COMPRESSION TEST

[klmnla]

I finally did a compression test today. 5 of the cylinders are right at 143-145 PSI. Cyl# 3 is at 135. Although this falls into the 10% or less difference in pressure, should I be worried? This was my next step before I look at the cam for a possible worn or flat lobe.

 

[fastblackracing]

I finally did a compression test today. 5 of the cylinders are right at 143-145 PSI. Cyl# 3 is at 135. Although this falls into the 10% or less difference in pressure, should I be worried? This was my next step before I look at the cam for a possible worn or flat lobe.

Does the car run ok or are there issues? I would not worry to much if its running ok. You can take the hose assembly off your comp gauge and hook it up to a compressed air source to pressurize the cylinder and check for valve leaks if you hear air in the exhaust or intake not good. There will be some go past the rings into the oil pan that's normal. Also remove the oil fill tube and watch #3 rockers with engine running.

 

[klmnla]

It runs fine until it starts to hit boost, and then starts cutting out. I have been chasing this problem for 5 years with no luck. I have done everything twice as far as troubleshooting. The last item on my checklist is checking for a worn cam lobe. I wanted to do the compression test first. I have replaced or swapped out every other possible cause at least once, and my scanmaster numbers are good. I am going to take the valve covers off and look at rocker movement while cranking the engine. If a cam fixes it, that would be fine by me.

 

[CGASTON]

I finally did a compression test today. 5 of the cylinders are right at 143-145 PSI. Cyl# 3 is at 135. Although this falls into the 10% or less difference in pressure, should I be worried? This was my next step before I look at the cam for a possible worn or flat lobe.

I wouldn't be worried with that kinda difference. At least not something to rebuild the motor over. Now if it were around 110, then I would be worried.

Sent from my iPhone using Turbo Buick

 

[fastblackracing]

It runs fine until it starts to hit boost, and then starts cutting out. I have been chasing this problem for 5 years with no luck. I have done everything twice as far as troubleshooting. The last item on my checklist is checking for a worn cam lobe. I wanted to do the compression test first. I have replaced or swapped out every other possible cause at least once, and my scanmaster numbers are good. I am going to take the valve covers off and look at rocker movement while cranking the engine. If a cam fixes it, that would be fine by me.

Yep def check the cam let us know what you find and good luck.

 

[Nick Micale]

.......... should I be worried? This was my next step before I look at the cam for a possible worn or flat lobe.

It could be a worn or bad cam/lifter, but it might be a bad valve?

The simple thing to do at this point is to hook up a vacuum gauge and see if the needle is steady, or does it fluctuate?

If the needle is moving, you could have a bad valve or seat.