zigroid

iTrader: (22)

I used to know these a few years ago but I cant remember lol and search yields two different answers.

STOCK LT1 heads. what combustion chamber volume? 54cc or 58cc?

THIS SITE says...
which would mean LT1 combustion chambers are 54 cc. goes on to say LT4 pistons are the reason for it's .4 c/r increase.
THIS POST says the volume is 58cc while just the second post up from it says its 54cc.

the one where it says the cylinder head volume is 58cc using the following variables:
Cylinder bore (Stock LT1 = 4.00in)
Stroke (Stock LT1 = 3.48in)
Combustion Chamber Volume (Stock LT1 = 58cc = 3.539 in3)
Piston Volume (Stock LT1 = 4.5cc = 0.274606 in3)
Deck Height (Stock LT1 = 0.015 in)
Head Gasket Crush Thickness (Stock LT1 = 0.05 in)

gives a compression ratio of 10.44:1, which is very close to GM's advertised 10.4:1 c/r.

the figures I always thought were correct were...
Cylinder bore 4"
Stroke 3.48"
Combustion Chamber Volume 54cc
Piston Volume 8cc
Deck Height .020"
Head Gasket Crush Thickness .05"

which gives a 10.38:1. this is also very close to GM's advertised 10.4:1 c/r.

reason for asking is Im planning on assembling a 355 with stock stroke, 6" rods, and 5cc dish mahle pistons. I don't have the cash for ported heads so I have to reuse my stock ones. Im leaning towards a cc503 (224/230 112lsa) or a slight variation of it (depending on how my c/r turns out) since I don't want anything too radical like my last LE3 383. Im trying to get my DCR as close to 9:1 without going over so I can have that kickass midrange torque.

here are the variables I am using...

Cylinder bore 4.03"
Stroke 3.48"
rod length 6"
Combustion Chamber Volume 54cc
Piston Volume 5cc
Deck Height 0 (zero)
Head Gasket Crush Thickness .039" (fel pros)
IVC of 70* abdc (for a off the shelf cc503, 112lsa with no advance ground in)

SCR = 11.83:1, DCR = 8.98:1
this would be perfect. I have a new radiator, 160* t-stat, tuning (obviously), and 93+ octane readily available.

however, if the cylinder heads combustion chamber is 58cc my SCR becomes 11.22:1 and my DCR is now 8.53. not exactly low, but I would like to optimize my setup as much as I can.

keeping the LSA the same and advancing it 2 degrees (110 icl) puts the DCR at 8.68. grinding it on a 110lsa and advancing it 2 degrees (108 icl) puts the DCR at 8.82 which is close to where I want to be.

so what is it?


thanks

vanilla89

iTrader: (8)

I think 56cc is stock for lt1's,54cc for lt4's

infinitebird

iTrader: (11)

stock chamber size is 54cc.

Note that a lot of this basic info is in this sticky: https://ls1tech.com/forums/lt1-lt4-modifications/298077-ultimate-lt1-newbie-faq.html

zigroid

iTrader: (22)

thank you, but did you click the links I posted? there are two volumes posted in that thread. one being 58cc, the other 54cc.

infinitebird

iTrader: (11)

lol my bad, yeah that's kind of odd.

95FbFormula

iTrader: (25)

The only way you can be really sure is to measure it your self or have a machine shop do it i assume it wouldn't cost that much maybe $10

zigroid

iTrader: (22)

I would do it myself but I don't have the proper tools to do it. guess I'll just find a machine shop to do it like you suggested. hopefully theyre that cheap!

wrd1972

iTrader: (12)

I doubt such a simple thing as nailing the LT1 combustion chamber size will ever be settled.