Kubs

I am having a good time reading this. I will be selection a custom ground cam in the near furture and this info will come in handy! I sure I too will be posting a topic for your guys' suggestions.

Good Luck with the build Jake!

Orr89rocz

Go to speedtalk.com to the forums and talk to CamKing. He is Mike Jones from Jones Cams. He knows more about cams than just about anyone.

Overlap and duration split will be dependant on your particular combo. What works for one motor wont necessarily work for another motor. IE, some heads/intake setups will want tighter lsa/wider exhaust duration when other motors make like wider lsa and less exhaust duration split.

Some cam grinders prefer to do things a certain way as well. I said i wanted as much power as i could get by 6400 rpm or so shift by 6500-6600 and i was looking for atleast 400whp thru my auto, with my 383 AFR 195 head motor with stealth ram. Cam came back as a 230/245 on a 109 lsa. I was surprised as the duration split when his LT1 grinds are more like 3-4 degree splits. Cam made 400whp and peaked at 6300 rpm and i could shift it by 6600. So my goals were met it just came out looking different from what i expected.

Mike Jones set me up with a 240/243 grind on a 108lsa for the same 383 motor as above when i asked about peak power by 6500 rpm shift nearer 7K. I decided to build a twin turbo motor and now have a 233/233 on a 112 by Jones for a close to 5800 rpm peak hp on a 400 small block.

Duration and LSA play important roles in total overlap and how the cam makes power in a motor.

My suggestion is getting a custom grind for your specific goals and you'll be happy. Off the shelf grinds can work ok if you know what your looking for but generally you can make more power with a custom grind.

1989TransAm

X2 on Mike Jones.

95wht6spd

I have the LE2 heads/cam 230/230 .6 w1.6rr and 107LSA on a 350.
I like it a lot but wouldn't go bigger for a daily driver. I think the tight LSA in combination with the correctly designed heads is what gives it more power than the average H/C LT1.

Only downside is it is really smelly without cats and be prepaired to clean exhaust tips A LOT!

bobmic93

Love to hear it, do you have a audio/video clip?

bobmic93

The tuner will play a huge roll. I used two different reputable pro tuners and got very different results. Even the exhaust note was way different between the tuners. I think your smart by consulting a tuner before you make your selection.
Tighter LSA the better!

Kubs

Doesnt the application of power make a difference in the LSA you choose? Since a wider LSA makes a broader power curve with less peak power, it would be ideal for road course racing where the engine spends a lot of time between 3000 and 6500 RPM. However a tighter LSA would give a higher peak power but over a smaller RPM range so this would be ideal for drag racing where you want a strong top end. Am I correct in thinking this way? Wouldnt a 111-113 LSA be better for roadcourse racing and 107-110 better for drag racing?

JAKE

Actually what I am looking for are the factors which were taken into consideration when selections were made for either duration split and/or LSA.

I knew, right up front, if I included the specs of the engine I'd get recommendations all over the map. So what I was hoping to get is why you or your engine guy chose one LSA/duration split cover another.

Why was the correct choice a LSA 107 Vs 113; why did one guy choose a 10 or 12 degree of duration split over, say 4 or 6 degrees of split.

The "reasoning" behind the choice is what I'm trying to zero-in on; the "why". Why was it chosen; why, why, why (it was chosen) as opposed to what, what, what (what was chosen). See what I mean?

Posting that "I'm running a 107 LSA" or "I'm running a 113 LSA" is okay and helpful, but that doesn't tell me the "Why". It doesn't tell me why that partricular LSA was chosen.

Here's an example: I'm leaning toward ordering a split duration cam. The "Why" is my intake/exhaust ratio is 66%. From what I've read, 70% is the point at which a single pattern cam should be used. Since mine is below 70% my cam would be better if it was a split duration profile. See, that's the "why".

Of course that brings up another issue - How much of a split should I shoot for: 6 degrees; 8, 10 more? I know it's not a 'one size fits all' situation since engine combinations and intended purposes differ but the "why" should be a constant, applicable to all our engines.

I've got intake/exhaust head flow ratio and the flow of the total exhaust system (manifolds, pipes, CATs, mufflers) pretty much nailed. But should trans type, rear end gear ratio, converter, weight of car, any unique characteristics of the LT1 engine or its PCM, also be considerations? Any thing else? I know a lot of that factors when selecting duration, but does it also apply to selecting LSA and duration split.

Id just like to make an informed decision rather than shooting in the dark or simply taking someone else's choice. I like to do it myself - sink or swim.

Hope this clears away some of the fog and will also help others in their future cam selection.

By the way, I sent Bryan at PCMFORLESS a message asking about the tuning difficulties of a tight LSA cam. Haven't head back yet. When I do, I'll share.

Jake

West Point ROCKS!

cv67

Jake you have a decent head, you dont need the tight lobe center. 1 deg difference btw youll almost never notice. Wider the lsa is the powerband will extend further although it will not be as peaky. The narrower it is it will come on hard early but give up early. Dont get sucked into all the rumpity rump crap, sounds good but overrated these days. TPIS cams were designed for (mostly) stock heads and really need a large split on them.Look at the valve opening and closing events, overlap that will tell you much more about the cam.

95wht6spd

Well my reasoning was: since I didn't know, I let the expert decide based on what I told him I wanted in the car, and to choose a "package", where the cam was designed for the ported heads.

Orr89rocz

Its application specific so the "why" is based on your combination and goals as to what LSA you get and how much duration split you get.

larger duration splits help with nitrous but most 4 degree split cams for n/a work well with nitrous up to 200 shot which is more than most intend to spray anyway.


As far as broad power curve, my torque curve was flat as kansas. Over 350wtq from 3200-5600 rpm with a peak of about 380 at 4000-4400. My cam has huge duratino split and 109 lsa. So wide or tight, it depends on the setup. The intake manifold will determine most of the torque/hp curve, the cam just helps bring out that power thru the heads/intake characteristics

bobmic93

Talk to anyone who's in to racing at the track or talk to most high power N/A drag car owners, they mostly use tight LSA. It boils down to either being aggressive or conservative with your car. IMOP, we drive vettes and vettes are meant to go fast ,quick! Do you need a tight LSA? Hell no. Will it put you in your powerband faster? YES. The OP should not pick his own custom grind. Have a pro help you come up with a profile. Listen to this little cam thats on a 110 LSA. This has no vacume issues or surging what so ever.http://videos.streetfire.net/video/9...ette_86403.htmThis little cam gets my car in the low 12's with 1.7 60' times. Completly tuneable!

JAKE

Okay, I'm beginning to get some info I can use. However, "My cam has huge duration split . . ."; okay, what is huge? How about some numbers? That is, of course, if you're willing to share.

Same thing as saying "My car is fast!" Okay, how fast, how 'bout some numbers.

Let me try to give an example:

If my heads flow XXX cfm on the intake and XXX cfm on the exhaust, then that tells me I need to go toward XX on the duration split and some where around XXX on the LSA.

Continuing; If my exhaust flows about XXX cfm, that tells me my LSA and duration split should be in the area of XXX and XX.

Then if my intake manifold flows XXX cfm, that tells me - fill in the blank.

See what I mean? What other factors were considered in choosing XXX LSA and XX duration split. The WHY, in specifics. I admire that fact that your torque curve is flat, just wondering why you chose the LSA and duration split that got that for you.

For example: why did you choose 109 instead of 114? What parts made you go that route?

I already know what advancing or retarding a cam does; I already know what a wide or narrow LSA does, I already know what a wide or narrow duration split does. I'm just trying to find out what factors you guys consider when making those choices.

I'm not going to let someone else pick my cam for me; that's out. If I called three different techs I'd get four different recommendations. LOL They rarely agree. Besides, I love doing this myself; it's at least half the fun.

I have Engine Analyzer Pro and have plugged in lots of numbers to come up with the best torque curve. Oops, I forgot to mention, my goal is to maximize this engine for torque. So I also know that means to keep the duration short.

Once I plug in all the engine specs, including head flow, exhaust, C.R., etc., EAP uses a Chain Calculation function to test several different LSA, or duration splits or advance, on and on. It tells me, not so much the raw numbers it calculates, but trends. However, it's only a tool among others I'm using.

So far, I'm over 400/400 and I'm getting close to my final selection of the cam, but I just want to be sure I'm not missing something.

I really appreciate all the feed-back.

Jake

West Point ROCKS!

JAKE

If another Forum member had put up a post like the one I did, here's what I'd do: This pretains to cam duration split.

THIS IS ONLY AN EXAMPLE; NOT MY SPECS

"First I'd get all the flow numbers I could find on my particular heads. Since my heads are out of the box and unported, and since different sites post different flow numbers for the same exact heads, I'd gather together all the flow numbers I could find and I'd then average them. If you're heads were flowed, you can just use those numbers.

Now, I know that it's generally accepted that the exhaust should flow at least 70% of the intake, so I'd do the math and crunch the numbers.

So, since the results I got show that my exhausts only flow 60% of my intakes I know that I'll need a pretty wide duration split so that the longer exhaust duration on the cam would help the exhaust gases get out of the engine.

Then I'd find out what the intake flows and, if the numbers are from more than one source, I'd average them too.

Next I'd be confronted with determining how much of a split do I need.

So I'd look at other heads that have a similar somewhat weak exhaust flow and see what cam was used in an engine running those heads. Specifically, I'd want to see the duration split that was used.

Right away the ZZ9 comes to mind because I remember that TPIS put a 14 degree split on that cam. I'd then review the TPIS article to see what heads were on that engine and try to find the flow numbers of those heads.

If those TPIS heads had a similar int/exh flow ratios as mine and since TPIS achieved the best power with that 14 degree duration split, I'd know I was moving in the right direction.

I'd then look at the exhaust system and intake on that particular engine and see if it close to mine.

If they're close, I'd be pretty confident that I should get a cam with 14 degrees of duration split."

That would provide the "Why" I chose a certain duration split. It's a time consuming process, but, for me, that's half the fun.

I'm beginning to think that most guys may know WHAT they're running and many have the results they achieved. They just don't know WHY, other than it's something someone told them to run.

I'm different and much prefer to figure this stuff out for myself and make my own decisions. But that's just me; to each his own.

Jake

West Point ROCKS!

ChrisWhewell

Deleted !!

JAKE

That was a nice write up for someone versed in fluid dynamics or perhaps an engineer, but all it did was make my eyes glaze over. I don't have the skill, training or the equipment to crunch those numbers or understand what you wrote. I'll bet I'm not alone in that either.

What I need is something I can really use. Do us all a favor and write it so that guys still learning how to set lifter preload can understand and make use of it. Remember, these responses serve to benefit more than just the original poster.

My field is Law Enforcement. I can talk to you about Preliminary Hearings, Grand Jury procedures, Miranda Warnings, Search and Seizure, etc., but when it comes to what you posted, I don't have a clue. Not ashamed to admit it either. LOL

I was taught to "Speak to your audience". How about taking another shot at it?

Jake

West Point ROCKS!

ChrisWhewell

That's ok. I'm neither an engineer, nor versed in fluid mechanics either. My field is law at the federal level, a wife of 20 years and three kids !! I have read alot about engines though over the years, and like to bounce ideas off others at times and thought this would be a good forum for that.

I'll refrain from sharing any further thoughts / opinions, and get back to work.

Good luck in your quest, and have a good evening.

Later.

Orr89rocz

To answer some of your questions on my setup:

383 with 11 to 1 compression, AFR 195's that flow 281/221 from the average numbers a few members have gotten out of several 195 heads on the same bench. They flow as advertised.
Holley stealth ram mildly ported.
Cam 286/306 advertised, 230/245 at .050. .603/.613 on a 109 lsa. Installed on a 108 ICL. So its a 109+1 basically. Wide duration split of 15 degrees at .050...thats huge

Long tube headers, 1 3/4" primaries, 3" collector into 3" ypipe into 4" single exhaust.

700r4 automatic with 3600 stall.

Car made 392/371 hp/tq on the dyno on the 10 run with engine boiling at over 205 degrees... with 90+ degree shop temps. heat soaked to hell and torque dropped the last 3 runs so its got to be around if not over 400whp and 380's or more wtq.

3450 lbs it ran 11.47 at 118-119 in 80 degree summer temps with a mediocre 1.55 60 foot.
10.63 at 127 with a 1.45 60 foot on a 150 shot.


Cam was designed to peak at 6200-6300 and shift by 6500 or so. It did just that. But power was flat to 6800 or so since i shifted there and ET never changed more than a tenth with varying 60 foots. Car was strong.

My criteria was a strong top end, and the cam just came out like that. I have heard that road race grinds for broad power curves use wide duration splits and somewhat tight lsa's. LS7 corvette uses a 211/230 grind but on a wide lsa go figure but LSx like wide lsa's for some reason.

Again its the way the cam came out and my stealth ram/head combo made the power i wanted and made a flat curve because thats what the stealth ram and miniram for that matter does. short runners make wide torque curves.

When i chose another grind, it came out like 300/304 240/243 i think it was on a 108. that was for 6500 rpm peak for my same 383. I was gonna do that but decided to build a twin turbo 400 motor.

That motor designed to peak around 5800 and he chose a 292/292 233/233 on a 112 lsa.


its not always about duration and LSA and overlap. you can have same LSA and overlap but different durations with different lobe designs. They are not symetrical these days and can have fast intake opening (which is good) and slower exhaust closing rates (which also can be good) and provide good cylinder filling for a particular head/intake setup and rpm range.

Thats why i say its hard to classify combos based on duration/lsa and performance for so many different engine combos. Its application specific generally.

GREGGPENN

Jake,

Wondering if/what you found out from PCM4Less.....

Anyway, I'd always thought 111 was about the smallest LSA recommended for computer controlled cams. This thread has applications that are smaller. So, I went back and reviewed many of the discussions I had with LE. Here's what he said....

"Anything over a 106-108 LSA is gonna be a compromise for smoother idle, etc, that is gonna cost HP and TQ across the board. The only reason to use a 112 LSA or wider is for emissions purposes or for boosted set ups.

A wider LSA (109 to 111, 111 to 113, etc) just makes for less effective
exhaust timing events that allows more burnt exhaust gas to remain in the cylinder. This exhaust left in the cylinder is like a big EGR valve and takes up space that clean and fresh intake charge can not occupy so you have less cylinder filling, smaller explosion on combustion and less HP and TQ at every RPM. You end up with slightly more overlap (compared to the same duration on a wider LSA) but we are dealing with small duration cams anyway that are gonna have a pretty smooth idle."

After saying all this, he recommended 111LSA. That was for a 220ish cam (350ci) where I wanted good low-end power/manners. So, depending on your goals (or your son's goals), it looks like you could go lower.

gp

JAKE

Orr89rocz, thanks a ton for that input and those numbers. gp your feed-back well received, too. It gave me some insight into Lloyd's thinking. I was pleasantly surprised to see he recommended the 111 LSA.

Now I've got something I can sink my teeth in. So I'll re-read and re-re read both of your comments and try to put it all together. Then dove-tail everything into my plan.

Thanks again,

Jake

West Point ROCKS!