Ed Curtis

Unless you get Scooter, better get a REAL cam designer, not some $6.00 per hour, 800 number, catalog user..

Ed

Billiumss

iTrader: (11)

What do you mean "Scooter"?

Hey RedReaper, Whose heads you have now? Whats your whole set up?

Bill

Cstraub

iTrader: (1)

Scooter Brothers, owner of comp.

Chris

MUSTANGEATER

iTrader: (10)

Hey Chris or Ed wanna design a cam for me? lol

Ed Curtis

All it takes is money...

Ed

MUSTANGEATER

iTrader: (10)

I've got that and the intake, just need the AFR heads and a couple opinions wonder who could get me some AFR's?

Colonel

"LSA should be the byproduct of the valve events you (or your cam designer) selects. Many cam companies talk about the LSA as if it is an adjustable feature. They will usually spec a wide LSA for street use and a tighter one for race use. The justification is that the wider LSA gives a better idle. The real truth here is that the LSA for optimum results, within a specified power band, for a given engine, is not adjustable. Only one LSA will produce optimal torque and power for a given engine spec and powerband. Any time it is suggested that the LSA be spread to improve idle quality it is a sure sign that the duration chosen is too long for the job! Sure a wider LSA will spread the powerband and improve the idle, but the price paid for spreading the LSA to achieve a certain idle quality is a substantial reduction in torque and power."

I guess GM is using cams that are too big for their applications.

There's nothing wrong with considering LSA as a design parameter of the cam. To say otherwise is a bunch of hooey, IMO. You could say that using a narrow LSA is a crutch to using a cam that is too small for the job. That would make just as much sense. It all just depends on what you want. Say you want a cam that idles smoothly at 600 RPM, makes good power, and drives great. You can either go with a small duration cam and a narrower LSA or you can go with more duration and a wide LSA. Let's say you did this in such a way that both cams idled exactly the same. What's gonna be the difference? You'll have to spin the larger duration/wider LSA cam higher to take full advantage of the powerband....oh, and it'll wax the first cam's *** in a race due to this. The first cam would be better suited to a truck or to someone who doesn't want to spin the engine up very high for whatever reason. Like I said, both cams have their place. "But wait" you might say, "you can just retard the smaller cam a few degrees to make it spin higher for racing." Well now you're crutching a too small cam. It's still going to be slower.

Ed Curtis

Err...

Dozen or so Fords and some GM's sitting on the shelf in Rhode Island...

But wait.... I can't say that... No banner... Sorry....


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BTW...Colonel.... For fear of being banned from this web site for life, I won't even get into why your LSA comments are completely wrong...

Ed

Ragtop 99

iTrader: (7)

If you have something of technical merit to add, post it up. nobody gets banned for a techincal discussion.

Colonel

Fire away Ed. Heck, you might even change my mind about things (doubt it).

Just be sure that you specifically quote what it was I stated that was incorrect and then specify how it is incorrect. I just read back through it and I'm thinking perhaps you may have misunderstood something I said.

99 Black Bird T/A

iTrader: (4)

Billiumss,

What did you heads flow thru the intake? How high do you plan to spin the motor?

Something in the 236 to 240 range on a 113-115 LSA might work well depending on what the heads flow w/intake.

Billiumss

iTrader: (11)

I think Jay at Absolute Speed flows them with an intake right?

The heads flow on the intake side:

.550 - 303
.600 - 306

I might get them redone or get new ones for the 4.030 bore.

I plan to spin it to 6500-6600

My car is more a show car than drag car, so with that said, I'd like to have that dyno graph that says "500+RWHP"

necrocannibal

iTrader: (5)

Right now I have Absolute Speed Stage 2 heads, flpw about 300 @ 600 lift. 6.0 Liter iron block bored 4.030. The cam is a 234/242 .598/.610 114+4. Diamond Pistons, 11 to 1 compression w/ 2cc valve relief. 6.100 rods. Eagle forged crank, 4.000. Ls6 Intake. Shaner S3 TB. Hooker 1 3/4 Longtubes. Custom 3" Y pipe. Exhaust sucks, its stock except the Flowmaster muffler. I am waitng on True Duals. Spec Stage 5 clutch.


Like I said that made 440 rwhp and 450 rwtq. The tuner told me that my Y pipe was costing me about 20 rwhp because the guy that built it built it wrong an that my heads are choking the motor. He said to get some true duals and to get some stage 3 LS6 or 6.0 liter heads and I should be right around 500 rwhp.

CHRISPY

In very general terms the shorter duration with "wider" LSA "can" give similar intake valve timing events and similar rpm horespower peak as a longer duration "narrower" LSA cam.

The biggest factor in determining the rpm of power peak is the intake valve events. Figure out the valve events you want and the LSA is just a byproduct.

However saying that you can design the cam with certain compromises in mind (emissions say) but still maintain similar intake valve timing.

Also you can design a 108LSA cam that will idle like a champ in these cars

DAPSUPRSLO

iTrader: (14)

Ok, I'll take a wack at this one. I see what the Colonel is saying but also have some things to add. Say you have a big duration cam with wide separation and a small duration cam with narrow separation

All numbers discussed will be at 0.50. It gets complicated when you talk about different lobe designs with different lobe intensities (difference between advertised duration and at 50 duration with the small number yielding a more aggressive lobe).
Big Duration, wide lobe: 230/230 114lsa (cam a)
Small Duration, narrow lobe: 226/226 110lsa (cam b)

Everyone agrees that these two cams have the same overlap (again we are talking at 0.50 lift duration numbers) right? Now, lets both assume that these cams are installed at a 110icl (4 degrees advanced for cam a, and straight up for cam b). What does that mean. That means that cam a will open the intake valve two degrees earlier then cam b and close the intake valve two degrees later then cam b (remember the duration number is split in two between the opening side and the closing side). NOW IT GETS TRICKY. Now you have to account not only for the lobe sized difference but the lobe separation angle difference. Remember that the exaust centerline is what moves when widening or narrowing the lobe separation angle, not the intake center line. So cam a's exaust valve closes two degrees earlier then cam b and cam a's exhaust valve opens six degrees earlier then cam b.

Cam a's intake opening two degrees earlier then cam b's and cam a's exhaust closing two degrees earlier then cam b's yields the same effective overlap at 0.50" and up. Now you have to look at the whole picture in why cam a will produce a flatter longer power band. I believe this is because the much earlier exhaust opening which helps scavenging at higher rpms and the earlier and later closing of the intake valve contributes also to higher rpm.

Now cam a will not produce the same amount of peak dynamic cylinder pressure as cam b because it will be bleading off more force from the combustion process during the power stroke because the exhaust valve will open earlier, sometimes even before the full stroke has been reached. This is why short duration tight lsa cams make big torque because they don't open the exhaust valve until later allowing the piston to travel farther down in the cylinder during the combustion process before opening the exhaust valve and bleading of the cylinder pressure.

Now if you were to retard cam b and make its events occur later and you had a very aggressive gear ratio this cam could run very well at the track as it will make a much more pronounced power curve (peak very hard and fast and fall of very hard and fast). You must keep this cam in its narrow power band or it will not produce optimal results. However, this is not very practical on a street car.

These are my thoughts and are open for debate.

DAPSUPRSLO

iTrader: (14)

Had to do some editing, messed up the overlap explanation but should make sense now.