Compression Guage Question
Thread Starter
Le Mans Master
Joined: Jan 2001
Posts: 6,938
Likes: 1
From: San Diego CA
Compression Guage Question
I am using a compression guage to check for #1 TDC as per http://forums.corvetteforum.com/zerothread?id=701268 and just realized this. The guage has a needle check valve to allow reading the compression whether the piston has already gone past TDC it will still stay at 115lbs so you can get your reading without having to have your face stuck to the guage or getting the widely fluctuating (hard to read) needle. That's great for getting compression readings but sucks for finding #1 TDC Compression as I found last night. I bumped the car over and it read 115 however by looking at the timing mark on the dampner it was damn near on the other side. The guage's check valve opens upon pressure but shuts and maintains 115 lb reading when the piston goes down. Well that defeats the whole purpose of using it to find #1 TDC. By the time I looked up and saw 115lbs. the dampner was probably on the # 8 or #4 compression stroke not #1 which is what I'm trying to find!! Is there a way to temporarily remove the guage's check valve without ruining the guage to actually sense cylinder presssure so it will spike at # 1 TDC compression and go back to vacuum on downstroke so I can tell where the hell I'm at?!!!!
:confused:
:confused:
Drifting
Joined: Apr 2002
Posts: 1,720
Likes: 19
From: Manhattan Beach Ca
Re: Compression Guage Question (Cali,68,L-79)
Couldnt you try putting some plug like thing in the hole, then as you bump it up on comp stroke, you can watch the thing pop out right before it reaches TDC?
Thread Starter
Le Mans Master
Joined: Jan 2001
Posts: 6,938
Likes: 1
From: San Diego CA
Re: Compression Guage Question (Surfer69)
True true but I want to use the guage I paid all that money for and have never used. Anyone now how to turn a check valve, it comes with a special key. I think if I turn it one way or another it allows paasage of air both ways so it reads actual staic cylinder pressure whie another (as it is currently) it reads pressure until it bleeds down such as on intake and the check valve closes. It looks like the end of a tire valve (schraeder) sticking out the side of the guage face.
Race Director
Joined: Mar 1999
Posts: 10,258
Likes: 1
From: Calif.
Re: Compression Guage Question (Cali,68,L-79)
Use your finger in the (empty) spark plug hole. Crank it. You'll feel it "puffing." Stop cranking at the beginning of a "puff." turn the engine over by hand until the timing mark is lined up at zero. Check the distributor to see the rotor is pointed at the No. 1 terminal on the cap. Then triple-check the valves on No. 1 to see they're both closed.
Viola!
No. 1 is at TDC on the compression stroke. :party:
Viola!
No. 1 is at TDC on the compression stroke. :party:
Team Owner
Joined: Sep 2003
Posts: 88,393
Likes: 2
From: eville in
Re: Compression Guage Question (The Dude)
yep, use your finger, bump, it so you don't go past TDC you may also feel
some compression before ex. opens bump it around a few times you'll get
the feel of it, company's also sell a tool called a wistler that some like, it goes
in the plug hole and makes noise when piston coming up to TDC on compression stroke
some compression before ex. opens bump it around a few times you'll get
the feel of it, company's also sell a tool called a wistler that some like, it goes
in the plug hole and makes noise when piston coming up to TDC on compression stroke
Advanced
Joined: Sep 2003
Posts: 91
Likes: 0
From: Denver Colorado
Re: Compression Guage Question (Cali,68,L-79)
"It looks like the end of a tire valve (schraeder)"
It is a schrader valve, it is only slightly different in that the spring is not as heavy. You can use the same tool to remove it, that you use to remove a tire valve. but dont loose it, because while a tire valve will fit, it will make your compression gauge read off several pounds, ask me how I know? :rolleyes:
It is a schrader valve, it is only slightly different in that the spring is not as heavy. You can use the same tool to remove it, that you use to remove a tire valve. but dont loose it, because while a tire valve will fit, it will make your compression gauge read off several pounds, ask me how I know? :rolleyes:
Thread Starter
Le Mans Master
Joined: Jan 2001
Posts: 6,938
Likes: 1
From: San Diego CA
Re: Compression Guage Question (Garrett1972)
"It looks like the end of a tire valve (schraeder)"
It is a schrader valve, it is only slightly different in that the spring is not as heavy. You can use the same tool to remove it, that you use to remove a tire valve. but dont loose it, because while a tire valve will fit, it will make your compression gauge read off several pounds, ask me how I know? :rolleyes:
It is a schrader valve, it is only slightly different in that the spring is not as heavy. You can use the same tool to remove it, that you use to remove a tire valve. but dont loose it, because while a tire valve will fit, it will make your compression gauge read off several pounds, ask me how I know? :rolleyes:
Advanced
Joined: Sep 2003
Posts: 91
Likes: 0
From: Denver Colorado
Re: Compression Guage Question (Cali,68,L-79)
My compression gauge has a large rubber end to fit in the spark plug hole, while some one bumps the motor over, you watch the gauge. The reading should rise, and reach its highest reading about the same time that the timing mark comes around to the pointer. That should be top dead center, If the reading starts to go down you have gone to far. If you leave the schrader valve in the gauge you will only get the maximum pressure reading. If you take to long, the pressure will bleed off (think leak down test).
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
2027 Corvette vs The World: Every C8 vs Its Closest Competitor
Joe Kucinski
10 Most Common Corvette Problems of the Last 20 Years!
Joe Kucinski
Thread Starter
Le Mans Master
Joined: Jan 2001
Posts: 6,938
Likes: 1
From: San Diego CA
Re: Compression Guage Question (Garrett1972)
Bawahaha!! I fogot to tell you guys last night as I bumped over the car I had forgot to ensure the guage was tightly fit into the quick disconnect hose fitting and as I bumped it over I heard a pop and saw the guage fly across the garage. Luckily it went into the rag bin and didn't scratch it.
:rolleyes:
:rolleyes: