I know you can run as tight as you want but obviously from a performance standpoint what is "ideal". I can't decide between a 106 and 108. I'll probably go 108 unless someone can offer benefits of going tighter than 108 (looking for more average power and torque here).

It's an a4 dd so overrev is not too important (in reference to shortening the powerband) No emissions. Driveability is not a problem. Will be tuned.

The specs I am thinking are 270/276 218/224 (perhaps shorter on the advance duration i.e. xfi) How will this lope in comparisson to a standard lobe (non xe/xfi etc.) Will it be better worse or the same?

I calculate 57 degrees total overlap (w/ 108) which is 2 degrees more than the xe503 and crane227. I am hoping my vaccum will still be decent and idle won't be that bad but am I wrong in thinking that roughly the same amount of total lope will idle roughly the same? I think the xe lobes are supposed to improve vaccum and idle? I would like the car to run and I don't think I will have a problem looking strictly at overlap but it is hard to find people with smallish cams ground on tight lsa's. Really want to know if lsa or total overalp is more key to determining vaccum.

Now for every article I read on tighter lsa's improving lowend torque I read one about them causing loss of lowend torque (not as reputable imo). I would believe that is true with large durations but not with a small cam. I don't want my car to be dead until 3k as that is the area of the powerband I'm trying to improve. From what I have seen peak remains the same but average increases when tightening the lsa so all looks good but they were different applications (carbed 350, 383, etc.) It really seems that lsa is the most misunderstood part of the camshaft and I think these myths get help from some of the cam grinders as their catalogues of full of cams for driveability while sacrificing horsepower. Then there are the people who tell you a 114lsa will make more torque That might be true in an engine with VERY good heads as overlap would not be that beneficial. Also in an engine with great flowing heads a single pattern makes more horsepower and torque than a split everywhere in the curve.

Anyone with lsa overlays or knows where to find test etc. please post

 

Get some professional (cam) help. No offense intended, but all of the things you are concerned about need to be factored into the cam design. Doing it yourself if that's not your profession is a lot like DIY surgery; yes it could be successful, or the 'patient' might die.

A properly spec'd custom cam would be best for your situation, IMO. The next best would be a 'shelf' cam from GM or a major cam company. There will be more compromises in these, but it's very unlikely that just picking numbers from what you've read will achieve better results.

If you decide to do a cam, make sure you use all the correct/compatible valvetrain parts to go with it.

Good luck!

 

That should be a nice small cam that make good torque. The overlap is what determines who rough the motor runs, but just be careful with the intake closing point so that you don't end up with very high DCR.

 

just let me know when you want my 218/224 that i have for sale

 

One of my cams that Crower has put in there line up is a 218/224@50 and can be ground on any ICL or LSA.I ran it on a 110+4 in a 355 with 11.6 compression and ported heads.
Ya might want to call Dave Crower and see what he recommends for your set up and head flow(which ya didn't include in your post).Have ALL your engine info at hand when ya call.
Very hard to EVEN guess without knowing more about the engine.

Or get in touch with SSStrokerAce on the board 'cause he builds cams too.

 

There was a pretty good article in the winter 2005 Engine masters mag, called "separating the power"...I'd post it but my scanner is broken, if you have a fax I could send it that way ..Anyway, the test engine was a chevy 355 with stock 190cc AFR heads, 1 3/4 longtube headers, 10:1 compression, and just some other regular stuff(nothing real special)....the cam specs were 234/240 @ 50 and 496/504 lift....They had ALL five cams ground for the same specs but on different LSA's 106, 108, 110, 112, and 114.......in short, the cams with the shorter LSA's consistantly made peak torque 400-600 RPM's lower, and horsepower peaked at almost the same exact RPM for every cam(within 200 rpm's)......the cam on the 108 was WAY ahead of the rest with 476 HP at 6400 RPM's(it was also well ahead for both "peak and average" HP and torque figures).......and the 112 was the worst at 452 HP at 6200 RPM's........the 106 and the 110 LSA cams made nearly identical horsepower and torque(470 HP/431 TQ) , but the torque with the 106 cam just peaked earlier(as earlier mentioned with all the shorter LSA cams here).......(Just my opinion's here)..Personally, 90% of the time (on a street driven 350-355 "WITH" good heads) I prefer a cam on a 107-108 LSA.....most of the time cams that are ground on 112's and 114's are giving up power in one way or another for engine idle vacuum.......

 

Thanks Joe. I would love to read that article but don't have a fax.

 

www.jfax.com You can receive faxes free.
You get a real fax number, the incoming faxes come into your inbox.
I've been using that for years.

If you don't want one of your own, you are welcome to use mine.
I'll fwd it to your email address. (707)598-7028

 

could you e-mail it to me too if you get it?

 

I'll convert it to a gif and upload it to my photobucket, then everyone can read.

 

It's not too bad of quality, considering it was faxed and converted to .gif.
I'll see if I can pretty them up tomorrow.

http://i38.photobucket.com/albums/e1...power_1of4.gif
http://i38.photobucket.com/albums/e1...power_2of4.gif
http://i38.photobucket.com/albums/e1...power_3of4.gif
http://i38.photobucket.com/albums/e1...power_4of4.gif

I wasn't able to find the article online, but I do have an accompanying article from the
same author http://www.superchevy-web.com/techni...ams/index.html

 

I agree. I am not even close to Old Strokers knowledge. But read this article. There are so many things to cam design. Call an expert.
http://www.popularhotrodding.com/tec...mshaft_basics/

 

Thanks James for uploading that! 108 seems to be about ideal for a 350 sbc. And that is according to David Vizard who also states that:

"There is much said about LCAs that needs to be thrown out with the garbage. First let me make one major point quite clear. For a given spec of engine there is only one LCA that will give optimum torque and horsepower. It is not, as many cam company techs would have you believe, a variable parameter."

That seems to fly in the face of those who state that valve events are more important than the lca. Of course, that is not to say that the valve events are not important rather that lca plays a much larger role in power production. My point is don't be afraid of running a smallish cam on a tighter lsa (lca same thing). In many cases a smaller cam with a tighter lsa will outperform a bigger cam with a wider lsa. The LE grinds are on a tight lsa and make great power (hmm.. might mean something) Shelf cams are far from ideal.

I don't think 108 is ideal for everyone. But for NA 350's it sure seems to be. I don't know how well it would work with blower/nos/turbo/383/409/etc. Head flow plays a role as well and the angle of the valves. I think that with excellent flowing heads a wider lsa might work better (300cfm+) as overlap would not help as much. Single pattern camshaft also produce more power than splits on a engine with good exhaust flow.

 

btw most cam companies I talk to go dumb when lsa is mentioned. The above came from research and talking with people who put the theories into practice. I prefer to be different and not follow the norm of 112 as most do blindly.

 

Yeah 107-108 is where it's at for N/A and NOS cams.
You really need more seperation for forced induction.