383 Compression Test
08-03-2007, 07:55 AM
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Staging Lane
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383 Compression Test Yes, I've searched and found a load of threads concerning this. Of these threads, there are no solid solutions, only speculations on the cause. Someone has to have solved the oil consumption on these stroked motors.
1) I read that w/ the longer stroke, the piston MAY be coming below the bottom of the cylinder walls, which may cause the piston to tilt a puss-hair which MAY cause the rings to not seal.
-If this is the case, why would the rings not be destroyed upon re-entry to the bottom of the cylinder? You say the rings are not leaving the bottom of the cylinders? Then how could this possibly be a cause?
2) Read also that valve seals could be the culprit.
-If this is the case, does anyone have a stronger valve seal to replace the current ones with that will correct this? Would an adjustable pressure release valve to the crank case/oil pan be an easier solution?
-What about vacuum pumps? What purpose would this serve? Would creating more pressure in the intake track equalize the pressure to what is in the crank case and preven the oil from being forced through the seals?
3) Compression testing the cylinders. I done the compression test w/ the TB Closed since I was looking for consistency, not a value to compare to a book. The Driver's side was 235ish, the passenger side was 250ish. Yes, I checked each cylinder on each head. The difference between each cylinder varried by no more than 5 on either side. (Yes, I have a pretty good idea why one is 20 greater than the other) According to the scanning and other signs, the side with the 250ish may be causing some tuning issues.
4) Oil in the FAST 90 intake. Maybe 1-2oz of oil puddling in the intake.
-Where is it coming from, rings? seals? pcv?
-what is the most cost effective fix?
-What is the permanent fix?
Engine is a 383 w/ 11.9-12.2 compression. As it is, on ET Street Radials, full weight (2800 w/ driver) it is trapping 122mph. We need to correct the oil consumption issue (1qt / 300 miles) before continuing the tuning. I'm afraid the oil is screwing w/ O2 sensors and the WBO2.
Theree are hundreds of posts concerning these related issues. Can we list the solutions for the people who hate driving their cars because of the consumption issues?
Thanks
1) I read that w/ the longer stroke, the piston MAY be coming below the bottom of the cylinder walls, which may cause the piston to tilt a puss-hair which MAY cause the rings to not seal.
-If this is the case, why would the rings not be destroyed upon re-entry to the bottom of the cylinder? You say the rings are not leaving the bottom of the cylinders? Then how could this possibly be a cause?
2) Read also that valve seals could be the culprit.
-If this is the case, does anyone have a stronger valve seal to replace the current ones with that will correct this? Would an adjustable pressure release valve to the crank case/oil pan be an easier solution?
-What about vacuum pumps? What purpose would this serve? Would creating more pressure in the intake track equalize the pressure to what is in the crank case and preven the oil from being forced through the seals?
3) Compression testing the cylinders. I done the compression test w/ the TB Closed since I was looking for consistency, not a value to compare to a book. The Driver's side was 235ish, the passenger side was 250ish. Yes, I checked each cylinder on each head. The difference between each cylinder varried by no more than 5 on either side. (Yes, I have a pretty good idea why one is 20 greater than the other) According to the scanning and other signs, the side with the 250ish may be causing some tuning issues.
4) Oil in the FAST 90 intake. Maybe 1-2oz of oil puddling in the intake.
-Where is it coming from, rings? seals? pcv?
-what is the most cost effective fix?
-What is the permanent fix?
Engine is a 383 w/ 11.9-12.2 compression. As it is, on ET Street Radials, full weight (2800 w/ driver) it is trapping 122mph. We need to correct the oil consumption issue (1qt / 300 miles) before continuing the tuning. I'm afraid the oil is screwing w/ O2 sensors and the WBO2.
Theree are hundreds of posts concerning these related issues. Can we list the solutions for the people who hate driving their cars because of the consumption issues?
Thanks
