Need to lower compression > Are 6.0 heads the answer?
Thread Starter
TECH Fanatic
Joined: Nov 2001
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From: SW Florida
Re: Need to lower compression > Are 6.0 heads the answer? y2khawk .....
That sure is a nice looking engine! <img border="0" title="" alt="[Eek!]" src="gr_eek2.gif" />
Looks like a nice selection of parts.
Thanks everyone....
That sure is a nice looking engine! <img border="0" title="" alt="[Eek!]" src="gr_eek2.gif" />
Looks like a nice selection of parts.
Thanks everyone....
TECH Senior Member
Joined: Nov 2001
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Re: Need to lower compression > Are 6.0 heads the answer? Another vote for pistons here too <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />
Definitely the way to go IMO <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />
Then get a nice aggressive port on your stock heads and heavy duty 2.02/1.57 valves with a decent turbo cam.
Cheers,
Chris
Definitely the way to go IMO <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />
Then get a nice aggressive port on your stock heads and heavy duty 2.02/1.57 valves with a decent turbo cam.
Cheers,
Chris
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From: Phoenix, AZ
Re: Need to lower compression > Are 6.0 heads the answer? OK, here I am! I posted also in the FI section but didn't get answers. I spend so much time in there I forget there are other forums <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />
I know doing the bottom end is the best way . . . I really don't want to take it to that limit though. I'm soooooo tired of working instead of driving. I just need something that will help me get past the bad combo of 10.1 CR / 115F temps / 91 octane. I also spoke with TEA and they said they could safely get it close to 9:1 CR. And I'm of the thought that these pistons can handle some serious power as long as you stay away from detonation. Don't the GN's and TTA's have hypereutic ( sp ) pistons also??
- Dug
I know doing the bottom end is the best way . . . I really don't want to take it to that limit though. I'm soooooo tired of working instead of driving. I just need something that will help me get past the bad combo of 10.1 CR / 115F temps / 91 octane. I also spoke with TEA and they said they could safely get it close to 9:1 CR. And I'm of the thought that these pistons can handle some serious power as long as you stay away from detonation. Don't the GN's and TTA's have hypereutic ( sp ) pistons also??
- Dug
Teching In
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Posts: 42
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From: Korea
Re: Need to lower compression > Are 6.0 heads the answer? Hey Kimchee and Rice what part of Korea do you have to go back to because I was on my midtour from June 20 to July 18 and now I'm back here listing to my wife say yah, I just raced an SS and laughing in my face. But let me know I'm in Osan for another 5 and a half months.
98 BLK WS6 M6, hurst shifter, SLP loudmouth, C/F MTI lid, freemods, ported MAF, Z06 clutch 331rwhp 358rwtq.
98 BLK WS6 M6, hurst shifter, SLP loudmouth, C/F MTI lid, freemods, ported MAF, Z06 clutch 331rwhp 358rwtq.
Adkoonerstrator
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From: Deep in the seedy underworld of Koonerville
Re: Need to lower compression > Are 6.0 heads the answer? You don't like my "Spark plug spacer" idea?
<img border="0" alt="[bullshit]" title="" src="graemlins/gr_bs.gif" /> <img border="0" title="" alt="[Razz]" src="gr_tounge.gif" /> <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" /> <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />
<img border="0" alt="[bullshit]" title="" src="graemlins/gr_bs.gif" /> <img border="0" title="" alt="[Razz]" src="gr_tounge.gif" /> <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" /> <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />
Thread Starter
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From: SW Florida
Re: Need to lower compression > Are 6.0 heads the answer? I will be back in Korea on Sun 28, Jul
I run the flight simulators down at Camp Humpherys. Thats a 30 minute drive south of Osan.
Ron,
I run the flight simulators down at Camp Humpherys. Thats a 30 minute drive south of Osan.
Ron,
Thread Starter
TECH Fanatic
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From: SW Florida
Re: Need to lower compression > Are 6.0 heads the answer? XLR8NSS....
The infamous "Spark Plug Spacer Mod"!...
Thats the best one i've heard in a long while.
Great Idea! <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />
The infamous "Spark Plug Spacer Mod"!...
Thats the best one i've heard in a long while.
Great Idea! <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />
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Verdad Gallardo TECH Resident
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From: Phoenix, AZ
Re: Need to lower compression > Are 6.0 heads the answer? MellowYellow . . . it ain't broke, but it ain't working like it should either. I just raced what appeared to be a stock C5 the other day. I didn't beat him by much, and I'm twin-turbo. So in that regard, it's broke for me! It's just too damn hot here in the summer to get anything out of the car, I don't even bother racing it. For the money I've spent, I'm not happy. I need to do something or it was a waste in my mind.
- Dug
- Dug
Teching In
Joined: May 2002
Posts: 25
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From: Nottingham, Notts, England, UK
Re: Need to lower compression > Are 6.0 heads the answer? IMHO 6.0 heads with bigger chamber volumes and decent ports will be a step in the right direction and if you don't want to change to lower comp pistons then fit thinner gaskets to reduce the squish clearence for a faster burn. You will make the engine much more efficiently. If you use low/modest boost (9psi) for short runs it should be fine plus you can always fit water injection if you are concerned about detonation issues. Later on you can go for 30cc bowls in your pistons! Mike
Re: Need to lower compression > Are 6.0 heads the answer? Thinner gaskets ehh... That would bring your compression back up. People are running 9lbs on 10.1:1 compression w/out issues. I would think you could run more boost if your compression is lower. Could you elaborate on that more MATE''
TECH Regular
Joined: Feb 2002
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From: the moon
Re: Need to lower compression > Are 6.0 heads the answer? here you go, 73cc polished chambers done by me.
These are new old stock 98 ls1 heads, they actually CC out at just under 70 CC STOCK. NOT THE FACTORY PUBLISHED 67.3CC.
I have now cc'd 2 sets of 98 heads at 70cc and another professional cnc head shop also got 70cc on a set of 98 heads.
So opening them up to 73cc was not to hard.
Using a felpro gasket at .041" vs the stock .052, I also decreased the squish for more efficient burn.
Running these heads with my pistons that have -2.5CC reliefs puts me around 9.3-1.
That plus water/alcohol injection and I am confident I can run 12+psi no problems.
<img src="http://www.tech-ls1.com/extras/chamber11.jpg" alt=" - " />
Steve
These are new old stock 98 ls1 heads, they actually CC out at just under 70 CC STOCK. NOT THE FACTORY PUBLISHED 67.3CC.
I have now cc'd 2 sets of 98 heads at 70cc and another professional cnc head shop also got 70cc on a set of 98 heads.
So opening them up to 73cc was not to hard.
Using a felpro gasket at .041" vs the stock .052, I also decreased the squish for more efficient burn.
Running these heads with my pistons that have -2.5CC reliefs puts me around 9.3-1.
That plus water/alcohol injection and I am confident I can run 12+psi no problems.
<img src="http://www.tech-ls1.com/extras/chamber11.jpg" alt=" - " />
Steve
Teching In
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From: Nottingham, Notts, England, UK
Re: Need to lower compression > Are 6.0 heads the answer? Hi Vince, my pistons have .020" more comp height so they will be well into the gasket squish area. They also have very big bowls. I will be using 6.0 heads and a twin throttle plenum which is in the early stages of patterning before casting in aluminium. Basically if you can suppress the premature detonation of the end gasses by a more efficient squish band area you can actually run with more compression and still use the boost plus the engine is also more efficient and definately sharper and more throttle responsive off boost. Ford and GM have been tightening up the squish bands in recent years to produce more efficient engines. The LS1 is no exception. I have also been building Cosworth V6's with only .020" clearance between piston and head. The pistons are clean, no carbon around the squish area. Could go tighter but it's probably not worth the risk/effort. My LS1 will start with a .020" squish clearance or thereabouts. On racing 2 strokes we used to use .008" squish area.
Thread Starter
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From: SW Florida
Re: Need to lower compression > Are 6.0 heads the answer? Let me ask you 6.0 head guys a question...
Can I use regular 5.7 GM head gaskets with 6.0 heads, or do they make 6.0 specific head gaskets?
Want to use the stock type GM graphite gaskets. NAPA now sells these 5.7 gaskets. Think they also sell the 6.0 gaskets (if in fact there is a difference)?
Ron,
BTW, this is on a stock bore 5.7
<small>[ July 21, 2002, 06:15 PM: Message edited by: Kimchee and Rice ]</small>
Can I use regular 5.7 GM head gaskets with 6.0 heads, or do they make 6.0 specific head gaskets?
Want to use the stock type GM graphite gaskets. NAPA now sells these 5.7 gaskets. Think they also sell the 6.0 gaskets (if in fact there is a difference)?
Ron,
BTW, this is on a stock bore 5.7
<small>[ July 21, 2002, 06:15 PM: Message edited by: Kimchee and Rice ]</small>
Re: Need to lower compression > Are 6.0 heads the answer? Thanks Mike.. Your explanation was over my head, but I think I get where you are coming from. You mentioned your pistons. What about our pistons? Opening up the 6.0L heads to drop the compression and using a thinner gasket is what you suggested. Will this work on stock LS1 pistons as well?
Teching In
Joined: May 2002
Posts: 25
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From: Nottingham, Notts, England, UK
Re: Need to lower compression > Are 6.0 heads the answer? Hi Vince, you could probably fit the thinner gaskets and improve combustion just by doing that. By using bigger chambered heads you would lower the compression so really this could be done at the same time. What you are achieving with a tighter squish band(the area above the diameter of the piston at tdc)is the forcing of tail end/trapped gasses at the outside of the bore to be sent at huge speed (probably supersonic) towards an expanding flame front which started moving outwards from the spark plug. This way nearly all the fuel gets burned plus the LS1 head has a quench area which helps to cool/remove the heat in the gasses. If you send the burn towards the centre of the chamber then theoretically the quench area stays cooler and you should delay detonation IMHO! This kind of detailing would help most engines. Manufacturers know this stuff and their engines get better all the time (well some do) but they have to allow for worst case scenario production tolerences.