383 piston selection
03-28-2004, 12:01 PM
#16
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rskrause thanks man your awesome! I was going to have the block decked to .005. What is the thickness of the 1074's right now I am running the impala gasket but cant remember the part number. Thanks for all the advice. So as long as I deck the block I should be ok??? All advice is greatly appreciated!
03-28-2004, 12:23 PM
#17
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Originally posted by rskrause
Assuming zero deck (flat part of piston crown flush with block deck), and the FelPro #1074 gasket the DCR with the CC306 would be 8.25:1 with a -16cc piston. This is a little high for 93 octane, but close. So, it looks like you did pretty good just guesstimating it! You might want to consider a -0.010" deck. This would lower DCR to 8.06:1 but would also increase the quench to the upper limit of what is desireable. The general opinion is that quench should be not >0.045". However, I question that to a point when I consider that the stock LT1, which runs pretty good for a high CR motor on pump gas, has a quench of ~0.075". If it were me, I think I'd go 0.005" or 0.010" down in the hole with the -16cc pistons to lower the DCR just a tad.
Rich Krause
Assuming zero deck (flat part of piston crown flush with block deck), and the FelPro #1074 gasket the DCR with the CC306 would be 8.25:1 with a -16cc piston. This is a little high for 93 octane, but close. So, it looks like you did pretty good just guesstimating it! You might want to consider a -0.010" deck. This would lower DCR to 8.06:1 but would also increase the quench to the upper limit of what is desireable. The general opinion is that quench should be not >0.045". However, I question that to a point when I consider that the stock LT1, which runs pretty good for a high CR motor on pump gas, has a quench of ~0.075". If it were me, I think I'd go 0.005" or 0.010" down in the hole with the -16cc pistons to lower the DCR just a tad.
Rich Krause
The Fel Pro 1074 gaskets have a gasket bore of 4.125" and a compressed thickness of .039".
www.smokemup.com has a great CR calc.
03-28-2004, 04:29 PM
#18
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Originally posted by Dave88LX
Is there a write-up somewhere of static vs dynamic CR?
The Fel Pro 1074 gaskets have a gasket bore of 4.125" and a compressed thickness of .039".
www.smokemup.com has a great CR calc.
Is there a write-up somewhere of static vs dynamic CR?
The Fel Pro 1074 gaskets have a gasket bore of 4.125" and a compressed thickness of .039".
www.smokemup.com has a great CR calc.
Rich
03-28-2004, 07:21 PM
#21
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For a brief explanation of DCR that I wrote you can go to www.kennedysdynotune.com and click on "Tech Tips" at the bottom of the left hand menu. Follow the link to "Dynamic Compression Ratio Explained".
Here's a DCR calculator: http://www.kb-silvolite.com/calc.php?action=comp
Rich
Here's a DCR calculator: http://www.kb-silvolite.com/calc.php?action=comp
Rich
03-28-2004, 08:06 PM
#22
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Search "Advanced Tech" for more on "dynamic compression".
Yeah, I remember when this was a new term here at CamaroZ28.com.
By the way, target DCR for my engine was, "somewhere between 8.5-9.0:1". This coming from a gentlemen who has countless hours of dyno time in developing power with his own LT1. I took that advice, settling on 8.8:1 DCR. No detonation here fwiw.
-Mindgame
Yeah, I remember when this was a new term here at CamaroZ28.com.
By the way, target DCR for my engine was, "somewhere between 8.5-9.0:1". This coming from a gentlemen who has countless hours of dyno time in developing power with his own LT1. I took that advice, settling on 8.8:1 DCR. No detonation here fwiw.
-Mindgame
03-28-2004, 08:21 PM
#23
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Originally posted by Mindgame
Search "Advanced Tech" for more on "dynamic compression".
Yeah, I remember when this was a new term here at CamaroZ28.com.
By the way, target DCR for my engine was, "somewhere between 8.5-9.0:1". This coming from a gentlemen who has countless hours of dyno time in developing power with his own LT1. I took that advice, settling on 8.8:1 DCR. No detonation here fwiw.
-Mindgame
Search "Advanced Tech" for more on "dynamic compression".
Yeah, I remember when this was a new term here at CamaroZ28.com.
By the way, target DCR for my engine was, "somewhere between 8.5-9.0:1". This coming from a gentlemen who has countless hours of dyno time in developing power with his own LT1. I took that advice, settling on 8.8:1 DCR. No detonation here fwiw.
-Mindgame
Rich
03-28-2004, 08:25 PM
#24
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Hey to you Rich.
We're in agreement. It is always better to err on the safe side of things.
I know when I discussed this with our good pal Chuck Riddeck here a year ago he mentioned alot of cooling system modification for running in the 9.0 (+ or - .2) range safely.
Then it depends on the temps where you live! Can imagine that this would be alot tougher in Las Vegas than say, Michigan. Those ambient temps play in there too. So yeah, safe is good.
-Mindgame
We're in agreement. It is always better to err on the safe side of things.
I know when I discussed this with our good pal Chuck Riddeck here a year ago he mentioned alot of cooling system modification for running in the 9.0 (+ or - .2) range safely.
Then it depends on the temps where you live! Can imagine that this would be alot tougher in Las Vegas than say, Michigan. Those ambient temps play in there too. So yeah, safe is good.
-Mindgame
03-29-2004, 09:43 AM
#26
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This has definitly turned into a helpful topic! Hey since everyone is here....does it make any difference that the cam is ground on a 114 LSA?(cc306) or if I switch to a similar or bigger XE grind cam? What would that do for DCR? Thanks alot!!!
03-29-2004, 11:01 AM
#27
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Check out poly dyn in houston, tx. They offer coated wiesco piston/ring sets for what summit or jegs offer for noncoated. Have them in son's 383 LT1. Work very well with about 10:1 comp. http://www.polydyn.com/
03-29-2004, 11:06 AM
#28
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Depends on what you're using the car for.... If you're using it strictly NA, I'd say that you'd be good getting a cam on a 110 or 112 LSA and 106-108 ICL.
For Nitrous and NA, I'd go 112 LSA.
For a blower car, I'd say 114-116 LSA.
You can somewhat lower the DCR with a bigger cam with more valve overlap on a lower LSA.
Honestly, though.. for a 383, I wouldn't go anything less than a CC306, unless you're looking at a blower motor.
Mike
For Nitrous and NA, I'd go 112 LSA.
For a blower car, I'd say 114-116 LSA.
You can somewhat lower the DCR with a bigger cam with more valve overlap on a lower LSA.
Honestly, though.. for a 383, I wouldn't go anything less than a CC306, unless you're looking at a blower motor.
Mike
03-29-2004, 11:14 AM
#29
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The car already has a cc306 114lsa installed. I did that last yr and has very low miles so I was thinking about just running that adgain this yr. But cams are cheap and with it torn apart I could swap it in a sec. That is why I am thinking of going to a bigger XE grind. The car made plenty of power but I would liike a lower power band. Car will be sprayed on occasion. 150hit max. If you can recomend a better cam for the 383 throw the numbers at me. Thanks again.
04-18-2004, 12:43 PM
#30
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I'm in a similar boat with my 383 rebuild build - I've selected my cam, pistons and heads and want a compression ratio where I can stay on pump gas when N/A, but run a race gas mix (or all race gas if neccesssary) when spraying 250-300 shot.
Cam 236/248 comp XE on 114 - with 1.7/1.6 rockers 600/600 lift
Wiseco flat tops - 5.4 cc dish (valve reiefs actually)
5.7 rod
61cc chamber AFR LT4
Problem is, when my engine was orginally built 5 years ago, neither I, nor the machinist remebers if the block has been decked. I dont think it has, so I'd like to take it to .005 this time, but I've got to make sure it will live at zero.
Rich - can you tell me what the DCR would be with .005 and 0.0 deck height?
I've calculated the static to be 11.315 and 11.46 respectively.
Any help would be appreciated.
BTW - I'm currently running the 236/248 cam, and am pretty fixed on the rod and piston choice - but the head chambers can be 56-74, as long as I dont wait to long to place the order change.
Cam 236/248 comp XE on 114 - with 1.7/1.6 rockers 600/600 lift
Wiseco flat tops - 5.4 cc dish (valve reiefs actually)
5.7 rod
61cc chamber AFR LT4
Problem is, when my engine was orginally built 5 years ago, neither I, nor the machinist remebers if the block has been decked. I dont think it has, so I'd like to take it to .005 this time, but I've got to make sure it will live at zero.
Rich - can you tell me what the DCR would be with .005 and 0.0 deck height?
I've calculated the static to be 11.315 and 11.46 respectively.
Any help would be appreciated.
BTW - I'm currently running the 236/248 cam, and am pretty fixed on the rod and piston choice - but the head chambers can be 56-74, as long as I dont wait to long to place the order change.