i think it is 234º on the intake side...

 

You are partly right.....

I have a hard time with making a cam for a setup that has less than optimum parts. Only because the cam will not be the best for the application and that basically negates the point of a custom cam. There is no big secret that I like beehive springs, lots of reasons for that. They aren't cheap but they do the best job on this type of motor, hell i've even seen them work on a Solid Roller and PICK UP 8 points on the average power..... Good article in Pop Hot Rodding on Richard Holdeners experience in the 2004 Engine Masters brings this point up.

I also like billet cam cores. Mostly because a cast core has some weaknesses and they also can have soft lobes. It's few and far between but when a guy says "my cam wiped out a lobe and I have to rebuild my motor" I personally feel like **** and between me, Comp or any other cam company that's basically a "thats what it takes to play the game" response. I wish I could afford to rebuild a motor when this happens, but quess what, at $310 a cam (billet) and $260 (Cast) there is no room in there to do that. So I take the safe route and go to the billet core and all is well, plus you get the benefits of a stiffer cam that is more accurate. To me if you get a "custom" cam and pay more than $300 for it, it better be a billet core.

Back to springs.....

What lift a certain spring is good too means absolutely nothing. Now if you give me a coil bind height, spring rate, seated pressure at one height and a mass of the spring and retainer (that's why Ti and beehives are nice) you can actually tell what the spring is good for. The CMS springs good to .625" or whatever aren't really unless you are running a flat tappet cam that's not very agressive. Just no way to get the seated pressures and the open pressures high enough with that spring in those situations...... Take out some of the lift and shim the springs up right and you have a chance at it.

The way I see it there are always guys out there who can or think they can pick out their own cam. Good for you. A lot of guys have situations where it's not a easy choice. One thing I have found is that guys like engineers, doctors, lawyers, professionals and other engine guys want the right choice for a motor and they seem to be who work with me the best. I don't rip people off in parts, in fact they are in line with the best places out there, I just choose not to pick out junk parts so in the end it costs more, and I think you get the most for your money that way.

There are a lot of off the shelf cams that are good. The reason they are known to the masses is because guys have tested them in their cars over and over and over again. Some guys don't have that situation and don't want to go thru 3-4-5-9 cams to get the right one, so it's better to get REALLY close the first time.

Back to Jon's setup........

We are talking about headers, and a CAI. That's it, no good gaskets like a Imp gasket, no electric water pump, no TB nothing. If you optimized a setup like that there is probably 20-30hp there at the tires. I think the fact that at peak it's close to 60hp says most of it and at even higher RPM points we are talking 90-100hp increases at the tires.

I never said I was the cheapest, I've always thought you can be the Ferrari, the Corvette or the Civic in business. To me the vette always wins, the best bang for the buck in terms of everything. You can always get a Z28 faster for less money but it's still playing with lower quality parts and never quite getting there. Civics are a comprimise in everything for price, it gets you where you need to go and the Ferrari bumps your ego for the extra money and goes just as fast as the vette.

Bret

 

on the heels of what bret already said about springs. just because you arent shooting ducks doesnt mean you have good control of your valves and are making max power. i've seen it a TON in lt1 cars, guys on here tend to all use the same springs for a crap load of different cams and setups just because they're easy to get and put on and have fit/work whatever. and then they get mad when thier motor lays over at 5700 just like a half a dozen other cams both smaller and larger sometimes by as much as 20*. the problem most people have is they get shell shocked when it comes time to talk about pricing for the parts to match the cam. they do not want to hear that they need a $120 set of pushrods and a $250+ spring and retainer setup. my guess is that its because those parts dont seem glamerous as a cam or rockers, never the less thier role is every last bit as important.

 

Man some of you guys are really being picky over a few HP differences from dyno to dyno. They are tools! Lots of things can and do affect them. Unless you are on the same day, same dyno, 5hp-10 hp differences arent worth looking at IMO.

Things I suggest as have already been said:
Match your components for your intended use and to the cam.
Measure, do your math, measure and redo your math. Get your stuff installed at the right height and right pressures.
Research, and if you are lost, pay someone like Bret. I felt plenty confident in picking out the 847. However, the new combo i put together is past me, and I believe everyone has that point. Ive been in contact with bret and after i get a few runs out of the car hes going to spec something out for me too. No shame in paying those who know to do a job. You go to a surgeon for open heart surgeory right? Well go to an engine builder for a cam. Thats how they make their living.

Jon had Bret spec a cam for HIS needs. I specced the 847 for my needs. Would I have been faster on a true custom grind, eh prolly not, but i wouldnt have been slower either. I think we are talking about hundreths of a second difference in a drag race between the cams. Only so much air you can get through a stock head. Anyways, Im happy with what i have, Jon seems very happy with where he is. Isnt that what matters?

 

Hmmm....guys, tell me if I'm missing something here.....

Kreinmc, are you going to stay with the stock heads, or have them ported/get different heads later?

If you're staying with stock heads, don't the ports on stock LT1 heads stall on flow at about .500 valve lift? What good does it do to lift the valve more than that if head flow won't support it?....Bret?

 

Oft asked, and oft answered. If the cam gives .500 lift, how long is the valve at .500 lift? A microsecond? A nanosecond? If the cam gives a bunch more lift, how long is the valve at or above .500? Much longer. More total flow.

 

Hmmm....ok....so why are stock eliminator guys so fast with stock lift cams?....probably because the lobes on their cams are shaped like rounded-off squares, kind of the point I was trying to make.

Jon, you're only about 45mi away from me....who are you having your head done by?

 

Because they have to run stock lift.

 

You can lift the valve higher than the peak flow lift.

For example:

.400 245
.500 265
.550 270
.600 270
.650 268
.700 265

Cam that has a lift of .700 is used in a situation like this.....

That's not a bad thing, like Jon said it's only there for a short amount of time, but if we want to get into this even more it can be explained for a few more reasons.

Now I doubt that most engine guys even understand this, but a agressive lobe is not always the lobe with the most lift for a given duration. This is hard to grasp but lobes like stock elminator lobes aka "Max Area" or lobes that are "shaped like rounded-off squares" are much harder to control. You need very fast acceleration ramps on the cam to generate this area, then you limit the max lift of the cam due to lift rules so you basically have a situation where the lobe falls away from the lifter. Lots of spring pressure over the nose is needed here, along with very stiff parts to make it work. Usually light parts to go along with it. A high lift lobe can have the same fast ramp but it controls the valve over the nose of the lobe better to start with and at the same time builds up pressure with the added valve lift since it compresses the spring more.

So in the end the reason for the extra lift and why is pays off is the area gained. On top of that.... wouldn't you rather have the valve open at any point over .500" than open less than .500" The average flow of the valve realtive to the lobe profile is what you are after.


97bowtie "Because they have to run stock lift."


Jon has a set of LE3 heads.

Bret

 

Bret, thanks for taking the time to answer all my questions.....

So....you're saying a cam with "max area" lobes are much harder on valvesprings (and much harder to control the valves) than a cam of higher lift lobes, right?.....

Brent

 

Yeap that's it....

It's also harder on the parts since there are more loads and changes in force going on too. Pushrods, Rockers all need to be stiffer in these situations or you can have a hell of a time with valve bounce and toss. Toss can be a good thing but it's super hard on springs.

Bret

 

Bret, what lobe would you say is the best "max area" lobe design then? Oh and something with a max lift of .585".

 

All depends on the rocker, the duration, the lifter type etc....

Basically "Max Area" referers to the lobe area for a given duration.

We've talked about the Comp 319X series lobes being very aggressive but they also have lots of lift.

Bret