Gene
A Valve is a likely culprit all right. Often a worn valve guide will permit
the valve to seat a bit off axis and give results like this also- whats your
blowby situation? Bad knocking or high revs running the top ring into the
ridge at the cylinder top can break the top piston ring and drastically
lower compression without any other problems like extra oil comsumption.
Pull the pcv valve and block the port and watch at the crankcase air intake
from the air filter housing for blowby vapours. If theres a very smooth flow
and minimal volume ( steaming like a cup of tea, not blowing violently like
a boiling kettle) it is probably fine and the valve is the place to look.
Ideally, there is no blowby on a warm idling engine, and just the tinyest
wisp apparent under a small load like say putting it in 'drive' range.
You can pull the rocker covers off and wiggle the valves on the affected
cylinders to see if the guides are loose.
Doubt it will hurt anything for the moment to drive it so long as it seems
to work OK and not use extra oil and gas.
Good luck, let us know what you discover!
Brent
- ----- Original Message -----
From:
To:
Sent: Wednesday, 25 August, 1999 10:43 AM
Subject: Re: GMC: engine problems
>I decided to check my engine compression before IOWA AND ALBU.
>I got three readings of around 70 and the rest were150 and 160 with one at
>130.oil in the cylinder only helped by about 10.
>Does this sound like valve problems?
>I'm sure going to have to work fast get ready.
>Gene
>73 GLACIER
>
A Valve is a likely culprit all right. Often a worn valve guide will permit
the valve to seat a bit off axis and give results like this also- whats your
blowby situation? Bad knocking or high revs running the top ring into the
ridge at the cylinder top can break the top piston ring and drastically
lower compression without any other problems like extra oil comsumption.
Pull the pcv valve and block the port and watch at the crankcase air intake
from the air filter housing for blowby vapours. If theres a very smooth flow
and minimal volume ( steaming like a cup of tea, not blowing violently like
a boiling kettle) it is probably fine and the valve is the place to look.
Ideally, there is no blowby on a warm idling engine, and just the tinyest
wisp apparent under a small load like say putting it in 'drive' range.
You can pull the rocker covers off and wiggle the valves on the affected
cylinders to see if the guides are loose.
Doubt it will hurt anything for the moment to drive it so long as it seems
to work OK and not use extra oil and gas.
Good luck, let us know what you discover!
Brent
- ----- Original Message -----
From:
To:
Sent: Wednesday, 25 August, 1999 10:43 AM
Subject: Re: GMC: engine problems
>I decided to check my engine compression before IOWA AND ALBU.
>I got three readings of around 70 and the rest were150 and 160 with one at
>130.oil in the cylinder only helped by about 10.
>Does this sound like valve problems?
>I'm sure going to have to work fast get ready.
>Gene
>73 GLACIER
>
