I have a 84 12a I have been working on this car for some time now. Over the summer I have had the motor out and apart several times. I thought I had the motor finally running great but last weekend I checked compression and it's a little low. I have good apex seals, earlier this summer all were over 8 mm. What else can cause low compression? I running mixed gas. I did a large Street port on the motor. All the plates and housing look to be in good condition. there was one scratch on one plate but it was not that deep and was on the exhaust side. What else causes low compression? The car is running and driving but I would think I should have over 100 psi with good apex seals, shouldn't I? I think I enjoy working on the motor more than I do driving the car.