DCR question
06-16-2007, 10:38 AM
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DCR question Is 9:1 DCR too much for pump gas? I'm looking at building a 383 and with the heads I want and my current cam it pushes my dcr up to 9.3:1 or so with a SCR of around 12.5:1. I don't have Excel on this computer to see the real numbers but this is about what they were. This is going from a 346 to 383
I can get 93octane and even 110 here at the gas station but would prefer it to run on 93 since I like to travel and most places only carry up to 93.
Thanks
Ricky
I can get 93octane and even 110 here at the gas station but would prefer it to run on 93 since I like to travel and most places only carry up to 93.
Thanks
Ricky
06-16-2007, 10:43 AM
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http://www.empirenet.com/pkelley2/DynamicCR.html
It appears that most gas engines make the best power with a DCR between 7.5 and 8.5 on 91 or better octane...Race engines, using high octane race gas, can tolerate higher DCR's with 8.8:1 to 9:1 a good DCR to shoot for.
06-16-2007, 12:19 PM
#3
The link above, while giving an excellent explanation of DCR and how valvetiming affects it, appears to be written about Gen I small block chevy tech. That means we're not taking into consideration modern engine management or combustion chamber design. Since the original poster noted they are going from 346 to 383 cubes, I think we're safe assuming this is a Gen III engine.
I've seen several people here run DCR's as high as 8.8 with 93 octane pump fuel. You would be pushing to go to 9.0. At that level, you'll need a spot on tune, and even then you might need to add a little 110 when you're going to push it, or in hot air. I think 9.3 is probably too much to chance. It would be hella snappy at light loads, but the octane requirement is going to be a lot higher.
I've seen several people here run DCR's as high as 8.8 with 93 octane pump fuel. You would be pushing to go to 9.0. At that level, you'll need a spot on tune, and even then you might need to add a little 110 when you're going to push it, or in hot air. I think 9.3 is probably too much to chance. It would be hella snappy at light loads, but the octane requirement is going to be a lot higher.
06-16-2007, 03:47 PM
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Maybe a little more info might help. Being that the Z06 is the lightest OEM car with an LS1/LS6, and a manual trans, your resistance to detonation will be higher than say an automatic with a low stall converter in a heavy GTO or convertible F-Body.
If you are willing to share some more details, you may not be all that far off the mark...
If you are willing to share some more details, you may not be all that far off the mark...
06-16-2007, 06:12 PM
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I live in Milwaukee now so it doesn't get too hot up here very often. The car is 346 6speed. The cam is a custom grind 235/242 646/622 on a 111+0 icl. The cam looks like it will work well in a 346. As far as the 383 goes I was going to put a stroker kit in it only because the car has almost 70k miles and I would already have half of the engine apart. I do take the car on long trips like down to south GA (where my daughter lives) and down to Tampa.
As far as the heads I haven't ordered them yet. There are a lot of good choices out there. But I could get any cc that would help lower the DCR also.
Ricky
As far as the heads I haven't ordered them yet. There are a lot of good choices out there. But I could get any cc that would help lower the DCR also.
Ricky
