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Old 02-21-2007, 08:46 PM
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benefits of high compression ratios

im building a 383 and i dont kno whether to grab a 66cc head, or a 72cc head
the 66 gives me 10.8:1 and the 72's give me a 10.1:1
the car is going to be a car that is very hi-performance, and will see a little more time on the track than the street.....if i do run the 10.8:1 cr wat gas would i have to run? would 98 or 101 work? what would the benefits of a higher comp ratio be as opposed to the 10.1....i want power
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Old 02-21-2007, 08:56 PM
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What heads?
what pistons?
what cam?
what rods?
what gas do you want to run?
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Old 02-21-2007, 09:09 PM
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Quote:
Originally Posted by xntrik
What heads?
what pistons?
what cam?
what rods?
what gas do you want to run?
heads are the World Sportsman 2 200cc 2.02's
pistons are kb 5cc flat tops
cam is a lunati .500/.515 solid lifter
5.7 rods
a decent octane, like a 98 or 101
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Old 02-21-2007, 09:51 PM
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Go with the 66cc....Smooth(round over) all the sharp edges in the chamber, including around the perimeter. Dial the cam back a little, advance your spark, and go.
Strictly my .02....If I ever get ahold of another Chevy.....I've got alot of ideas to try....
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Old 02-21-2007, 09:53 PM
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Quote:
Originally Posted by BigBlockBanjo
Go with the 66cc....Smooth(round over) all the sharp edges in the chamber, including around the perimeter. Dial the cam back a little, advance your spark, and go.
Strictly my .02....If I ever get ahold of another Chevy.....I've got alot of ideas to try....

ya that sounds the best hell ya...strap in and hold on...haha
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Old 02-22-2007, 09:04 AM
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the cam you chose, is Lunati's mildest solid lifter "bracketmaster" for "mild performance bracket racing" and "street driving with a lopey idle"

not a great choice for 200cc heads, 11/1CR "very hi-performance"

call the lunati tech line 1-662-892-1500, then call world products to confirm the lunati recommendation

gooogle:383 stroker motor
lots of long blocks and crate motor build specs with hp results
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Old 02-22-2007, 11:23 AM
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Quote:
Originally Posted by mista-nova
heads are the World Sportsman 2 200cc 2.02's
pistons are kb 5cc flat tops
cam is a lunati .500/.515 solid lifter
5.7 rods
a decent octane, like a 98 or 101
What you've chosen doesn't fit the criteria of "very high performance,..... I want power".

What you are looking at is a 5800 rpm engine with a strong low-mid range.

Rods are short, heads are small, cam is mismatched, induction is unknown, exhaust is unknown. Compression/octane is not a cure-all.

I suggest you rethink your desires and your parts combination, and see if a financial compromise can be reached.

"You can build a 420 hp engine with a fuel problem, or a 400 hp engine that will run on junk." = Steve Henderson, engine builder
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Old 02-22-2007, 12:01 PM
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To answer your initial title question.
One full point of compression, from 10/1 to 11/1, increases your power about 2-4% depending on whom you talk to. So roughly 9-18 hp on a 450 hp engine.
Higher compression is necessary for longer duration cams.


By your saying high performance- track car, sometimes street driven, I suggest that you might need

a head that flows 240 cfm at .500 lift and the cam of .550+ lift., 210+ intake ports

a roller cam of 244* duration, 106* LSA, 1.6 rocker arms

850 cfm carburetor on a high rise single plane intake or
dual 500s on a tunnel ram.

Everthing else to make it work and be RELIABLE at 6500 rpm.
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Old 02-22-2007, 12:32 PM
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I assume the cam you are looking at is this one http://www.holley.com/00013.asp I would recommend something with a little less duration at .050 but more lift. The heads you are looking at will be good for lower power, probably ~6000-6300 RPM max power on a 383. If that is what you are after, they should work fine. As for the cam with the 200cc heads, I would not recommend going larger than something like the comp XS282S (244 252 @.050 .520 .540 lift and probably some 1.6 rockers to take the lift to .550 .570). If you used a cam like that, I would also recommend a 3500 stall. That cam would be pushing the limits of 10:1 compression, and you may want to call comp to make sure they agree with that choice if you plan on going that way. If you are ok with running a more stall, larger heads, and more cam, it will probably make your car faster, but less streetable. As for 10.8:1 compression with 100 octane gas, I dont think you should have any problems. A call to a fuel company would not hurt though. On the other hand, you could probably run 91 octane with 10:1 if it is built right and save some money on gas making about the same power. The only reason I see that the greater compression would be a good idea if your case is if you plan on running the larger head/cam setup. The bigger cam will need more compression to run correctly.

Adam
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Old 02-22-2007, 01:01 PM
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mista-nova,
just so you know, the sportsman II heads need to be machined for pushrod clearance to use 1.6 rockers with whatever cam
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Old 02-22-2007, 05:03 PM
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wat i am looking for is strong torque and horsepower in the 2500-6500 range
wat heads do i need?
wat cam do i need?(solid)
im using 5.7 rods
wat manifold?
wat carb?
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Old 02-23-2007, 10:20 AM
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mista nova,
no disrespect, but I would recommend you shop and buy a 383 long block...

your buying a proven combo built by experienced people......

most are approx $4k (good grief, speedomotive has a Edelbrock ETEC build for $3800 as an example)...which is very very close to what you will spend to build it yourself....they will recommend the intake/carb/ign

to learn more about everything, go to the knowledge base link on the board main page, under engines/engine articles/misc is a number of links for 383 motors.....from the basics to one link that has 50 combo's or so with dyno results

Morgan Hill= NJ?......several members here have performance build engine shops in your back yard
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