Need help calculating DCR
07-02-2013, 10:13 AM
#1
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Need help calculating DCR After my first build it became apparent that I overlooked some detail regarding compression, so I'm going back through to fix it before it goes in my truck. I'm not a wizard, so I Googled a DCR calculator and went from there. However, I'm getting mixed results. Just looking to see if anyone can clear this up for me.
LS6
3.898x3.622
58cc chambers
4cc valve pockets
6.125" rods
.036" gaskets (3.910 bore)
Zero deck
Intake Valve closes 71 degrees ABDC
I figure this should put me around 8.5:1 DCR, but one calculator insists that I'm much lower than that. I haven't ordered the gaskets yet, but everything else is done. If I can clear this up I can order the correct gaskets and get her put together! Thanks again for all your help!
LS6
3.898x3.622
58cc chambers
4cc valve pockets
6.125" rods
.036" gaskets (3.910 bore)
Zero deck
Intake Valve closes 71 degrees ABDC
I figure this should put me around 8.5:1 DCR, but one calculator insists that I'm much lower than that. I haven't ordered the gaskets yet, but everything else is done. If I can clear this up I can order the correct gaskets and get her put together! Thanks again for all your help!
07-02-2013, 11:53 AM
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I've done some searching and I think 8.5 should be safe for pump gas but still aggressive. Anyone have some input on that before I make it happen?
07-02-2013, 12:44 PM
#4
from what I've read, 9.0 seems to be about the max you'd want to go assuming 93 octane. your mileage may vary though as it kind of varies setup to setup - but tight quench really helps with your detonation resistance. you've got the right idea running those 0.036" gaskets.
just my 0.02..
just my 0.02..
07-02-2013, 12:52 PM
#5
I'm about 8.5 with a tight quench and I am still getting a bit of detonation above about 80F at high throttle input. I just stepped down to TR6 plugs to see if that would help, but I doubt it. I was going to move my catch can, but decided where I was going to put it was a nice place to put a methanol pump. So I also just finished a meth injection system. I kinda wish I had a little more DCR now. .
FYI, you may need to back the timing off a bit from my experience to run 8.5. . .but probably not much. I'd say that's about as far as I'd push it unless I was committed to running race fuel or meth.
FYI, you may need to back the timing off a bit from my experience to run 8.5. . .but probably not much. I'd say that's about as far as I'd push it unless I was committed to running race fuel or meth.
07-02-2013, 01:11 PM
#6
8.5:1 seems about right. Why is it zero decked? Did you assemble the LS6 or buy a crate motor?
Also for weasel - are you running 93 octane? I'm going to be 8.5:1 DCR in mine (unless I flycut and mill down - then I'm aiming for 8.7:1 optimally or maybe 8.8:1 to get a little more aggressive). And I'm in Florida where it's 95+100% humidity. My engine will be breathing hot, wet soup.
I have looked into doing a methanol kit tho. That was suggested by some knowledgeable people as a way to increase timing and safety even NA with high DCR.
Also for weasel - are you running 93 octane? I'm going to be 8.5:1 DCR in mine (unless I flycut and mill down - then I'm aiming for 8.7:1 optimally or maybe 8.8:1 to get a little more aggressive). And I'm in Florida where it's 95+100% humidity. My engine will be breathing hot, wet soup.
I have looked into doing a methanol kit tho. That was suggested by some knowledgeable people as a way to increase timing and safety even NA with high DCR.
07-02-2013, 01:19 PM
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Well to be honest, I haven't properly checked my deck. OK OK I guess I will......but those pistons come up damn flat with the deck. I put the motor together myself. Anyways, I'm gonna put the gaskets on order and worst case scenario, if I can't get it to stop detonating (if it even does) then I can simply swap gaskets. Then there's pushrods...oh nothing can be easy can it?
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07-02-2013, 02:43 PM
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I really do know better. I'll have to borrow or purchase a dial indicator but that's no big deal. If I recall correctly, a fingernail won't catch on it but damn it's sooo close. But to answer my question, are my calculations (given the mentioned values) correct? At least that way I'll know for sure I'm on the right track when I get that last piece squared away.
07-02-2013, 03:49 PM
#13
8.5:1 seems about right. Why is it zero decked? Did you assemble the LS6 or buy a crate motor?
Also for weasel - are you running 93 octane? I'm going to be 8.5:1 DCR in mine (unless I flycut and mill down - then I'm aiming for 8.7:1 optimally or maybe 8.8:1 to get a little more aggressive). And I'm in Florida where it's 95+100% humidity. My engine will be breathing hot, wet soup.
I have looked into doing a methanol kit tho. That was suggested by some knowledgeable people as a way to increase timing and safety even NA with high DCR.
Also for weasel - are you running 93 octane? I'm going to be 8.5:1 DCR in mine (unless I flycut and mill down - then I'm aiming for 8.7:1 optimally or maybe 8.8:1 to get a little more aggressive). And I'm in Florida where it's 95+100% humidity. My engine will be breathing hot, wet soup.
I have looked into doing a methanol kit tho. That was suggested by some knowledgeable people as a way to increase timing and safety even NA with high DCR.
07-02-2013, 03:52 PM
#14
Also for weasel - are you running 93 octane? I'm going to be 8.5:1 DCR in mine (unless I flycut and mill down - then I'm aiming for 8.7:1 optimally or maybe 8.8:1 to get a little more aggressive). And I'm in Florida where it's 95+100% humidity. My engine will be breathing hot, wet soup.
I have looked into doing a methanol kit tho. That was suggested by some knowledgeable people as a way to increase timing and safety even NA with high DCR.
I have looked into doing a methanol kit tho. That was suggested by some knowledgeable people as a way to increase timing and safety even NA with high DCR.
