Stumped dcr/scr

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Nov 2, 2008 | 01:56 AM

WhiteRhino

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From: NV

Stumped dcr/scr

I've been messing with a couple different dcr calculators. Not sure if i'm doing it wrong or what. My dcr is between 9.1 and 9.9. My scr comes up between 12.0 and 12.99. Using caclulaters from here and some I googled. Wondering if someone could give me a hand. I need to get head gaskets and I want to make sure I get the right ones for my application, quench;etc. I haven't measured out of the hole. It's standard deck height. I was using .007 and .008 in the calculators.

3.905" bore
4.000" stroke
6.125" rod
-8cc Wiseco pistons, part #K394F3905

67cc Patriot p/p 806's with 2.05I-1.60E

Comp xr281hr 228-230/571-573
from cam card @.006 I-31--btdc 71--abdc
e-76--bbdc 28--atdc
duration @.006 tappet lift 281-283
110 icl/112lsa

I also have 1.8 crane/vinci gold race rockers. They're from my other motor, but i'm going to run them on this one as well.

Any help would be mighty appreciated !

Nov 2, 2008 | 03:41 AM

sandragnx

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With a .060 compressed head gasket,I come up with 10.2 to 1.

Nov 2, 2008 | 11:18 AM

405HP_Z06

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From: Arlington, Tx

Quote:

Originally Posted by WhiteRhino

I've been messing with a couple different dcr calculators. Not sure if i'm doing it wrong or what. My dcr is between 9.1 and 9.9. My scr comes up between 12.0 and 12.99. Using caclulaters from here and some I googled. Wondering if someone could give me a hand. I need to get head gaskets and I want to make sure I get the right ones for my application, quench;etc. I haven't measured out of the hole. It's standard deck height. I was using .007 and .008 in the calculators.

3.905" bore
4.000" stroke
6.125" rod
-8cc Wiseco pistons, part #K394F3905

67cc Patriot p/p 806's with 2.05I-1.60E

Cam:
Comp xr281hr 228-230/571-573
from cam card @.006
I-31--btdc 71--abdc
E-76--bbdc 28--atdc
duration @.006 tappet lift 281-283 110 icl/112lsa

I also have 1.8 crane/vinci gold race rockers. They're from my other motor, but i'm going to run them on this one as well.

Any help would be mighty appreciated

Using the above information and ASSUMING the block deck height is stock (9.240"), your piston deck height should be 0.

Calculation using a stock GM LS6 MLS head gasket:

Calculation using a custom Cometic 3.930" bore, .040" thick head gasket:

Nov 3, 2008 | 12:22 AM

WhiteRhino

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From: NV

That sounds better. I checked the block. It was decked. It's 9.228 instead of 9.240. I brought up a piston and put a straight edge on it. It's flush with the deck.

I'm still not sure about the scr though. On Wiseco's website it says with that piston it should be around 10.9 with a 67cc head. With a 4" stroke and 6.125 rod. I'm just confusing myself pretty good, overthinking. Here's a link to the Wiseco chart. It's under the ls 4" stroker-reverse dome chart.
http://www.wiseco.com/Catalogs/Automotive/Chevrolet.pdf

I want to get around 11.0 to 11.5 scr. I plan to mill the heads if need be.

Thanks for any help!

LS 4” Stroker- Reverse dome, Nitrous/Turbo 2618 alloy
Kit
Part # Bore Comp.
Ht. Stroke Rod 0 Deck at Std.
Deck Ht.
Avg.
Wt. Volume Compression ratio at:
65cc 67cc 68cc 70cc
Pin Part #
(Included

Nov 3, 2008 | 06:52 AM

405HP_Z06

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From: Arlington, Tx

Something doesn't add up. According to the Wiseco literature, a zero deck is achieved at a block deck height of 9.240 with the physical specifications provided. If I change the block deck height in the calculation to 9.228, the pistons should be .012 OUT of the hole for a -.012 piston to deck height. To ensure your compression ratio is correct, check to make sure your at absolute TDC for a few cylinders and recheck piston deck height.

Concerning the advertised compression ratios in the Wiseco literature, I do not know how they come up with the numbers they do. Math does not lie as long as all the parameters are correct, so if you see something incorrect please let me know and I'll change it. Otherwise, you have what you have.

Here is the calculation with a 9.228 block deck height:

To get 11:1 with the data provided, you would need to mill the heads from 67cc to 64cc (approximately .020 @ .0065 per cc). Here's the calculation:

To get 11.5:1 with the data provided, you would need to mill the heads from 67cc to 60cc (approximately .046 @ .0065 per cc). Here's the calculation:

Calculations use the following data points:
Block Deck: 9.228
Bore: 3.905
Stroke: 4.00
Rod Length: 6.125
Cam IVC: 71 @ .006
Piston CH: 1.115
Piston Dish: 8cc's
Piston Crown to top of top ring: .270
Piston deck height: -.012
Head gasket bore: 3.930
Head gasket thickness: .040

HTH,

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