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Old 07-23-2013, 09:00 PM
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Rpm range

What would be the estimated rpm range for a cam with 230@50 278adv. 575 lift on a 110? A hydraulic roller in a 383 with 9.5:1 and 3:73 rear with 33'' tires..

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Old 07-23-2013, 09:38 PM
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header size? head flow numbers?
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Old 07-23-2013, 09:56 PM
How fast is fast enough?
 
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Assuming a mildly built combo that will peak around 5800rpm. The high side for a street only car.
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Old 07-24-2013, 02:15 AM
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Profiler 195, 1 3/4 headers....
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Old 07-24-2013, 04:23 AM
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Ought to make power out to 6000 rpm, give or take. This obviously assumes the induction and exhaust are right.
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Old 07-24-2013, 09:54 AM
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So the valve lift has little effect on rpm range? What about taking the lift up to .600? Is it just about getting the most lift the heads can flow and selecting duration for the desired rpm range?
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Old 07-24-2013, 10:30 AM
How fast is fast enough?
 
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So the valve lift has little effect on rpm range? What about taking the lift up to .600? Is it just about getting the most lift the heads can flow and selecting duration for the desired rpm range?
The lift has some effect, not as much as duration though. your duration needs to be picked according to your ACTUAL usage, not your "lets make a street car with a bracket engine that will never see more than 5,000 rpm" dream usage.

For a hot street car that will see some track time the mid 220's duration is usually about right, for street only, mid 210's. FWIW picking a cam that is too big for the ACTUAL application will make you run slower, burn more fuel, and wear through parts faster. Those specs are for hydraulic cams BTW.

If you want something that will win at almost every stop light go with low 220's, a higher stall (3500+) and deep gears (4.56 or deeper with those tires).



On a side note, if you go with .575" lift you better make damn sure your valve train and geometry is dead nuts on or you'll be wearing through guides.
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Old 07-24-2013, 12:28 PM
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So the valve lift has little effect on rpm range? What about taking the lift up to .600? Is it just about getting the most lift the heads can flow and selecting duration for the desired rpm range?
Not sutable for a street driven engine. High lift equals high wear. Among all the other problems with clearances of parts at extreme lifts comes unbelievable wear between lifter and cam lobe, pushrods to lifter and rocker, rocker fulcrum unless roller and valve stem tip to rocker and valve stem to guide wall. Once you cross .5 inch lift it's a whole different world requiring very expensive parts at great attention to the details of clearances and lubrication.

Most heads don't flow well over .5 inch lift unless you're looking at pricey race heads or some Chinese heads like ProComps that flow quite well at extreme lifts but unfortunatly under perform otherwise similar port sized heads at lesser lifts.

When I look at your first entry what comes to mind is you need to be quite more specific about how the engine will be used and what you expect and how large is your budget. Especially when it comes to budgets they can be a sobering experience over the distance between what you want and what you can afford. The other sobering experience is the distance between what's a streetable engine especially for a daily driver to a street/strip engine.

As for RPMs to a very large extent for cams beyond the most mild to moderate timing, say up to about 200 degrees at .050; it is the valve spring that will establish the rev limit. If you pass that restriction the next big limiter is bottom end strength. As the engine gets to 350-400 hp and is turning 5800 to 6000 RPM you are at the limit of OEM rods including Chevy's pink rod. For an OEM bottom end you can explore this now and then, but frequent hard running will ventilate the block with rod parts. So now you've got to beefup the crank assembly and that also means the damper.

So you need to kind of draw a line around how you intend to use this thing and how many bucks you can put into it.

Bogie
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Old 07-24-2013, 07:57 PM
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stock new ZO6 corvette uses a cam with about 218 duration,.550 lift,114 lobe separation. The head flow is very very good.The engine runs smooth at idle and makes 505 hp,,,claimed by GM.
The cam makes peak power around 6300 RPM and redlines at 7,000 rpm.
of course this is a modern LS engine,,,but,
explain why you cant have similar performance using premium parts?
re valve train stability,the ZO6 uses rocker shafts and 1.8:1 ratio

good news,you can buy rocker shafts for a gen 1 sbc too and you can use different ratios
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Old 07-24-2013, 08:29 PM
How fast is fast enough?
 
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More to it than rockers but that's a good start. It also has better cam cores, pushrods, rockers, valve springs, retainers, valves, etc, and that's just the valve train. Better intake, heads, block, etc too. A comparison of a bbc and a sbc would be a better comparison than a sbc and an ls.

But with premium parts you can run .600" lift on a sbc for a long time with no problems, all it takes is money.
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