Can someone educate me on what the difference is and which is better for hi performance?

 

Here are the spec on my current cam followed by what I am looking at going to.

Current:
Crane Cam
part# 110691
Grind# H238/3347-2s-6
lift 502/516
Duration 238/244
Lobe separation 106

What Im thinking of going to:
Comp Cam
12-443-8
XR300HR-10
Lift 562/580
Duration 248/254
Lobe Separation 110

what does the lobe separation do? What is the difference between Hydr roller and Hydr? Is this cam going to be so radiacal that its not streetable anymore?

Thanks guys...

 

I looked up your Crane cam and it's really hot. 106 is more of a racing cam without consideration for gas mileage or idle quality. It probably has a rough idle and low on vacuum. I'm running the Crane PowerMax solid 238/248 only it's ground on a very mild 114 lobe center. It doesn't have the radical idle and it has a big broad Tq courve. I use 7000 rpm as my red line.

Going from 106 to 110 will improve things if you keep the same duration. that extreem roller your talking about would only work on 400+ ci and even then it's max HP would be at or near the H-Rollers 6500 rpm limit.

 

The guys at AFR (Air Flow Research tell me I can go with a bigger cam more lift than my current 502/516. What would you guys suggest? What does the duration do for me? Im running a 383 stroker.

 

bhmyers:
What is your desired 'goal' here; a streetable motor, a high-RPM screamer; a 'bracket-style' motor; or a 'rump-rump' 'Pro-Street' motor?
What do you got (CID, heads, intake, converter, gear, weight, etc.), and whadaya want it to 'do'???

 

I want a pro street that screams at the track. I have a 383, AFR 190 heads, RPM performer intake 1 3/4 headers, Demon 750 carb. 3800 stall, with a TH400. Im probably around 3300-3400 lbs

 

Describe to me how your present cam performs. Roller cams can run bigger duration than their flat lifter counter parts. I'm running a solid roller and it really comes on hard about 4000 - 7500. If i'm in second gear going about 30 mph and floor it. It's amazing how fast it's swinging past 7000 rpm and the speedo is reading about 90 mph. Same thing in third. If i'm going down the highway and shift from OD 4 to third and floor it from 55 mph it doesn't take long and it's swing through 7000 and the speed is about 125 mph.


I will tell you right off I don't like or trust AFR. I'm having a set of 210 heads repaired and upgraded. Heads of a certian CFM of flow will only support so much hp. So increasing the cam gives very little gains

 

High performance is directly related to RPM`s. For MAXIMUM performance a solid lifter cam is required. They are completely streetable as are all the high performance early Vettes. :)

 

By 'track', I assume you mean the drag-strip?
#1, if you don't run good tires, it probably won't hook; if it DOES hook, you might break the rear-end, but that's another story...

Since nobody has answered your 'question' about hydraulic vs. hydraulic-roller, lift, duration, I'll 'try'...

A V8 camshaft has 17 'lobes' (8 intake, 8 exhaust, 1 for the mechanical fuel-pump) on it. (I'm only discussing the intake/exhaust 'lobes' here...)
These 'lobes' are 'egg-shaped', and a 'lifter' (hydraulic, solid, roller, or hydraulic-roller), nothing more than a 'cylinder' sitting in a bore (hole) sits against the lobe.
On the 'other' end of the lifter, a 'push-rod' is inserted; at the 'other' end of the push-rod is the 'rocker-arm' (think of a 'see-saw' with an off-center balance-point). In a stock small-block Chevy, this 'off-set' results in a 1.5:1 ratio of movement.
At the opposite end of the rocker-arm is the 'tip' of the valve; the rocker-arm pushes the valve 'down-ward', or 'open', allowing incoming air/fuel to enter the chamber, and spent gases to exit the chamber, out the port, into the headers, & out from the car.

(If I'm being redundant or simplistic, please forgive me; many people, even Corvette-owners, don't KNOW how this works?

OK, back to camshaft-lobes. The 'center-line' of the cam is towards the 'big-end' of the 'egg', which is the 'base-circle'. When the lifter is against this portion (big-end), there is a bit of 'slack' in the valve-train, and the valve is 'closed'.
As the cam is rotated, the 'pointed-end' pushes the lifter/push-rod against the rocker-arm, the valve moves 'down', or opens, etc...

Cam-makers list many 'specs' of their cams; lift, duration, duration @ .050" lift, LSA, etc.
LIFT: is how far the valve 'opens' (when the 'pointed-end' is at max-lift {the 'nose'}, or in a straight-line with the lifter/push-rod) with the 1.5 ratio
(i.e.; a .450" lift cam has a 'nose' that protrudes .300" above the 'base-circle'. .300" x 1.5 ratio = .450" lift).
DURATION: is how many degrees of the cycle the valve is 'off it's seat' (open)
DURATION @ .050" LIFT: is just what it 'says. Since very little 'flow' occurs when the valve is 'slightly open' (less than .050"), this figure is very important.
I've run 2 cams with 292* duration in my Z28 over the years; one had 218* @ .050", the other had 244* @ .050". The 2nd one had MUCH steeper 'ramps' (and 'filled' the chamber faster), resulting in a 'choppy-idle', while the 1st had 'gradual' ramps (slower-filling, but better idle), and was easy on the valve-train. Consider this, too...
LSA: is just what IT says, too; the Angle of Seperation between the intake Lobe, and the exhaust Lobe (LSA!) during a 'cycle'.
'Generally, a wide LSA (112-114* or more) results in better idle quality, and a broad power band, than a 'tight' LSA (110* or less).

'Hydraulic lifters' (oil is 'pumped' into the lifter to lessen shock-loads) offer little-to-no maintainence, and decent performance;
'solid-lifters' (no internal-oiling) offer more 'aggressive ramps', but periodically need 'adjusted';
'roller-lifters' (lifters with 'wheels' rolling against the cam lobe) offer outrageous lobe 'profiles', and less 'friction' (the hydraulic & solids just 'rub' against the cam), and
'hydraulic-roller-lifters' offer the best of both worlds: aggressive 'profiles' (due to the 'rolling-effect') with less 'shock' and maintainence (oil in the lifter).

By mixing-n-matching the lift, duration, duration @ .050", and LSA, you (and/or the cam-grinder) can tailor-make the cam that best suits your needs and combination....

Now, all you guys who REALLY know what I'm 'trying' to describe, FLAME-AWAY at me!!!!!
:lol:

 

That helps a lot, thanks. My heads are flowing about 270 cfms. I would like to get them cnc ported and get them to flow around 300. The cam I have been looking at has a higher lobe seperation than what I have now, 106 Vs 110. So based on the above specs of the cam Im looking at, do you think it will make more power? I blaze my tires any where in first gear. I also think it shifts very quick into 2nd. I can run the 1/8th mile track in 2nd gear, Im turning around 6k at about 83-84 MPH when I pass the line.

 

Wider lobe seperation tends to reduce upper end hp and increase mid range torq so for 2 cams with identical specs other than lobe seperation the one with the narrower lobe seperation will make more hp but at a higher rpm and will not have as much midrange torq. If you are going for ***** out hp then get the narrower lobe seperation.

 

Fevre you got that exactly opposite. A norrow LSA generally produces more tq in the mid range, and a wider LSA will have a broader flater tq curve, and higher hp potentail.

If you want a pretty radical street machine I would go with a solid roller or a solid flat tappet, particularly in a motor that will see more than 6300-6500 rpms. If that were my 383 it would see 7000 rpms, my 454 does :)

 

I can turn 6500 with no problem, any advise on a radical cam for my above specs?

 

Heres my specs: can someone suggest a radical cam?

385 ci (stroker bored .040)
10:1 CR
Demon 750
RPM Performer intake
1 3/4 headers
Cutouts
AFR 190 heads flows about 270 CFM's
3500 stall
373 rear end
TH400
MSD ignition

What else do you need to know?

 

Guess there is a little more to it:

http://ctfba.tripod.com/main/technic.../cambasics.htm


Now is looks like I got the midrange rpm wrong but what about the upper rpm? :confused:


[Modified by Fevre, 12:57 PM 11/3/2003]

 

A wide LSA will make the cam "hang in there"longer on the big end.

Wide LSA = flat and wide torque curve.
Narrow LSA = peaky torque curve. Narrow LSA also gives you a better midrange punch which most consumers want.

Wide LSA improves idle, off idle throttle response, emissions and upper rpm power.

Now for the original poster: First decide your budget and how much maintenance you're willing to do. This will dictate the type of cam. Your choices:

Hydraulic flat tappet: Low maintenance (Set it and forget it). Low cost.

Solid flat tappet: Higher maintenance. You should reset the valves every 6-12 months. More power than hydraulic flat tappet. Higher rpm potential. Low cost.

Hydraulic roller: Much higher cost than flat tappet. Great choice for high-perf street with many miles driven. Low/no maintenance, long life. Good power potential but rpm limited to about 6500.

Solid roller: About the same (high) cost as hyd roller. The most maintenance as the lifters should be rebuilt every 15k miles or so. Best power potential and good for very high rpm.

 

Sorry, getting terms confused, I mean to say that greater overlap creates more hp in the upper rpm's. Sorry to cause any confusion.

But still am getting info that conflicts with what has been stated:


"The shorter lobe separation angle produces more peak horsepower, but with a loss
of low-end torque. Shorter lobe separation angle is better for a drag
engine than a street machine, due to an increase in valve overlap. "

http://www.newcovenant.com/speedcraf...camshaft/6.htm

:confused:

 

"The shorter lobe separation angle produces more peak horsepower, but with a loss
of low-end torque. Shorter lobe separation angle is better for a drag
engine than a street machine, due to an increase in valve overlap. "

Fevre - if you get the program like Desktop Dyno 2000 You can see it on a graph. With everything being eqaul the 106 -110 cam with give a slightly higher peak TQ over a narrow rpm range. Yes that's idea in a car with a 5 speed and 4.56 rear end gears.

A 106 cam would have a higher peak hp over a very narrow range also.

What makes a car the best overall is the highest average tq & hp. I would rather have a cam like mine that makes 500+ foot pounds of tq average from 3000 - 6500. Where a 110 or less might have a peak 15-20 lbs higher at a small range of rpm . So the under 3000 rpm would really suck and over 6500 is again dead. The total average is also down.

Increased valve overlap works best in drag racing and street machines because they tend to run open or very free flowing exhaust

 

Gkull: gotta disagree with the narrow LSA will give a higher peak HP reading. Narrow LSA cams are for strong mid and some upper range power. In drag racing cars with autos (2-3 spds) will often have LSA's as narrow as 106 degrees, when you go to a four speed the power band can be more narrow and you see the LSA's widen to 108 -112. These motors suffer less rpm drop between shifts so you can concentrate on a peakier upper power band. In the pro stock five speeds you see LSA's as wide as 118-120. These motors are desinged to make max power in a very narrow rpm band and due to the fact they suffer very little rpm drop between shifts they are built to make max power in this narrow band.

Narrow LSA cams are desinged to "Recover" after a huge drop in rpms after a shift, that is why they make so much peak mid range power. A drag car with a 2 spd autp will drop several thousand rpms after a shift and to be fast the motor has to be able to produce lots of tq to pull through this.

In general wide LSA cams idle better, make more low end tq and more top end power, but less mid range grunt. Driving a car with a 106 LSA is lazy in the bottom comes alive like a 2 stroke motor and then runs out of breath. A wider LSA just seems to have a more constant pull and likes to rpm a bit more before you need to shift.

For the motor for the guy who posted a solid flat tappet (or roller) in the 245 at .050 on a 110 or even 108 LSA if the stall is high enough. Since you are buying the heads from AFR I would listen real close to what they have to say

 

This gets to ba pretty wild discussion....

But one thing that has to be mentioned here is WHY Pro Stock and others run huge LSA. They could care less about idle quality, but they really do idle better than many street cars.

They are using HUGE lobes that have lift in the 1.2" range, yet these days they really are cutting back on the duration. Much less than in the past. That means an almost square looking lobe that moves the valve VERY quickly. Better flowing heads have allowed them to use less overlap. And that is what they are really fighting with the wide LSA. As lobes get bigger on any cam, overlap naturally increases. But there is a point where it is just too much, so the only choice is to use smaller lobes or spread LSA out some. They have wide LSA out of necessity for the huge lobes they use.

And I'll jump in here with my .02 worth. Narrow LSA is great for midrange...lots of roundy pounders use them down to 102-104 even. It also works great on street stuff. Make cam "lumpier" but if you are limited on how much duration or lift you can use, it's another way to help power. They usually make great power in the "normal" under 6500 rpm range. Once you get into the stratoshere on RPM, you usually need bigger lobes and longer duration, so wider LSA's come into play again to control overlap. Some overlap is good, too much is bad.

Wide LSA does idle better, so it's a way to calm down a big nasty cam to be more streetable. But a smaller cam with a tighter LSA can run just as well. Kind of depends on what heads you use, what they flow, rpm, exhaust, intake and all.

I've run wide and narrow LSA's and can tell you the street manners are good with wide. But the engine is typically a little lazier. Tighter ones' help that out.
Sounds like you have good bottom end with the tight LSA. If you are happy with it overall, I'd look at the next stage up while comparing overlap to see if you can keep it similar. Any signs of reversion into intake?

On a dyno you can see where a cam with a big overlap figure works. It will have a pronounced peak in the midrange whereas a cam with less overlap will have a smoother broader curve.


JIM