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Old Feb 23, 2006 | 03:29 PM
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dynamic compression calculator available

was wondering if there is a dynamic calculator out there like a static?
 
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Old Feb 23, 2006 | 03:30 PM
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Yep. It's been in about 1/2 of my recent posts too.

http://www.kb-silvolite.com/calc.php?action=comp
 
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Old Feb 23, 2006 | 03:40 PM
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where it says "ABDC @ 0.050 lift plus 15 degrees" and the cam closes at 35 degrees so do i put 50 in? just making sure. also whats the rod length of a 390 that it's asking for?
 
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Old Feb 23, 2006 | 05:44 PM
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the rod length is 6.49". what cam are you useing?
 
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Old Feb 23, 2006 | 06:46 PM
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crane 941...so am i right about adding 15 to the listed 35 closing degrees on the intake valve? if so then i have 8.269 dynamic compression. sound good for low grade?
 
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Old Feb 23, 2006 | 07:17 PM
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Yes, 35 + 15 = 50. That is the number you enter. Rod length is 6.488".

At that dynamic compression ratio, if you've got good quench you'll get by fine. If you dont, you may have to buy premium.
 
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Old Feb 23, 2006 | 07:18 PM
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what pistons and head gasket did you use?
 
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Old Feb 23, 2006 | 10:43 PM
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I entered my 428+.030 engine specs and came up with 9.146 dynamic compression. I run it on 87 octane with no pinging issues unless I load it down in a high gear.
 
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Old Feb 23, 2006 | 11:10 PM
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Amazing. Maybe this quench thing is worth more that I had thought?

What thermostat are you running?
What head gasket?
What pistons?
What altitude are you running at?
What heads? (iron or aluminum?)
 
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Old Feb 23, 2006 | 11:41 PM
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The quench on my combo is about .040-.045. I am not sure on the Victor gasket thickness.
1.Stant 180 degree
2. Victor stock replacement
3. TRW L2303NF+.030
4. Varies from 1600 to 5200 feet above sea level
5. C1AE-A ported by myself

I think some of it is the very clean combustion chamber(nearly polished) and the extensive exhaust porting, altho i am running Dynomax headers(ports too small). The head chambers were some of the cleanest after running for 70000 miles that the local machinist had ever seen...in over 15 years of engine rebuilding. Or maybe I am just lucky!!
 
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Old Feb 23, 2006 | 11:49 PM
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Huh. According to this article, (the chart is at the bottom), you should need about 95 octane:

http://www.popularhotrodding.com/tec...power_squeeze/

I guess for every rule there's an exception! That thing must be tuned to perfection.
 
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Old Feb 24, 2006 | 12:16 AM
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Perfection-no, but I have tinkered with it for 24 years(the truck) and nearly 10 years with the present engine. The previous 390 had 9.4:1 and did not ping either(same heads), but larger cam.


We seem to have got a bit off the original topic Sorry
 
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Old Feb 24, 2006 | 07:29 AM
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who cares this is confidence building 101!!
 
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Old Feb 24, 2006 | 07:46 AM
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(meant for previous post-too quick to hit enter)

See this is what i need to hear...guys that have been there done that. Not that your quench ideas are wrong by any means kurt but i have a really hard time building a $2500 motor by the specs of what someone (whom i don't know and haven't seen his work) just told me online. I think you're right about quench to a certain point but for whatever reason it just hasn't lined up with the engines i've seen in the past. Again i'm not bashing you at all kurt, you seem to really know your stuff but i've gotta have hard evidence to know what i'm doing is right, otherwise i would've taken the first guys advice and who knows what i would have built. Anyways thanks Putt for the input and fyi i'm going with victor gaskets too and mine are said to compress to .035 so we'll see!! i'm getting real excited as i should be building and running this thing here in 2 weeks! wish me luck and i'll keep ya'll posted as to how she turns out!
 
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Old Feb 24, 2006 | 09:01 AM
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What is the part number of the Victor head gasket?? BTW, Kurt is quoting a VERY well known and respected authority in David Vizard(PHR link).
 
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