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Old 10-28-2018, 05:27 PM
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i have a 396 Big block motor with stock large oval port heads. Upgraded springs and rockers. stock rocker ratio. hardened pushrods etc. Stock crankshaft and new but stock style rods and pistons. It has a compcams #11-250-3 Cam in it. It has a choppy idle but has all the power at the high RPM range for a street car (67 Camaro). Duration Int/Ext: 284/296 -- Valve lift: 574/578 -- LSA 110. I'm looking for a cam that can deliver most its power in the lower to mid RPM range, and something that wont lose a lot vacuum. what can you guys recommend me? Thank you.

other info: TH400 tranny, 3.73 rear gears, 305mm rear tires,edelbrock performer air gap intake, 750 holley carb.
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Old 10-28-2018, 09:09 PM
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What compression are you running? Where is the cam installed? A cheap fix could be to advance the cam timing. This lowers the power band and usually increases torque output.
It's difficult to say as there are so many options and variables, but for streetability I like to stay around 230 degrees duration at .050 lift
While you are at it you might want to think about converting to hydraulic roller cam. They can make similar power with less duration, keeping the rpm down and will survive with today's oils.
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Old 10-28-2018, 11:45 PM
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Quote:
Originally Posted by 67_camaroRS View Post
i have a 396 Big block motor with stock large oval port heads. Upgraded springs and rockers. stock rocker ratio. hardened pushrods etc. Stock crankshaft and new but stock style rods and pistons. It has a compcams #11-250-3 Cam in it. It has a choppy idle but has all the power at the high RPM range for a street car (67 Camaro). Duration Int/Ext: 284/296 -- Valve lift: 574/578 -- LSA 110. I'm looking for a cam that can deliver most its power in the lower to mid RPM range, and something that wont lose a lot vacuum. what can you guys recommend me? Thank you.

other info: TH400 tranny, 3.73 rear gears, 305mm rear tires,edelbrock performer air gap intake, 750 holley carb.
Th guys at chevelles.com are big cam gurus especially for big blocks.
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Old 10-29-2018, 05:27 PM
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I would check with the camshaft manufactures such as Crane .Iskey
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Old 10-30-2018, 08:50 PM
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I agree with above post, 220 to 240 max at 050. Don’t worry about lift as much, duration is much more important, if your really just street drinving, stick closer to 220, that’s how you pull stumps out of the ground off idle, I think your cam duration numbers are not at 050 valve lift and if they are it’s a huge camshaft, also if the heads have really big ports that will work against you. My.02

Last edited by alex n; 10-30-2018 at 08:53 PM.
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Old 10-31-2018, 02:30 AM
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Quote:
Originally Posted by Tinker View Post
What compression are you running? Where is the cam installed? A cheap fix could be to advance the cam timing. This lowers the power band and usually increases torque output.
It's difficult to say as there are so many options and variables, but for streetability I like to stay around 230 degrees duration at .050 lift
While you are at it you might want to think about converting to hydraulic roller cam. They can make similar power with less duration, keeping the rpm down and will survive with today's oils.

its a 10.25:1 compression ratio motor. I want to stay at a hydraulic flat tappet. very true its hard finding oil for it but i have found my way for now.. But right now im looking at a cam: Duration 256/262 @.50" 213/219 Valve Lift 515/530 LSA: 112. it was recommended to me.
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Old 10-31-2018, 02:35 AM
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Quote:
Originally Posted by alex n View Post
I agree with above post, 220 to 240 max at 050. Donít worry about lift as much, duration is much more important, if your really just street drinving, stick closer to 220, thatís how you pull stumps out of the ground off idle, I think your cam duration numbers are not at 050 valve lift and if they are itís a huge camshaft, also if the heads have really big ports that will work against you. My.02
I just posted the advertised duration. but the @.50" duration is 240/246. Um, i believe they are stock size ports.
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Old 10-31-2018, 10:03 PM
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Quote:
Originally Posted by 67_camaroRS View Post
its a 10.25:1 compression ratio motor. I want to stay at a hydraulic flat tappet. very true its hard finding oil for it but i have found my way for now.. But right now im looking at a cam: Duration 256/262 @.50" 213/219 Valve Lift 515/530 LSA: 112. it was recommended to me.
That will definitely lower the rpm range, but that seems like a huge swing. I hope you don't lose too much top end. With 10.25 compression and comparitively little overlap, detonation is a possibility. I don't know who recommended this cam, but if it's someone with experience that you trust, then follow their lead. I could show you some fairly accurate numbers of what that cam should do for peak power curve compared to current cam if you would like.
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Last edited by Tinker; 10-31-2018 at 10:07 PM.
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Old 11-01-2018, 06:49 PM
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Okay, I am guessing the cam you were recommended is a Lunati voodoo. I do like those cams.
Your current cam should be about 420hp@6500 404ft lb@3000

The lunati 256/262 376hp@5500 434ft lb@ 3000 you will definitely feel 30 ft lb of torque


I suggest going one bigger to the 262/268 for 384hp@6000 432ft lb@3000

That's 8hp more for only 2ft lb of torque.

The next one up is a 268/276 and it gives up another 7 ft lb of torque which you don't want.


Hope this sheds more light on it for you.
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Old 11-02-2018, 09:29 AM
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Much better cam. The advertised duration is the first set of numbers and at.050 you get the smaller numbers. That cam is perfect for what you want to do
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