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

Compression question

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Old Feb 20, 2010 | 06:00 PM
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Default Compression question

what would be the final compression ratio with a 46cc-47cc head on a completely stock untouched lt1 motor. thanks...
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Old Feb 20, 2010 | 06:02 PM
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Need head gasket thickness, Stock ?
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Old Feb 20, 2010 | 06:08 PM
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say the mr. gasket 5716 believe its a .026 or even a stock size. just tryin to get an idea.
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Old Feb 20, 2010 | 06:35 PM
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Between 12.2 and 12.8:1 static, depending on deck height (.015 - .030").
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Old Feb 20, 2010 | 06:36 PM
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around 11.5 to 1 I think. I don't know if my specs are right for a stock bottom end.
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Old Feb 20, 2010 | 06:38 PM
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Originally Posted by RamAir95TA
Between 12.2 and 12.8:1 static, depending on deck height (.015 - .030").
Hey do you know the pin hieght on the lt1 piston and the cc volume of it?
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Old Feb 20, 2010 | 06:41 PM
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Seems like RamAir knows his stuff, from what I remember to do SCR you need:
what type of piston being used, dished etc
gasket thickness
Deck hieght,
Heads CC
where the pistons are at TDC how much are they in or above the cyclinder walls, But I have forgotten. I haven't look up how to do compression in a while.
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Old Feb 20, 2010 | 06:43 PM
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Originally Posted by jaycenk
Hey do you know the pin hieght on the lt1 piston and the cc volume of it?
Stock pistons are -5cc 4-valve relief.

Stock piston height is 1.56" IIRC.
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Old Feb 20, 2010 | 06:50 PM
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Originally Posted by kaganader
Seems like RamAir knows his stuff, from what I remember to do SCR you need:
what type of piston being used, dished etc
gasket thickness
Deck hieght,
Heads CC
where the pistons are at TDC how much are they in or above the cyclinder walls, But I have forgotten. I haven't look up how to do compression in a while.
well its going to be a completely untouched shortblock so all internals are stock. stock deck height on block, heads are 46cc-47cc, pistons will be at .025-.035 roughly down in the hole at tdc just want to know what final compression be. i know lt1's are generous on ptv clearence on a big cam im not worried about that. but thanks to all that have responded so far. honestly i was thinking like 11.5-12.1 something in between. just want to make sure ill be fine on pump gas thats all.
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Old Feb 20, 2010 | 06:51 PM
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ok thanks man,
To OP don't look at mine the calculator I used is way off.
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Old Feb 20, 2010 | 06:54 PM
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never mind I figured out my problem. I show 12.77 to 1
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Old Feb 20, 2010 | 06:56 PM
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Oh and thats with -.025 deck height. falls right into what RamAir95TA said
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Old Feb 20, 2010 | 06:57 PM
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Originally Posted by jaycenk
ok thanks man,
To OP don't look at mine the calculator I used is way off.
its all good man. actually i was thinking in line the same as you. with the cam grounded the way it is i need to have as much compression anyways. just trying to get an estimate. thanks guys....
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Old Feb 20, 2010 | 07:02 PM
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Please keep in mind that your static compression ratio means jack squat in terms of performance. It's only a static calculation used in the physical characteristics of the build.

Do a search for dynamic compression ratio, and read, read, read.
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Old Feb 20, 2010 | 07:12 PM
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ok well going through my emails just now i got one from lloyd.

im going to just call him and speak to him over the phone directly. from what hes saying and what i heard so far on here is a big difference. anyways thanks for all your help guys i really do appereciate it.
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Old Feb 20, 2010 | 07:16 PM
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Is he milling them that much? Just curious for future reference The ones he did for me he milled to where the chamber cc is around 51.5 to 52cc
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Old Feb 20, 2010 | 08:16 PM
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Originally Posted by jaycenk
Is he milling them that much? Just curious for future reference The ones he did for me he milled to where the chamber cc is around 51.5 to 52cc
no these werent from him. i just emailed him and wanted to figure some specs out. btw really nice guy to email and talk to. hands down one of the best guys to go for help. even though he knew i was just asking for help and i wasnt buying parts from him he was such a nice guy, after speaking with him i felt bad not buying a set of heads/cam from him lol.
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Old Feb 21, 2010 | 11:37 PM
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Originally Posted by RamAir95TA

Stock piston height is 1.56" IIRC.
Correct.
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Old Feb 22, 2010 | 12:11 AM
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what's the point of raising the compression in a stock bottom end motor if it means nothing performancewise?
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Old Feb 22, 2010 | 12:13 AM
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Originally Posted by MasterTomos
what's the point of raising the compression in a stock bottom end motor if it means nothing performancewise?
Who said that?

EDIT: Notice I said "static compression ratio."

Last edited by RamAir95TA; Feb 22, 2010 at 12:49 AM.
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