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  #16 (permalink)  
Old 12-23-2012, 02:15 PM
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Quote:
Originally Posted by cdminter59 View Post
bjautos7, The XR282HR will work fine with your combination. Using CamQuest6 software your combination will produce around 470 hp. I think that is in the hp range you wanted. Like you said your compression is 10.017 and the DCR is 8.521 with the xr282hr-10 camshaft. It should run fine on your 98 octane gas.

thanks for that and hoping to push it a bit more with the 1.6 rocker , with port matching the intake with the heads and adding a 1 inch spacer.
i to worked out the static compression to be 10.017 but come up with 7.879 for dynamic compression.

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  #17 (permalink)  
Old 12-23-2012, 06:41 PM
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Quote:
Originally Posted by cdminter59 View Post
bjautos7, The XR282HR will work fine with your combination. Using CamQuest6 software your combination will produce around 470 hp. I think that is in the hp range you wanted. Like you said your compression is 10.017 and the DCR is 8.521 with the xr282hr-10 camshaft. It should run fine on your 98 octane gas.
Looks like a winner to me
Should make a really stout runner.
Thanks for the calculations CD.
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Old 12-23-2012, 09:44 PM
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Quote:
Originally Posted by bjautos7 View Post
thanks for that and hoping to push it a bit more with the 1.6 rocker , with port matching the intake with the heads and adding a 1 inch spacer.
i to worked out the static compression to be 10.017 but come up with 7.879 for dynamic compression.
The intake valve closing number you are using is at 0.006 lift. You need the intake valve closing at .050 which is .041.
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Old 12-23-2012, 11:41 PM
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Originally Posted by cdminter59 View Post
The intake valve closing number you are using is at 0.006 lift. You need the intake valve closing at .050 which is .041.
ok thanks , yes i did work it at when the intake closed at abdc which is 67 which give me 7.879 for dynamic compression.

can you please show me how you calculated the intake valve closing at abdc 0.50 lift.
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Old 12-24-2012, 02:01 AM
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Originally Posted by bjautos7 View Post
can you please show me how you calculated the intake valve closing at abdc 0.50 lift.
Here, I'll show you how to do it.....
We'll use this cam since I already have it copied.....
http://www.compcams.com/Company/CC/c...x?csid=87&sb=0
Draw a circle on a piece of paper, about 1" to 2" in diameter. Size doesn't matter (in this case, LOL). Visualize the circle as an analog clock face. Make a mark on the circle line at 11:00 O'Clock. Mark it IVO. This will be the intake opening point @0.050". Make a mark on the circle at 4:00 O'Clock. Mark it IC. This will be the intake centerline, or highest lift point of the lobe. Make a mark at 8:00 O'Clock. Mark it IVC. This will be the intake closing point @0.050".

You see on the cam card that the intake duration @0.050" is 230 degrees. Write 230 in the middle of the circle so you can reference it. Draw a line under the 230 and write 115 (half the 0.050" duration) so you can reference it.

Now, beginning at IC, move counter-clockwise around the circle until you reach 115 degrees from the IC. You will be using up 106 degrees to get back to top dead center and will have 9 degrees left over. Write in 9 at the 11:00 O'Clock mark you made on the circle. Now we know that the intake valve opens @ 9 degrees before top dead center. We can prove this by adding 9 plus 106 to equal 115. See, that's why I had you write 230/115 in the middle of the circle, so you could prove your work.

Now, we know that the intake valve will not close before the piston gets to the bottom of the stroke and heads back toward top dead center. Therefore, going clockwise from the intake opening point, we can add 9 and 180 and find that we have 189 degrees of 0.050" duration from the time the intake valve opens to the time the piston gets to bottom dead center. (180 degrees in a half-circle). Referring to the middle of your circle and using the 230 you have written there, subtract 189 from 230 and find 41 degrees. That's the intake closing point @0.050" tappet lift. Prove your work by adding 189 and 41 to produce 230.

After you have done this a number of times, you can do the math in your head without the circle.

One of you guys could do a good deed by posting this on the wiki. I don't need any more wiki credit, let's get someone else started......
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  #21 (permalink)  
Old 12-24-2012, 03:33 AM
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thank you so much , will have go through it a couple of time's to get my head around it. just go's to show a little mistake can have a big impack on a engine build.
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Old 12-24-2012, 07:36 AM
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new build 383 and a big hi

I do it a different way. Take your cam's intake duration at .050 which is 230. Divide 230 by 2 = 115 add the LSA 110, 115 + 110 = 225 - the ground in advance, LSA - ICL = ground in advance, 225 - 4 = 221 - 180 = 41 for intake valve closing at .050. If you want intake valve closing on the seat you take the advertised intake duration 282/2=141 141+110 = 251-4 = 247-180= 67 intake valve closing on seat. Comp cams says this happens at 0.006 lift.
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Old 12-24-2012, 09:18 AM
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bjautos7, I do it a different way than either cdminter59 or techinspector1. I just go to this webpage with a cam degree calculator and enter the intake duration, exhaust duration, LSA, and ICL, it does the rest! wallaceracing.com cam degree calculator Here's a screenshot of the calculator, it's very easy to use:



After entering the advertised figures for your cam and clicking on "calculate" here's the screen shot:



I don't mean to hijack bjautos7's thread, but I will direct this question to techinspector1 and cdminter59. Using the KB dcr calculator and the Wallace Racing cam degree calculator I get the same figures you guys are quoting. But, the figures using advertised duration and the figures using the .050 duration plus 15* are so different, about .6. Since the KB calculator uses a "generic" rule of using the .050 duration plus 15*, and the cams have much more than 30* difference between the advertised and the .050 durations, wouldn't the figures using the advertised duration be more accurate? Since the answers give a difference in the dcr of about .6? I have also figured with the Pat Kelley dcr calculator and the figures are almost exactly the same as the figures I get using the KB calculator and the Wallace Racing calculator using the advertised durations.

Last edited by BigEd36; 12-24-2012 at 09:29 AM.
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Old 12-24-2012, 06:17 PM
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Quote:
Originally Posted by cdminter59 View Post
I do it a different way. Take your cam's intake duration at .050 which is 230. Divide 230 by 2 = 115 add the LSA 110, 115 + 110 = 225 - the ground in advance, LSA - ICL = ground in advance, 225 - 4 = 221 - 180 = 41 for intake valve closing at .050. If you want intake valve closing on the seat you take the advertised intake duration 282/2=141 141+110 = 251-4 = 247-180= 67 intake valve closing on seat. Comp cams says this happens at 0.006 lift.
thanks this is great , makes it easyer to under stand and remeber.
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Old 12-24-2012, 06:29 PM
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new build 383 and a big hi

BigEd36, After reading the webpage again from Pat Kelly I agree with you that using the advertised duration would be more accurate. According to this article it makes more sense to use seat times to calculate the DCR.
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  #26 (permalink)  
Old 12-24-2012, 06:59 PM
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Originally Posted by cdminter59 View Post
BigEd36, After reading the webpage again from Pat Kelly I agree with you that using the advertised duration would be more accurate. According to this article it makes more sense to use seat times to calculate the DCR.
so are you saying i had it right at 7.879 for dynamic compression then , as i use the the seat which was 67.
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Old 12-24-2012, 07:48 PM
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Originally Posted by bjautos7 View Post
so are you saying i had it right at 7.879 for dynamic compression then , as i use the the seat which was 67.
That's exactly what I came up with, 7.879. But if you use the KB calculator's instructions of "intake closing angle at .050 plus 15 degrees" you will get an intake closing angle of 41*, 41* plus 15* equals 56*, if you use that figure you will get the 8.521 that cdminter59 came up with.
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Old 12-25-2012, 02:34 PM
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That's exactly what I came up with, 7.879. But if you use the KB calculator's instructions of "intake closing angle at .050 plus 15 degrees" you will get an intake closing angle of 41*, 41* plus 15* equals 56*, if you use that figure you will get the 8.521 that cdminter59 came up with.

thats great would rather have at 7.8 for a street car , and will just run fine on pump gas.
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Old 12-25-2012, 03:29 PM
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Originally Posted by F-BIRD'88 View Post
Vinny:
Their pump gas octane rating is no the same as ours R+M/2.
Theirs is European Din rated. Essentially R only rated. Their 98 is the same as our 92.
Oh!..... Now THAT'S starting to put things into perspective.. i'tallways had my head screwed how you guys could run those compression ratios on say 91
No way in da e'fen world I could run my stuff on our 91 here in AUS
I'm assuming NZ and AUS use the same rating now..

Thanks F-BIRD'88 for that bit of info, REALLY clears up a LOT of questions for me!

Duke
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Old 12-26-2012, 08:11 PM
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.. I would have used flat top pistons for a cam that size and just added some kerosene or other octane booster to the gas if needed. Yielding 500+ HP. Better MPG for extensive street use. I like to make power with high compression and great heads, self-ported, with backcut radiused valves and radiused seats, rather than an oversized cam like the XR300...

.. Although not a high compression engine, this article shows how an engine with well ported stock heads and a smallish 204/214 cam can make a surprising amount of power:

Chevy Small Block Build - Mildly Amusing - Super Chevy Magazine

.. And this dyno chart compares 11:1 350" (top curve) to 11:1 327" (2nd curve) and 9:1 350" (bottom curve). Both 350's have same cam, 327 has slightly smaller cam. Shows what high compression can do for you:


Last edited by BuzzLOL; 12-26-2012 at 08:38 PM.
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