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Old 07-08-2005, 10:03 PM
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SBC Rocker Arm Geometry

I'm working on putting together a 383 for the little S10 and wanted to know what you guys with the experience thought about the different full roller rockers available. I've pretty much decided to go with the 1.5 (or 1.52 as it may be) and make up for any lift that would benifit me with the camshaft. I'll be running a cam with these kind of specs: 258/270* duration at .050, 112* lsa and a 108 intake centerline. I thought the comp cams pro magnums would be ideal since they're chromoly, but I haven't got a clue in the geometry department. Have a friend of mine using Harland Sharps for the better geometry, but he's using a BBF so I doubt his word would apply to the Small block Chevy. Hopefully this will bring out some good discussion also, thanks in advance.

Matt
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Old 07-12-2005, 07:25 AM
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Harlan Sharp makes excellent roller rockers.
I have factory GM 1.6 on my engine ( SBC ) but ran the Harland Sharp on my BBC for years.

Ratio varies with stamped steel rockers. They are stamped and not as accurate as machined rockers in the ratio department. Rollers also reduce friction and lowers oil temperatures.

Sounds like you have a lot of camshaft............1.5 should do well.
I believe ( just me.... ) that it is better to get the lift off the camshaft and 1.5 rockers than try to get the same lift with a smaller camshaft and 1.6 rockers...
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Old 07-12-2005, 09:43 AM
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Quote:
Originally Posted by Deuce
:
I believe ( just me.... ) that it is better to get the lift off the camshaft and 1.5 rockers than try to get the same lift with a smaller camshaft and 1.6 rockers...
Deuce -- just curious why you think that?
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Old 07-12-2005, 01:28 PM
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It's better to get your lift from the rocker rather than the cam. You have less weight,(Lifter, Pushrod, End of Rocker) moving a given distance(moment of inertia) and it's easier to control with the spring. You won't notice till .700 total lift's with 500 pounds over the nose and 7500 rpm. With spring pressures that high, you need 7/16 pushrods with .120 walls and solid offset rollers. They come in at nearly half the weight of the rocker tip, retainer, lash cap, spring, 2.25 valves.
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Old 07-12-2005, 06:56 PM
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Quote:
Originally Posted by pmeisel
Deuce -- just curious why you think that?

I do not run camshafts at .700 lift on a SBC........and most others here do not either........


I like to run a camshaft with the total lift I think I need with the 1.5 rockers........and IF I need more I can experiment with the 1.6 rockers..

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Old 07-15-2005, 12:12 PM
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Thanks for the replies so far. I suppose a better question would be, are there any noticable differences between different rocker arm manufacturers? Differences between same ratios, any of them prone to cracking (aluminum), and has anyone personally used the Comp Cams Pro Magnums full chromoly rockers? Again, I appreciate the feed back, especially the thing about less weight moving by using the bigger ratio rockers. My question is, do you loose a noticable rocker arm strength because it's longer in these ratios? I don't know much about them, they may not be any longer, just angled differently, but that's why I'm asking .
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Old 07-15-2005, 09:51 PM
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PRO mag are good. The other magnums are less quality. Made for street kinda stuff.

The physical size doesn't change much. The ratio comes from moving the pushrod cup closer to the pivot point. As far as getting then set right. Any good rocker manufacture will have what you need for pushrods. Why a cam that big? and 1.5 rockers?
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Old 07-16-2005, 10:44 AM
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Quote:
Originally Posted by johnsongrass1
Why a cam that big? and 1.5 rockers?
Just building a hot 383 for the street/show stuff. I was directed to the making lift with the lobe by the cam grinder dude at Lunati (Mark, if anyone is familiar with them). I suppose I could go with some 1.6's, would the less valvetrain weight help with SLIGHT street use and any harmonics that develop at ~7000? It will probably be twisted up to 7500-8000 at the strip when I do go, which won't be often after I get the nitrous system tuned. Even then, most runs will be 1-2 shifts and shutdowns while tuning. The goal is low 9s with the little S10.
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