What are good cold compression numbers?

[Old & In the way]

Re: What are good cold compression numbers?

Hi,
AQ130D from Seloc VP manual:
Compression Ratio: 9.5 : 1
Compression @ starter motor speed (200 rpm) 170-200
other stuff:
HP 130
CID 121
FO 1-3-4-2
Ign:
Basic: 8 degrees btdc
Strob: 25-27 degrees at @3000 rpm
Dwell: 62 +3
Points: .016 - .020
Plugs: .028 - .032
Idle: 900
Max: 5100

I hope this helps.
ed

 

[Old & In the way]

Re: What are good cold compression numbers?

Hi

I'm here to learn too.
I'm confused about the note by dontask about needing it to be at WOT during the compression test, I don't think we have a choke on this engine - so would the throttle position matter that much ?
thanks.
ed

 

[mkast]

Re: What are good cold compression numbers?

Ask yourself how much air makes it past the closed throttle plates as opposed to wide open?

 

[PiratePast40]

Re: What are good cold compression numbers?

I'm finding out that the compression numbers are for a new motor or a motor with a fresh rebuild. Another issue with mine is that it hasn't run enough in the last 2 years to reseal the rings. The last test gave the cylinders a consistant 120psi with a bump up to 140 or 150 after squirting WD40 in the cylinders. I've been told that my tests are essentially worthless until there is some recent run time on the motor and that my numbers aren't terrible - just the sign of a worn but not necessarily worn out motor.

 

[Old & In the way]

Re: What are good cold compression numbers?

Throttle plates ?

Don't thinks so..

ed

 

[Old & In the way]

Re: What are good cold compression numbers?

I'm finding out that the compression numbers are for a new motor or a motor with a fresh rebuild. Another issue with mine is that it hasn't run enough in the last 2 years to reseal the rings. The last test gave the cylinders a consistant 120psi with a bump up to 140 or 150 after squirting WD40 in the cylinders. I've been told that my tests are essentially worthless until there is some recent run time on the motor and that my numbers aren't terrible - just the sign of a worn but not necessarily worn out motor.

------------------------------
Sound good -
I saw this on the internet for testing the low compression cylinder:
All a "wet test" entails is a bit of oil in the low cylinder...
11. Add one capful (1-2 tablespoons) of oil to the cylinder with low compression.
12. Let it sit for a minute to allow the oil to flow down and coat the sides of the cylinder and piston. If there are any gaps in the rings, the oil will seal them for the next few minutes.

13. Crank the engine for 4 revs, remembering to floor the throttle.
14. If the reading improved significantly (more than 30 psi), your rings are probably worn.

15. If there is little or no improvement, take it to a garage that can perform a leak-down test to determine where the compression is escaping (intake, exhaust, crankcase, gasket, etc.).

16. Replace the plugs, preferably in the same cylinders they came out of. You may want to clean or re-gap them first, or put in new ones. A dab of anti-seize on the threads would be a good idea.


----------------

don't know if this is valid info-

ed

 

[PiratePast40]

Re: What are good cold compression numbers?

Sounds like some more good troubleshooting info. For my motor, I'm going to run it (assuming I can get the thing in the water) and do all the checks again.

On the throttle position thing - it makes sense to me (on a carb engine) to have the throttle butterfly wide in order to allow air into the cylinders.

 

[SeanMcl]

Re: What are good cold compression numbers?

Hey Pirate, what's with using WD40 for the wet test? Is this some secret I am unaware of? Since the motor will have regular oil in it when it runs, I've always just dribbled a capful of oil down the spark plug hole. Hit me with the clue stick, por favor.

 

[Tacklewasher]

Re: What are good cold compression numbers?

Hey Pirate, what's with using WD40 for the wet test? Is this some secret I am unaware of? Since the motor will have regular oil in it when it runs, I've always just dribbled a capful of oil down the spark plug hole. Hit me with the clue stick, por favor.

I'm thinking the WD-40 is a bad idea for this test. It will do more to clean oil from the cylinder walls than to seal rings.

Also seen it with a squirt of oil from an oil can.

 

[Old & In the way]

Re: What are good cold compression numbers?

Hey Pirate, what's with using WD40 for the wet test? Is this some secret I am unaware of? Since the motor will have regular oil in it when it runs, I've always just dribbled a capful of oil down the spark plug hole. Hit me with the clue stick, por favor.

I have seen a friend use wd-40 for a seized outboard in the cylinders but agree that it sounds counter-productive to coat the walls for the rings.

ed

 

[chumslinger]

Re: What are good cold compression numbers?

i seem to remember reading a post where someone had a similar problem. after using the engine for a short time, the compression numbers started looking better. i would just run the engine for a while, and hope it checks out better after using it awhile. i think it was something like the rings were sticking in the pistons, but after some use, the rings freed themselves and started sealing better. worth a shot! good luck

 

[JustJason]

Re: What are good cold compression numbers?

the biggest thing with low compression is you lose a proper idle and end up compensating by cranking up the idle to a level that the gears are going to not like.
If it hold a decent proper idle, and your getting decent wot performance. I'd say leave it.

Compression in the 1-teens isn't that aweful. Just and old engine. Run it till it breaks.