Will the XE's have better low-end and midrange? I'm considering a cam for my autocross car with stock or mildy ported heads with a valve job.

 

Good point. 75% is usually the point where experts recommend a single pattern cam. Perhaps 6* is enough split.

 

hey
i need help with picking a cam for my car, my choices are between the cc305/lt4 hotcam kit/xe224 230
my car will be a street car. might go to track
once a year. I want a kick azz street machine, but i live in chicago, so i must pass emissions
can someone help me, i'm back and forth on which cam

 

An XE 218/230 is a good alternative to the hotcam for stock heads. Get it with a 112 LSA and a 110 intake centerline.

 

i'm just going to make a suggestion here. since you have emissions to worry about you you'd like to keep the car tame. you seem to have a pretty good grip on cams and how they work. but since you dont want to spin that high.... well here goes. why not try a 3190 intake lobe and a 3314 exhuast lobe. that exhaust lobe is the same thing as the intake lobe on the cam you suggested. look at the .200 duration numbers on the 214* intake lobe i suggested vs. the .200 duration numbers of the 224* lobe you're looking at. its only like 4 degrees there and my lobe ends up with another .030 lift than yours which will almost assuredly help a little with your ported heads. so heres my suggestion.

intake 214* .565" lift
exhaust 224* .536" lift
111 or 112 icl
112lsa.

given the rpm range you wanted to stay within. this thing should put out a very nice power curve, and peak right about where you wanted to shift. it would probably like a little more compression somewhere in the low 11's which is only slightly more than you'll have so it should be good. imho if you have to advance a cam 4* or more you need to start thinking about another cam. that intake lobe will be hard on lifters though and it might be agressive enough to collapse a stocker i'm not sure maybe some of the blower guys will chime in. thats my suggestion. and i know you've went mild before and you have been a little disapointed if i'm thinking of the right guy. but for what you want this cam might be just right. just my very opinionated .02

 

I will refer you to this comment by Bret, aka SStrokerAce, at his second to last comment to my question.

 

I read all that stuff guys, and at least theoretically it works to a great extent....to shorten up duration and use a higher/later ICL.

But I'm not necessarily in the mood to go out on a limb this time, I want something relatively tried and proven. I'm incorporating a little of that theory by going with the 114LSA on a 110 ICL rather than a 108 ICL...this will bump the power up in the RPM range a little as compared to the 224/230 off the shelf grind.

To make best power with these heads I should probably go with the 230/236 or bigger, so I guess I already see a 224/230 114+4 as a reasonable compromise.

And WS6terror, you are right, that 3100 series lobe would eat lifters and valvesprings...this is a daily driver and I'd like to keep the reliability up as much as possible, which is why I'd like to stick to 3300 series lobes.

Thanks for the suggestions though. I will run some simulations with your suggested cam, gives me another dimension to think about.

edit: I e-mailed Brett last week and he seemed to like the 218/230 (I was going to do 112 LSA, 110 ICL), but at the time I was going to go with the stock sized valves. Since I'm stepping up to the big valves, I think a little more duration is needed to get the most out of the heads.

 

the 224/230 is what i would call a higher rpm cam when set up properly engine combo wisethe 224/230 will without a doubt be better on emmissions than the 236 jsut because of overlap.

as for your comment on going with something tried and proven well moving the icl to 110 will have it closing later which lowers dcr... which will in turn bleed off some low speed tq which... is just the opposite of what you said you wanted in your original post the amount might be minute but still thats going to be the trend. the 224/230 is a bit big for what you want in this application. its not a BIG cam. but not wanting to turn over ~6k. that cam would not be my choice unless i had plans of spinning higher. let me put it this way stock head guys are spinning 6200 or 6400 rpms with that cam you'll have more flow and the ability to support more rpm will come along with it. and the stock head guys are having it ground as is from comp with a 108 icl and a 112lsa which gives them more tq i dont understand why with a bigger cam you're trying to move the icl and open up the high rpm power... that really doesnt apply here the way i see it. if you want it ground on a 114 lsa that'd be 6 degrees advanced which is indeed a lot but there you have it again, if you have to do more than 4* advance/retard to get what you want... maybe its time to look at other cams.

that comment about needing to go to a bigger cam simply because of the valves being different well... i dont know how true that is. from what i've seen most of what is to be gained is in the higher lift and its only about ~10cfm anywhere in the flow curve.

on a side note i would tend to agree with bret on that 218/230 cam. i was just trying to use the 31xx type lobes to get you the most out of your heads more lift will mean more flow with less duration assuming agressive ramps are used.

i hope that all made sense, i really need to sleep at night

 

"The 224/230 is a bit big for what you want in this application. its not a BIG cam. but not wanting to turn over ~6k. that cam would not be my choice unless i had plans of spinning higher. let me put it this way stock head guys are spinning 6200 or 6400 rpms with that cam you'll have more flow and the ability to support more rpm will come along with it. and the stock head guys are having it ground as is from comp with a 108 icl and a 112lsa which gives them more tq i dont understand why with a bigger cam you're trying to move the icl and open up the high rpm power... that really doesnt apply here the way i see it."

Most guys running the 224/230 make peak power at 5800 RPM. the same cam on a 114+4 will have an intake closing at 42 degrees, which should put peak power at 6100 RPM. This will require maybe a 6250 shift, a little higher than I want, but I'd rather go a tad more than be too conservative again. (40* closing puts power at about 6000, 44* at 6200, etc.)

"that comment about needing to go to a bigger cam simply because of the valves being different well... i dont know how true that is. from what i've seen most of what is to be gained is in the higher lift and its only about ~10cfm anywhere in the flow curve."

I wouldn't need to go bigger, but the heads would support more power so why not harness it?

"on a side note i would tend to agree with bret on that 218/230 cam. i was just trying to use the 31xx type lobes to get you the most out of your heads more lift will mean more flow with less duration assuming agressive ramps are used. "

With fully ported heads I think the 218/230 would be giving up too much on the intake side. Also, going back to earlier posts in this thread, I'm not so sure that much split is necessary for the heads ported as well as they are. The 218/230 112/112 and 224/230 114/110 have the same curves in Engine Analyzer, so I guess I am saying err on the side of caution and go with the 224/230 because it is a more proven cam in this setup.

I think my conundrum is that if a new cam and heads only nets me 30 peak hp because I was too conservative, what then is the point of it. If I'm going to go through this process again I want to make gains comensurate with the effort and money spent. So, taking that in to consideration I am willing to give up some driveability to get there.

 

One thing to remember that a cam installed stright up, if matched with the heads correctly, will always make more power then a cam adv or retarted. if your looking for nothing more then 6000 rpm then I would look at a cam like the zz9. It seems to make good lowend on their package with decent topend.

 

I refuse to buy from TPIS...overpriced.....just a stand on principle. Plus their lobes are not very intense..pretty lazy ramp rates compared to the Comp XE's.

Just comparing here:

Current cam 210/220 .050 duration, 266/276 adv. duration
the XE 218/230 would have a 270/282 adv. duration, that's only 4 degrees more intake duration than what I have now.

the XE 224/230 is 276/282 adv. duration.

So in terms of adv. duration I'm only looking at an increase of 10 degrees in real terms, although it is 14* at .050. However, low lift flow, adv. duration, is where the cyl pressure bleed-off is going to occur. This would make the XE cams seem less radical in the car than their .050 duration specs would indicate.

Also compared the total seat-to-seat overlap of the three:

Current cam 266/276 114+0: 43* overlap
XE 218/230 (270/282) 112+0: 52* overlap
XE 224/230 (276/282) 114+0: 51* overlap

So the 224/230 114+0 is actually going to have slightly less overlap than the 218/230.

 

you've got a real good handle on things but intake closing point IS NOT EVERYTHING. to say that something WILL peak here or there based on intake closing point is rediculous. there is a lot more to consider rather than just the @ 50 or advertized durations here. look at the .200" lift numbers your 224 lobe while 10* bigger @ 50 is only 4* bigger at .200" and its total lobe area and head flow when you figure out powerband not intake closing point. and for what its worth a lobe with similar flow area and less duration should always be faster down the track that just goes to more tq and vol. efficiency. so it revs faster than the big cam and is more responsive on the street. but what i think you're saying is that you've made up your mind and the 224/230 is a good cam so i'll leave it at that.

 

I'm not trying to completely crap all over your arguments, Just presenting counter points to your points, which is the same thing you're doing with my points.

This is a constructive argument and I think its good for others to read and quite frankly this level of technical discussion is getting rare in the LT1 tech forum.

Yes I'm getting pretty set on the 224/230 114+0 but don't let my percieved stubborness prevent you from sharing your thoughts/advice.

 

i guess what i was trying to say is that, i'm all out of ammo from the lobe catalog... i guess i could look at other catalogs... but i'm lazy. its just that you're going to get more overlap with the 224/230 and its going to be a higher rpm cam. overlap will have something to do with rpm just as much as intake closing point will. and to beat a dead horse the higher your dcr is the more tq you should have and the more responsive it should be. the proven combo's arent always proven, and sometimes it takes a little more consideration than people here like to think it takes. since you dont want to replace a bunch of crap to support 31xx lobes that 224/230 should work great i'm just not completely sure about emmissions. i just wish comp would damn well make a 31xx series lobe for every 33xx series one they have or just maybe they'd make something in between. i know it would be a pain to carry a couple dozen more lobes but it would make me happy for sure

 

So Chris what kind of HP and TQ numbers do you expect with the 224/230 with the newly ported heads? Just so I know where I stand. Basically we will have the same setup. I have an A4 though.
I am trying my best to understand this discussion but I think you guys left me in the dust. I'm looking for 400+ HP basically. I think that is attainable.