Guest EaStW00d Posted September 4, 2008 Share Posted September 4, 2008 Hello everyone. I have a 1976 280z and I just got done rebuilding the head. I have replaced the dist rotor, plugs, cap, plug wires, master cylinder, fuel filter, gaskets, and thermostat. My problem is that my compression in my #1 cylinder is only around 30 to 40 psi. All my other cylinders are fine. I know the car is timed correctly because I bought a timing light and set it. My fuel pressure is 36psi so that is all good. I also have good spark in all the plug wires so I doubt that is the problem. I'm going to pull out my injectors today and test them to see if they are working properly even though I can hear them clicking when the engine is running. The car will run but the acceleration is horrible due to the low compression. I have noticed that when i remove the injector plug from the #1 cylinder nothing happens to my RPMs. I just wanted some more opinions so that if it wasn't my injector then I would have some more things to try out. Thanks in advance! Quote Link to comment Share on other sites More sharing options...
jeffer949 Posted September 4, 2008 Share Posted September 4, 2008 The stuff you mentioned your going to check really has nothing to do with the compression on cylinder 1. What you need to do is do a wet compression test. Take like 5cc's of oil and put it in each cylinder and then do a compression check. Also have you adjusted your valves correctly? Quote Link to comment Share on other sites More sharing options...
Guest EaStW00d Posted September 4, 2008 Share Posted September 4, 2008 The valves were done by a local mechanic who rebuilt my head for me. I never really checked the valve clearances because he had the books and knew what to set them at but I guess that could be it. Quote Link to comment Share on other sites More sharing options...
Tony D Posted September 4, 2008 Share Posted September 4, 2008 Adjust your valves, and hope you didn't nick the top of the piston and bust a valve guide/bend a valve in the process. BTW, what does "Fine" quantify to for the other cylinders? Quote Link to comment Share on other sites More sharing options...
Guest EaStW00d Posted September 5, 2008 Share Posted September 5, 2008 I'm about to go do adjust my valve clearances but here are the results from my compression test earlier. #1 89 #2 155 #3 150 #4 150 #5 120 #6 150 Those numbers are all from a normal compression test. I then did the wet test and got 97psi on #1 and 140 psi on #5. I don't believe that is a large enough difference to suggest a broken ring. I'll let you know how the compression is after I do the adjusting. Quote Link to comment Share on other sites More sharing options...
Guest EaStW00d Posted September 6, 2008 Share Posted September 6, 2008 I adjusted my valves and here is what my new compression test was. #1 156 (67 increase!) #2 155 #3 155 #4 155 #5 160 (40 increase) #6 155 So my valve clearances were my problem. All my other cylinders increased by at least 5psi after the adjusting. Quote Link to comment Share on other sites More sharing options...
jeffer949 Posted September 7, 2008 Share Posted September 7, 2008 Now those are some good numbers. Good job Quote Link to comment Share on other sites More sharing options...
woldson Posted September 7, 2008 Share Posted September 7, 2008 Bet that made you happy;) Quote Link to comment Share on other sites More sharing options...
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