How much compression for new motor in summer Florida heat?
05-16-2010, 12:56 PM
#1
How much compression for new motor in summer Florida heat? Building a new LS3 to replace the LS1, and I've read a few posts about the motor actually making better power when you reduce the compression a little bit, because it allows you to run more timing before you encounter knock retard... and I've heard the LS3 likes timing. I have access to 92-93 octane, but it can contain up to 10% ethanol IIRC.
LS3 compressed gasket: .051
LS3 gasket bore diameter: 4.083
Deck clearance: 0.011 above deck
Stroke: 3.622
Cylinder Bore: unsure, honed for piston below, maybe 4.072?
piston diameter: 4.07
piston volume: flat top w/ 5cc reliefs
rod: 6.125
top land height: 0.177 (guess)
piston to wall clearance: .002 (guess)
With a 64cc chamber, that seems to put my SCR around 10.95, and with an advertised IVC of 65-66, DCR should be around 8.6. 65cc would be 10.8/8.5, etc.
So, what are the chances I'll run into premature knock? If there is cause for concern, how much should I drop the compression?
Thanks!
LS3 compressed gasket: .051
LS3 gasket bore diameter: 4.083
Deck clearance: 0.011 above deck
Stroke: 3.622
Cylinder Bore: unsure, honed for piston below, maybe 4.072?
piston diameter: 4.07
piston volume: flat top w/ 5cc reliefs
rod: 6.125
top land height: 0.177 (guess)
piston to wall clearance: .002 (guess)
With a 64cc chamber, that seems to put my SCR around 10.95, and with an advertised IVC of 65-66, DCR should be around 8.6. 65cc would be 10.8/8.5, etc.
So, what are the chances I'll run into premature knock? If there is cause for concern, how much should I drop the compression?
Thanks!
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05-17-2010, 10:16 PM
#9
I have run 12:1 SCR and over as well on the street, but the cam timing will have more to do with detonation than your 11:1 or 12:1 SCR.
Jim:
.006 lift 271/279
.050 lift 222/230
112 LSA
IV close @ 41 ABDC
I'll show you how to check it out and verify to be sure.
Jim:
.006 lift 271/279
.050 lift 222/230
112 LSA
IV close @ 41 ABDC
I'll show you how to check it out and verify to be sure.
05-18-2010, 09:01 AM
#10
This is what I'm seeing as calculated, actual may be different... assuming a 65.5 advertised IVC (which what I used above), that leaves me at 10.95 SCR and 8.6 DCR. I guess we'll need to degree the cam before milling the heads. Can we determine the .200 durations while degreeing?
Code:
0.006 0.05 Intake Duration 271.0 222.0 Exhaust Duration 279.0 230.0 IVO 25.5 1 IVC 65.5 41 EVO 73.5 49 EVC 25.5 1 Overlap 51 2 Overlap Bias 0.0 0.0 Neutral Neutral Lobe Separation Angle 112.0 Intake Centerline 110.0 Exhaust centerline 114.0
05-18-2010, 04:26 PM
#18
You just need to make sure its all working PROPERLY and clean. And that means clean the condensor every 2 years, its the most overlooked maintenance item for a cooling system. A dirty condensor KILLS your cooling ability.
The best mod though, is to put in an LT1 radiator in place of you LS1 radiator, it truly makes a noticable difference. I did this like 6 years ago and my 427ci down here in hot *** south Florida runs crazy cool, no matter what I'm doing.
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05-18-2010, 06:57 PM
#19
I'm not spending a $1000 on a Dewitts radiator LOL. I've never heard about using a LT1 radiator instead of a LS1... what's the physical difference? I've not personally cleaned out the condenser since I bought the car, I do not know if a shop may have done so during previous jobs. Maybe we'll have time to check/clean it out this time.
05-18-2010, 07:23 PM
#20
I'm not spending a $1000 on a Dewitts radiator LOL. I've never heard about using a LT1 radiator instead of a LS1... what's the physical difference? I've not personally cleaned out the condenser since I bought the car, I do not know if a shop may have done so during previous jobs. Maybe we'll have time to check/clean it out this time.
The LT1 radiator simply has more cooling area, from what I've heard something like 30% more. When I put mine in I noticed the extra cooling big time. The only thing you need to do is cap off one extra port. One clamp, one cap. As far as the install, you would never know you are putting an LT1 radiator in......I didn't lol. When I ordered mine the parts guy ordered the wrong one, I took it home and put it in. I just figured the extra port was something they did for the later model LS1's, so I actually use that as my new drain valve for flushing. Works great and I don't have to mess with that cheesy petcock drain that takes all day to drain. And a new LT1 radiator is only like $100.
Post #6, your thread about Florida coolant temps. That is my condensor when I cleaned it the first time, I think in 2002. So thats 4 years of debris jamming up my condensor. I would come to a stop with my A/C on and it would start warming up immediately and my engine temp would immediately start to climb. When I started moving it would get cold again and the engine temp would also go down from that strong ram air, fans just can't keep up when your stopped or moving slowly in traffic. After I cleaned it my A/C was ice cold no matter what, no matter how hot it was outside, even stopped in traffic....and the overall temp was considerably cooler, maybe 15 degrees on the guage. And I know they're just gauges, but it was showing much cooler. I clean my condensor ever year or so.
https://ls1tech.com/forums/general-m...ning+hot+a%2Fc
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Last edited by LS6427; 05-18-2010 at 07:48 PM.