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-   -   Compression numbers ? (https://forums.wmpdevserver1.com/community/showthread.php?t=17676)

Joker2 05-29-2012 01:29 PM

Compression numbers ?
 
I took some numbers today with a known good tester. My engine was rebuilt as some of you have seen my story in the past. Running good just wanted to know what you thought of these #'s

Cold with all plugs out.
1,103 3, 100 5, 100

2, 115 4, 115 6, 112-115

Hot with all plugs out.
1, 97-99 3, 97-99 5, 97-99

2, 105 4, 105 6, 105

They seem to be within the limits even though they all are a little low, from what I have read they should be more around 120, wondering if this is because of the rebuild ?

THEFERMANATOR 05-29-2012 01:39 PM

What would concern me is the drop of 10 PSI when hot on the 3. That sounds to me like to much ring end gap. They don't look that bad as it looks like they are even on each bank. It looks like it was decked on one side. Not to sure what to expect out of that 60 degree looper. I wonder what tsubaki gets out of his as he has a simliar engine?

smokeonthewater 05-29-2012 01:40 PM

You DID do this test at WOT didn't you?

Joker2 05-29-2012 01:50 PM

No, I did not

smokeonthewater 05-29-2012 01:57 PM

try again with a warm engine at wot... I'd bet dollars to doughnuts that you like the numbers better

tsubaki 05-29-2012 02:24 PM

I don't remember testing mine so I'm no help.
From what I remember wide open throttle is the only correct way to get a reliable reading.
Remember my Father telling me he picked up an engine for parts. The guy he bought it from said it ran like crap and had low compression, basically burned up. A good while later Daddy cleaned the carbs, done a compression test and it ran as good as any he had ever owned. He later ran across the guy he got the motor from and questioned him on the low compression. The guy did the test in the idle position.

Is it possible the side with the lower compression might be head gasket related or the like?

Joker2 05-29-2012 02:28 PM

Thanx I will try that

Joker2 05-29-2012 02:31 PM

Just bury the shifter forward, that would be putting it in gear, is this OK. My shifter is not the kind you can pull out and rev in nuetral. I can't rev my engine in nuetral, only a little with the fast idle lever.

tsubaki 05-29-2012 02:34 PM

Yes or while you are at the rear of the engine, you can just open all the butterflies to do the same thing.
I assume you are jumping the starter solenoid to do the test. As the starter won't engage with the shifter in forward by using the key.

Joker2 05-29-2012 05:09 PM

I was just using the key with the emergency lanyard disengaged, that will not work with the shifter forward right?


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