Typical camshaft ICL and LSA for 383? - Hot Rod Forum : Hotrodders Bulletin Board
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Old 04-11-2013, 11:01 PM
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Typical camshaft ICL and LSA for 383?

Hey guys. Picked up a lightly used retro hydraulic roller cam (looks brand new) for my AFR headed 383. The cam is made by Crane but the previous owner had it regrinded to more street friendly profiles. I just finished degreeing the cam installed in the short block and I am fairly pleased with the results of the profiles, should be a good match for my combo...... I think.

Duration at 0.050":
Intake: 234*
Exhaust: 234*

Lift:
Intake/Exhaust: 0.350" at lobe; 0.560" at valve with 1.6:1 rockers

Intake Centerline:
103* ATDC

Exhaust Centerline:
118* BTDC

Lobe seperation (LSA):
110*

How do these numbers look to you? Again this is with the cam installed straight up at 0. From looking around at cams these numbers seem to be what I am looking for with this 383 build. The only number I am really concerned about is the low 103* intake centerline angle. Does this seem a tad bit advanced? A more common number I see is a 108*-112* ICL. I triple checked it and it is dead on at 103*. What could I expect from this low ICL?

Thanks,
Keith

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Old 04-12-2013, 01:00 AM
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Quote:
Originally Posted by 383SBC View Post
Hey guys. Picked up a lightly used retro hydraulic roller cam (looks brand new) for my AFR headed 383. The cam is made by Crane but the previous owner had it regrinded to more street friendly profiles. I just finished degreeing the cam installed in the short block and I am fairly pleased with the results of the profiles, should be a good match for my combo...... I think.

Duration at 0.050":
Intake: 234*
Exhaust: 234*

Lift:
Intake/Exhaust: 0.350" at lobe; 0.560" at valve with 1.6:1 rockers

Intake Centerline:
103* ATDC

Exhaust Centerline:
118* BTDC

Lobe seperation (LSA):
110*

How do these numbers look to you? Again this is with the cam installed straight up at 0. From looking around at cams these numbers seem to be what I am looking for with this 383 build. The only number I am really concerned about is the low 103* intake centerline angle. Does this seem a tad bit advanced? A more common number I see is a 108*-112* ICL. I triple checked it and it is dead on at 103*. What could I expect from this low ICL?

Thanks,
Keith
hi I might be wrong but for a 383 you be better with a intake centreline angle at 106 -108 , myself I would use the 102-104 intake centreline angle for big block. I think the low 103 will effect idle and low end torque. I don't think it will be suitable for the street, . I always dial my cam in at the intake centreline angle for maxim lift. what do other think.
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Old 04-12-2013, 06:36 AM
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Im opposite to bjautos7,I use a low I.C.L. for a 283,or low compression engine. closing the intake earlier will give you more cylinder pressure.You did not mention anything about your engine for support parts and what you want the engine to do well.
looks like your choice would give you a lumpy idle and be all done by 6k or lower
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Old 04-12-2013, 07:08 AM
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In "simple" terms, the lower ICL will "pull" the power band "down" in the RPM range. That's "advanced". Raising it has the opposite effect. I'm in agreement to set it up at a 106-108 ICL. With 234 @ .050, you're going to rev to about 6,200 pretty easily. Don't waste that high-end power by making too much low-end... SBC's advantage is the high-end. A 383 offers good low-end, so it's a good "match".

Jim
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Old 04-12-2013, 10:57 AM
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It will have the same basic rpm range. (3000-6000+) But , within the same rpm range the advanced cam will make the low part of that same rpm range more punchy at the cost of some power a the top of that same rpm range.
it does not make a big cam into a small cam.

it will still need a 3000+++ stall converter. and some gears. It still wants run in the 3000+ to 6000 rpm range.
If you want to see how it runs, install it and try it.
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Old 04-12-2013, 10:59 AM
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If you really want to make some serious power get a solid street roller.
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Old 04-12-2013, 07:19 PM
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Thanks for the info guys, much appreciated.

I guess I should give you more details of the engine build and application. It is going into a second generation Camaro with a t56 6 speed trans. AFR 195 aluminum heads, 10.1:1 Compression with forged flat tops, Edelbrock air gap dual plane, Holley 750 double pumper. This is going to be a street/strip build. I'm going to set the rev limiter at 6000 or 6250 max. cause of the hydraulic lifters and I have a 6 speed so I wont need to wind the crap out of it. Rear gears is 3.42:1. It will most likely be seeing a 100 shot of nitrous in the future at some point as well, which changes the ICL optimum setting once again. Any more info needed?

Also, as was mentioned, this cam will make good power up to around 6000rpm as judging by the numbers. However, remember this is a 383 and NOT a 350 so it will actually be making power a little lower than that. A cam that makes power in a certain rpm range in a 350 will need an additional 10* or so of duration to maintain that power band (3-6000rpm). All cam speculations are based off a 350 from the manufacturer. So, with that in mind, my 234* of duration at 0.050" will make power in the same range as a similar cam with only 224* duration in a 350. If this were a 350 then I could see this 234* of duration posing a problem to low end torque for street driving, but since this is a 383 I think it will complement my combo nicely and get me up to that 6000rpm producing some nice numbers

I think at this point it would be in my best interest to remove the balancer, cover, gears, etc. and retard the cam 2 degrees to give me an ICL of 105.5* (the ICL was actually 103.5 by my math but I wasn't going to pull hairs). Or, since I have a multiple keyway crank key, I could retard it 4 degrees to give me an ICL of 107.5*. What is the consensus about this? Which should I do or just leave it and see how it runs (although its MUCH easier to mess with it while on the stand). F-Bird I always take what you have to recommend very seriously as you have proven your wealth of knowledge on this board and I would like to know what you recommend as far as where to set my ICL.

Thanks,
Keith
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Old 04-12-2013, 07:35 PM
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AFR heads are a good choice
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Old 04-12-2013, 10:42 PM
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Run it as is.
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Old 04-13-2013, 01:15 AM
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Not worth the effort to retard it that miniscule amount I take it. I would rather run it as is so I dont have to pull and press with the balancer/gear and disrupt more than I have already up to this point. Out of curiousity how much of an effect or noticable difference would there even be by say retarding the cam by 4 degrees? How bout advancing it by 4 degrees? Are we talking night and day noticable differences in power and driveability or is it such a small change that for the most part it would be a wash?
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Old 04-13-2013, 07:28 AM
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change in cam timing

Quote:
Originally Posted by 383SBC View Post
Not worth the effort to retard it that miniscule amount I take it. I would rather run it as is so I dont have to pull and press with the balancer/gear and disrupt more than I have already up to this point. Out of curiousity how much of an effect or noticable difference would there even be by say retarding the cam by 4 degrees? How bout advancing it by 4 degrees? Are we talking night and day noticable differences in power and driveability or is it such a small change that for the most part it would be a wash?
we used to use 4=300 rpm just as a guideline.If you are at the max at one end then moving the cam might just deplete the other end
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Old 04-13-2013, 11:45 AM
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You are not going to feel the difference. If thats what you mean.

With your mild gears you need torque. Run it as is and stop worrying about it.
Get some sticky tires and traction bars so you can make use of the power.
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Old 04-13-2013, 01:07 PM
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If when you move the camshaft in a motor, one of three things will result.
1. It will run a little bit quicker
2. It will run a little bit slower
3. It will run the same.

It does not change the rpm. Or the rpm range.
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Old 04-13-2013, 01:48 PM
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Fbird,you are partially correct. the peaks in the power curve move.The peak RPM hp will move up or down a little.The engine will rev higher than the peak hp numbers rpm.do you need a detailed explanation,Im sure you can extrapolate the information by yourself and you can also do your own math.I know you understand
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