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Old 01-21-2012, 02:32 PM
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Optimum LSA for Strip oriented SBC

I been having thoughts about different camshaft's in my engine, also have been reading my *** off, without getting nowhere !
The thing is I was hoping to get some recommendations regarding a good camshaft for my 350 Chevy engine. 4.000"x3.48" street/strip usage.
The block and crank is std unit. rods are aftermarket I-Beam with ARP bolts. Pistons are old Speed Pro forged flat tops, floating pin. 10.25:1 Compression
Heads are off the box 64cc Edelbrock Performer RPM 185cc, 2.02"/1.6" valves. 1.5 ratio rocker arm's
Intake manifold's a Holley Strip Dominator Single plane with 750 CFM Holley Double Pumper carburetor
I'we got 1.3/4" long tube headers with 3" collector into dual 3" exhaust with flowmaster mufflers

Current camshaft is some kind of comp cams nitrous cam. Hydraulic Flat Tappet. 12-568-4 113+5
Valve lift Gross - 507 / 525
Duration at .006 Tappet lift 284 / 305
Duration at 0.50 lift 240 / 253
Valve timing at 0.006 dur io 34 btdc /ic 70 abdc / eo 90 bbdc / ec 34 atbc
Lsa - 113, Ica 108
Lobe lift 3380 / 3500
RPM range 2800-6800

My question is. Would i gain some performance going to a tighter LSA ? some guidelines ? Since I have thought's about running this engine N/A only. I'm Also open for a switch to mechanical (solid) lifter camshaft, since this is Monza spends more time on the strip than on the street !

The engine is in a 2800 LBS H-body Chassis (MONZA) race reddy
TH-350 Transmission with 3500-3800 Stall converter.
Rear axle is GM 12 bolt with 4.11 gears and Spool. Tires are 28x12.5 Et streets.

Best regards.
Monzter.

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Old 01-21-2012, 05:45 PM
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I think I would switch to a solid roller,and yes a tighter lobe center if NA. as far as guidlines I'm sure somebody will chime in . I would do some research myself before listening to a hundred different ideas. weight of car, tranny, converter, gear , rpm. size of tire , carburation, lots of variables to consider best to talk to somebody close to what u have and get some ideas
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Old 01-21-2012, 06:08 PM
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It will pick up a little power by tightening the lsa. Keep in mind that true "nitrous" camshafts are designed for large shots of nitrous, 250+. You can run an n/a camshaft all day long in a car and whack it with a 150 shot and it won't be a benefit to switch to a nitrous grind for that small of a shot. Something like a 242/248 on a 108 would work with those heads. It will go to 7k easy.
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Old 01-22-2012, 07:33 AM
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So im clearly leaving some hp on the table by running this wide LSA cam ?
Would some off the shelf cam be good for my combo, or is it neccesary to go with a custom ground one ?

Regards
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Old 01-22-2012, 07:52 AM
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Cams are a place where you get what you pay for. Power can be gained with an off the shelf unit, BUT more can be had with a custom cam. The 242/248 108 cam suggested earlier would be a good place to start if you're looking at a tight lash solid cam. If you're going hyd then drop the durations by about 8 degrees.
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Old 01-22-2012, 09:22 AM
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Try one of these Isky solids:

201534 282-288 248-254 .534 .525 106LSA 100 to 102 in C/L

201CC1 290-296 254-260 .525-.520 106LSA 100 to 102 in C/L

need open headers and will like collector extensions.

either will run very well on nitrous too.
www.iskycams.com
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Old 01-22-2012, 01:55 PM
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Quote:
Originally Posted by monzter
I been having thoughts about different camshaft's in my engine, also have been reading my *** off, without getting nowhere !
The thing is I was hoping to get some recommendations regarding a good camshaft for my 350 Chevy engine. 4.000"x3.48" street/strip usage.
The block and crank is std unit. rods are aftermarket I-Beam with ARP bolts. Pistons are old Speed Pro forged flat tops, floating pin. 10.25:1 Compression
Heads are off the box 64cc Edelbrock Performer RPM 185cc, 2.02"/1.6" valves. 1.5 ratio rocker arm's
Intake manifold's a Holley Strip Dominator Single plane with 750 CFM Holley Double Pumper carburetor
I'we got 1.3/4" long tube headers with 3" collector into dual 3" exhaust with flowmaster mufflers

Current camshaft is some kind of comp cams nitrous cam. Hydraulic Flat Tappet. 12-568-4 113+5
Valve lift Gross - 507 / 525
Duration at .006 Tappet lift 284 / 305
Duration at 0.50 lift 240 / 253
Valve timing at 0.006 dur io 34 btdc /ic 70 abdc / eo 90 bbdc / ec 34 atbc
Lsa - 113, Ica 108
Lobe lift 3380 / 3500
RPM range 2800-6800

My question is. Would i gain some performance going to a tighter LSA ? some guidelines ? Since I have thought's about running this engine N/A only. I'm Also open for a switch to mechanical (solid) lifter camshaft, since this is Monza spends more time on the strip than on the street !

The engine is in a 2800 LBS H-body Chassis (MONZA) race reddy
TH-350 Transmission with 3500-3800 Stall converter.
Rear axle is GM 12 bolt with 4.11 gears and Spool. Tires are 28x12.5 Et streets.

Best regards.
Monzter.
For an engine with no power adders there needs to be a lot of overlap. To get this race type cams tend to run less LSA usually in the 106 to 110 degree area. You can fake your engine into thinking there is more overlap by using 1.6 ratio rockers which will get the valves open further and sooner which will result in it breathing like there is more duration and less LSA.
You're really into tuning, I know that changing cams and lifters isn't thought of as tuning, but there is a point, and you're a bit past that point, where tuning involves more than jets, plugs, and points or modules.

How do you arrive at this 10.25 compression. If I assume flat top pistons with a 4.5 cc valve relief, a .038 gasket, .015 in the deck, with 64 cc heads; my SCR model generates 9.9. I haven't run the numbers for a DCR but my intuition tells me that 9.9 or even 10.25 SCR isn't enough, especially with the gears you've got.

Bogie
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Old 01-22-2012, 04:27 PM
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I had thoughts about running a thin steel shim head gasket.
In terms of LSA difference between 106-110-114 ? In drag racing...
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Old 01-22-2012, 05:25 PM
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There are 5 cycles in our motors. Most people assume there are just 4, intake, compression, ignition, and exhaust. But there is a 5th which is more of a phenomenon than a planned cycle. It's called the "exhaust induced intake event". Basically as the exhaust is rushing at a VERY high rate of speed out the exhaust port it creates a low pressure area behind it (think vacuum). Then the intake valve opens and it is "jump started" into the cylinder far beyond what it would have been capable of by the cylinder itself. The more overlap you have, the more it will help to drive the intake charge in, but it comes at a price. With a lot of overlap you will lose low speed power, and you will tighten up piston to valve clearance. More fuel will go straight out the exhaust at low speed as well. There's more to overlap than simply the LSA. You have to figure in the duration as well. A small duration camshaft with 212/220 on a 106 will have far less overlap than a camshaft of 256/260 on a 110 even though the LSA is tighter. You have to look at the cam card to be sure what you are getting.
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Old 01-22-2012, 05:43 PM
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I was aware that duration plays big part in overlap degrees. I also have this solid roller cam Comp xe lobes 242/254 @ 50 lift 280/292 adv 571/583 lift 114 lsa on 110 icl. 58" overlap. I assume this would not be the best n/a cam for 350 engine. ? As it was ground as nos/sc cam
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Old 01-23-2012, 01:14 PM
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Does lsa affect manifold selection ? Dual plane VS Single plane intake ?
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Old 01-23-2012, 01:27 PM
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Quote:
Originally Posted by monzter
I had thoughts about running a thin steel shim head gasket.
In terms of LSA difference between 106-110-114 ? In drag racing...
Check this out

http://www.compcams.com/technical/FAQ/LSAproperties.asp

Bogie
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Old 01-23-2012, 05:56 PM
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Quote:
Originally Posted by monzter
Does lsa affect manifold selection ? Dual plane VS Single plane intake ?
Not by itself but the camshaft size in relation to how many cubes it's trying to feed, dictates where the powerband will be and what manifold will suit it the best. A big cam with small cubes to feed will make power way up top and will benefit with a single plane. A performer rpm intake is usually the best choice out there unless the engine is going to see a lot of time above 6500rpm.
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Old 01-24-2012, 01:10 PM
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Do you guys have any oppinion about this solid roller cam i have ?
Would it be an improvement over what i have in it now ? Or should i go with narrower Lsa ?
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Old 01-24-2012, 06:48 PM
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Quote:
Originally Posted by monzter
Do you guys have any oppinion about this solid roller cam i have ?
Would it be an improvement over what i have in it now ? Or should i go with narrower Lsa ?
Less LSA reduces vacuum so if you need power brakes on the street or strip, you either want more LSA or a booster vacuum pump on the brakes. If this isn't a concern and you're willing to live with low vacuum and a rasty idle and don't mind if the torque and horsepower peaks are pushed up the rev band, put closer together, made bigger, and the anything that looks like gas mileage is out the window, then the answer is less LSA. Less LSA begets more power (torque) that times RPM makes horsepower but for a street engine it's a bit of a sloppy way of getting the power. This really comes down to which situation you rather live with.


Bogie
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