As I have said before, what's acceptable to one person may not be to another. And as Mindgame and others have pointed out, gearing and transmission have a major impact on drivability of big cams. That said, here are my reccomendations based on experience. These generalizations are based on roller cams in small block motors. By referring only to duration, there is a degree of oversimplification. For the same duration, narrower LSA will make the cam "peakier" and vice versa. Similarly, advancing the cam lowers the rev range and retarding it will raise the rev range. And so on. To tame a big cam, close gear ratios, a loose converter, and high rear end gears play a major role.

Adv. duration (typical duration at 0.050")
270 (215): one step up from stock, very streetable with stock gears/converter. Will run with stock computer on a mass air car. Peak hp in the 5-5,500rpm range.
280 (225): moderate performance upgrade from stock. Needs gears/converter. Slightly rough idle. Benefits from tuning. Vacuum still good for brakes. Peak 5,200-5,700rpm
290 (235): street/strip use. Rough idle, marginal vacuum (will need a 900-1,000 idle or so). Needs gears/converter, PCM reprogramming. Peak ~6,200rpm.
300 (245): this is the "limit" for most people on the street. It will have a rough idle at about 1,200-1,500rpm. Low speed throttle response and torque will be noticibly less. It will need gears or a loose converter. Peak hp will be in the 6,500rpm range.
310+(250+): when you get to this point I'd say you ought to be in an SR cam. This is "race cam" territory though some people drive them on the street.

My present cam is in the 290 range on the intake side. Idling at 950rpm it has 12" of vacuum. It's pretty lazy at low rpm but this is masked by the loose converter (4,200stall) and the blower. I see boost as soon as the throttle is opened with the loose converter. Peak power is at 6,400rpm. I wouldn't go bigger with an HR cam and would go SR. Can't see an HR race car cam.

Rich Krause

 

Exactly. I too am having Bret grind me a cam as we speak. He will be netting me close to 40rwhp on my setup by choosing his custom cam over the off the shelfer I was gonna get (and thats still passing emissions according to Bret).

As mentioned by others...
Try a custom grind from Bret Bauer, Joe Overton, LE Packages, AI packages...

I would do that rather then just by off the shelf cams that have been arounf for 5+ years. Those off the shelf cams are generic performers that will work fine with all sorts of setups. Get a cam to match YOUR setup.

 

A friend of mine out in Indiana is running a 240/250 @ 0.050", forget what the exact lift is, but I believe it's somewhere around 0.575"/0.575", 114 LSA. It's installed in a 355 LT1. 4L60E (race built), 2800 Vigilante stall, 3.73 gears. The car freakin' screams and he's very happy with how streetable it turned out to be. No dyno numbers or ETs yet though...still waiting on him to get to the track.

I'm still waiting on getting my motor back together after the "incident"...when it's all said and done, it'll be a 385 with mildly ported stock heads. The cam that's going in is a 242/248 @ 0.050", 0.575"/0.600" lift, 114 LSA. I'm also running a race built 4L60E with a 2800 Vigilante and have a set of 3.73s waiting to go in. I'll let you know how it turns out if it ever gets completed.

 

Is your LSA a result of the design process, or a pre-determined factor?

I have a few questions: What effect does the increase in displacement have on the 'levels' of duration, up to the limits of percieved 'streetability'? Rich has posted the effects of the various levels of cam durations - does that apply universally regardless of displacement? I realize there is some generalization - there has to be without discussing a specific engine with all parameters disclosed - but what specific effects does larger displacement have on these aforementioned 'levels'? I assume, right or wrong, that the increase in duration will 'absorb' (please excuse my nomenclature and ignorance) the effects the larger cam would have on an engine with less displacement.

 

I've always been told (and it has always seemed like) extra displacement "swallows up" a cam, meaning it behaves better in a larger displacement engine than it does in a smaller displacement engine. My old Crane 234/242 was pretty wild in my 350, but seemed more tame in my 383.

As for how I ended up with my current cam...we were drunk one night and it came about from a "wouldn't it be cool if..." conversation. The 114 LSA was specified for a wider powerband. I guess we'll find out if it works or not.

 

Not to start a fight or anything but why do you think that tightening the overlap up is going to widen the powerband Type_O?

A sincere question but I think alot of people are confused on this one. If you are throwing so much duration at the engine that you need a wide lsa to make it idle then you should have went with a smaller camshaft.

I'll throw this in because it's from one of the best articles I've read on the subject.....

Consumers are often given the impression that cams need to be wider for street use than performance/race use so as to preserve idle quality. If a cam has to be ground on a wider LCA to preserve idle quality it is because the duration selected was too much to begin with. Fixing one cam selection mistake with another is not the way to go!

........................The best way to cover this is to start from an optimum and see what we lose by first going too tight (a smaller number) then too wide (a larger number). If we have an optimally spec’d LCA for a race engine then we find that as the LCA is widened torque over the entire rpm band used drops off quite rapidly. For example, in a 350 SB Chevy, two degrees too wide can mean a loss of 20 or more ft.lbs. throughout the rpm range. On the other hand 2° too tight will have almost no effect on the output over the rpm range used while racing. If the LCA is too tight the motor needs to turn higher rpms before it comes on-the-cam and the idle is rougher. For a race engine then it is best to err on the tight side rather than the wide side. Because the idle quality goes as overlap is increased it is better to err slightly on the wide side if we are talking street usage. Here I am talking 2° off optimum, not the 4° to 6° and even 8° that is often seen. If you are installing such cams in commonly modified engines then you might want to consider upgrading your source of cam advice.

-David Vizard

If you care to read the whole article you can find it here

http://www.engine-builder.com/index.htm

Go to search back issues, type in cam events and read article 6. Enlightening.

On another note, and perhaps on a tangent of thought.......

Duration at .050 is a useful perameter but it can be a bit misleading if you don't factor lsa and the actual overlap period into the equation. When the intake valve opens and exhaust valve closes are the most critical events. If you get them right (all dependent on the setup) then the engine will make a good deal more power than a cam that is "close". That is going to require a good deal of accurate simulation to arrive at. Every parameter of the engine will have to be accounted for... especially intake and exhaust lengths, diameters, cross section areas, along with plenum and collector volumes and a whole slew of other things.

Which is why it is best to work with a "Pro" when you are really after making the most hp possible. Granted, there's always going to be a bit left on the table but these guys know how to find some of it.
If you look at the cam manufacturers, well they have a few grinds geared towards the LT1, but do you honestly think they are still working to develop better grinds for these engines with the LSx on the table?
I'd venture to say that they took what was available from the aftermarket at that time and came up with a few grinds for the LTx. Keep in mind that some of these grinds have been around for a while.

Do you think you'd be better off with one of these grinds or one that's built specifically to the changes you've made?

Now take a look at the guys who are really pushing the LTx to better numbers.... many frequent this forum. These are the guys with the expertise, dyno time and dedication to providing the customer with a cam that is custom taylored to their needs. Not only that, they can provide you with a valvetrain package on the same level.

mei sentio

-Mindgame

 

Another enlightening post with excellent references.

The quote above is important, and is the overwhelming reason I chose to enlist a pro to do my cylinder heads and select the most appropriate valvetrain for my 383. I just find the ongoing developments very interesting, and I like to know more about the decisions made about my combination and why the specific components were selected without inundating Phil with 10 phone calls a day when I discover something I think is 'new'.

 

this is my exact same setup!! Runs great!!

 

Here's the head flow numbers yall.

http://web.camaross.com/forums/showt...hreadid=272698

Now it's time to find the cam! I want a monster yall. Any input will be great.

I'll have a six speed, 411 or 456 gear ratio, stock weight car, and I'm going to shoot 200 to 250hp nitrous. I'll have 4340 steel crank with H beam rods and forged pistons balanced, 11.0 to 1 compression. I'll try and turn this baby up to 6500 to 7000 rpms.

Thanks

D Moss

 

That quote was by me in the first post!

Here is what I'm talking about. I called comp cams, talked to them, told them EVERYTHING under the sun about my car, and get this.

He told me for the max hp for my car would be comp cam 07-503-8! HA. This is the cam that I already have. This is not the best cam for my car. I told him to find a custom grind, and he said that this is sufficient. There's no reason to grind one when it already exists.

This is that this post is for, to keep me from talking to sh*theads like this who doesn't know the LT-1 world that we live in......computers doesn't controll the car, WE controll the PCM.

What would YOU put in this car for a no nonsence ride. If no one replys with ideas, then I'll buy a cam, so then everyone can talk trash about I went the wrong route because I didn't pay someone a wad of money to help me figure out which big cam to get.

Come on yall, I need a big cam. Help.

Thanks

D Moss

 

Call steve Stumph(SAR2K) at thunder racing. he should be able to help ya out. He is running a BIG hyd. roller in his car with a stock bottom end and ended up wtih 450 rwhp. There are very few shops out there doing testing on the lt1 anymore so most of those places..including the cam company sales monkeys just want to sell you what they have on the shelf.

 

Thanks 95bird!

 

A number of folks are telling you the same thing, but I believe your mind is already made up. You say you don't want a cam that makes best power/torque for your application, you just want a BIG one, at least the way I read you.

My guess is that if you paid a pro to design a cam for your particular setup, you wouldn't be happy unless it was a "big" as you think it should be. That's a "lose-lose" situation for both you and the cam guy. He doesn't want to give you a cam that's too big for your combo because there's a good chance when it underperforms he'll get the blame. You want performance (I think) but are more concerned with "size". You know the old saying about size not being everything...

To answer your question: What would YOU put in this car for a no nonsence ride? I would have a pro design a conmplete valvetrain which would give me the best performance in the rpm range I planned to run the engine with the SMALLEST cam that would accomplish this.

Then, if I wanted to make folks think I had a monster cam when I sit at a light or cruise the car show, I'd rig up either my PCM or a controlled vacuum leak or maybe both so that I could make it sound BAD at the push of a button. Screwing with the idle speed and mixture and the EGR and shutting down a cylinder or two (with the PCM) just might accomplish this.

My guess is that you've scared away most of the cam designers who frequent this forum.

My $.02.

Good luck.

 

Sorry but really didn't want to read whole thread. I run a 355 with steel rods, and a stock crank. I have TEA ported heads and a comp cam custom grind.
Cam is 248/252 5**/5** 108 lobe sep.

car went 10.98 @ 120

 

THANK YOU KAMBA!!

This is what I'm after! I've had a few, and thank you for them. As for the others......well....

Thats like my flows, I know there is no need to get crazy with lift, because some of them dissipate after .500, but there is room for duration changes if I plan on buzzing my way up to 6500 to 7000 rpms, and some overlap for that killer chop. (LSA and duration, of course)

Keep em comming.

D Moss