LT1-LT4 Modifications 1993-97 Gen II Small Block V8

Safely raise compression?

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Old Apr 12, 2010 | 12:33 PM
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Default Safely raise compression?

Question.

As my rear end is down for the moment I have decided to do some maintenance/mods to the engine. I have longtubes on the way, getting true duals, new opti, valve job, etc. I may even have the heads ported here in town if the price is right. Lets say I dont mess with the heads other than a gasket match, could I use a thinner headgasket such as this one http://www.summitracing.com/parts/FPP-1094/ to raise my compression a bit? Any idea what kind of gains if any that may net?

Thanks!
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Old Apr 12, 2010 | 01:48 PM
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I run impala HG's which bump it up to 11:1.. I doubt you'll see a noticeable gain w/o cammin it or getting some head work done tho
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Old Apr 12, 2010 | 04:07 PM
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what are the impala compressed size at? Im running .026 and was just curious. Sorry to hijack.
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Old Apr 12, 2010 | 04:29 PM
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.029 -damn 'too short' messages..
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Old Apr 12, 2010 | 04:50 PM
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that gasket you will need to mod a tad from what i read..i just did quick math and the the mr gasket .26 thick gives you 11.10 and that one gives your around 11.44,,there is nothing wrong with upping compression for performance..what you would gain would be hard to say...some say .2 or .4 percent plus for cars under 450hp n/a is a rule i hear all the time..

im going after the bolt on lt1 record while i build my real motor and the z1094 is the one im going to use if i pop my gasket at all..which would put me out of the running for the record but **** it..no biggie

with the heads ported,that gasket and say 1.7 rockers on a good tune an stock cam would hurt peoples feelings..lol
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Old Apr 13, 2010 | 04:24 PM
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Isn't that gasket for GEN1 engines?
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Old Apr 13, 2010 | 04:42 PM
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You can LOSE hp if you go to far.

Detonation can quickly become prominent and cause you to need HIGHER octane and or less timing.

Plan the total system not pick this then that approach that most apply since they hear someone gained this doing that. Cam, CR, porting, valve size, gears, stall etc all work together if you piece meal it expect to get less than optimal performance.

FEW cars are setup taking everything into account and that is why so many perform poorly.

Good luck
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Old Apr 13, 2010 | 05:00 PM
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Originally Posted by boosted LT1
You can LOSE hp if you go to far.

Detonation can quickly become prominent and cause you to need HIGHER octane and or less timing.

Plan the total system not pick this then that approach that most apply since they hear someone gained this doing that. Cam, CR, porting, valve size, gears, stall etc all work together if you piece meal it expect to get less than optimal performance.

FEW cars are setup taking everything into account and that is why so many perform poorly.

Good luck
I'll second that, compression increases are best matched/joined with camshaft duration increases to balance out cylinder pressure. Camming a stock engine without increasing compression is leaving some power on the table and raising compression without increasing duration gives more opportunity for spark knock. Just generally speaking here. I'm sure our motors have a bit of safety margin built in for compression increase over stock.
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Old Apr 13, 2010 | 05:34 PM
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yes it is a first gen gasket but if you open up the water ports and the oil ports on it she works..theres a couple people on here,ls1lt1 an camaroz28 that are using them with no problems.


i agree dont expect just bumping the compression to help a ton,,toss in some bigger rockers,porting,headers,cai,160 therm and a tune and you will have a nice motor..

also seeing you go your heads porter plan to port the intake atleast or upgrade it..something people always do is have ported heads or bigger heads and **** dont run like it should..reason being they over looked the intake..a head can only flow as much air as the intake can flow..i could have the baddest 23 degree heads on the plant flowing and having a csa to support a 900 n/a motor but if i go stick a plane jane out the box hurrican single plane on it..guess what she aint going to do dick..just a helpful hint,you almost never see people flowing there heads with the intakes on them.
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Old Apr 13, 2010 | 05:57 PM
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Originally Posted by suicidal racing
yes it is a first gen gasket but if you open up the water ports and the oil ports on it she works..theres a couple people on here,ls1lt1 an camaroz28 that are using them with no problems.


i agree dont expect just bumping the compression to help a ton,,toss in some bigger rockers,porting,headers,cai,160 therm and a tune and you will have a nice motor..

also seeing you go your heads porter plan to port the intake atleast or upgrade it..something people always do is have ported heads or bigger heads and **** dont run like it should..reason being they over looked the intake..a head can only flow as much air as the intake can flow..i could have the baddest 23 degree heads on the plant flowing and having a csa to support a 900 n/a motor but if i go stick a plane jane out the box hurrican single plane on it..guess what she aint going to do dick..just a helpful hint,you almost never see people flowing there heads with the intakes on them.
I have seen some flow tests that included the intakes bolted to the heads (NOT LT1's) and the results were interesting to say the least. For the most part, the intake could be a huge bottleneck, but some designs performed well even though they were a restriction on high flowing heads. Probably due to plenum volume and/or ramming effect.
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Old Apr 13, 2010 | 06:26 PM
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yep both and the port lay out....wet flow is a very neat thing to look at also..engine masters had a cool article on intakes and flowing them on the heads a couple yrs ago..they where using afr heads and diff sets of intakes an stuff along with spacers..

Last edited by suicidal racing; Apr 13, 2010 at 06:47 PM.
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Old Apr 13, 2010 | 06:35 PM
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suicidal racing where is ur home track?
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