C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

A dumb question

Old Mar 5, 2002 | 07:50 PM
  #1  
92BAV's Avatar
92BAV
Thread Starter
Burning Brakes
 
Joined: Nov 2000
Posts: 864
Likes: 0
From: Kelowna BC
Default A dumb question

I've seen it mentioned in other posts, and I am just wondering what testing for 'blowback' is, and how is it done? :confused: :crazy:

Thanks.
Reply
Old Mar 6, 2002 | 08:33 AM
  #2  
TrueBlue ChevyDude's Avatar
TrueBlue ChevyDude
Drifting
20 Year Member
Conversation Starter
All Eyes On Me
 
Joined: May 2001
Posts: 1,630
Likes: 0
From: Brandywine, Chester and Ridley Valleys Pennsylvania
Default Re: A dumb question (92BAV)

If you mean "blow-by", I've taken it to mean what gets past the rings, out of the combustion chamber and into the valve cover area. Too much of it, and there's most likely a problem. Use your nose to sniff or your hand to feel for excess pressure (I guess you'd need experience with engines to tell what's good and what's not.)
Reply
Old Mar 6, 2002 | 01:04 PM
  #3  
92BAV's Avatar
92BAV
Thread Starter
Burning Brakes
 
Joined: Nov 2000
Posts: 864
Likes: 0
From: Kelowna BC
Default Re: A dumb question (TrueBlue ChevyDude)

If you mean "blow-by", I've taken it to mean what gets past the rings, out of the combustion chamber and into the valve cover area. Too much of it, and there's most likely a problem. Use your nose to sniff or your hand to feel for excess pressure (I guess you'd need experience with engines to tell what's good and what's not.)
Ah hah! blow-by is what I meant; I'm just dumb I guess. ;) Thanks for the info. :)

-Sheppe
Reply
Old Mar 6, 2002 | 01:37 PM
  #4  
SPD DMN's Avatar
SPD DMN
Le Mans Master
20 Year Member
 
Joined: Oct 1999
Posts: 9,713
Likes: 3
From: Sachse Texas
Cruise-In I Veteran
Cruise-In II Veteran
Default Re: A dumb question (92BAV)

Bloy-by is the amount of air that is going by the rings from the combustion chamber. You can test the amount of blow-by with a leak down tester, a dual pressure gauge, single regulator tool. This is done using an air supply (compressor) and the tool. You screw the end of the tool into the spark plug socket, and attach the compressed air source to the other end. You then regulate the air to 100 PSI, then the second presure gauge will show the percentage of "kept" air. Usually the LT1 will have 96-98 PSI of air pressure for a regulated 100 psi of air. That would show a 2-4% leakdown in a cylinder. I made a leakdown tester for about $20 worth of parts from Autozone and the cable from my compresion test tool. Most places wanted over $55 for them.
Reply
Old Mar 6, 2002 | 02:14 PM
  #5  
92BAV's Avatar
92BAV
Thread Starter
Burning Brakes
 
Joined: Nov 2000
Posts: 864
Likes: 0
From: Kelowna BC
Default Re: A dumb question (Vette92)

Bloy-by is the amount of air that is going by the rings from the combustion chamber. You can test the amount of blow-by with a leak down tester, a dual pressure gauge, single regulator tool. This is done using an air supply (compressor) and the tool. You screw the end of the tool into the spark plug socket, and attach the compressed air source to the other end. You then regulate the air to 100 PSI, then the second presure gauge will show the percentage of "kept" air. Usually the LT1 will have 96-98 PSI of air pressure for a regulated 100 psi of air. That would show a 2-4% leakdown in a cylinder. I made a leakdown tester for about $20 worth of parts from Autozone and the cable from my compresion test tool. Most places wanted over $55 for them.
Once again, thanks for the info! :)

-Sheppe
Reply
Old Mar 6, 2002 | 05:46 PM
  #6  
Rich B.'s Avatar
Rich B.
Melting Slicks
20 Year Member
 
Joined: Aug 2001
Posts: 2,516
Likes: 0
From: Lockport NY
Default Re: A dumb question (Vette92)

If your cars' PCV valve is constantly pushed back up out of its' rubber grommet, that's a good indication that you have too much blow-by...

...If you *have* a PCV valve in your valve cover... :D
Reply

Get notified of new replies

To A dumb question



Thread Tools
Search this Thread

All times are GMT -4. The time now is 07:44 PM.

story-0
10 Ugly Corvettes That We Still Kinda Love

Slideshow: 10 ugly Corvettes that we still kinda love.

By Joe Kucinski | 2026-06-03 10:34:17


VIEW MORE
story-1
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer

A lot of money has changed hands at the online auction house over the years.

By Brett Foote | 2026-06-03 10:21:50


VIEW MORE
story-2
10 Things Every Corvette Owner Needs (2026 Edition)

Slideshow: 10 great gifts Corvette enthusiasts actually want for Father's Day!

By Michael S. Palmer | 2026-06-03 15:43:40


VIEW MORE
story-3
8 Most "Only Corvette Owners Understand" Quirks and Problems

Slideshow: These are the quirks, annoyances, and oddly lovable problems that every Corvette owner eventually learns to live with.

By Pouria Savadkouei | 2026-05-28 09:31:39


VIEW MORE
story-4
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years

Slideshow: 10 reasons why the C6 Z06 is still a performance benchmark after 20 years.

By Joe Kucinski | 2026-05-27 17:20:09


VIEW MORE
story-5
How Much Horsepower Every Corvette Engine "LOST" in 1972

Slideshow: How much horsepower every Corvette engine lost in 1972.

By Joe Kucinski | 2026-05-27 16:54:53


VIEW MORE
story-6
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!

Slideshow: How to Protect A Convertible Top: 10 DOs & DON'Ts

By Michael S. Palmer | 2026-04-03 00:00:00


VIEW MORE
story-7
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!

Slideshow: The 10 most explosive Corvettes ever built based on power-to-weight ratio.

By Joe Kucinski | 2026-05-20 07:23:03


VIEW MORE
story-8
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter

Slideshow: From C1 to C8 we compare every Corvette generation by the numbers.

By Joe Kucinski | 2026-05-12 16:54:12


VIEW MORE
story-9
8 Coolest Corvette Pace Cars (and Replicas) of All Time

Slideshow: Some Corvette pace cars became collectible legends, while others perfectly captured the look and attitude of their era.

By Verdad Gallardo | 2026-05-11 09:50:51


VIEW MORE