fireman

I posted this thread in LT1 Tech and can't get a straight answer.

What is the stock combustion chamber volume on stock '95 LT1 heads?(cc)
Some people swear its 58cc and others say its 54cc and others say its 54.8cc(!).

Zero_to_69

The answer is 58 cc. supported by several web site
links.


https://www.spoperformanceparts.com/...html?CATID=856

It's possible the others are getting flucations
because of the spark plug considerations when
measuring?

Hope that helps out.

Mindgame

CC the combustion chamber. That way you know for sure.

-Mindgame

Highlander

If I am not mistaken the Combistion chambers on an LT1 are 54.4cc

Thanks

kmook

Engine Bore (in.) 4.000
Engine Stroke (in.) 3.480
Deck Height (in.) 0.025
Gasket Thickness (in.) 0.049
Cyl Head (cc) 58
Piston valve reliefs (cc) 2

Compression Ratio: 10.52:1

----------------------------------------------------------------

Engine Bore (in.) 4.000
Engine Stroke (in.) 3.480
Deck Height (in.) 0.025
Gasket Thickness (in.) 0.049
Cyl Head (cc) 54
Piston valve reliefs (cc) 2

Compression Ratio: 11.06:1

-----------------------------------------------------------------

It is about 58cc for LT1s, and yes the best way to find out always is like Mindgame said. And ill move this to LT1 Tech. Thanks.

87iroc-vert

I have a 95 impala ss motor(cast heads) what cc would that have?

Highlander

You are not taking into consideration that the cylinder head gasket has a 4.166 bore ...

With that it will be 10.5 to 1 CR with 54.4cc heads

kmook

Try it here: http://www.smokemup.com/auto_math/compression_ratio.php
I used the "4.166" Gasket Bore...

Calculate Compression Ratio

Bore (Inches) 4.000
Stroke (Inches) 3.480
Connecting Rod Length (Inches) 5.7
Cylinder Head Volume (cc) 54
Deck Height (Inches) 0.025
Head Gasket Bore (Inches) 4.166
Head Gasket Thickness (Inches) 0.049
Piston to Cylinder Wall Clearance (Inches) 0.003
Top Ring Land Height (Inches) 0.25
Piston Dish Volume (cc) 2

Compression Ratio:
10.933 : 1

Bore / Stroke Ratio:
1.149 : 1

Rod / Stroke Ratio:
1.638 : 1

Total volume:
788.912 cc's

Compressed volume:
72.162 cc's

----------------------------------------------------------------------------

Bore (Inches) 4.000
Stroke (Inches) 3.480
Connecting Rod Length (Inches) 5.7
Cylinder Head Volume (cc) 58
Deck Height (Inches) 0.025
Head Gasket Bore (Inches) 4.166
Head Gasket Thickness (Inches) 0.049
Piston to Cylinder Wall Clearance (Inches) 0.003
Top Ring Land Height (Inches) 0.25
Piston Dish Volume (cc) 2

Compression Ratio:
10.411 : 1

Bore / Stroke Ratio:
1.149 : 1

Rod / Stroke Ratio:
1.638 : 1

Total volume:
792.911 cc's

Compressed volume:
76.161 cc's

Highlander

http://home.tir.com/~steveher/lt4.html

check it out where it says

* Combustion chambers are almost identical (there was a negligible .4cc difference) Volume for LT4 Combustion chambers are 54.4cc's.

Thanks

Mr. Horsepower

Seems to be a popular arguement on this board. Seems to happen about once a year.
Highlander is right. The LT1 chamber is usually about .5 ccs larger than the LT4 which puts it right at about 55 ccs. The rest of the compression difference is in the piston-pocket volume. The LT1 has a valve relief volume of approximately 7 ccs vs the LT4's shallow 4.5 cc reliefs. Now do the math and see where it stands.

The other thing to remember here is that heads are cast and castings are prone to variation. As Mindgame stated, you need to cc them to be sure... for paper, 55 cc LT1 combustion chamber volume is a good approximation.

Chuck Riddeck
Progressive Race Engine Development

kmook

Chuck, please enlighten me. I did the math again with 55cc chambers and 7cc valve reliefs and get way low c/r-

Bore (Inches) 4.000
Stroke (Inches) 3.480
Connecting Rod Length (Inches) 5.7
Cylinder Head Volume (cc) 55
Deck Height (Inches) 0.025
Head Gasket Bore (Inches) 4.166
Head Gasket Thickness (Inches) 0.049
Piston to Cylinder Wall Clearance (Inches) 0.003
Top Ring Land Height (Inches) 0.25
Piston Dish Volume (cc) 7

Compression Ratio:
10.17 : 1

I still dont see where the standard 10.5:1 c/r is comming from for an LT1, if the chambers are 54-55 cc, with or without a 7cc valve relief. FWIW my stock chambers were right about 58cc before they were increased to 62cc...

Highlander

Using 54cc chambers and 6.2 valve release will give you
10.386:1

which is the 10.4 that is supposed to be.

Mindgame

KMook, I've never seen a 4.0" bore type gasket that was 4.166.. that'd be the gasket used on the 4.125+ bore blocks. Most for the 4" hole motors are 4.09, so try that. Are you sure about the compressed gasket thickness? I seem to remember reading that they're .039 stock?? Using those numbers and Chuck's figures I get the results we should be getting. The LT1 heads I just pulled from my motor were 56cc, fwiw.

-Mindgame

kmook

I was just seeing what #s came up using the 4.166 # because that's what The Highlander brought up. I am not sure if that is the compressed gasket thickness or not offhand, but the 1074 felpro gaskets are .039 and stock are .049 last time i checked...

I think the heads on these cars just vary widely. You got 56 on yours, I got 58 on mine, some get 54...

Curt (pres AAMC & ZAA)

I like this CR calculator better:
http://www.gafba.com/calculators/cmpratio.asp?mode=ntr

FWIW, my stock heads were exactly 54cc (at least the one they checked was).