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Topic: Compression ratio

in Forum: C3 Engines

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Compression ratio (1/5)
12/8/20 4:36pm

BillHanna
Standard Member
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Cana, VA - USA

Vette(s):
1975 Stingray 71 350 engine Flat top pistons Sniper fuel injection Hyperspark ignition Vintage Air air conditioning Borgeson power steering box

Joined: 7/3/2016
Posts: 369

Does anyone know what the compression ratio may be for a 350 engine bored .030 over with flat-top pistons?

The heads are 76cc and the head gasket compressed thickness is .041.

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Re: Compression ratio (2/5)
12/8/20 5:33pm

manchestershark

Lifetime Member
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Equinunk, PA - USA

Vette(s):
1972 conv, 4-speed, 350, 200hp, numbers match, rally wheels, war bonnett yellow w/white top. good condition, nice driver.

Joined: 10/31/2007
Posts: 2465

Close to 9.3 to 1. Depends on the cam too.

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Re: Compression ratio (3/5)
12/8/20 7:49pm

73shark
Limited Member
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Overland Park, KS - USA

Vette(s):
1973 Orange Metallic Coupe (orig owner), L82, 4 spd (WR), PS, (A/C & PW (I installed from wrecked 73)), leather, AM/FM Stereo, ran with '65 FI unit earlier & will again some day. 2023 Accelerate Yellow HTC Stingray

Joined: 7/9/2003
Posts: 911

A stock '73 L-82 had 76 cc. heads, steel head gasket, and flat top pistons with a slight valve relief and was rated 9.0 CR.

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1973 L-82 4 spd

Re: Compression ratio (4/5)
3/5/21 1:32pm

Rich Wahne
Former Member
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Troutdale, OR - USA

Vette(s):
1968 Roadster - 327cid 350 hp - Both Tops - My dad was the original owner, and now, I'm in the process of restoring it to like new condition.

Joined: 3/4/2021
Posts: 1

Here is a great compression ratio calculator.

Compression Ratio Calculator

I'm rebuilding my 1968 327, and the calculator says that I'm at 9.74:1...just right for 350hp on premium pump gas.

Re: Compression ratio (5/5)
3/5/21 5:07pm

Rich Wahne said:

Here is a great compression ratio calculator.

Compression Ratio Calculator

I'm rebuilding my 1968 327, and the calculator says that I'm at 9.74:1...just right for 350hp on premium pump gas.

Thanks! This is a handy tool. Mine comes out to 9.62 CR.

I always liked the 327. When I was 17 I bought a 360 HP crate engine from GM for my '62 Chevy II. That was one high-revving powerful engine. Wish I still had both of those!

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