Too much DCR?

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Launching!

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Too much DCR?

I used the calculator at United Machine, which seems to be pretty simple, and the results were a bit disturbing, to say the least. Mike @ TEA told me the heads are OTW, so install time is soon. The numbers I came up with are kind of scary, so I'm hoping I did it wrong. The particulars are stock LS6 bottom, heads milled to 61cc, and Cometic .040 gaskets. The cam is a Crane 228/232 .600/.600 @ 112 LSA +0 advance. The cam card says intake closes at 45.0 ABDC @ .050 lift and 236 Deg. duration. Advertised duration is 298/302 at 80.0 ABDC and .004 lift. I'd sure appreciate any help/suggestions, as the calculator said static was 11.3, which is not too bad, but DCR worked out to 10.2.

Jul 7, 2006 | 02:21 PM

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From: Victoria, TX

Your calculator uses duration at .006". You're using duration at .004". Big difference sometimes. Try plugging in 278/282 for the duration at .006". With .600" lift, the grind is very close to a Comp XE-R lobe in valve action, so just add 50 degrees to the duration at .050" to get the duration at .006".

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Jul 7, 2006 | 02:25 PM

slow67

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I'm not sure how you got 10.2 DCR, but I managed to get 9.5 using .050 ABDC +15 and 8.0 using advertised duration. I think you'll be okay with that cam and those heads.

Jul 7, 2006 | 02:26 PM

ringram

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You need to put in the duration at 0.006 not 0.050.

Jul 7, 2006 | 02:33 PM

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According to cranes website, the .006 duration for that cam is 290/294. With those specs, you'll have 11:5:1 SCR and 8:1:1 DCR. You could use a little more DCR, but it's pretty good.

Jul 7, 2006 | 02:33 PM

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Wow, those lobes are pretty lazy compared to Comps.

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Jul 7, 2006 | 02:39 PM

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Quote:

Originally Posted by Patrick G

Wow, those lobes are pretty lazy compared to Comps.

Yea, Crane has never had a really quick lobe. That's why I checked after I saw your first post. Seemed kinda strange.

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Jul 7, 2006 | 02:56 PM

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From: Shreveport, LA

Quote:

Originally Posted by exSSer

Cranes most aggressive is still fairly lazy compared to Comps. I'm using the same calculator as you, but the number one thing I can see, is that you need to enter -.007" for your deck height.
Assuming you have a stock short you should enter:
61cc's
0
.040
3.910
3.898
-.007
3.622
6.100 (guessing on rod legnth)
77* IVC

Jul 7, 2006 | 03:09 PM

#10

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Launching!

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Quote:

Originally Posted by Beast96Z

OK, thanks. I plugged in your numbers and got SCR of 11.5, and DCR or 8.2. Two more stupid questions. Would these be OK on 92 oct, and how did you arrive at the 77* number for IVC? The Crane card says @ .050 lift, the IVC is 45 deg and 236 duration, and if I add 15 to this I get only 60*. It seems the IVC number is vitally important to these calcs, and also the most elusive.

Jul 7, 2006 | 03:13 PM

#11

ArcticZ28

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8.1:1 DCR will be fine on 92.

Jul 7, 2006 | 03:14 PM

#12

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From: Victoria, TX

Using J-Rod's calculator, I come up with 11.30:1 SCR and 8.05:1 DCR. I trust this DCR figure based on how it compares to other cams of comparable duration, LSA, and ICL.

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Jul 7, 2006 | 03:25 PM

#13

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Launching!

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Thanks for the help, guys. I don't have Excell, so I can't use the calculators based on that, and the one @ united machine doesn't even use duration numbers, just IVC @ .050 plus 15*. Since everything depends on this number to make the DCR, that # is easily skewed.(screwed) If that SCR is OK with pump gas, I guess I'll stick with the Cometics, and not use the MLS GM gaskets.

Jul 7, 2006 | 03:29 PM

#14

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If your pistons are not flycut, you may run into P to V problems with 290/294 @ .006". Be sure to check before you turn over the motor.

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Jul 7, 2006 | 03:34 PM

#15

ringram

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The united machine calc assumes 0.006 duration I believe, it says at 15* as an approximation. What you should really do is put in the 0.006 duration, which is what I think Beast96Z did for you.

Jul 7, 2006 | 03:54 PM

#16

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Launching!

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Quote:

Originally Posted by Patrick G

If your pistons are not flycut, you may run into P to V problems with 290/294 @ .006". Be sure to check before you turn over the motor.

Actually the 290/294 is at .004 via Crane.

The heads are the Trickflows, which give more PTV. Anyway, TEA said they'd work. We brainstormed the pkg, and came up originally with 10.6 SCR, so decided to mill to 61.(from 64)

Just don't want to screw it all up with the wrong cam. I was going for a good low-end, but even better mid range, with decent drivability, and a mild lope. Car's NOT a racer, but a weekend plaything/ occaisional short trip car. ('02 ZO6)

Jul 7, 2006 | 06:09 PM

#17

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Quote:

Originally Posted by exSSer

Actually the 290/294 is at .004 via Crane.

In your first post, you said advertised at .004" was 298/302. No were on Cranes sight did I see it say the 290/294 was at .004". Going by Cranes lobe profiles, the 290/294 seems about right for .006". To get the IVC I was using, use the IVC calculator. 294 divided by 2, plus ICL, minus 180, equals IVC @ .006".

Jul 7, 2006 | 07:21 PM

#18

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Launching!

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Quote:

Originally Posted by Beast96Z

I originally printed out the wrong cam card. The first one is for a 236 cam. The actual numbers for the cam I have are 290*/294* advertised dur. @ .004, and IVC 76ABDC at same. Sorry. So I have to convert the 290/294 to their correct values @ .006 lift, and Iwas told to add 50 to the duration @ .050, which is 228*. So instead of starting with the 290, I should start with 278, right?

Jul 7, 2006 | 07:31 PM

#19

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From: Victoria, TX

That gets me back to my original post of 278/282.

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Jul 7, 2006 | 09:35 PM

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