viewing pleasure

I have been looking at cams that give similar valve events as my 236/242 110LSA 110ICL cam but are more emissions friendly (less overlap) and will have excellent idle manners

Here is what I have come up with so far. Which is your favorite? I prefer to add a little exhaust duration as there are cats on the car.

I dont think the added exhaust duration will drastically affect whether or not the car passes emissions...

Thoughts appreciated!! My current cam peaks at 6000rpm and carries power well to 6700rpm.

Cams from left to right:

236/242 110/110

226/232 115/115

224/230 116/116

220/226 118LSA/118ICL

IVO 8 -2 -4 -8
IVC 48 48 48 48
EVO 51 51 51 51
EVC 11 1 -1 -5
ECL 110 115 115 118
OL 19 -1 -5 -13

Thanks to Jrod for the cam spreadsheet, saves so much time!!

JS

iTrader: (4)

I like the 116 cam...
Tha'll pass and make great power in your big motor with a stock like idle.
DO IT

Ragtop 99

iTrader: (7)

That's a ton of overlap that you are giving up. Overlap has a direct bearing on passing emissions, but giving up that much overlap is bound to cost you some power somewhere. I guess the question is where do you want to cut power? I agree that with cats that a little extra exhaust duration might make sense.

Of your choices, cam 1 would be my choice, but I think the LSA is too high. Put it on a 113 LSA. A 228/232 114 114 would be very mild and should be on your list. I would not consider the 118 LSA cam.

CHRISPY

Thing is I am not so much interested in the LSA as I am in the IVC and EVO numbers.

I just found it very interesting that a 16 degree duration difference can still yield similar IVC and EVO valve events

Pro Stock John

iTrader: (34)

But some of those 116-118 cams might not work as good on the track for the first half of your pass...

Patrick G

iTrader: (14)

The 115 cam is right on. It would rock on your larger cube motor and make peak power at exactly the same rpm as your current cam (because of the same intake closing point). I like an intake closing point of 44 degrees for a 346 so 48 degrees should be ideal for a streetable, but kickass 385! Good job!

Ragtop 99

iTrader: (7)

Chris:

I agree those 2 valve events match up. I also know that if 206/210 125 LSA cam would make kick *** usable power, most of us would use a real high LSA cam to have a nice idle and pass emissions. (BTW, the IVC and EVO fit your pattern... )

JS

iTrader: (4)

Opps I meant the cam Patrick mentioned. (Cam #2)
The added dur and the 115 LSA should idle well and make great power in your 385....

Ragtop 99

iTrader: (7)

The first cam is what he has now, so I assume that cam 1 refers to the first alternative cam (115 lsa). Clear as mud, right?

Trojan T/A

iTrader: (1)

I assume you think these IVC and EVO are the values, but I dont think you are giving enough importance to overlap or duration. Valve events are very important, but if there isnt time to fill or evacuate the combustion it still wont perform like it should. Even on your most aggressive alternative you are giving up 20 degrees of overlap at .050. I think option#4 is way too small and you are giving up way too much overlap just to idle better. I would definitely cross that off your list as that is a mild 346 cam. Option #3 is better than 4, but it still gives up too much duration for the bigger motor to make good power. I was looking at a 224/230 115 for a 346 blower emissions cam which means its probably not enough for a 385. Option 2 is the best of your alternatives if you are set at staying under 0 degress of overlap.

CHRISPY

My preference is 226/232 115/115 as well.

This is more of a post to generate discussion and to show that smaller duration can behave like larger duration (to a certain extent)
I havent gotten into the duration differences at different lifts with the various XE-R lobes

Thanks for the comments keep them coming!

2000SSNB

iTrader: (4)

In some of the cam reference articles I read that the the largestimpact on
cam events is the IVC event, around 71...73 deg ABDC. Is your 44 degress
at .050 lift of .004 lift?

Gert

Patrick G

iTrader: (14)

Yes, 44 degrees is measured at .050 lift.

LS1derfull

I can attest to small changes in IVC making a noticeable change in torque characteristics. I retarded my 220*/220* on a 112*lsa from 110*ICL to 114*
It went from explosive torque at 2k and up, spinning the tires from idle, to much smoother stock zo6 like accelleration on up to around 6500.
My MMS 220* is a SBC Magnum lobes ground on a LS1 blank, this "grows" the specs to 276*@.006" 226*@.050" and .585" My Ivc is at 46*ABDC with ICL at 114*. I havent ran car at track to test this adjustment but my plan is to run fasteron street tires by moving torque peak up. My point for posting is I feel that the motor is very sensitive to this change and assuming a 115*LSA and a late IVC point is a general ball park move, would be a mistake. I didnt change cam size and yet car feels completely different and has required several Edit tunes, for "Big Cam" DTC's and driveability issues.

JS

iTrader: (4)

I see that 1st cam is in his car now.Thanks for clearing that up Rag,I think if he wants smooth gradual power with good emmissions this 115 would be the cam.

I for one like 114 to 108 LSA w/adv

CHRISPY

I am not sure I understand your post.

My goal is to smooth the idle out for emissions/drivability reasons while keeping valve timing events similar to maintain the rpm peak horsepower occurs and to try and keep the power level between the two cams relatively close to each other (within 5RWHP of each other)

As long as the car makes similar horsepower from 4000-6500rpm I'll be happy.

The car completely overpowers street tires now even in third gear. I'll sacrifice a little torque to improve drivability and emissions testing.

I think the power differences between the two cams will be quite marginal but the drivability will be much improved.

I will definitely be retuning the car after the change. (if I indeed swap cams)

JS

iTrader: (4)

Chris are u running open or closed loop.
I figured closed since u have cats...

CHRISPY

running closed loop but looking at open loop solutions as the car has a hesitation at part throttle that drives me banannas sometimes

open loop and cats dont get along though, that is part of the reason I was looking at a friendlier cam

Ragtop 99

iTrader: (7)

If you think that you can drastically cut your duration and overlap, and significantly increase your LSA and make within 5 HP, then either your first cam sucked ***, or you have discovered a magic formula that you need to patent. Maybe you'll prove me wrong, but you are making a radical change here.

CHRISPY

It looks radically different but the valve timing events are virtually the same.

The reduction in overlap/duration with wider LSA will hurt absolute peak power numbers somewhat but will actually help power past peak. (the powerband will be less peaky and not fall off as much.

The duration numbers at .200 and up from lobe differences will have an effect but I dont think it'll be too severe.

I am guessing 5-8RWHP difference tops if that.