|
|
|
06-27-2009, 10:37 AM
|
#1 |
|
Registered User
 
Join Date: Feb 2004
Location: Idaho
Posts: 4,034
|
Low Compression?
I have 90psi in cylinders 1,2,3,4,7,8 and 60psi in cylinder 6, 110psi in the remaining cylinder. I did not do a wet test. Stock 350, any clue or ideas on life left in the motor?
Other then low compression, runs with a slight miss.
__________________
"Remember, They can Kill You, but they can't eat You, That's against the law!!!!!!!!!" |
|
|
|
06-27-2009, 04:47 PM
|
#2 |
|
Gearhead and audio junkie
Join Date: Aug 2008
Location: nunyah
Posts: 452
|
Re: Low Compression?
Could be your valves, or worn rings. how many miles does it have?
|
|
|
|
|
06-27-2009, 05:22 PM
|
#3 |
|
Size Matters
Join Date: Aug 2007
Location: Lyman, SC
Posts: 9,189
|
Re: Low Compression?
Before you did the compression test, how long had it been since the truck ran? If it has ran recently, I doubt if a wet test will improve it significantly. If this is in fact the case, you are probably looking at a rebuild. X2 on the how many miles?
__________________
"Reading the owners manual is only for quitters." Jason Harper, Bloomberg News.   ...WOOOO HOOOO!!!!
|
|
|
|
|
06-27-2009, 07:23 PM
|
#4 |
|
Senior Member
Join Date: Dec 2006
Location: Studio City, Calif.
Posts: 2,861
|
Re: Low Compression?
Once I got 1/2 through a "compression test" and realized that I forgot to set the throttle wide open and readings came right back up when done correctly.
I'm not trying to suggest that you would do a dumb thing like I did. But thought I'd say it anyway. But if those are the real figures I'd say it's toast.
__________________
'69 GMC C2500 Custom Camper, 8 1/2' bed, New GM 350, NP 435 Close Ratio 4spd. Trans., 3.73 Dana-60 open.Camper and Trailer wiring, PS, PB, AC, tach , three gas tanks, 2nd owner, Work-Truck supreme. Best $300 I ever spent. |
|
|
|
|
06-27-2009, 11:08 PM
|
#5 |
|
its all about the +6 inches
Join Date: Jan 2001
Location: Hilliard Ohio
Posts: 2,693
|
Re: Low Compression?
I was wondering the same thing as WLH.... did you use the tool properly?
If those are real numbers, then i wouldn't even bother with a wet test, and I'd start looking for another engine. |
|
|
|
|
06-27-2009, 11:25 PM
|
#6 |
|
My Carbon Footprint
Join Date: Oct 2008
Location: Orygun
Posts: 5,527
|
Re: Low Compression?
run er till she blows.
|
|
|
|
|
06-28-2009, 01:57 AM
|
#7 |
|
Registered User
Join Date: Dec 2006
Location: Porter Ranch, CA
Posts: 978
|
Re: Low Compression?
With compression like that, you could run one hell of a BLOWER on that thing!!! For about 10 minutes...
|
|
|
|
|
06-28-2009, 04:40 AM
|
#8 |
|
Senior Member
Join Date: Jul 2001
Location: Muskegon,MI,USA
Posts: 6,026
|
Re: Low Compression?
If you connect compressed air to each cylinder the noise of the escaping air will indicate where the problem is. I do the test with the valve covers off to make sure the valves of the cylinder being tested are closed.
Not knowing the history of the engine, I would not rule out valve adjustment. Jim
__________________
1971 Shortbox step side 4x4, 350 sbc, 3:07 rear end 1965 Impala SS 400 sbc, Muncie rock crusher 1966 Impala SS 396 bbc, TH 400 1969 El Camino, 350 sbc, TH 350 1971 Snowplow built on a Blazer frame 1972 GMC Short bed, stepside, TH 400, 427 BBC |
|
|
|
|
06-28-2009, 07:22 AM
|
#9 |
|
sharp as a marble
Join Date: Jan 2007
Location: atlantic beach,florida
Posts: 1,082
|
Re: Low Compression?
all of the above. I also will do what JIMK says. It will allow you to determine if the problem is in the head or if it is the rings. If the air blows out the carb, it is an intake valve, thru the exhaust, exhaust valve, thru the engine a ring. The last one is a bit tricky, got to listen close
|
|
|
|
|
06-28-2009, 12:57 PM
|
#10 |
|
Registered User
Join Date: Feb 2004
Location: Idaho
Posts: 4,034
|
Re: Low Compression?
Thanks for all the help,
All that I did to check the compression was remove the plug, insert the compression tester, crank the motor and let it run.
__________________
"Remember, They can Kill You, but they can't eat You, That's against the law!!!!!!!!!" |
|
|
|
|
06-28-2009, 01:27 PM
|
#11 |
|
its all about the +6 inches
Join Date: Jan 2001
Location: Hilliard Ohio
Posts: 2,693
|
Re: Low Compression?
then those numbers don't mean anything at all.
Full charge on battery All 8 plugs removed install tester in a plug hole Hold throttle wide open crank while observing guage Should have all bee in the instructions with the guage. |
|
|
|
|
06-28-2009, 03:37 PM
|
#12 |
|
Size Matters
Join Date: Aug 2007
Location: Lyman, SC
Posts: 9,189
|
Re: Low Compression?
Yep. Since you ran the engine with the gauge installed, there may be damage to the gauge. There is a shrader valve in the hose that may not hold pressure. If you show no compression or very low compression when you check it as LHM says, check that valve. I saw a guy pull a head off a V12 once due to a bad valve in his gauge...nothing wrong with the compression on the V12. Doh!
__________________
"Reading the owners manual is only for quitters." Jason Harper, Bloomberg News. ...WOOOO HOOOO!!!!
|
|
|
|
 |
| Bookmarks |
| Thread Tools | |
| Display Modes | |
|
|
Hybrid Mode
