v10 engine compression

[v10snk]

Am I doing something wrong? I rented a compression test guage. I got all the spark plugs out, but the engine was not hot any longer. I tested 1-80 3-90 5-75 7-100 9-82 2-90 4-82 7-72 8-82 10-75. I have read they are supposed to be around 175. I just have a hard time believing every cylinder is testing bad. Car is down 100hp on dyno reason for cylinder test. 11k miles on car.

Anybody???

 

[Viper Specialty]

If you are down 100 horsepower, something major is going on. It is quite possible that all cylinders are worn. Some kind of a major contamination could cause that.

-Are you sure the tester is sealing on the spark plug seat?

-Make sure the car cranks fast. A low battery will give lower readings.

-Try putting in a teaspoon of oil, and see if the compression jumps.

 

[v10snk]

Car dyno was 530 to rear wheels with paxton and dc box tune.

 

[Black Moon]

Car dyno was 530 to rear wheels with paxton and dc box tune.

Isn't that within the norm? Just curious.

Is it worth opening the throttle while testing? Dan?

 

[plumcrazy]

the numbers should be ~ 180 IIRC.

did you do the test on a cold engine or warm ? that will make a difference too

 

[KNG SNKE]

Did you remove all of your spark plugs at once? I ran this test not too long ago on a cold engine. Remove all spark plugs, install gauge in cylinder, floor the gas pedal and crank the engine over at least 10 times. you should see the gauge peak out.

 

[EllowViper]

+1...What KNG SNKE said.

 

[v10snk]

Guys--I removed all the spark plugs first. The engine was not hot by the time I got them all removed. Hooked test gauge up throttle to the floor and got those numbers. I am going to have a professional look at this next week.

 

[SquadX]

Test ur tool on another car for comparison. If it's reading low on that then ur tool is faulty.

 

[v10snk]

Thanks for your help guys. I'll let you know what I find out.

 

[v10snk]

Got some great news this week on the viper. I do not need to ever pic up a wrench again. I had A.R.T. take a look at the viper. The viper went in with 545 to the rear and came out with 650 to the rear. David was great to deal with and educated me along the way. They did not have a special spring needed for the fuel PSI, but are ordering the part and should bump the fuel pressure to 100psi and get around 680 to the rear. It was a long drive, but I could not be happier. Thanks Guys!!!!!

 

[SquadX]

glad to hear it worked out. I've had conversations with A.R.T. and was very helpful with great advise.

 

[ScrewDrvr]

so what turned out to be the problem?

 

[v10snk]

Sorry---should have been more clear. Car had a bad tune.