Compression test - VP 3.8 II

[Gemadore]

Hi guys/gals,

I finally got hold of a compression gauge and conducted a test on the Gemini's V6. The results ranged between 110-120 PSI on all six pots.
A teaspoon of oil brought up the comp by 5 psi.

From memory, I think the donor car had about 200 - 240k on it when it was ripped out and put in the gemini.

Does anyone have figures for what is considered normal PSI compression for the Buick 3.8 Series II engine?

Is this considered a 'healthy' engine or am I still destined to chat with a rebuilder?.

Cheers

Mark

 

[Pub247]

a fresh motor ie rebuilt or new should be in the 160-180 bracket. Having siad that if if all the pots are within 10 poitns as you say your are then there is nothing major wrong with it . if the oil trick made minimal difference than a leak down test would be next step but i'd its not worth it.

Really 120 is fine for a motor with a lot of kays might be a little low on comp but not bad

 

[padrickz88]

Also when you done the compression test, did you do it without all the spark plugs out? then let the engine crank over until the gauge wouldn't go any higher?

 

[Gemadore]

Also when you done the compression test, did you do it without all the spark plugs out? then let the engine crank over until the gauge wouldn't go any higher?

I went around to each cylinder with the comp gauge and then left the plug out as the next one was done. I only cranked over for 2-3 seconds each time. Is there a special way to conduct the test?

 

[padrickz88]

The way I was told to do it is take out all spark plugs, test each cylinder (I do each cylinder twice, just to be sure) and then wen all cylinders are tested then put all your spark plugs back in.

I usually crank for about 3-4 seconds (that's me).

 

[cruzn]

Nothing particulary wrong with those figures, although judging by those readings the engine is a fair bit worn out. Still should work good though.

 

[chargedvx6]

The way I was told to do it is take out all spark plugs, test each cylinder (I do each cylinder twice, just to be sure) and then wen all cylinders are tested then put all your spark plugs back in.

I usually crank for about 3-4 seconds (that's me).

:smoking:..........

 

[m1lky]

I was told you need to have the engine warm to get accurate results. This allows for expansion etc etc

 

[NPreston]

Stop being a tight arse Mark and buy a workshop manual. Engine should be warm, remove all spark plugs, isolate fuel pump, accelerator flat to the floor and crank engine. The manual gives a minimum figure but no maximum reading. All cylinders must be minimum of 100psi. Do the test again, properly this time and see what you get.

 

[padrickz88]

:smoking:..........

HAHAHAHA I knew someone would pick up that, I was thinking the same thing as I typed it hahaha