LT1-LT4 Modifications 1993-97 Gen II Small Block V8

what the hell

Thread Tools
 
Search this Thread
 
Old May 21, 2011 | 07:33 PM
  #1  
LigHtEmUp01's Avatar
Thread Starter
TECH Apprentice
 
Joined: Feb 2010
Posts: 319
Likes: 0
Default what the hell

so i ran a compression test and the right side cylinders were around 130 and the left side the highest i had was 90 the rest were 80 and 85. what could this mean?
Reply
Old May 21, 2011 | 08:30 PM
  #2  
robmnrd's Avatar
Staging Lane
 
Joined: Jul 2010
Posts: 51
Likes: 0
Default

It could mean it's time for a rebuild with all the goodies.
Reply
Old May 21, 2011 | 08:46 PM
  #3  
BlackBird87's Avatar
TECH Regular
iTrader: (6)
 
Joined: Dec 2009
Posts: 419
Likes: 0
From: Elmwood Park
Default

explains why youre down on power, prob need to be torn down again
Reply
Old May 21, 2011 | 08:58 PM
  #4  
trilkb's Avatar
TECH Addict
iTrader: (4)
 
Joined: Jul 2005
Posts: 2,106
Likes: 80
Default

This is just a shot in the dark here....but i would say from the information givin it means that you are having some kind of a...ah whats the word? i guess you could call it a "compression loss"(??) due to the numbers being lower on the left side of the engine vs the right side of the engine.

I guess what im trying to say here is there is a difference in the numbers you have stated. this gives me the idea that its losing compression on the left side vs the right side.

Perhaps turn your headlights on and try again? if this doesnt work, get the codes cleared.
Reply
Old May 21, 2011 | 09:11 PM
  #5  
defaultexistence's Avatar
TECH Fanatic
iTrader: (11)
 
Joined: Sep 2005
Posts: 1,954
Likes: 1
From: fort walton beach,fl
Default

Originally Posted by trilkb
This is just a shot in the dark here....but i would say from the information givin it means that you are having some kind of a...ah whats the word? i guess you could call it a "compression loss"(??) due to the numbers being lower on the left side of the engine vs the right side of the engine.

I guess what im trying to say here is there is a difference in the numbers you have stated. this gives me the idea that its losing compression on the left side vs the right side.

Perhaps turn your headlights on and try again? if this doesnt work, get the codes cleared.

Boy you sure come across as an up and coming smart *** ******** with that ****

I'm sure since he can do a compression test ..he knows he has compression loss..
some explanations could be improperly set up valve lash ,cam timing ,worn /bent valves ,blown head gasket,cracked head,...
OP ,have you had motor apart recently or just finished build ??
Reply
Old May 22, 2011 | 02:04 AM
  #6  
Big Al's Avatar
TECH Resident
iTrader: (1)
 
Joined: May 2005
Posts: 970
Likes: 1
Default

Remove the valve cover and tap the top of the valves in the lowest cylinder lightly with a small hammer, then test it again. It it stays the same, put a few drops of oil in the spark plug hole and see if it goes up. From that you can determine what's going on.

I would first be sure you're getting a good seal to the compression gauge, and be sure the battery is not running down. Tie the throttle open part way. Disable the ignition. Most good testers screw into the plug hole. Don't discount the battery. If the RPM slows the numbers will go down. Crank through five compression strokes and stop. It's best to do the test with the engine at operating temperature. On my Z28 that would cause major burns, so it's not an option. Cold engines will read lower compression numbers than warm engines, high numbers are not important, even numbers are.

Al 95 Z28
Reply
Old May 22, 2011 | 02:29 AM
  #7  
96LT1355Z28's Avatar
10 Second Club
15 Year Member
Photogenic
Photoriffic
Liked
iTrader: (2)
 
Joined: Nov 2007
Posts: 841
Likes: 9
From: Holden, MO (KC)
Default

^^ Good explination, also it helps to unplug your injectors so your not washing down the cylinder walls.
Reply
Old May 22, 2011 | 07:57 AM
  #8  
lttransam's Avatar
Launching!
iTrader: (12)
 
Joined: Sep 2009
Posts: 212
Likes: 0
From: burton mi
Default

i had compression issues all last summer, pulled the motor and ended up being the heads.. i had 3 valve seats that cracked and wasn't sealing, i feel for ya man i HATE compression issues..
Reply
LS1 Tech Stories

The Best V8 Stories One Small Block at Time

story-0

Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph

 Verdad Gallardo
story-1

Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked

 Pouria Savadkouei
story-2

Top 10 Most Powerful Chevy Trucks Ever Made!

 
story-3

Hennessey's New Supercharged Silverado ZR2 Has 700 HP

 Verdad Gallardo
story-4

Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes

 Verdad Gallardo
story-5

Awesome K5 Blazer Restomod Comes With C7 Corvette Power

 Verdad Gallardo
story-6

10 Camaros You Should Never Buy

 
story-7

10 LS Engine Myths That Refuse to Die

 Verdad Gallardo
story-8

Five Reasons the Camaro Was the Most Pivotal Player in the Pony Car Wars 2.0

 Brett Foote
story-9

10 Reasons the LS7 Is GM's Most Extreme Naturally Aspirated V8 Engine Ever

 Verdad Gallardo
Old May 22, 2011 | 08:05 AM
  #9  
trilkb's Avatar
TECH Addict
iTrader: (4)
 
Joined: Jul 2005
Posts: 2,106
Likes: 80
Default

lol default, He knows compression is down, he knows the numbers, i honestly read it and didnt understand what else he needed to know lol.
Reply
Old May 22, 2011 | 07:03 PM
  #10  
LigHtEmUp01's Avatar
Thread Starter
TECH Apprentice
 
Joined: Feb 2010
Posts: 319
Likes: 0
Default

obviously i know im low on compression the question here was what could cause one side to be so low? im leaning more toward valve issues. this motor has less than 800 miles on it
Reply
Old May 22, 2011 | 07:31 PM
  #11  
96capricemgr's Avatar
11 Second Club
iTrader: (1)
 
Joined: Sep 2004
Posts: 11,975
Likes: 15
Default

Obviously the difference is critical but have you ever used the gauge on another known good engine??

I have never seen a stock LT1 crank below 180psi or so and after an AutoRX treatment that engine at over 180k miles was back up over 195psi. All my modded stuff has been 225+psi.

Same gauge read 70-75psi on my 40yo 6hp boat motor which was right in spec so I have faith in my gauge, it doesn't just read high.
Reply
Old May 22, 2011 | 07:41 PM
  #12  
RedHotG8's Avatar
TECH Fanatic
iTrader: (1)
 
Joined: May 2010
Posts: 1,419
Likes: 1
From: Chicagoland
Default

If you only have 800 miles on the motor, you should ask the engine builder why the compression readings vary so much, not us guys.
Reply
Old May 24, 2011 | 09:51 PM
  #13  
LigHtEmUp01's Avatar
Thread Starter
TECH Apprentice
 
Joined: Feb 2010
Posts: 319
Likes: 0
Default

he said because the rings are not seated yet i used a different gauage and the lowest i got was 165 and highest 205
Reply
Old May 24, 2011 | 10:08 PM
  #14  
96capricemgr's Avatar
11 Second Club
iTrader: (1)
 
Joined: Sep 2004
Posts: 11,975
Likes: 15
Default

IMO is the rings aren't seated yet, they wont. Was the tune really really bad at first or anything?
Reply
Old May 24, 2011 | 10:10 PM
  #15  
RedHotG8's Avatar
TECH Fanatic
iTrader: (1)
 
Joined: May 2010
Posts: 1,419
Likes: 1
From: Chicagoland
Default

When the rings get seated do another compression test. If the readings still vary your engine builder better have a better answer for you.
Reply




All times are GMT -5. The time now is 08:09 AM.

story-0
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph

Slideshow: A modern Camaro transformed into a retro icon, this limited-run "Bandit" build blends nostalgia with brute force in a way few revivals manage.

By Verdad Gallardo | 2026-04-21 13:57:02


VIEW MORE
story-1
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked

Slideshow: Cadillac didn't just crash the high-performance luxury vehicle party, it showed up loud, supercharged, and occasionally a little unhinged...

By Pouria Savadkouei | 2026-04-16 10:05:15


VIEW MORE
story-2
Top 10 Most Powerful Chevy Trucks Ever Made!

Slideshow: Top ten most powerful Chevy trucks ever made

By | 2026-03-25 09:22:26


VIEW MORE
story-3
Hennessey's New Supercharged Silverado ZR2 Has 700 HP

Slideshow: Hennessey has turned the Silverado ZR2 into a 700-hp off-road monster with supercharged V8 power and a limited production run.

By Verdad Gallardo | 2026-03-24 18:57:52


VIEW MORE
story-4
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes

Slideshow: A one-off sports car that looks like a vintage Italian exotic-but hides a C6 Corvette underneath-just sold for the price of a new mid-engine Corvette.

By Verdad Gallardo | 2026-03-23 18:53:41


VIEW MORE
story-5
Awesome K5 Blazer Restomod Comes With C7 Corvette Power

Slideshow: A heavily reworked 1972 K5 Blazer swaps its off-road roots for a low-slung street-focused build with modern V8 power.

By Verdad Gallardo | 2026-03-09 18:08:45


VIEW MORE
story-6
10 Camaros You Should Never Buy

Slideshow: There are thousands of used Camaros on the market but we think you should avoid these 10

By | 2026-02-17 17:09:30


VIEW MORE
story-7
10 LS Engine Myths That Refuse to Die

Slideshows: Which one of these myths do you believe?

By Verdad Gallardo | 2026-01-28 18:10:11


VIEW MORE
story-8
Five Reasons the Camaro Was the Most Pivotal Player in the Pony Car Wars 2.0

The world was a better place when it was still around.

By Brett Foote | 2026-01-23 09:20:37


VIEW MORE
story-9
10 Reasons the LS7 Is GM's Most Extreme Naturally Aspirated V8 Engine Ever

Slideshow: The 7.0-liter LS7 was designed for absolute cutting-edge performance.

By Verdad Gallardo | 2026-01-07 18:36:00


VIEW MORE