Vacuum requirements for '79 C3?

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Aug 28, 2023 | 05:56 PM

100amps

Thread Starter

Heel & Toe

Joined: Nov 2022

Posts: 24

Likes: 4

Vacuum requirements for '79 C3?

I have searched here and not found my particular question answered.
I am planning the build of a replacement engine for my '79 C3 and I'm thinking about the cam specs currently, which will be influenced by the vehicle's vacuum requirements. How much (or how little actually) vacuum will I need to have available for the brakes, headlights, etc. before running into trouble with these? I'm primarily at sea level.

Aug 28, 2023 | 08:01 PM

REELAV8R

Le Mans Master

Joined: Apr 2011

Posts: 6,284

Likes: 1,171

From: Hermosa

A lot of us can run 10" without any problems. It depends on how tight your system is mostly.

Aug 29, 2023 | 09:05 AM

drwet

Melting Slicks

Joined: Dec 2009

Posts: 3,233

Likes: 657

From: Thunder Bay

I have about 232 degrees of intake duration on a 427 small block, which gives me about 12” of vacuum and everything works fine.

Aug 29, 2023 | 09:08 AM

Jebbysan

Dr. Detroit

Joined: Mar 2012

Posts: 10,097

Likes: 4,027

From: New Braunfels Texas

I run 11" and it is fine....wiper door and headlights....the key is NO LEAKS.....a leaky 15" of vacuum is probably the same as a sealed 11" of vacuum......

Jebby

Aug 29, 2023 | 04:38 PM

100amps

Thread Starter

Heel & Toe

Joined: Nov 2022

Posts: 24

Likes: 4

Thanks all. Greatly appreciated.

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