LS7, compression ratio, boost questions

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Jan 7, 2014 | 05:43 AM

mittens

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From: Huntsville Alabama

LS7, compression ratio, boost questions

Ok LS7
bored .016 (Making it a 431)
ARP Main Bolts, Rod Bolts, and Head Bolts
Heads milled .040 (63.5cc chambers)
Wisco Forged Pistons

Compression ration 11.41 : 1

What do you guys thank about adding a little boost? like 5lbs... Si trim with 4 inch pully should keep it pretty low.

Or is the compression to hi already?

I do not want to add meth, just a 93 pump gas car.

Jan 7, 2014 | 08:13 AM

ZO6er

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I'm the least smartest on this board but adding boost will create the c.r. to be higher iirc. anything over ~13 needs higher octane.
others will correct me.

BTW, why put pistons and only want 5lbs of boost? Afraid if the "mod bug" lol

Jan 7, 2014 | 08:41 AM

mittens

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From: Huntsville Alabama

Quote:

Originally Posted by ZO6er

The car is running and driving NA build right now, and makign good power, but I am thinking about a blower... and Not going to swap pistons on a new build just cause. I already have these forged ones. So the question at hand is would it be safe, at that level just to bump up a already breathing good engine with just a little boost to push it over the 700 ish mark? IF not I will stay NA, but my thoughts are if a car that makes 600 on motor, and another 150 from the a little boost is better then the same 750 hp, that is made form 12-15lbs of boost on a stockish motor.

Last edited by mittens; Jan 7, 2014 at 08:45 AM.

Jan 7, 2014 | 10:47 AM

ZO6er

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In that case yes, I had a D1 on But needed the meth to keep IATs down. I'm sure it was used for "boost" also but not sure, I didn't tune it.

Jan 7, 2014 | 11:01 AM

jon6.0

Melting Slicks

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From: Phoenix

You could do it, but meth would make it safer. It would allow you to get more timing in it since your IAT's will go up during a pull and the tune will be pulling timing for the increased IAT's. You could also spend about $2500-$3000 and do a nitrous system with a dedicated fuel cell for the nitrous. My buddies Z06 was nasty as hell with a Livernois heads/cam package and a 150hp shot. Nitrous Outlet makes everything you need. If you want to do a supercharger you can also have the cam ground that takes into account the higher compression and your octane limitations. Ed Curtis of Flowtech Induction or Mark at Bullet Racing Cams would be two good folks to talk with about that.

Last edited by jon6.0; Jan 7, 2014 at 11:03 AM.

Jan 7, 2014 | 11:01 AM

Unreal

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From: Gilbert AZ

Just put a 100-200shot on it IMO.

Jan 7, 2014 | 11:20 AM

user_name

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From: Houston

I wouldn't do it unless you have a cam bleeding off some compression.

Jan 7, 2014 | 11:32 AM

Chance42

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Quote:

Originally Posted by Unreal

Just put a 100-200shot on it IMO.

My thoughts exactly. 175-200 shot and go cut some low 9s.

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Jan 7, 2014 | 11:54 AM

mittens

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From: Huntsville Alabama

I dont want to fill meth tank, or fill NO2 bottles.

I want all the power it makes when ever I randomly feel the need.

Jan 7, 2014 | 12:06 PM

#10

Unreal

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From: Gilbert AZ

Then I would change the cam and heads. In fact, just change the whole motor.

Jan 7, 2014 | 12:34 PM

#11

jon6.0

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From: Phoenix

Quote:

Originally Posted by mittens

I dont want to fill meth tank, or fill NO2 bottles.

I want all the power it makes when ever I randomly feel the need.

When you use the washer fluid tank as your meth tank it will tell you when it needs filled. I use a metric ton of meth. More than most on here. I go through about a gallon of meth every 1000-1500 miles I drive. I live in the boonies and can wind out 4th gear on a daily basis when I drive to work.

You also can tune the car so it's only adding timing if the meth is spraying. You do this by only adding timing in the low IAT areas. Like less than 32F IAT's. So if you run out of meth it will be just fine since your IAT's will never get below 32F without meth spraying. If you insist on using the heads you have, you need a different cam that will account for your higher than stock compression. Ideally I would just swap your heads for heads with a larger chamber and do a custom cam. You can get away with just doing a cam and blower if you keep the boost low. It will definitely be more snappy with the higher compression.

Jan 7, 2014 | 12:41 PM

#12

yur2slo

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From: Fort Lauderdale & Prospect FL & CT

I'd be a tad careful now that you made the already thin cylinder sleeves even thinner by boring it out. Agree with the nitrous hit over boost on that set up.

Jan 7, 2014 | 12:43 PM

#13

jon6.0

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From: Phoenix

I imagine at that compression on 93 he would benefit just doing a meth kit on that NA motor. Get the IAT's down and add some timing into it.

Jan 7, 2014 | 01:20 PM

#14

mittens

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welcome inputs guys, I really do, keep them coming.

But the option of pulling motor that has 4k on it is not going to happen I will keep it NA.

so its a boost, or not....

Jan 7, 2014 | 01:23 PM

#15

jon6.0

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From: Phoenix

Quote:

Originally Posted by mittens

welcome inputs guys, I really do, keep them coming.

But the option of pulling motor that has 4k on it is not going to happen I will keep it NA.

so its a boost, or not....

Are you willing to change heads? Cam?

What are your current cam specs?

Jan 7, 2014 | 01:57 PM

#16

mittens

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No I will keep it NA before I pull the motor back apart, it was just finished 4k ago (along with the new RPM Tranny, and RPM diff, Twin disk clutch). its my DD. I was just thinking a used blower to bump it up a little more.

here is the motor (has intake and headers, and other supporting mods)

Ragin Racin ported LS7 Throttle Body
Ragin Racin ported LS7 Intake
Lingenfelter 660 heads, Milled 0.040 to 63.5cc chamber size (OEM GM castings, new bronze valve guides, Manley Stainless exhaust valves)
ARP head studs
Ragin Racing Stalker cam (224/246 .660/.660 @ 115+4)
PRC .675" EHT Double Valve Springs
Hardened Push Rods
Titanium retainers
C5R Timing chain/set
Comp Cams Trunion Upgrade
Block Bored/honed to 4.1410 (431ci) (Bored 0.016 Over from stock 4.125 bore)
Block Deck Height = 9.232 (Milled -0.008 from stock 9.24)
Wiseco forged pistons (4.1400 bore, -10cc dome, 1.165 compression height = compression ratio 11.41:1)
(Stock forged steel crank & titanium rods)
ARP rod bolts
ARP main bolts

Last edited by mittens; Jan 7, 2014 at 02:01 PM.

Jan 8, 2014 | 07:23 PM

#17

blackz97

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Quote:

Originally Posted by mittens

That small intake lobe on a 111 ICL is going to be closing pretty early so your NA DCR is probably already aggressive for pump gas and surely not ideal for boost. Perhaps e85 is a viable option if you really must go FI.

Jan 9, 2014 | 12:03 AM

#18

mittens

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From me searching and a few threads, its sounds like this i a no go unless i change pistons or heads.

SO its goingto stay NA. I just wanted to hit 200 in the mile. haha

Jan 10, 2014 | 10:22 PM

#19

gtodoug

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From: Miami FL

don't be discouraged. i have a high compression setup. it doesn't make much power but is a ton of fun to drive. I have 12.25:1 compression. 3.5psi of boost. car made 670whp 600wtq with 9 degrees of timing in it up top.

The tq pick up makes the car a lot more fun. I'll add 2psi and some meth until I can afford a motor.