cylinder compression test
Thread Starter
Melting Slicks
Joined: Jul 2011
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From: Bornem
cylinder compression test
I checked the compression of my 1963 327 Not sure what version it is, looks like basic 250hp, but may have been modified.
Following are the readings:
Cyl 8: 163 psi
Cyl 6: 165 psi
Cyl 4: 165 psi
Cyl 2: 175 psi
Cyl 7: 154 psi
Cyl 5: 160 psi
Cyl 3: 185 psi
Cyl 1: 175 psi
I had the engine run, idle was not very stable (but the carb is definitely not well tuned), higher rpm seemed to be ok with not strange noises.
Is this block still useable? Or should I consider a replacement? (I don't wanna race with it, just cruising)
Following are the readings:
Cyl 8: 163 psi
Cyl 6: 165 psi
Cyl 4: 165 psi
Cyl 2: 175 psi
Cyl 7: 154 psi
Cyl 5: 160 psi
Cyl 3: 185 psi
Cyl 1: 175 psi
I had the engine run, idle was not very stable (but the carb is definitely not well tuned), higher rpm seemed to be ok with not strange noises.
Is this block still useable? Or should I consider a replacement? (I don't wanna race with it, just cruising)
Thread Starter
Melting Slicks
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From: Bornem
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Burning Brakes
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Ideally you want less than 10% variation, but if the engine is running fine then you may as well wait for something else to go wrong or for one of the numbers to really drop. What I like to do it track my numbers over time so I can tell if there is something going on. If they hold steady, then there is no wear related issues and the car should maintain as it is.
If it ain't broke, don't fix it. As a cruiser, you might be able to go ten or more years with an engine that does have problems, assuming you are not driving a ton of miles.
I would also guess the engine has been rebuilt, as those numbers imply a static compression ratio of over 10:1 (maybe 12:1?).
If it ain't broke, don't fix it. As a cruiser, you might be able to go ten or more years with an engine that does have problems, assuming you are not driving a ton of miles.
I would also guess the engine has been rebuilt, as those numbers imply a static compression ratio of over 10:1 (maybe 12:1?).
Race Director
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From: Close to DC
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Those numbers look very good. How many miles on the engine? If you start to consistently see a puff of blue smoke after startup, the valve seal are waring. It's an easy fix if necessary. 
Dennis
Dennis
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Assuming your gauge is accurate, according to one book I have it states that it should be 160 #’s, +/- 20 #’s.
The higher readings could be carbon on the pistons.
Providing there is no sign of oil deposits on the plugs and as you say there are no noises, I see no reason not to put it back in service.
Joe
The higher readings could be carbon on the pistons.
Providing there is no sign of oil deposits on the plugs and as you say there are no noises, I see no reason not to put it back in service.
Joe
Last edited by plaidside; Oct 16, 2011 at 08:07 AM. Reason: typo
Thread Starter
Melting Slicks
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From: Bornem
Assuming your gauge is accurate, according to one book I have it states that it should be 160 #’s, +/- 20 #’s.
The higher readings could be carbon on the pistons.
Providing there is no sign of oil deposits on the plugs and as you say there are no noises, I see no reason to put it back in service.
Joe
The higher readings could be carbon on the pistons.
Providing there is no sign of oil deposits on the plugs and as you say there are no noises, I see no reason to put it back in service.
Joe
I measuered it all twice, to be sure.
All my readings were after 3 compression cycles. 90% of the value reached after first cycle.
Thread Starter
Melting Slicks
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From: Bornem
hi Dennis,what is 'an easy fix', working on valves sounds scary to me ;-)
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Race Director
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If your not ready to take MikeM's advice you should probably look for a leak down testing gage. It will provide a better picture of the condition of the engine and if the rings or valves are leaking some compression.
Race Director
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From: Clayton NC
Ideally you want less than 10% variation, but if the engine is running fine then you may as well wait for something else to go wrong or for one of the numbers to really drop. What I like to do it track my numbers over time so I can tell if there is something going on. If they hold steady, then there is no wear related issues and the car should maintain as it is.
If it ain't broke, don't fix it. As a cruiser, you might be able to go ten or more years with an engine that does have problems, assuming you are not driving a ton of miles.
I would also guess the engine has been rebuilt, as those numbers imply a static compression ratio of over 10:1 (maybe 12:1?).
If it ain't broke, don't fix it. As a cruiser, you might be able to go ten or more years with an engine that does have problems, assuming you are not driving a ton of miles.
I would also guess the engine has been rebuilt, as those numbers imply a static compression ratio of over 10:1 (maybe 12:1?).
Le Mans Master
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Jim
Thread Starter
Melting Slicks
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From: Bornem
This may be a very stupid question, don't shoot ;-) Given that I have one piston a bit out of range with the others, is just replacing the rings on the worst piston a possible fix?
Le Mans Master
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These cars sit a lot. Drive it a while and retest. Your numbers are not bad. You may see the compression come up in the weak cylinders just by driving it some. Take it up a good hill, something that keeps your engine loaded for a bit. A loaded engine puts pressure on the rings and might seat them better. Adding oil to your cylinder as you did makes the rings seal better. You are not far off, drive it and see what happens.
Good luck with your new toy.
Good luck with your new toy.
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