My latest test results are as follows:
#1 - 120 ft./lbs.
#2 - 125
#3 - 112
#4 - 132
The Haynes manual says 93 minimum on any cylinder and 21 maximum difference between cylinders. Between #3 and #4 is, of course, my concern. Is it time for a rebuild or can I wait for a while, monitoring as I go? I have to yank the engine now anyway for some other work, so that's an argument in favor of doing it now, but that being said, if I can get away with it for a year or so, I'd rather wait (for financial reasons). What say all?
Full Version: Compression Test Results
Not really a complete test to make a decision.
Compression test sucks air in, and compresses it.
So, intake port differences, intake valve adjustment differences both affect your readings.
A leak down test will add more information to your readings.
I would check the valve adjustments and do the test again.
Throttle body pinned wide open.
Compression test sucks air in, and compresses it.
So, intake port differences, intake valve adjustment differences both affect your readings.
A leak down test will add more information to your readings.
I would check the valve adjustments and do the test again.
Throttle body pinned wide open.
QUOTE(r_towle @ Aug 26 2013, 09:42 PM) 
Not really a complete test to make a decision.
Compression test sucks air in, and compresses it.
So, intake port differences, intake valve adjustment differences both affect your readings.
A leak down test will add more information to your readings.
I would check the valve adjustments and do the test again.
Throttle body pinned wide open.
Engine is supposed to be hot, and all plugs removed while cranking also.
QUOTE(bulitt @ Aug 26 2013, 10:04 PM)
QUOTE(r_towle @ Aug 26 2013, 09:42 PM)
Not really a complete test to make a decision.
Compression test sucks air in, and compresses it.
So, intake port differences, intake valve adjustment differences both affect your readings.
A leak down test will add more information to your readings.
I would check the valve adjustments and do the test again.
Throttle body pinned wide open.
Engines is supposed to be hot, and all plugs removed while cranking also.
Good point.
Rings won't fit right till its hot.
The engine was hot and all the plugs were removed - the valves were adjusted only 400 miles ago. I ran the same test two months ago with similar results. I haven't had a leakdown test done, though.
As I said, the difference between #3 and #4 concern me, though it hasn't gotten any worse lately.
As I said, the difference between #3 and #4 concern me, though it hasn't gotten any worse lately.
I'd suggest an "engine rebuild" savings account. And a compression check every oil change. When the numbers start to drop, stop driving it and use your savings account to (partially?) fund your rebuild.
--DD
--DD
It will drive for thousands of miles still. But time to save up.
QUOTE(john_g @ Aug 26 2013, 05:37 PM)
My latest test results are as follows:
#1 - 120 ft./lbs.
#2 - 125
#3 - 112
#4 - 132
The Haynes manual says 93 minimum on any cylinder and 21 maximum difference between cylinders. Between #3 and #4 is, of course, my concern. Is it time for a rebuild or can I wait for a while, monitoring as I go? I have to yank the engine now anyway for some other work, so that's an argument in favor of doing it now, but that being said, if I can get away with it for a year or so, I'd rather wait (for financial reasons). What say all?
I would note that your car passes the Haynes spec. Not by too awfully much, but it passes. A leak down test will tell more, but so will looking for things like a puff of smoke when you let off (guides) or just plain bluish smoke when you pull away from a stop light (probably worn rings). The saving for a rainy day, especially if you work under cover, is great advice. Meanwhile, drive on.
Yes, leak down test is recommended....
I Remember an old mechanik with master degree.
He allways said, engine must cleaned up first. He warmed up the engine, fill a quarter liter of break fluid step by step into the carb and open throttle.
What will i say, sometimes it helps to upgrade compression test.
I Remember an old mechanik with master degree.
He allways said, engine must cleaned up first. He warmed up the engine, fill a quarter liter of break fluid step by step into the carb and open throttle.
What will i say, sometimes it helps to upgrade compression test.
I can't claim to be an expert, but with air cooled airplane engines, compression tests have been pretty much discredited as indicators for a rebuild. Doesn't anyone do borescoping to look at the actual condition inside the cylinder?
Just sayin'
Just sayin'
drive it really hard for a couple of hundred miles with some seafoam in the gas or what ever your favorite topengine cleaner is.
you just might notice an improvement in the cylinder sealing.
the above is often referred to as an "Italian tune up"!
you just might notice an improvement in the cylinder sealing.
the above is often referred to as an "Italian tune up"!
QUOTE(timofly @ Aug 27 2013, 07:40 PM)
I can't claim to be an expert, but with air cooled airplane engines, compression tests have been pretty much discredited as indicators for a rebuild. Doesn't anyone do borescoping to look at the actual condition inside the cylinder?
Just sayin'
And now you can buy a USB bore camera for 30$
just drive it
There are diffrent possible reasons for a lost compression, if the piston rings stuck, no camera can show this.
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