vacuum check question
Thread Starter
Intermediate
Joined: Jan 2007
Posts: 49
Likes: 0
vacuum check question
I STARTED MY VACUUM CHECKS TONIGHT AND HAVE GOTTEN (SO FAR) THE FOLLOWING RESULTS ON MY L-71:
INTAKE: 15HG
HOSE 1: 15 HG
CHECK VALVE 1: 15 HG
HOSE 2: 14-15HG
CHECK VALVE 2 (WIPERS AND HEADLIGHTS SPLIT AT THIS POINT) 10 HG TO LIGHTS, 5 HG TO WIPER DOOR
WOULD THIS BE EXPECTED?
ALSO, WHAT IS THE MINIUM REQUIRED VACUUM TO RUN THESE COMPONENTS EFFECIENTLY?
THANKS, I'LL POST THE REMAINING READINGS TOMORROW NIGHT.
INTAKE: 15HG
HOSE 1: 15 HG
CHECK VALVE 1: 15 HG
HOSE 2: 14-15HG
CHECK VALVE 2 (WIPERS AND HEADLIGHTS SPLIT AT THIS POINT) 10 HG TO LIGHTS, 5 HG TO WIPER DOOR
WOULD THIS BE EXPECTED?
ALSO, WHAT IS THE MINIUM REQUIRED VACUUM TO RUN THESE COMPONENTS EFFECIENTLY?
THANKS, I'LL POST THE REMAINING READINGS TOMORROW NIGHT.
Just another Corvette guy
Joined: Feb 1999
Posts: 8,518
Likes: 3,865
From: Palm Springs, CA.
Unless you've got a pretty lumpy cam those readings are too low.
Optimal vacuum should be 18-21 inches at the manifold.
Does the vacuum reading increase if you advance your timing?
Greg
Optimal vacuum should be 18-21 inches at the manifold.
Does the vacuum reading increase if you advance your timing?
Greg
Melting Slicks
Joined: Jul 2004
Posts: 2,867
Likes: 195
From: Maryland
If the engine in question is a L71 15" Hg at idle is normal. The cam in a SHP 427 has quite a lot more overlap than a base engine SB.
Le Mans Master
Joined: Dec 2006
Posts: 8,837
Likes: 1,028
I STARTED MY VACUUM CHECKS TONIGHT AND HAVE GOTTEN (SO FAR) THE FOLLOWING RESULTS ON MY L-71:
INTAKE: 15HG
HOSE 1: 15 HG
CHECK VALVE 1: 15 HG
HOSE 2: 14-15HG
CHECK VALVE 2 (WIPERS AND HEADLIGHTS SPLIT AT THIS POINT) 10 HG TO LIGHTS, 5 HG TO WIPER DOOR
WOULD THIS BE EXPECTED?
ALSO, WHAT IS THE MINIUM REQUIRED VACUUM TO RUN THESE COMPONENTS EFFECIENTLY?
THANKS, I'LL POST THE REMAINING READINGS TOMORROW NIGHT.
INTAKE: 15HG
HOSE 1: 15 HG
CHECK VALVE 1: 15 HG
HOSE 2: 14-15HG
CHECK VALVE 2 (WIPERS AND HEADLIGHTS SPLIT AT THIS POINT) 10 HG TO LIGHTS, 5 HG TO WIPER DOOR
WOULD THIS BE EXPECTED?
ALSO, WHAT IS THE MINIUM REQUIRED VACUUM TO RUN THESE COMPONENTS EFFECIENTLY?
THANKS, I'LL POST THE REMAINING READINGS TOMORROW NIGHT.
Le Mans Master
Joined: Dec 2006
Posts: 8,837
Likes: 1,028
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
You definitely have some leakage at one [or more] locations. The reservoir can should stabilize the vacuum level to maybe 1 or 2" Hg below sealed-off manifold vacuum. Check out the lines downstream of the engine area. Since it is difficult to check behind the driver's side instrument panel area, check at the wiper door switches and relay to see what it is there. Just work methodically plugging off and testing along the vacuum routing...you'll find the culprits.