Compression Tests Results Question

I have a question concerning "compression tests results" that I took this last week. I hope that you won't mind that these compression tests were on a Chevy Inline 6 (230ci) and not a Ford Inline 6, which I also have (a 200ci) and post on here regularly, but here goes: My first time around on taking compression tests on the 230ci engine, I disarmed the coil, opened the carb throttle plate, and then tested one cylinder at a time, with the other 5 spark plugs still in the block. Here were the results, or the #'s: (**Note: according to the engine spec's on the 230ci engine the compression is 130psi) #1-116, #2-135, #3-130, #4-114, #5-122, #6-124. Then I did a followup compression test(s) where I removed all of the spark plugs before I started testing each individual cylinder, and here are the results: #1-90, #2-90, #3-100, #4-90, #5-100, #6-95.!

Here is my question on these numbers. What would be the explanation for why the numbers are larger on the first set of tests results, where all of the spark plugs are still in the block (except for the cylinder I am testing), than on the second set of test results where all of the spark plugs have been removed. I am sure there is a reasonable explanation??? Does it have to do with the fact that the engine turns over easier when "all of the plugs" are removed??? Thanks for any explanations. James

i am not exactly an expert, but i would imagine that the best explanation for this would be the valves being open slightly to multiple cylinders as well as the equalization in compression from the exhaust and probably intake. im not sure about this, but it makes sense to me.

It cooled off?
Tests should be done on a warm engine.

Jackfish, I do not believe the engine had cooled off, because after the first set of compression tests I ran the engine to charge the battery. Thanks, Jim

IIRC the actual numbers are important but not near as important that the lowest number be within 80% of the highest number. Yours seem close.

The first set seems a bit low but not bad.

The cylinder walls have less oil on them after the first test & you lost some ring seal.
With all the plugs out put oil in the cylinders & run another compression test.

More air in the intake from camshaft overlap with 5 plugs in the engine causing a larger gulp of air on the intake stroke????

Leaking head gasket from adjacent cylinder??? Bill

Thanks for everyone's explanations on the drop in compression numbers. I should have inclued the results of the "wet test" ( a tablespoon of oil) following the "dry test", when all the plugs were in the block (other than the cyl. I was testing).Here were the the "dry" and the "wet" test results: #1-dry-116, wet-125, #2-dry-135, wet-137, #3-dry-130, wet-145, #4-dry-115, wet-125, #5-dry-122, wet-125, #6-dry-124,wet-142. I mentioned earlier that between the tests (the one test with all of the plugs in the engine block, versus the test with all of the plugs removed), I had started up the engine in order to charge the battery and ran it for 5 minutes, so I believe the cylinder walls would have/should have been re-lubricated with oil.
**Note: I did not do a "wet test" following the testing when all of the plugs had been removed; only after the testing when I was removing one plug at a time. Thanks again, James

wsa111/Bill.... you wrote: "MORE AIR IN THE INTAKE FROM CAMSHAFT OVERLAP WITH 5 PLUGS IN THE ENGINE CAUSING A LARGER GULP OF AIR ON THE INTAKE STROKE"

I like that explanation the best, but what do I know.(?) Ha! - James

wsa11/Bill, you also wrote the following: "LEAKING HEAD GASKET FROM ADJACENT CYLINDER"???

Were you pointing to any specific numbers/cylinders that may be of concern by your comment?? Just curious? - James

I will assume that the second set of numbers (the numbers that averaged between 90 - 100); or I should say the numbers from the test that had "all" of the spark plugs removed, to be the correct test/numbers, or the numbers to go by ???? Do these 90 - 100 numbers, which are on an engine that spec's out 130psi (in the tune up spec's), decent enough??? Before I start on some other modifications to this particular engine, I wanted to be sure that the numbers justify further upgrades, etc., to this engine??? Thanks for your input everybody. James