I always read/hear about how mostely everyone over cams there car and that the car can run better on a smaller cam. Iv been thinking about it for a while now and i cant figure out why. Isnt the object of power is getting air in and out the fastest you can? Then how is a cam too big?

 

I think what guys mean when they refer to over camming is the cars setup. Alot of people throw a huge cam in thier cars without the supporting mods. mostly picking a cam with a higher power range than the parts they have will spin to. This translates into poor results. My cam in my 383 could use a set of 4.10 to optimize it. The power range is 2500rpm to 6500rpm. I have been shifting it at 6200. It feels like it wants to spin up to 7000. Its built to spin that hard, just have been hesitant trying it.

Prime example: A bone stock 04 m6 GTO with exhaust a cold air ran 13.7. Later has a t-rex 615lift 22xdur 110lsa cam installed, and runs 13.8's. The car is making more peak power but the torque loss down low causes to much momentum loss. If he would add 4.10 gears, supension mods, dr's, and more rpm, the GTO would see huge gains!

 

it all depends on how your other components are matched up to it. Big lift = high rpm. So if your running a 3000 stall on say a cc306 cam, you aren't gonna be in your powerband. You also got to have the right heads, tires and gears, along with all the other goodies. There is a write up on Katech's ls7 powered f-body in the new GM High Performance Magazine. Awsome magazine by the way, it is running an LS-7 with 640hp and 55lb-ft of torque on all motor. The 2000 ss uses a 233/276 at .050,.630 lift camshaft. They were launching at 5500 and 6000 rpm in that thing. They were running high 10s in a six speed.

I am just a young punk with not much experiance but thats what i understand to be true, talkin to the older guys who have been doin this for a long time and reading alot of material.

By the way I see you got a tune by MadZ28, how is it? I am thinking of getting one by him.

 

its a good tune to at least drive around on but im sure theres a lot more power to be had on a dyno tune. But for $125 its a good tune to get you goin.

I know what your saying about the rpm range, tire size, stall and so on. But say if i switched my 847 cam to a 503 cam, how would that make me more power? Or does it just put me at a better power range in turn make my car faster with the same amount of power.

 

Power under the curve is always faster than peak power. That is what you need to look at. If you have all the supporting mods to spin your car at higher rpms, then dropping to a smaller cam would not help.

 

i assume the 503 has a bigger lift, so that would give you more horsepower providing your injectors, fuel pump, fuel pressure regulator and throttle body are up to the task. So you get that extra horsepower out of it but it will be at a higher rpm. So you look at your dyno sheet and see how to make the most out of your powerband.

Basically high lift big cams = Racing
Smaller lift cams= Street
That is part of the reason why you don't see to many cam monsters on the streets. Alot of people who are running those cams on their daily driver or street car are never running in their powerband and don't have the components to back it up, so their car may sound like a monster but their are actually making their car slower.

 

From what I've found over the last 13 or so years messing with the LT1s is that, generally, With both 350/383 LT1s with LT1 heads (ported stock castings) that you should go no more than 230 degrees of duration @ .050 and keep valve lifts to no more than .570...lsa can vary for the N/A, nitrous, FI applications...Like someone said before its all about the area under the curve...thats where the fun lies...The late John Lingenfelter was the original R&D man for these types of cams...smaller durations and bigger lifts make the most of the LT1 heads..The added benefits are making power at lower rpms and, therefore, not having to spin the thing to the moon to make power...

...BUT its all in the combination...Everything has to work together...The cam to the converter to the rear gear...Bigger duration cams require more converter and more gear and for most street/strip guys this makes for an unacceptable combination...

Unfortunately many folks still "overcam" their motors with the misconception that bigger is always better..Some cams work better on paper than in the car...

--Alan

 

so whats the differance between a cam with big dur./smaller lift vs. smaller dur. and bigger lift? And im also noticing the specs. "older" cams ave both bigger dur/lift on the exhaust side where when i look at specs. on late model, fuel inj. cars the intake lift/dur is now bigger then the exhaust side. Any advantage there?

 

You're much more likely to over cam a car with duration and overlap.

 

On most all heads, the intake flows much better than the exhaust. So, for the most part, most engines will benefit from a cam that is exhaust biased. Lately theres been a proliferation of intake biased cams. Personally I have yet to see a combination that would really benefit from one.

 

Not an LT1, but I once bought a 79 Z28 that came with a huge cam, 9.5 to 1 compression, 3500 stall, dual plane intake, 780 holley, and 3.73 gears. This thing was a misery to drive. It was sluggish as hell and drank gas like I've never seen. I changed the cam for a much smaller one, swapped to a 2500 stall and a 650 carb. Not only did the car come alive, picking up several tenths in the quarter, but the gas milaege almost doubled.

Like everyone else said, it's all relative to the combination of parts. I believe this is one of the reasons people have such great results with custom ground cams.

 

I think my car is overcammed.When this cam was in Steve Quins LT1 it went 9.7`s and the best I have got was a 10.7 I am sure I need better flowing heads and I think he was about 300 lighter than me.Also maybe I need a bigstuff 3 also cause I can only go upto 7200-7300 with the stock pcm.


edit:cam is 264/271 .688/.660 108lsa

 

Nice thread here.

 

so you can have too much overlap also? Thats new to me. So the famous 503 cam, lets say cut on a 110/108 would be just as bad as a big lift/dur. cut on a 112??

 

I purposely got a custom to avoid this situation. Ended up with a 22x/23x .6xx/.6xx 10x. Hauls *** and drives great. Gas mileage is sucky obviously.

The lower duration, high lift stuff really makes LT1s run. The XFI grinds would have been my next choice, or maybe an LPE grind.

 

Do you want your 401K to gain 1% a month all year or .5% per month january through october and then 2% november and december?
I know we all wish we had a 401K that good but numbers were picked for ease of math.

That is sort of what we are saying, on a street based application a broad wide torque band will be king. Now a race application where you can keep the engine in a 1500rpm slot the whole pass then yeah, a big peak number can work.

 

I'm running a Comp XFI 224/230 574/570 113 lsa (1.6 rockers) The car is getting faster every time I tweek it. (useing Tuner Cat) My heads are my limiting factor at the moment. Ported by a SAM student, stock valve size, no flow numbers (LE2s will be on soon) and STILL ran a 12.0 with a 1.64 60'. 3600 lbs thru the traps. 6400 rpm shift points. Still drive it to work. Something to be said about relatively small cams. Glad its being said here. Good thread!

Mec

 

so for my car... if i switched to a smaller cam id pick up a few tenths... BUT if i keep the 847 cam and bought some le2/3 heads then ill make a lot more power then a smaller cam on stock heads. If thats the case, i plan on buying heads in the spring time after winter so ill keep my bigger cam now and get my heads done for that cam. I want to build the car more for the track vs. drivabilty cause its not my DD so i want to get pretty radical with it slowely but surely.

 

For a good street/strip car, average power is the name of the game. High duration will over cam an engine much faster then high lift, and will have a large effect on where the engine wants to be. More duration will push the powerband up in the rpm range, sacrificing low end tq and average horsepower for peak numbers. Think of those super high hp turbo supras who's dyno graphs look like this:

_______^

That makes the car a total beast from a highway roll, but with no power worth mentioning until 6k+ rpms, they are dogs from a roll without a shot of nitrous and steep gears, and will run embarassing times for the power they put out without a really well built setup. A bit of an extreme example, but thats the basic idea of average power.

The big cams work great - you just need the steep gears, great flowing heads, and bottom end to spin it nice and high and keep it there the whole run. Not fun at all for the street! As an extremely simplified rule, choose the cam with the best lift numbers your heads can support, then get the duration and LSA for the rpm range you feel comfortable using. There are many much more complicated things that will effect the rpm ranges and how the cam will act - that is why it is best to have a custom one made by a knowledgeable professional, who can predict how the car will act within a narrow rpm range.

My cam falls into the proven "late 22x/mid 23x" range of custom grinds that are growing in popularity, with .570 lift on a 110 LSA. I know my "stage 2" heads are the current limiting factor right now, but even with better heads I would still run a very similar cam - just with more lift. The car gets driven every day to work, and screams down the track w/ a streetable 3200 stall and stock 3.23 gears.

If anything it is a tad big for stock cubes, and the cam would really tear it up in a 383...which is where it will be eventually assuming tolerances are correct when I get ready to rebuild/stroke it.

Assuming you also get more aggressive gearing(big cam autos like 4.10s for the track) and can spin to 6500+ and keep it up there with a higher stall then that 3200, you will run faster times with that 847. If you are not willing to do that, then the smaller cam may run quicker.

Specifically power wise, like you said, the larger cam will almost always make more peak power. I just don't even think about cams in terms of "power" because that is not always an accurate reflection of what the car will run. I automatically think about parts, especially cams, in seconds - not horsepower

 

If you want a track car you get the nasty cam(240+dur)w/110 or 108lsa, add steep gears(4.10-4.56) to keep it up in the power. 28" slicks, probably a 3500stall or higher.
I agree the 847 cam on le2/3 heads would make alot more peak power than a small cam on stock ported heads. Which is what you want for the track. You will suffer on the street with drivability and would get pulled from a low rpm kick with a smaller cam setup that makes better low end power. So I think you are on the right track with your setup, for what you are wanting out of it!